20200086 Ver 1_1915_SIA_2nd CD Submittal_20200309

FedEx Freight
STORMWATER IMPACT ANALYSIS
5203 Chin Page Road
Durham, North Carolina
Horvath Associates Project Number: 1915
i � � i�, 2019
RRe4ed Q^t r23:2-0
Revised March
NCBELS NO: C-0676
Prepared by: Horvath Associates, P.A.
Engineers - Planners - Landscape Architects
16 Consultant Place, Suite 201
Durham, North Carolina 27707
[phone]

Table of Contents

Project Narrative

Stormwater Development Review Submittal Checklist

Reference Materials

Peak Flow Analysis

Summary of Results
HydroCAD Runoff Analysis

SCM Sizing Calculations

Nutrient Loading Calculations

Maps

Narrative

A. Project Data

 Project Name: FedEx Freight
 PIN: 0748-91-06-3841, 0748-91-73-3991
 Address: 5203 Chin Page Road
 Stormwater Regulatory Basin: Lower Neuse
 River Basin: Neuse
 Existing Impervious Area: 18,075 sf (On Baseline Date for Stormwater Calculations)
 Proposed Impervious Area: 1,141,350 sf
 Area of Disturbance: 40.25 ac
 TMDL: None
 Watershed Protection Overlay: None

B. Site History

The site in its current state is mostly wooded and vacant. There are a few single-family
homes and driveways located on the property. Aerial photographs indicate that no
impervious surface has been added to the property since at least 1994.

1994 Aerial Photo 3/28/1998 Aerial Photo

2/28/2002 Aerial Photo 2013 Aerial Photo

C. Project Description
The project will involve constructing a FedEx freight transfer facility. The development
will include a main warehouse building, two ancillary buildings, loading docks, parking
areas for trailers, and a parking lot for employee vehicles.

The development will also involve extending Crown Parkway from the development
northeast of the site to Chin Page Road to the south.

D. Quantifying Land Disturbance and Changes in Impervious Surface
The project will involve greater than 12,000 sf of land disturbance and will add more
than 2,000 sf of new impervious area. This exceeds all thresholds found in the City of
Durham Stormwater Performance Standards; therefore, the site will not be exempt from
any stormwater requirements. The pre-development impervious surface utilized in the
runoff and nutrient loading calculations is that which existed on the baseline date. This
was determined from historical planimetric data provided by the City of Durham and
verified through aerial photographs. The existing impervious area shown on the site plan
is based on the provided survey and may not include driveways that have been
overtaken by vegetation or buildings that were removed. There is at least one building
in the southern portion of the site that was removed between 2002 and 2013

E. Watershed Protection Overlays
The property is not located in a watershed protection overlay.

F. Streams
There are four streams visible on the Durham County Soil Survey within the property limits.
An environmental assessment was performed, and two streams near the southwest
property corner were determined to be subject to the Neuse stream buffer rules. A 50-
foot buffer has been applied to each subject stream.

G. Floodplains
There is no FEMA regulated floodplain on the site.

H. Applicable Requirements

Peak Runoff Requirements

Sec. 70-738. Peak runoff control requirements.(a)Purpose. The purpose of this section is
to ensure that the increases in volume, velocity, and peak flow of stormwater discharges
from development are addressed, in order to mitigate the impacts on downstream
properties and receiving waters. All development, including development that may be
exempt from pollutant reduction requirements set forth in remaining sections of this
article, is subject to the requirements of this section unless exempted in subsection (b)
below.

(b)Applicability; calculation of prior impervious area. This section 70-738 applies to
the following development, assessed in comparison to pre-development prior
impervious conditions as defined in subsections (1) and (2) below: (i) relocation of
existing impervious area on a multifamily and other lot; (ii) increase in impervious
area on any lot subject to limitations on impervious area in an approved plat or plan
for reasons such as watershed protection or stormwater control measure
requirements; (iii) increase of more than 200 square feet in impervious area on a
multifamily and other lot; (iv) increase of more than 2,000 square feet of impervious
area on a limited residential lot. For purposes of calculating these thresholds, subject
development that is part of a common plan of development shall be assessed with
other portions of such common plan that have not previously complied with peak
flow requirements.
(1)For purposes of applying peak flow requirements for the two- and ten-year
storms, the land cover (including type and location) existing as of April 23, 1997
shall be considered the "pre-development conditions";
(2)For purposes of applying the peak flow requirement for the one-year storm,
the land cover (including type and location) that existed as of March 9, 2001
for land in the Falls Basin and Lower Neuse Basin, and as of March 17, 2009 for
land in the Jordan Basin shall be considered the "pre-development conditions";

(c)Requirements.
(1)Stormwater impact analysis. Development that is not exempt under
subsection (b) above shall submit a stormwater impact analysis or approved
alternative to such analysis that complies with city stormwater standards as
part of the application for site plan or subdivision plat approval, or if such is not
required, as part of submittals for construction drawings or utility permit
approval. Calculations shall be made in conformance with city stormwater
standards. No subdivision plats, site plans, utility permits, or construction
drawings shall be approved in the absence of a determination by the
stormwater division that required submissions have been made and approved.
(2)One-year storm. Development that increases the peak runoff rate from the
one-year storm from pre-development conditions shall provide stormwater
management facilities in accordance with city stormwater standards such
that there is no net increase in peak runoff rate.

Peak Runoff Analysis
There is one location where concentrated runoff leaves the property in the southeast
corner of the property. The runoff at this location is channelized and enters an existing
pipe where it is conveyed underneath the access road for the property to the west. This
location was utilized as the analysis point to demonstrate the development will not
negatively impact the existing streams or downstream infrastructure due to increase in
runoff.

Two wet detention basins are provided to attenuate the peak flow to below pre-
development levels for the 1-, 2-, and 10-year rainfall events. An analysis is provided
that demonstrates the post-development peak flow rate in the stream channels the wet
detention basins discharge to (labeled DP#1 and DP#3) do not increase for the 1-year
rainfall event. The peak flow rate leaving the site (DP#1) does not increase for the 2-
and 10-year rainfall events when compared to the pre-development rate.

Water Quality

Per section, 70-739 of the City of Durham Stormwater Ordinance the project is located in
the Lower Neuse Regulatory Basin, is part of a Common plan of development, and
disturbs more than 0.5 acres; therefore, the project is subject to the requirements for
stormwater pollutants found in sections 70-740 and 70-741 of the City of Durham
Stormwater Ordinance.

Required Reductions for Nutrients
Sec. 70-740. Required reductions for nutrients and TSS; alternatives; calculations.

Nutrient loading rate limits. Development not exempt under subsection 70-739 shall
construct and implement SCMs so as to limit the post construction loading rate of
nitrogen and phosphorus from the project area to the limits set forth in Table 2 below, or
shall comply with an allowed alternative as set forth in subsections (b) through (d)
below. A portion of the reduction requirements for nitrogen and phosphorus may be
met through off site measures or payments as set forth in section 70-741.
Table 2
Nutrient Export Loading Rate Limits
Project Location Export Limit lbs/acre/year
Nitrogen Phosphorus
Falls Basin 2.2 0.33
Lower Neuse Basin 3.6 not required

On-Site Percentage Removal Requirements
Sec. 70-741. On-site treatment requirements; offsite purchase and credit options;
bacteria control.
(a) On site nutrient treatment requirements. Nitrogen and phosphorus reduction
requirements may be met, in part, through offsite management measures or the
purchase of nutrient credits. At a minimum, however, in the Jordan and Falls Basins a
percentage of the required nitrogen and phosphorus reductions must be achieved
through onsite treatment, in the amount shown in Table 4 below. In addition to
meeting the percentage reductions below, in the Jordan and Lower Neuse Basins,
nitrogen export loading rates from the site must not exceed six pounds per acre per
year for limited residential, and ten pounds per acre per year for multifamily and
other (Note: offsite credit purchases do not meet TSS removal requirements which
must be met onsite).
Table 4
Onsite Nutrient Treatment Requirements
Project Location Minimum Onsite Nutrient Treatment
Nitrogen Phosphorus
Falls - General *50% of required
reduction
*50% of required
reduction
Falls Downtown Area *30% of required
reduction
*30% of required
reduction
Falls exceeding thresholds but
with less than 1 acre land
disturbance
*30% of required
reduction
*30% of required
reduction
Lower Neuse
No Percentage reductions
apply, but the 6/10 nitrogen
export limit described in
paragraph (a) above must
be met
Not required
*The "required reduction" is the difference between the post development loading in
pounds per acre per year multiplied by the site area in acres before treatment minus the
loading target, in pounds per acre per year multiplied by the acres. The percentage
shown in the chart above is applied to that difference and the resulting number is the
amount in pounds/year of nutrient reduction that must be achieved onsite.
(b)Offset payments to state approved nutrient mitigation banks. Development and
redevelopment shall have the option of purchasing nutrient credits from state-
approved nutrient banks to partially offset nitrogen and/or phosphorus loads as
allowed by state law and regulation, including but not limited to 15A NCAC
02B.0235, 15A NCAC 02B.0282, and 15A NCAC 02B.0240, as they may be amended
from time to time. In the Jordan Basin, calculation of credits required shall reflect
state approved delivery factors. The number of pounds for which credits are
purchased shall be increased by five percent if the nutrient bank is not located in
the city. The following additional requirements shall apply:
(1)Location of nutrient banks. Development in the Falls Basin must use nutrient
banks located in the upper Falls portion of the Falls Basin—the portion that is
north and/or west of Highway 50. Development in the Jordan Basin must use
nutrient banks located in the Upper New Hope arm of such basin, as defined
in state regulations.
(2)Certification of nutrient bank provider. Offset credits may only be obtained
from nutrient banks certified by the state.
(3)Utilization of NC Ecosystem Enhancement Program. Credits may also be
obtained from the NC Ecosystem Enhancement Program if such credits are
available, and if applicable state requirements regarding utilization of private
nutrient banks are first met.
(4)Certification of credits. Credits purchased pursuant to this subsection (b)
shall be verified by the state and proof of such verification that meets city
requirements shall be presented prior to approval of a final plat, or if no plat is
required, prior to issuance of the first building permit within the project, or such
earlier deadline as may be required by city stormwater standards.

The project is located in the Lower Neuse Regulatory Basin and is not considered limited
residential development; therefore, the nitrogen loading rate leaving the site cannot
exceed 10 lbs/acre/year. Through a combination of on-site treatment and purchase of
nutrient offset credits, The total nitrogen loading rate for the site must not exceed 3.6
lbs/ac/year. There are no phosphorous loading limits in the Lower Neuse Basin. Nitrogen
loading calculations demonstrate that the total site nitrogen loading does not exceed
10 lbs/ac/year. Additional loading that exceeds the 3.6 lbs/ac/year limit will be
mitigated by purchasing nitrogen credits from a state approved mitigation bank or NC
DMS.

Bacteria Control
Sec. 70-741. On-site treatment requirements; offsite purchase and credit options;
bacteria control.

(d)Bacteria removal; control of other identified stormwater pollutants. All
development which constructs stormwater control measures in order to comply with
this article and which is located in an area that is subject to a state approved total
maximum daily load for bacteria shall be required to have at least one SCM for
each stormwater discharge that is rated as medium or high for its ability to remove
bacteria from stormwater. Ratings shall be those that appear in the most recent
version of the NCDENR Stormwater SCM manual or as determined or approved by
the director. In addition, SCMs required to be constructed under this article must also
treat any other pollutant for which a total maximum daily load has been identified
for the area within which the SCM is located.

This project is not located in an area that is subject to a state approved total maximum
daily load for bacteria or turbidity; therefore, no bacteria or turbidity removal is required.

TSS Reduction
Sec. 70-740. Required reductions for nutrients and TSS; alternatives; calculations

(e)TSS reduction. When the impervious percentage of a development that increases
impervious area equals or exceeds 16 percent in the Falls or Jordan Basins, or 24
percent in the Lower Neuse Basin, TSS removal is required as further described in this
subsection (e). All impervious surfaces, as reasonably practical, must drain to an SCM
that is designed to provide a minimum of 85 percent TSS removal and is sized to
capture runoff from the first one inch of rainfall from all surfaces that drain to the
SCM. These requirements are expanded, and/or modified as follows:

(1)Piped areas in low density projects. Projects that do not require construction
of SCMs because their impervious percentage is less than that described in the
paragraph above must treat TSS from stormwater runoff that is conveyed in
non-vegetated conveyances, such as stormwater pipes, but excluding road
and driveway crossings.

(2)Overtreatment to address untreatable areas. Where treatment for TSS is not
reasonably practicable, as determined by the department, such as when
impervious areas include offsite transportation improvements or small
noncontiguous areas at the edge of a project, additional reductions of TSS
may be required in treatable areas, such as overtreatment in other project
areas or treatment of offsite runon.

(f)Calculations for nutrient loading and TSS removal. Pollutant loading calculations
shall be made using city stormwater standards. All increases in impervious surfaces
shall be included, including but not limited internal and off site transportation
improvements. Approved methodologies for calculating pollutant loading shall be
maintained in writing by the public works department, and shall include those
methodologies and calculations required to be used by the division of water quality
or DWQ-approved alternate methodologies.

(g)Submittals. An applicant shall submit pollutant loading calculations for the pre-
and post-development conditions as part of its application for approval of a
subdivision or site plan, utility permit, or construction drawings for a street or utility.

This project is subject to TSS removal requirements. All runoff from on-site impervious
surfaces will be captured in the proposed wet detention basins which will provide 85%
TSS removal.

Diffuse Flow
Each proposed stormwater outfall will discharge directly to the steam and has a wet
detention basin that provides 85% TSS removal for runoff from all added impervious
surfaces. This meets the Neuse Stream Buffer requirements for diffuse flow.

I. Methodology
 United States Geological Survey Map is the Southeast Durham Quadrangle.
 The FEMA Map associated with the site is Map 3720074800K; effective date October
19, 2018.
 Soil data to determine curve numbers in the watershed are from USDA Durham
County Soil Map # 36. Onsite soils are a mixture of HSG ‘B’ and HSG ‘C’.

J. Conclusions
1-, 2-, and 10-year rainfall event peak runoff rates will not exceed pre-development
levels at the site’s discharge points.

Two proposed wet detention basins will provide on-site nitrogen loading reduction so
that the loading rate leaving the site does not exceed 10 lbs/ac/yr. Any remaining
nitrogen loading exceeding 3.6 lbs/ac/yr will be mitigated by purchasing offset credits.

85% TSS removal will be provided in the wet detention basins for all on-site impervious
area.

Stormwater Development Review
Submittal Checklist
CITY OF DURHAM – STORMWATER SERVICES SITE PLAN SUBMITTAL CHECKLIST
Department of Public Works
101 City Hall Plaza | Durham, NC 27701
919.560.4326 | F 919.560.4316
Date: ____________________
www.durhamnc.gov
PROJECT INFORMATION
Project Name:
Phase: Planning Case Number:
Previous Project Name(s):
PIN(s):
Contact Person: Phone:
Company: Fax:
Email Address:
INSTRUCTIONS
For each review submittal, including re-submittals, the entire Stormwater Impact Analysis (SIA) and
submittal checklist shall be submitted. Partial SIA and checklist will result in notification of an
incomplete submittal with no review performed.
Contact Stormwater Services regarding redevelopment or expansion projects for modified requirements.
The following checklist outlines submittal requirements. Initial in the space provided to indicate the
following submittal requirements have been met and supporting documentation is attached.
A. GENERAL REQUIREMENTS
Initials
_____ (Check One) __ INSIDE __ OUTSIDE Watershed Protection Overlay (WPO).
Indicate the WPO(s) where the project is located:
(Check all that apply) __ F/J-A __ F/J-B __ E-A __ E-B __ M/LR-A __ M/LR-B
If inside WPO, notation of WPO Standards is required on plans.
_____ (Check all that apply) __ Jordan Basin __ Falls Basin __ Lower Neuse Basin
_____ A legible copy of the United States Geological Survey 7.5 Minute Quadrangle map is provided,
including map reference, with site boundary clearly shown and labeled. The map clearly shows
all streams.
_____ A legible copy of the published Durham County Soil Survey is provided, including map reference,
with the site boundary clearly shown and labeled. The map clearly shows all streams, soil types
and soil type boundaries.
_____ Tops of banks for the streams are shown on the plan. [Contact the North Carolina Department of
Environment and Natural Resources for stream identifications in the Neuse River Basin (Falls
and Lower Neuse Basins). Stream determinations in the Jordan Basin shall be submitted per the
Letter to Industry found on Stormwater Development Reviews’ web site at New Stream Buffer
Requirements [First Revision to LTI 07-03-08] (25August2011)].
_____ All Watershed Protection Overlay, Neuse River Basin, Jordan Basin, and City riparian buffers,
measured from the tops of the stream banks, are shown on the plan.
Page 1 of 6
11/26/2019
FedEx Freight
N/A D1900260
N/A
0748-91-06-3841, 0748-91-73-3991
Matt Jones, PE
Horvath Associates, P.A.
[phone]
[phone]
[e-mail]
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_____ The 10-foot no build setback, measured from all riparian buffers, is shown on the plan.
_____ Diffuse flow is achieved into riparian buffers.
_____ (Check One) __ Yes __ No Regulated floodplain located on site.
_____ A legible copy of the effective Federal Emergency Management Agency National Flood
Insurance Program Flood Insurance Rate Map is provided. Map number, map date, and site
boundary are clearly shown and labeled. [This map is required regardless of whether floodplain
is located on the site.] The effective and/or future FEMA 100-year floodplain, with base flood
elevations (if applicable), are shown on the plan.
_____ All applicable notes, per the Standard Notes section of the Reference Guide for Development,
have been added to the plan.
_____ Stormwater Impact Analysis (SIA) sealed and signed by a registered North Carolina Professional
Engineer (NCPE) is provided, including narrative report and drainage calculations. Note: If a site
is exempt from stormwater requirements then a narrative advising of the exemption can be
submitted by any designer.
B. PEAK DISCHARGE RATE EVALUATION
Initials
_____ An introductory narrative describing pre- and post-development site conditions and site
improvement changes, is provided. Note: The baseline conditions for the 1-year event varies
based upon the regulatory basin in which the project is located.
_____ Drainage area maps (one map for pre-development and one map for post-development) are
provided with the following items:
_____Scale and north arrow (Note: Except in the instance of site-to-drainage area maps, the
scale of each drainage area map shall not exceed 1” = 30’).
_____Sub-basin area(s) delineated with area(s) in acres indicated.
_____Analysis points clearly identified and labeled.
_____Segmented TR-55 time of concentration flow paths showing and labeling each segment.
_____ Methodologies and procedures are fully described.
_____ A site plan with contour lines or grading plan identifying pre- and post-development drainage
patterns is provided.
_____ Pre- and post-development times of concentration, calculated by TR-55 segmented approach,
are provided.
_____ Calculations for the pre- and post-development peak discharge rates are provided for the 1-, 2-,
10-, and 100-year, 24-hour storm using TR-55, TR-20, HEC-HMS, HEC-1 or Rational Method as
applicable. Note: The Rational Method is not accepted for the 1-year analysis, areas that drain
more than 50 acres, or watersheds that are not homogeneous.
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_____ A Summary of Results is provided in the following format:
Site Analysis Point #__________
Site Condition Storm Event (cfs)
1-year (cfs) 2-year (cfs) 10-year (cfs) 100-year (cfs) ____-year (cfs)
Pre-Development
Post-Development
without Detention
Post-Development
with Detention
_____ Conclusions providing detailed findings are provided.
_____ Stormwater control measure(s) (SCM[s]) are provided (indicate number of each type of SCM):
____Level Spreader w/ Vegetative Filter Strip ____Stormwater Wetland
____Wet Detention Basin ____Sand Filter ____Bioretention ____Grassed Swale
____Restored Riparian Buffer ____Dry Extended Detention Basin
____Permeable Pavement ____Green Roof ____Disconnected Impervious Surface
____Rainwater Harvesting System
____Proprietary Systems or Other________________________________________________
____Not required (provide explanation): ____________________________________________
_____ The SCM(s) indicated above are required to control the following peak discharge rates:
____1-year ____2-year ____10-year ____100-year ____Other_________________________
_____ A downstream analysis in accordance with the Reference Guide for Development is provided
with findings, or is
______Not required (provide explanation):
C. POLLUTANT CONTROL REQUIREMENTS
Initials
_____ The project is exempt based upon cumulative land disturbance as of the applicable baseline
date.
_____ 7KHSURSRVHGSURMHFWLVBBBBB•LPSHUYLRXV)DOOVDQG-RUGDQ%DVLQVBBBBB•
impervious (Lower Neuse Basin), 85% Total Suspended Solids (TSS) removal is provided for
this project, and all the impervious area as reasonably practical is treated by an SCM.
OR
The proposed project is _____ <16% impervious (Falls and Jordan Basins) / _____ <24%
impervious (Lower Neuse Basin), 85% Total Suspended Solids (TSS) removal for all runoff from
non-vegetated conveyances is provided for this project, and all the impervious area as
reasonably practical is treated by an SCM.
_____ The project is low density without non-vegetated conveyances, thus TSS removal is not
required.

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Post-development peak flow rates will not exceed pre-development rates.
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_____ SCMs for TSS removal are provided (indicate number of each type of SCM): Note: Not all of the
SCMs listed below provide 85% TSS removal as a stand-alone SCM and must be used in series
with other SCMs to achieve the minimum TSS removal of 85%.
____Level Spreader w/ Vegetative Filter Strip ____Stormwater Wetland
____Wet Detention Basin ____Sand Filter ____Bioretention ____Grassed Swale
____Restored Riparian Buffer ____Dry Extended Detention Basin
____Permeable Pavement ____Green Roof ____Disconnected Impervious Surface
____Rainwater Harvesting System
____Proprietary Systems or Other________________________________________________
____Not required (provide explanation):
_____ Both hard copies, and Excel-format electronic copies on a DVD or compact disc, of the following:
x Pre- and post-development nutrient calculations using the Jordan/Falls Lake Stormwater
Nutrient Load Accounting Tool found at
: http://portal.ncdenr.org/web/jordanlake/implementation-guidance-archive
or http://durhamnc.gov/ich/op/pwd/storm/Pages/SWDevReview.aspx
Note: Nutrient calculations are always required regardless if the project is exempt from
treatment requirements.
x The Nutrient Reporting Form (including the Compliance Worksheet tab) per the 3/7/2013
Letter to Industry http://durhamnc.gov/ich/op/pwd/storm/Pages/LTI-SWDevReview.aspx
_____ Pre- and post-development land use area maps that correspond to the categories used in the
Jordan/Falls Lake Stormwater Nutrient Load Accounting Tool for the nutrient calculations, to
scale no smaller than 1 inch = 100 feet. The maps shall show the map scale, north arrow, and
are to have the different land uses either hatched or shaded with areas indicated in a legend on
the maps. Note: The land use area maps are always required regardless if the project is exempt
from treatment requirements.

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_____ SCMs for nutrient control are provided (indicate number of each type of SCM):
____Level Spreader w/ Vegetative Filter Strip ____Stormwater Wetland
____Wet Detention Basin ____Sand Filter ____Bioretention ____Grassed Swale
____Restored Riparian Buffer ____Dry Extended Detention Basin
____Permeable Pavement ____Green Roof ____Disconnected Impervious Surface
____Rainwater Harvesting System
____Proprietary Systems or Other________________________________________________
____Not required (provide explanation):
_____ After meeting the minimum on-site treatment requirements, additional treatment and/or offsite
credit purchases, if needed, is provided by:
____Additional SCMs
____Nutrient Offset Payment to the North Carolina Ecosystem Enhancement Program
____Nutrient Offset Payment to an Approved Nutrient Bank
____Land Bank Credit Transfer (Commitments shall be made prior to October 1, 2015)
_____ The project site is located in an area subject to a state-approved Total Maximum Daily Load
(TMDL) for bacteria. (As of April 2014, only Northeast Creek has a TMDL for bacteria).
_____ SCMs rated as medium or high for bacterial removal are provided (indicate number of each type
of SCM):
____Bioretention Area ____ Stormwater Wetlands
____Wet Detention Basin ____ Sand Filter
____Level Spreader w/ Vegetative Filter Strip ____Restored Riparian Buffer
____Dry Extended Detention Basin ____ Permeable Pavement
____Other (specify)_____________________________________________________________
____Not required (provide explanation):
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The project is not located in a watershed that has a TMDL for bacteria.
D. WATERSHED PROTECTION OVERLAY REQUIREMENTS
Initials
_____ 85% Total Suspended Solids (TSS) removal is required for this project, and 100% of the
impervious area will be treated by an SCM. Note: Not all of the SCMs listed below provide 85%
TSS removal as a stand-alone SCM and must be used in series with other SCMs to achieve the
minimum TSS removal of 85%.
_____ SCM for TSS removal are provided (indicate number of each type of SCM):
____Level Spreader w/ Vegetative Filter Strip ____Stormwater Wetland
____Wet Detention Basin ____Sand Filter ____Bioretention ____Grassed Swale
____Restored Riparian Buffer ____Dry Extended Detention Basin
____Permeable Pavement ____Rooftop Runoff Management
____Disconnected Impervious Surface ____Rainwater Harvesting System
____Proprietary Systems or Other________________________________________________
____Not required (provide explanation):

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N/A
N/A

Reference Material
USGS The National Map: Orthoimagery. Data refreshed April, 2019.National Flood Hazard Layer FIRMette05001,0001,5002,000250FeetÜ78°50'24.55"W 35°54'4.69"N 78°49'47.10"W 35°53'35.55"N SEE FIS REPORT FOR DETAILED LEGEND AND INDEX MAP FOR FIRM PANEL LAYOUTSPECIAL FLOODHAZARD AREASWithout Base Flood Elevation (BFE)Zone A, V, A99With BFE or DepthZone AE, AO, AH, VE, ARRegulatory Floodway0.2% Annual Chance Flood Hazard, Areasof 1% annual chance flood with averagedepth less than one foot or with drainageareas of less than one square mile Zone XFuture Conditions 1% AnnualChance Flood HazardZone XArea with Reduced Flood Risk due toLevee. See Notes.Zone XArea with Flood Risk due to LeveeZone DNO SCREENArea of Minimal Flood HazardZone XArea of Undetermined Flood HazardZone DChannel, Culvert, or Storm SewerLevee, Dike, or FloodwallCross Sections with 1% Annual Chance17.5Water Surface ElevationCoastal TransectCoastal Transect BaselineProfile BaselineHydrographic FeatureBase Flood Elevation Line (BFE)Effective LOMRsLimit of StudyJurisdiction BoundaryDigital Data AvailableNo Digital Data AvailableUnmappedThis map complies with FEMA's standards for the use of digital flood maps if it is not void as described below. The basemap shown complies with FEMA's basemap accuracy standardsThe flood hazard information is derived directly from theauthoritative NFHL web services provided by FEMA. This mapwas exported on 7/29/2019 at 4:18:13 PM and does notreflect changes or amendments subsequent to this date andtime. The NFHL and effective information may change orbecome superseded by new data over time.This map image is void if the one or more of the following mapelements do not appear: basemap imagery, flood zone labels,legend, scale bar, map creation date, community identifiers,FIRM panel number, and FIRM effective date. Map images forunmapped and unmodernized areas cannot be used forregulatory purposes. LegendOTHER AREAS OFFLOOD HAZARDOTHER AREASGENERALSTRUCTURESOTHERFEATURESMAP PANELS81:6,000B20.2The pin displayed on the map is an approximate point selected by the user and does not represent an authoritative property location.SITE

1915 - Chin Page Road Industrial (FedEx Freight)

USGS MAP - SE Durham Quadrangle
SCALE 1:24,000 N
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SITE
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Water Resources
Environmental Quality
June 11, 2018
Bethpage Acquisition Partners II, LLC
Tri Properties, Inc.
Attn: Rob Griffin
4309 Emperor Blvd, Suite 110
Durham, NC 27703
Determination Type:
ROY COOPER
Governor
MICHAEL S. REGAN
Secretary
LINDA CULPEPPER
Interior Director
Subject: Buffer Determination Letter
NBRRO #18-156
Durham County
Buffer I Intermittent/Perennial
® Neuse (15A NCAC 2B .0233)
❑ Tar -Pamlico (15A NCAC 2B .0259)
❑ Jordan (15A NCAC 2B .0267)
(governmental and/or interjurisdictional
projects)
Project Name: Chin Page Road Site
❑ Intermittent/Perennial Determination (where local
buffer ordinances apply)
Address/Location: 5203 Chin Page Road, Durham
Stream(s): UTs to Stirrup Iron Creek
Determination Date: 06/08/2018
Staff: Jeremiah Dow
Stream
ER/Plrl
Not
Subject
Start@
Stop@
Soil
USGS
Feature
Subjectt2>
Survey
Topo
A
1/P
X
DWR Flag,
OffProp Property
X
35.897535,-78.835355
B
E
X
NA
NA
X
C
E
X
NA
NA
X
D
UP
X
DWR Flag,
Confluence with
X
35.897003,-78.835767
Feature A
E
E
j X
j
j NA
NA
X
� Nothing Compares:
State of North Carolina I Environmental Quality I Water Resources [ Raleigh Regional Office
1628 Mail service Center I Raleigh, North Carolina 27699-1628
919 7914200

Chin Page Road Site
Wake County
06/11/2018
Page 2 of 2
Stream EQ/P(t> Not z) Subject Start@ Stop@ Soil USGS
Feature Subject( Survey To o
F Previously classified as "not subject" in buffer determination #17-446.
Pond 1 NA X NA NA X
(1) E = Ephemeral, I = Intermittent, P =Perennial, NP=Not Present
(d) Refers to riparian bufferrules only. Stream. wetlavd or vnnd impacts are still suhievr rn annlinahle.vnmr n.arw �m.,,lnme sad ..- «:......,...:.-
Explanation: The stream(s)/pond(s) listed above has been located on the most recent published NRCS
Soil Survey of Durham County, North Carolina and/or the most recent copy of the USGS Topographic
map at a 1: 24,000 scale. Each feature that is checked "Not Subject" has been determined to not be an
intermittent stream, perennial stream, a pond connected to a stream feature, or the feature is determined
not to be present. Stream features that are checked "Subject" have been located on the property and
possess characteristics that qualify it to be subject to the buffer rules. There may be other streams located
on the property that do not show up on the maps referenced above and are therefore not subject to the
buffer rules. However, if the stream features are present on the tract they are subject to all other
applicable North Carolina stream standards and permitting requirements as outlined in 15A NCAC 0213,
and maybe considered jurisdictional according to the US Army Corps of Engineers.
This on -site determination shall expire five (5) years from the date of this letter. Landowners or
affected parties that dispute a determination made by the DWR may request a determination by
the Director. An appeal request must be made within sixty (60) days of date of this letter. A
request for a determination by the Director shall be referred to the Director in writing. Ifsending
via US Postal Service: c/o Karen Higgins, DWR — 401 & Buffer Permitting Unit, 1617 Mail Service
Center; Raleigh, NC 27699-1617. If sending via delivery service (UPS, FedEx, etc.): Karen Higgins;
DWR — 401 & Buffer Permitting Unit, 512 N. Salisbury Street, Raleigh, NC 27604.
This determination is final and binding unless, as detailed above, an appeal is requested within sixty
(60) days.
This project may require a Section 404/401 Permit for the proposed activity. Any inquiries should
be directed to the US Army Corp of Engineers (Raleigh Regulatory Field Office) at (919)-554-4884.
If you have questions regarding this determination, please feel free to contact Jeremiah Dow at (919)
791-4 48.
Si cerel ,
Danny S th
Supervisor, Water Quality Regional Operations Center
cc: RRO DWR File Copy
Kelly Roth, McAdams Company, via email at [e-mail]

5203 Chin Page Road, Durham
Buffer Determination #18=156
1 1
VIisE // ..,,: ..
, f� . r
Feature A: Subject,
W$C1% « Start at DWR Flag located Feature F: Not Subject per
at 35.897535,-78.835355 Buffer Determination 17-446
At
pt[ MfE
it
FeatureE: Not Subject OFF
., t
\\ �- J 1l,, i
rw. n+ C
�..
k
Feature D: Subject,
Start at DWR Flag located
at 35,8970031-78,835767
1 M,
Legend:
- Approximate Site Boundary
r
-�
Feature C: Not Subject
Feature B: Not Subject
Map provided by NCDEQ Division of
Water Resources
Locations are approximate and are pro-
vided for reference only::

I
Pond 1: Not Subject
Legend:
- Approximate Site Boundary
5203 Chin Page Road, Durham
Buffer Determination #18-156
`_J
fH11W E
J
Map provided by NCDEQ Division of
Water Resources
Locations are approximate and are pro-
vided for reference only ::

Peak Flow Analysis
Summary of Results
HydroCAD Runoff Analysis
1915_Summary of Results.xls
Summary of Results
Matt Jones, PE
3/4/2020
Site Condition DP#1 DP#2 DP#3
Pre-Development 12.66 3.97 3.42
Post-Development without
Detention 140.03 64.63 70.11
Post-Development without
Detention Percent Increase 1006% 1528% 1950%
Post-Development with
Detention 11.86 1.88 2.94
Site Condition 2-year (cfs) 10-year (cfs)
Pre-Development 22.42 65.88
Post-Development without
Detention 169.51 269.85
Post-Development without
Detention Percent Increase 656% 310%
Post-Development with
Detention 15.96 58.72
Runoff Analysis - Summary of Results
1915 - FedEX Freight
1-Year
Peak Flow (cfs)
Storm Event
DP#1
1
DP#1 TC Test
2
DP#2 TC Test
DP#1
Subcat DP#1
DP#2
Subcat DP#2
DP#3
Subcat DP#3
1L
DP#1
Routing Diagram for 1915_SIA_PRE
Prepared by Horvath Associates, PA, Printed 10/23/2019
HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_PRE
Printed 10/23/2019Prepared by Horvath Associates, PA
Page 2HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv.
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Subcatchment 1: DP#1 TC Test
Runoff=0.00 cfs 0.000 af
Subcatchment 2: DP#2 TC Test
Runoff=0.00 cfs 0.000 af
Runoff Area=19.93 ac 5.72% Impervious Runoff Depth>0.44"Subcatchment DP#1: Subcat DP#1
Flow Length=1,765' Tc=21.1 min CN=59/98 Runoff=5.86 cfs 0.731 af
Runoff Area=19.68 ac 0.00% Impervious Runoff Depth>0.33"Subcatchment DP#2: Subcat DP#2
Flow Length=1,566' Tc=20.3 min CN=60/0 Runoff=3.97 cfs 0.541 af
Runoff Area=6.19 ac 9.80% Impervious Runoff Depth>0.60"Subcatchment DP#3: Subcat DP#3
Flow Length=1,105' Tc=15.3 min CN=61/98 Runoff=3.42 cfs 0.308 af
Inflow=12.66 cfs 1.580 afLink 1L: DP#1
Primary=12.66 cfs 1.580 af
Total Runoff Area = 45.80 ac Runoff Volume = 1.580 af Average Runoff Depth = 0.41"
96.19% Pervious = 44.05 ac 3.81% Impervious = 1.75 ac
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_PRE
Printed 10/23/2019Prepared by Horvath Associates, PA
Page 3HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment 1: DP#1 TC Test
Runoff = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Depth= 0.00"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-Year Rainfall=3.00"
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.5 75 0.0270 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
1.3 417 0.1030 5.2 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.0 509 0.0180 4.3 17.39 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
17.8 1,001 Total
Summary for Subcatchment 2: DP#2 TC Test
Runoff = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Depth= 0.00"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-Year Rainfall=3.00"
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.5 75 0.0270 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
2.9 779 0.0770 4.5 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.2 648 0.0220 4.8 19.22 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
19.6 1,502 Total
Summary for Subcatchment DP#1: Subcat DP#1
Runoff = 5.86 cfs @ 12.18 hrs, Volume= 0.731 af, Depth> 0.44"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-Year Rainfall=3.00"
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_PRE
Printed 10/23/2019Prepared by Horvath Associates, PA
Page 4HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Area (ac) CN Description
3.17 70 Forest, good, HSG C
12.74 55 Forest, good, HSG B
0.79 98 Offsite Impervious, good, HSG B
0.10 98 Offsite Impervious, good, HSG C
0.30 74 Open, good, HSG C
2.58 61 Open, good, HSG B
0.10 98 Parking, good, HSG B
0.15 98 Roof, good, HSG B
19.93 61 Weighted Average
18.79 59 94.28% Pervious Area
1.14 98 5.72% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.5 75 0.0270 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
2.4 618 0.0710 4.3 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.0 642 0.0420 5.5 10.96 Channel Flow,
Area= 2.0 sf Perim= 4.0' r= 0.50' n= 0.035
2.2 430 0.0100 3.2 12.96 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
21.1 1,765 Total
Summary for Subcatchment DP#2: Subcat DP#2
Runoff = 3.97 cfs @ 12.20 hrs, Volume= 0.541 af, Depth> 0.33"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-Year Rainfall=3.00"
Area (ac) CN Description
3.41 77 Forest, good, HSG D
15.31 55 Forest, good, HSG B
0.56 80 Open, good, HSG D
0.40 61 Open, good, HSG B
19.68 60 Weighted Average
19.68 60 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.5 75 0.0270 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
3.6 843 0.0600 3.9 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.2 648 0.0220 4.8 19.22 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
20.3 1,566 Total
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_PRE
Printed 10/23/2019Prepared by Horvath Associates, PA
Page 5HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment DP#3: Subcat DP#3
Runoff = 3.42 cfs @ 12.10 hrs, Volume= 0.308 af, Depth> 0.60"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-Year Rainfall=3.00"
Area (ac) CN Description
2.98 55 Forest, good, HSG B
0.91 77 Forest, good, HSG D
0.00 98 Roof, good, HSG D
0.09 80 Open, good, HSG D
1.59 61 Open, good, HSG B
0.08 98 Parking, good, HSG B
0.08 98 Roof, good, HSG B
0.45 98 Offsite Impervious, good, HSG B
6.19 64 Weighted Average
5.58 61 90.20% Pervious Area
0.61 98 9.80% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
11.0 75 0.0530 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
3.7 802 0.0510 3.6 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.6 228 0.0530 6.2 12.31 Channel Flow,
Area= 2.0 sf Perim= 4.0' r= 0.50' n= 0.035
15.3 1,105 Total
Summary for Link 1L: DP#1
Inflow Area = 45.80 ac, 3.81% Impervious, Inflow Depth > 0.41" for 1-Year event
Inflow = 12.66 cfs @ 12.16 hrs, Volume= 1.580 af
Primary = 12.66 cfs @ 12.16 hrs, Volume= 1.580 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_PRE
Printed 10/23/2019Prepared by Horvath Associates, PA
Page 6HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv.
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Subcatchment 1: DP#1 TC Test
Runoff=0.00 cfs 0.000 af
Subcatchment 2: DP#2 TC Test
Runoff=0.00 cfs 0.000 af
Runoff Area=19.93 ac 5.72% Impervious Runoff Depth>0.65"Subcatchment DP#1: Subcat DP#1
Flow Length=1,765' Tc=21.1 min CN=59/98 Runoff=9.95 cfs 1.071 af
Runoff Area=19.68 ac 0.00% Impervious Runoff Depth>0.53"Subcatchment DP#2: Subcat DP#2
Flow Length=1,566' Tc=20.3 min CN=60/0 Runoff=8.01 cfs 0.864 af
Runoff Area=6.19 ac 9.80% Impervious Runoff Depth>0.83"Subcatchment DP#3: Subcat DP#3
Flow Length=1,105' Tc=15.3 min CN=61/98 Runoff=5.25 cfs 0.429 af
Inflow=22.42 cfs 2.364 afLink 1L: DP#1
Primary=22.42 cfs 2.364 af
Total Runoff Area = 45.80 ac Runoff Volume = 2.364 af Average Runoff Depth = 0.62"
96.19% Pervious = 44.05 ac 3.81% Impervious = 1.75 ac
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_PRE
Printed 10/23/2019Prepared by Horvath Associates, PA
Page 7HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment 1: DP#1 TC Test
Runoff = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Depth= 0.00"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-Year Rainfall=3.50"
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.5 75 0.0270 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
1.3 417 0.1030 5.2 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.0 509 0.0180 4.3 17.39 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
17.8 1,001 Total
Summary for Subcatchment 2: DP#2 TC Test
Runoff = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Depth= 0.00"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-Year Rainfall=3.50"
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.5 75 0.0270 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
2.9 779 0.0770 4.5 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.2 648 0.0220 4.8 19.22 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
19.6 1,502 Total
Summary for Subcatchment DP#1: Subcat DP#1
Runoff = 9.95 cfs @ 12.17 hrs, Volume= 1.071 af, Depth> 0.65"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-Year Rainfall=3.50"
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_PRE
Printed 10/23/2019Prepared by Horvath Associates, PA
Page 8HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Area (ac) CN Description
3.17 70 Forest, good, HSG C
12.74 55 Forest, good, HSG B
0.79 98 Offsite Impervious, good, HSG B
0.10 98 Offsite Impervious, good, HSG C
0.30 74 Open, good, HSG C
2.58 61 Open, good, HSG B
0.10 98 Parking, good, HSG B
0.15 98 Roof, good, HSG B
19.93 61 Weighted Average
18.79 59 94.28% Pervious Area
1.14 98 5.72% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.5 75 0.0270 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
2.4 618 0.0710 4.3 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.0 642 0.0420 5.5 10.96 Channel Flow,
Area= 2.0 sf Perim= 4.0' r= 0.50' n= 0.035
2.2 430 0.0100 3.2 12.96 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
21.1 1,765 Total
Summary for Subcatchment DP#2: Subcat DP#2
Runoff = 8.01 cfs @ 12.18 hrs, Volume= 0.864 af, Depth> 0.53"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-Year Rainfall=3.50"
Area (ac) CN Description
3.41 77 Forest, good, HSG D
15.31 55 Forest, good, HSG B
0.56 80 Open, good, HSG D
0.40 61 Open, good, HSG B
19.68 60 Weighted Average
19.68 60 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.5 75 0.0270 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
3.6 843 0.0600 3.9 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.2 648 0.0220 4.8 19.22 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
20.3 1,566 Total
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_PRE
Printed 10/23/2019Prepared by Horvath Associates, PA
Page 9HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment DP#3: Subcat DP#3
Runoff = 5.25 cfs @ 12.09 hrs, Volume= 0.429 af, Depth> 0.83"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-Year Rainfall=3.50"
Area (ac) CN Description
2.98 55 Forest, good, HSG B
0.91 77 Forest, good, HSG D
0.00 98 Roof, good, HSG D
0.09 80 Open, good, HSG D
1.59 61 Open, good, HSG B
0.08 98 Parking, good, HSG B
0.08 98 Roof, good, HSG B
0.45 98 Offsite Impervious, good, HSG B
6.19 64 Weighted Average
5.58 61 90.20% Pervious Area
0.61 98 9.80% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
11.0 75 0.0530 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
3.7 802 0.0510 3.6 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.6 228 0.0530 6.2 12.31 Channel Flow,
Area= 2.0 sf Perim= 4.0' r= 0.50' n= 0.035
15.3 1,105 Total
Summary for Link 1L: DP#1
Inflow Area = 45.80 ac, 3.81% Impervious, Inflow Depth > 0.62" for 2-Year event
Inflow = 22.42 cfs @ 12.16 hrs, Volume= 2.364 af
Primary = 22.42 cfs @ 12.16 hrs, Volume= 2.364 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_PRE
Printed 10/23/2019Prepared by Horvath Associates, PA
Page 10HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv.
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Subcatchment 1: DP#1 TC Test
Runoff=0.00 cfs 0.000 af
Subcatchment 2: DP#2 TC Test
Runoff=0.00 cfs 0.000 af
Runoff Area=19.93 ac 5.72% Impervious Runoff Depth>1.49"Subcatchment DP#1: Subcat DP#1
Flow Length=1,765' Tc=21.1 min CN=59/98 Runoff=28.29 cfs 2.467 af
Runoff Area=19.68 ac 0.00% Impervious Runoff Depth>1.35"Subcatchment DP#2: Subcat DP#2
Flow Length=1,566' Tc=20.3 min CN=60/0 Runoff=26.55 cfs 2.214 af
Runoff Area=6.19 ac 9.80% Impervious Runoff Depth>1.76"Subcatchment DP#3: Subcat DP#3
Flow Length=1,105' Tc=15.3 min CN=61/98 Runoff=12.68 cfs 0.907 af
Inflow=65.88 cfs 5.588 afLink 1L: DP#1
Primary=65.88 cfs 5.588 af
Total Runoff Area = 45.80 ac Runoff Volume = 5.588 af Average Runoff Depth = 1.46"
96.19% Pervious = 44.05 ac 3.81% Impervious = 1.75 ac
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_PRE
Printed 10/23/2019Prepared by Horvath Associates, PA
Page 11HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment 1: DP#1 TC Test
Runoff = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Depth= 0.00"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=5.10"
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.5 75 0.0270 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
1.3 417 0.1030 5.2 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.0 509 0.0180 4.3 17.39 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
17.8 1,001 Total
Summary for Subcatchment 2: DP#2 TC Test
Runoff = 0.00 cfs @ 0.00 hrs, Volume= 0.000 af, Depth= 0.00"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=5.10"
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.5 75 0.0270 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
2.9 779 0.0770 4.5 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.2 648 0.0220 4.8 19.22 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
19.6 1,502 Total
Summary for Subcatchment DP#1: Subcat DP#1
Runoff = 28.29 cfs @ 12.16 hrs, Volume= 2.467 af, Depth> 1.49"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=5.10"
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_PRE
Printed 10/23/2019Prepared by Horvath Associates, PA
Page 12HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Area (ac) CN Description
3.17 70 Forest, good, HSG C
12.74 55 Forest, good, HSG B
0.79 98 Offsite Impervious, good, HSG B
0.10 98 Offsite Impervious, good, HSG C
0.30 74 Open, good, HSG C
2.58 61 Open, good, HSG B
0.10 98 Parking, good, HSG B
0.15 98 Roof, good, HSG B
19.93 61 Weighted Average
18.79 59 94.28% Pervious Area
1.14 98 5.72% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.5 75 0.0270 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
2.4 618 0.0710 4.3 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.0 642 0.0420 5.5 10.96 Channel Flow,
Area= 2.0 sf Perim= 4.0' r= 0.50' n= 0.035
2.2 430 0.0100 3.2 12.96 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
21.1 1,765 Total
Summary for Subcatchment DP#2: Subcat DP#2
Runoff = 26.55 cfs @ 12.15 hrs, Volume= 2.214 af, Depth> 1.35"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=5.10"
Area (ac) CN Description
3.41 77 Forest, good, HSG D
15.31 55 Forest, good, HSG B
0.56 80 Open, good, HSG D
0.40 61 Open, good, HSG B
19.68 60 Weighted Average
19.68 60 100.00% Pervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
14.5 75 0.0270 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
3.6 843 0.0600 3.9 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
2.2 648 0.0220 4.8 19.22 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
20.3 1,566 Total
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_PRE
Printed 10/23/2019Prepared by Horvath Associates, PA
Page 13HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment DP#3: Subcat DP#3
Runoff = 12.68 cfs @ 12.09 hrs, Volume= 0.907 af, Depth> 1.76"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=5.10"
Area (ac) CN Description
2.98 55 Forest, good, HSG B
0.91 77 Forest, good, HSG D
0.00 98 Roof, good, HSG D
0.09 80 Open, good, HSG D
1.59 61 Open, good, HSG B
0.08 98 Parking, good, HSG B
0.08 98 Roof, good, HSG B
0.45 98 Offsite Impervious, good, HSG B
6.19 64 Weighted Average
5.58 61 90.20% Pervious Area
0.61 98 9.80% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
11.0 75 0.0530 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
3.7 802 0.0510 3.6 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.6 228 0.0530 6.2 12.31 Channel Flow,
Area= 2.0 sf Perim= 4.0' r= 0.50' n= 0.035
15.3 1,105 Total
Summary for Link 1L: DP#1
Inflow Area = 45.80 ac, 3.81% Impervious, Inflow Depth > 1.46" for 10-Year event
Inflow = 65.88 cfs @ 12.14 hrs, Volume= 5.588 af
Primary = 65.88 cfs @ 12.14 hrs, Volume= 5.588 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
DP#1
Subcat DP#1
DP#3
Subcat DP#3
WDB#1
Subcat WDB#1
WDB#2
Subcat WDB#2
1P
WDB#1
2P
WDB#2
1L
DP#1
2L
DP#2
3L
DP#3
Routing Diagram for 1915_SIA_POST
Prepared by Horvath Associates, PA, Printed 3/4/2020
HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 2HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv.
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Runoff Area=6.45 ac 19.74% Impervious Runoff Depth>0.81"Subcatchment DP#1: Subcat DP#1
Flow Length=374' Tc=12.2 min CN=60/98 Runoff=5.68 cfs 0.436 af
Runoff Area=2.42 ac 18.56% Impervious Runoff Depth>0.81"Subcatchment DP#3: Subcat DP#3
Flow Length=602' Tc=11.6 min CN=61/98 Runoff=2.19 cfs 0.163 af
Runoff Area=18.39 ac 79.42% Impervious Runoff Depth>2.29"Subcatchment WDB#1: Subcat WDB#1
Tc=5.0 min CN=63/98 Runoff=64.63 cfs 3.503 af
Runoff Area=23.26 ac 61.45% Impervious Runoff Depth>1.94"Subcatchment WDB#2: Subcat WDB#2
Tc=5.0 min CN=68/98 Runoff=70.11 cfs 3.762 af
Peak Elev=345.68' Storage=103,978 cf Inflow=64.63 cfs 3.503 afPond 1P: WDB#1
Outflow=1.88 cfs 1.742 af
Peak Elev=344.69' Storage=103,701 cf Inflow=70.11 cfs 3.762 afPond 2P: WDB#2
Outflow=2.94 cfs 2.247 af
Inflow=11.86 cfs 4.588 afLink 1L: DP#1
Primary=11.86 cfs 4.588 af
Inflow=1.88 cfs 1.742 afLink 2L: DP#2
Primary=1.88 cfs 1.742 af
Inflow=2.94 cfs 2.247 afLink 3L: DP#3
Primary=2.94 cfs 2.247 af
Total Runoff Area = 50.51 ac Runoff Volume = 7.864 af Average Runoff Depth = 1.87"
39.39% Pervious = 19.90 ac 60.61% Impervious = 30.62 ac
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 3HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment DP#1: Subcat DP#1
Runoff = 5.68 cfs @ 12.05 hrs, Volume= 0.436 af, Depth> 0.81"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-Year Rainfall=3.00"
Area (ac) CN Description
0.23 77 Forest, good, HSG D
1.17 98 Offsite Impervious, good, HSG B
0.10 98 Offsite Impervious, good, HSG D
0.36 80 Open, good, HSG D
1.78 61 Open, good, HSG B
0.00 98 Parking, good, HSG B
2.81 55 Forest, good, HSG B
6.45 67 Weighted Average
5.18 60 80.26% Pervious Area
1.27 98 19.74% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
11.0 75 0.0533 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
0.6 187 0.1180 5.5 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.6 112 0.0100 3.2 12.96 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
12.2 374 Total
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 4HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcatchment DP#1: Subcat DP#1
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)6
5
4
3
2
1
0
Type II 24-hr
1-Year Rainfall=3.00"
Runoff Area=6.45 ac
Runoff Volume=0.436 af
Runoff Depth>0.81"
Flow Length=374'
Tc=12.2 min
CN=60/98
5.68 cfs
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 5HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment DP#3: Subcat DP#3
Runoff = 2.19 cfs @ 12.05 hrs, Volume= 0.163 af, Depth> 0.81"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-Year Rainfall=3.00"
Area (ac) CN Description
0.09 80 Open, good, HSG D
0.08 77 Forest, good, HSG D
0.45 98 Offsite Impervious, good, HSG B
0.45 55 Forest, good, HSG B
1.35 61 Open, good, HSG B
2.42 68 Weighted Average
1.97 61 81.44% Pervious Area
0.45 98 18.56% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.1 75 0.0670 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
1.3 341 0.0760 4.4 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.2 186 0.0540 16.7 52.57 Pipe Channel,
24.0" Round Area= 3.1 sf Perim= 6.3' r= 0.50'
n= 0.013
11.6 602 Total
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 6HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcatchment DP#3: Subcat DP#3
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)2
1
0
Type II 24-hr
1-Year Rainfall=3.00"
Runoff Area=2.42 ac
Runoff Volume=0.163 af
Runoff Depth>0.81"
Flow Length=602'
Tc=11.6 min
CN=61/98
2.19 cfs
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 7HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment WDB#1: Subcat WDB#1
Runoff = 64.63 cfs @ 11.95 hrs, Volume= 3.503 af, Depth> 2.29"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-Year Rainfall=3.00"
Area (ac) CN Description
2.27 61 Open, good, HSG B
0.38 80 Open, good, HSG D
0.31 77 Forest, good, HSG D
0.14 100 BMP, good, HSG D
0.05 98 Roof, good, HSG D
9.33 98 Parking, good, HSG B
3.82 98 Parking, good, HSG D
0.82 98 Roof, good, HSG B
0.44 100 BMP, good, HSG B
0.81 55 Forest, good, HSG B
18.39 91 Weighted Average
3.78 63 20.58% Pervious Area
14.60 98 79.42% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment WDB#1: Subcat WDB#1
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Type II 24-hr
1-Year Rainfall=3.00"
Runoff Area=18.39 ac
Runoff Volume=3.503 af
Runoff Depth>2.29"
Tc=5.0 min
CN=63/98
64.63 cfs
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 8HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment WDB#2: Subcat WDB#2
Runoff = 70.11 cfs @ 11.95 hrs, Volume= 3.762 af, Depth> 1.94"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 1-Year Rainfall=3.00"
Area (ac) CN Description
1.65 77 Forest, good, HSG D
0.20 98 Offsite Impervious, good, HSG D
0.94 98 Roadway, good, HSG B
0.21 98 Roadway, good, HSG D
0.15 98 Sidewalk, good, HSG D
0.31 98 Sidewalk, good, HSG B
0.80 98 Parking, good, HSG D
4.83 61 Open, good, HSG B
1.91 80 Open, good, HSG D
9.83 98 Parking, good, HSG B
1.32 98 Roof, good, HSG B
0.01 98 Offsite Impervious, good, HSG B
0.53 100 BMP, good, HSG B
0.58 55 Forest, good, HSG B
23.26 86 Weighted Average
8.97 68 38.55% Pervious Area
14.29 98 61.45% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 9HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcatchment WDB#2: Subcat WDB#2
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Type II 24-hr
1-Year Rainfall=3.00"
Runoff Area=23.26 ac
Runoff Volume=3.762 af
Runoff Depth>1.94"
Tc=5.0 min
CN=68/98
70.11 cfs
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 10HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Pond 1P: WDB#1
Inflow Area = 18.39 ac, 79.42% Impervious, Inflow Depth > 2.29" for 1-Year event
Inflow = 64.63 cfs @ 11.95 hrs, Volume= 3.503 af
Outflow = 1.88 cfs @ 13.95 hrs, Volume= 1.742 af, Atten= 97%, Lag= 119.9 min
Primary = 1.88 cfs @ 13.95 hrs, Volume= 1.742 af
Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 345.68' @ 13.95 hrs Surf.Area= 31,911 sf Storage= 103,978 cf
Plug-Flow detention time= 401.2 min calculated for 1.738 af (50% of inflow)
Center-of-Mass det. time= 275.4 min ( 1,034.0 - 758.6 )
Volume Invert Avail.Storage Storage Description
#1 342.00' 256,908 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
342.00 22,247 0 0
342.50 25,486 11,933 11,933
343.00 26,567 13,013 24,947
344.00 28,777 27,672 52,619
344.01 29,241 290 52,909
345.00 30,835 29,738 82,646
346.00 32,417 31,626 114,272
347.00 34,018 33,218 147,490
348.00 35,641 34,830 182,319
349.00 37,288 36,465 218,784
350.00 38,961 38,125 256,908
Device Routing Invert Outlet Devices
#1 Primary 340.40'36.0" Round Culvert
L= 165.0' RCP, square edge headwall, Ke= 0.5?
Inlet / Outlet Invert= 340.40' / 339.50' S= 0.0055 '/' Cc= 0.900
n= 0.013, Flow Area= 7.07 sf
#2 Device 1 342.00'3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 344.00'6.0" W x 6.0" H Vert. Orifice/Grate C= 0.600
#4 Device 1 345.80'30.0" W x 12.0" H Vert. Orifice/Grate X 2.00 C= 0.600
#5 Device 1 347.40'60.0" x 60.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#6 Primary 347.50'50.0' long x 40.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63
Primary OutFlow Max=1.88 cfs @ 13.95 hrs HW=345.68' (Free Discharge)
1=Culvert (Passes 1.88 cfs of 61.59 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.45 cfs @ 9.1 fps)
3=Orifice/Grate (Orifice Controls 1.44 cfs @ 5.8 fps)
4=Orifice/Grate ( Controls 0.00 cfs)
5=Orifice/Grate ( Controls 0.00 cfs)
6=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 11HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Pond 1P: WDB#1
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Inflow Area=18.39 ac
Peak Elev=345.68'
Storage=103,978 cf
64.63 cfs
1.88 cfs
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 12HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Pond 2P: WDB#2
Inflow Area = 23.26 ac, 61.45% Impervious, Inflow Depth > 1.94" for 1-Year event
Inflow = 70.11 cfs @ 11.95 hrs, Volume= 3.762 af
Outflow = 2.94 cfs @ 13.32 hrs, Volume= 2.247 af, Atten= 96%, Lag= 81.7 min
Primary = 2.94 cfs @ 13.32 hrs, Volume= 2.247 af
Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 344.69' @ 13.32 hrs Surf.Area= 31,897 sf Storage= 103,701 cf
Plug-Flow detention time= 351.0 min calculated for 2.243 af (60% of inflow)
Center-of-Mass det. time= 236.2 min ( 1,005.2 - 768.9 )
Volume Invert Avail.Storage Storage Description
#1 341.00' 292,968 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
341.00 22,011 0 0
341.50 25,135 11,787 11,787
342.00 26,278 12,853 24,640
343.00 28,660 27,469 52,109
344.00 30,938 29,799 81,908
345.00 32,321 31,630 113,537
346.00 33,723 33,022 146,559
347.00 35,146 34,435 180,994
348.00 36,587 35,867 216,860
349.00 38,049 37,318 254,178
350.00 39,530 38,790 292,968
Device Routing Invert Outlet Devices
#1 Primary 337.20'30.0" Round Culvert
L= 90.0' RCP, square edge headwall, Ke= 0.5?
Inlet / Outlet Invert= 337.20' / 336.70' S= 0.0056 '/' Cc= 0.900
n= 0.013, Flow Area= 4.91 sf
#2 Device 1 341.00'3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 343.00'8.0" W x 8.0" H Vert. Orifice/Grate C= 0.600
#4 Device 1 344.90'18.0" W x 8.0" H Vert. Orifice/Grate C= 0.600
#5 Device 1 347.30'60.0" x 60.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#6 Primary 347.30'60.0' long x 25.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63
Primary OutFlow Max=2.94 cfs @ 13.32 hrs HW=344.69' (Free Discharge)
1=Culvert (Passes 2.94 cfs of 59.06 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.45 cfs @ 9.1 fps)
3=Orifice/Grate (Orifice Controls 2.49 cfs @ 5.6 fps)
4=Orifice/Grate ( Controls 0.00 cfs)
5=Orifice/Grate ( Controls 0.00 cfs)
6=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 13HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Pond 2P: WDB#2
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Inflow Area=23.26 ac
Peak Elev=344.69'
Storage=103,701 cf
70.11 cfs
2.94 cfs
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 14HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Link 1L: DP#1
Inflow Area = 50.51 ac, 60.61% Impervious, Inflow Depth > 1.09" for 1-Year event
Inflow = 11.86 cfs @ 12.06 hrs, Volume= 4.588 af
Primary = 11.86 cfs @ 12.06 hrs, Volume= 4.588 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Link 1L: DP#1
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)13
12
11
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=50.51 ac
11.86 cfs11.86 cfs
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 15HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Link 2L: DP#2
Inflow Area = 18.39 ac, 79.42% Impervious, Inflow Depth > 1.14" for 1-Year event
Inflow = 1.88 cfs @ 13.95 hrs, Volume= 1.742 af
Primary = 1.88 cfs @ 13.95 hrs, Volume= 1.742 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Link 2L: DP#2
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)2
1
0
Inflow Area=18.39 ac
1.88 cfs1.88 cfs
Type II 24-hr 1-Year Rainfall=3.00"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 16HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Link 3L: DP#3
Inflow Area = 23.26 ac, 61.45% Impervious, Inflow Depth > 1.16" for 1-Year event
Inflow = 2.94 cfs @ 13.32 hrs, Volume= 2.247 af
Primary = 2.94 cfs @ 13.32 hrs, Volume= 2.247 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Link 3L: DP#3
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)3
2
1
0
Inflow Area=23.26 ac
2.94 cfs2.94 cfs
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 17HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv.
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Runoff Area=6.45 ac 19.74% Impervious Runoff Depth>1.07"Subcatchment DP#1: Subcat DP#1
Flow Length=374' Tc=12.2 min CN=60/98 Runoff=7.92 cfs 0.574 af
Runoff Area=2.42 ac 18.56% Impervious Runoff Depth>1.07"Subcatchment DP#3: Subcat DP#3
Flow Length=602' Tc=11.6 min CN=61/98 Runoff=3.08 cfs 0.216 af
Runoff Area=18.39 ac 79.42% Impervious Runoff Depth>2.73"Subcatchment WDB#1: Subcat WDB#1
Tc=5.0 min CN=63/98 Runoff=76.96 cfs 4.180 af
Runoff Area=23.26 ac 61.45% Impervious Runoff Depth>2.35"Subcatchment WDB#2: Subcat WDB#2
Tc=5.0 min CN=68/98 Runoff=85.25 cfs 4.560 af
Peak Elev=346.07' Storage=116,666 cf Inflow=76.96 cfs 4.180 afPond 1P: WDB#1
Outflow=4.40 cfs 2.268 af
Peak Elev=345.28' Storage=122,642 cf Inflow=85.25 cfs 4.560 afPond 2P: WDB#2
Outflow=4.60 cfs 2.929 af
Inflow=15.96 cfs 5.987 afLink 1L: DP#1
Primary=15.96 cfs 5.987 af
Inflow=4.40 cfs 2.268 afLink 2L: DP#2
Primary=4.40 cfs 2.268 af
Inflow=4.60 cfs 2.929 afLink 3L: DP#3
Primary=4.60 cfs 2.929 af
Total Runoff Area = 50.51 ac Runoff Volume = 9.530 af Average Runoff Depth = 2.26"
39.39% Pervious = 19.90 ac 60.61% Impervious = 30.62 ac
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 18HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment DP#1: Subcat DP#1
Runoff = 7.92 cfs @ 12.05 hrs, Volume= 0.574 af, Depth> 1.07"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-Year Rainfall=3.50"
Area (ac) CN Description
0.23 77 Forest, good, HSG D
1.17 98 Offsite Impervious, good, HSG B
0.10 98 Offsite Impervious, good, HSG D
0.36 80 Open, good, HSG D
1.78 61 Open, good, HSG B
0.00 98 Parking, good, HSG B
2.81 55 Forest, good, HSG B
6.45 67 Weighted Average
5.18 60 80.26% Pervious Area
1.27 98 19.74% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
11.0 75 0.0533 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
0.6 187 0.1180 5.5 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.6 112 0.0100 3.2 12.96 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
12.2 374 Total
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 19HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcatchment DP#1: Subcat DP#1
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)8
7
6
5
4
3
2
1
0
Type II 24-hr
2-Year Rainfall=3.50"
Runoff Area=6.45 ac
Runoff Volume=0.574 af
Runoff Depth>1.07"
Flow Length=374'
Tc=12.2 min
CN=60/98
7.92 cfs
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 20HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment DP#3: Subcat DP#3
Runoff = 3.08 cfs @ 12.04 hrs, Volume= 0.216 af, Depth> 1.07"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-Year Rainfall=3.50"
Area (ac) CN Description
0.09 80 Open, good, HSG D
0.08 77 Forest, good, HSG D
0.45 98 Offsite Impervious, good, HSG B
0.45 55 Forest, good, HSG B
1.35 61 Open, good, HSG B
2.42 68 Weighted Average
1.97 61 81.44% Pervious Area
0.45 98 18.56% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.1 75 0.0670 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
1.3 341 0.0760 4.4 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.2 186 0.0540 16.7 52.57 Pipe Channel,
24.0" Round Area= 3.1 sf Perim= 6.3' r= 0.50'
n= 0.013
11.6 602 Total
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 21HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcatchment DP#3: Subcat DP#3
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)3
2
1
0
Type II 24-hr
2-Year Rainfall=3.50"
Runoff Area=2.42 ac
Runoff Volume=0.216 af
Runoff Depth>1.07"
Flow Length=602'
Tc=11.6 min
CN=61/98
3.08 cfs
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 22HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment WDB#1: Subcat WDB#1
Runoff = 76.96 cfs @ 11.95 hrs, Volume= 4.180 af, Depth> 2.73"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-Year Rainfall=3.50"
Area (ac) CN Description
2.27 61 Open, good, HSG B
0.38 80 Open, good, HSG D
0.31 77 Forest, good, HSG D
0.14 100 BMP, good, HSG D
0.05 98 Roof, good, HSG D
9.33 98 Parking, good, HSG B
3.82 98 Parking, good, HSG D
0.82 98 Roof, good, HSG B
0.44 100 BMP, good, HSG B
0.81 55 Forest, good, HSG B
18.39 91 Weighted Average
3.78 63 20.58% Pervious Area
14.60 98 79.42% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment WDB#1: Subcat WDB#1
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Type II 24-hr
2-Year Rainfall=3.50"
Runoff Area=18.39 ac
Runoff Volume=4.180 af
Runoff Depth>2.73"
Tc=5.0 min
CN=63/98
76.96 cfs
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 23HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment WDB#2: Subcat WDB#2
Runoff = 85.25 cfs @ 11.95 hrs, Volume= 4.560 af, Depth> 2.35"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 2-Year Rainfall=3.50"
Area (ac) CN Description
1.65 77 Forest, good, HSG D
0.20 98 Offsite Impervious, good, HSG D
0.94 98 Roadway, good, HSG B
0.21 98 Roadway, good, HSG D
0.15 98 Sidewalk, good, HSG D
0.31 98 Sidewalk, good, HSG B
0.80 98 Parking, good, HSG D
4.83 61 Open, good, HSG B
1.91 80 Open, good, HSG D
9.83 98 Parking, good, HSG B
1.32 98 Roof, good, HSG B
0.01 98 Offsite Impervious, good, HSG B
0.53 100 BMP, good, HSG B
0.58 55 Forest, good, HSG B
23.26 86 Weighted Average
8.97 68 38.55% Pervious Area
14.29 98 61.45% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 24HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcatchment WDB#2: Subcat WDB#2
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Type II 24-hr
2-Year Rainfall=3.50"
Runoff Area=23.26 ac
Runoff Volume=4.560 af
Runoff Depth>2.35"
Tc=5.0 min
CN=68/98
85.25 cfs
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 25HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Pond 1P: WDB#1
Inflow Area = 18.39 ac, 79.42% Impervious, Inflow Depth > 2.73" for 2-Year event
Inflow = 76.96 cfs @ 11.95 hrs, Volume= 4.180 af
Outflow = 4.40 cfs @ 12.74 hrs, Volume= 2.268 af, Atten= 94%, Lag= 47.4 min
Primary = 4.40 cfs @ 12.74 hrs, Volume= 2.268 af
Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 346.07' @ 12.74 hrs Surf.Area= 32,535 sf Storage= 116,666 cf
Plug-Flow detention time= 360.2 min calculated for 2.264 af (54% of inflow)
Center-of-Mass det. time= 240.5 min ( 996.8 - 756.3 )
Volume Invert Avail.Storage Storage Description
#1 342.00' 256,908 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
342.00 22,247 0 0
342.50 25,486 11,933 11,933
343.00 26,567 13,013 24,947
344.00 28,777 27,672 52,619
344.01 29,241 290 52,909
345.00 30,835 29,738 82,646
346.00 32,417 31,626 114,272
347.00 34,018 33,218 147,490
348.00 35,641 34,830 182,319
349.00 37,288 36,465 218,784
350.00 38,961 38,125 256,908
Device Routing Invert Outlet Devices
#1 Primary 340.40'36.0" Round Culvert
L= 165.0' RCP, square edge headwall, Ke= 0.5?
Inlet / Outlet Invert= 340.40' / 339.50' S= 0.0055 '/' Cc= 0.900
n= 0.013, Flow Area= 7.07 sf
#2 Device 1 342.00'3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 344.00'6.0" W x 6.0" H Vert. Orifice/Grate C= 0.600
#4 Device 1 345.80'30.0" W x 12.0" H Vert. Orifice/Grate X 2.00 C= 0.600
#5 Device 1 347.40'60.0" x 60.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#6 Primary 347.50'50.0' long x 40.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63
Primary OutFlow Max=4.39 cfs @ 12.74 hrs HW=346.07' (Free Discharge)
1=Culvert (Passes 4.39 cfs of 65.29 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.47 cfs @ 9.6 fps)
3=Orifice/Grate (Orifice Controls 1.62 cfs @ 6.5 fps)
4=Orifice/Grate (Orifice Controls 2.30 cfs @ 1.7 fps)
5=Orifice/Grate ( Controls 0.00 cfs)
6=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 26HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Pond 1P: WDB#1
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Inflow Area=18.39 ac
Peak Elev=346.07'
Storage=116,666 cf
76.96 cfs
4.40 cfs
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 27HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Pond 2P: WDB#2
Inflow Area = 23.26 ac, 61.45% Impervious, Inflow Depth > 2.35" for 2-Year event
Inflow = 85.25 cfs @ 11.95 hrs, Volume= 4.560 af
Outflow = 4.60 cfs @ 12.89 hrs, Volume= 2.929 af, Atten= 95%, Lag= 56.0 min
Primary = 4.60 cfs @ 12.89 hrs, Volume= 2.929 af
Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 345.28' @ 12.89 hrs Surf.Area= 32,714 sf Storage= 122,642 cf
Plug-Flow detention time= 344.3 min calculated for 2.929 af (64% of inflow)
Center-of-Mass det. time= 234.1 min ( 1,001.4 - 767.2 )
Volume Invert Avail.Storage Storage Description
#1 341.00' 292,968 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
341.00 22,011 0 0
341.50 25,135 11,787 11,787
342.00 26,278 12,853 24,640
343.00 28,660 27,469 52,109
344.00 30,938 29,799 81,908
345.00 32,321 31,630 113,537
346.00 33,723 33,022 146,559
347.00 35,146 34,435 180,994
348.00 36,587 35,867 216,860
349.00 38,049 37,318 254,178
350.00 39,530 38,790 292,968
Device Routing Invert Outlet Devices
#1 Primary 337.20'30.0" Round Culvert
L= 90.0' RCP, square edge headwall, Ke= 0.5?
Inlet / Outlet Invert= 337.20' / 336.70' S= 0.0056 '/' Cc= 0.900
n= 0.013, Flow Area= 4.91 sf
#2 Device 1 341.00'3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 343.00'8.0" W x 8.0" H Vert. Orifice/Grate C= 0.600
#4 Device 1 344.90'18.0" W x 8.0" H Vert. Orifice/Grate C= 0.600
#5 Device 1 347.30'60.0" x 60.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#6 Primary 347.30'60.0' long x 25.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63
Primary OutFlow Max=4.59 cfs @ 12.89 hrs HW=345.28' (Free Discharge)
1=Culvert (Passes 4.59 cfs of 61.77 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.48 cfs @ 9.8 fps)
3=Orifice/Grate (Orifice Controls 2.98 cfs @ 6.7 fps)
4=Orifice/Grate (Orifice Controls 1.13 cfs @ 2.0 fps)
5=Orifice/Grate ( Controls 0.00 cfs)
6=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 28HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Pond 2P: WDB#2
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Inflow Area=23.26 ac
Peak Elev=345.28'
Storage=122,642 cf
85.25 cfs
4.60 cfs
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 29HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Link 1L: DP#1
Inflow Area = 50.51 ac, 60.61% Impervious, Inflow Depth > 1.42" for 2-Year event
Inflow = 15.96 cfs @ 12.06 hrs, Volume= 5.987 af
Primary = 15.96 cfs @ 12.06 hrs, Volume= 5.987 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Link 1L: DP#1
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=50.51 ac
15.96 cfs15.96 cfs
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 30HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Link 2L: DP#2
Inflow Area = 18.39 ac, 79.42% Impervious, Inflow Depth > 1.48" for 2-Year event
Inflow = 4.40 cfs @ 12.74 hrs, Volume= 2.268 af
Primary = 4.40 cfs @ 12.74 hrs, Volume= 2.268 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Link 2L: DP#2
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)4
3
2
1
0
Inflow Area=18.39 ac
4.40 cfs4.40 cfs
Type II 24-hr 2-Year Rainfall=3.50"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 31HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Link 3L: DP#3
Inflow Area = 23.26 ac, 61.45% Impervious, Inflow Depth > 1.51" for 2-Year event
Inflow = 4.60 cfs @ 12.89 hrs, Volume= 2.929 af
Primary = 4.60 cfs @ 12.89 hrs, Volume= 2.929 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Link 3L: DP#3
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)5
4
3
2
1
0
Inflow Area=23.26 ac
4.60 cfs4.60 cfs
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 32HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv.
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Runoff Area=6.45 ac 19.74% Impervious Runoff Depth>2.05"Subcatchment DP#1: Subcat DP#1
Flow Length=374' Tc=12.2 min CN=60/98 Runoff=16.73 cfs 1.099 af
Runoff Area=2.42 ac 18.56% Impervious Runoff Depth>2.06"Subcatchment DP#3: Subcat DP#3
Flow Length=602' Tc=11.6 min CN=61/98 Runoff=6.51 cfs 0.415 af
Runoff Area=18.39 ac 79.42% Impervious Runoff Depth>4.18"Subcatchment WDB#1: Subcat WDB#1
Tc=5.0 min CN=63/98 Runoff=117.53 cfs 6.410 af
Runoff Area=23.26 ac 61.45% Impervious Runoff Depth>3.74"Subcatchment WDB#2: Subcat WDB#2
Tc=5.0 min CN=68/98 Runoff=136.08 cfs 7.244 af
Peak Elev=347.25' Storage=156,070 cf Inflow=117.53 cfs 6.410 afPond 1P: WDB#1
Outflow=25.80 cfs 4.264 af
Peak Elev=347.09' Storage=184,035 cf Inflow=136.08 cfs 7.244 afPond 2P: WDB#2
Outflow=11.27 cfs 5.309 af
Inflow=58.72 cfs 11.087 afLink 1L: DP#1
Primary=58.72 cfs 11.087 af
Inflow=25.80 cfs 4.264 afLink 2L: DP#2
Primary=25.80 cfs 4.264 af
Inflow=11.27 cfs 5.309 afLink 3L: DP#3
Primary=11.27 cfs 5.309 af
Total Runoff Area = 50.51 ac Runoff Volume = 15.168 af Average Runoff Depth = 3.60"
39.39% Pervious = 19.90 ac 60.61% Impervious = 30.62 ac
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 33HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment DP#1: Subcat DP#1
Runoff = 16.73 cfs @ 12.05 hrs, Volume= 1.099 af, Depth> 2.05"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=5.10"
Area (ac) CN Description
0.23 77 Forest, good, HSG D
1.17 98 Offsite Impervious, good, HSG B
0.10 98 Offsite Impervious, good, HSG D
0.36 80 Open, good, HSG D
1.78 61 Open, good, HSG B
0.00 98 Parking, good, HSG B
2.81 55 Forest, good, HSG B
6.45 67 Weighted Average
5.18 60 80.26% Pervious Area
1.27 98 19.74% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
11.0 75 0.0533 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
0.6 187 0.1180 5.5 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.6 112 0.0100 3.2 12.96 Channel Flow,
Area= 4.0 sf Perim= 6.0' r= 0.67' n= 0.035
12.2 374 Total
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 34HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcatchment DP#1: Subcat DP#1
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Type II 24-hr
10-Year Rainfall=5.10"
Runoff Area=6.45 ac
Runoff Volume=1.099 af
Runoff Depth>2.05"
Flow Length=374'
Tc=12.2 min
CN=60/98
16.73 cfs
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 35HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment DP#3: Subcat DP#3
Runoff = 6.51 cfs @ 12.04 hrs, Volume= 0.415 af, Depth> 2.06"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=5.10"
Area (ac) CN Description
0.09 80 Open, good, HSG D
0.08 77 Forest, good, HSG D
0.45 98 Offsite Impervious, good, HSG B
0.45 55 Forest, good, HSG B
1.35 61 Open, good, HSG B
2.42 68 Weighted Average
1.97 61 81.44% Pervious Area
0.45 98 18.56% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
10.1 75 0.0670 0.1 Sheet Flow,
Woods: Light underbrush n= 0.400 P2= 3.50"
1.3 341 0.0760 4.4 Shallow Concentrated Flow,
Unpaved Kv= 16.1 fps
0.2 186 0.0540 16.7 52.57 Pipe Channel,
24.0" Round Area= 3.1 sf Perim= 6.3' r= 0.50'
n= 0.013
11.6 602 Total
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 36HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcatchment DP#3: Subcat DP#3
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)7
6
5
4
3
2
1
0
Type II 24-hr
10-Year Rainfall=5.10"
Runoff Area=2.42 ac
Runoff Volume=0.415 af
Runoff Depth>2.06"
Flow Length=602'
Tc=11.6 min
CN=61/98
6.51 cfs
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 37HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment WDB#1: Subcat WDB#1
Runoff = 117.53 cfs @ 11.95 hrs, Volume= 6.410 af, Depth> 4.18"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=5.10"
Area (ac) CN Description
2.27 61 Open, good, HSG B
0.38 80 Open, good, HSG D
0.31 77 Forest, good, HSG D
0.14 100 BMP, good, HSG D
0.05 98 Roof, good, HSG D
9.33 98 Parking, good, HSG B
3.82 98 Parking, good, HSG D
0.82 98 Roof, good, HSG B
0.44 100 BMP, good, HSG B
0.81 55 Forest, good, HSG B
18.39 91 Weighted Average
3.78 63 20.58% Pervious Area
14.60 98 79.42% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment WDB#1: Subcat WDB#1
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)130
125
120
115
110
105
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
Type II 24-hr
10-Year Rainfall=5.10"
Runoff Area=18.39 ac
Runoff Volume=6.410 af
Runoff Depth>4.18"
Tc=5.0 min
CN=63/98
117.53 cfs
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 38HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment WDB#2: Subcat WDB#2
Runoff = 136.08 cfs @ 11.95 hrs, Volume= 7.244 af, Depth> 3.74"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 10-Year Rainfall=5.10"
Area (ac) CN Description
1.65 77 Forest, good, HSG D
0.20 98 Offsite Impervious, good, HSG D
0.94 98 Roadway, good, HSG B
0.21 98 Roadway, good, HSG D
0.15 98 Sidewalk, good, HSG D
0.31 98 Sidewalk, good, HSG B
0.80 98 Parking, good, HSG D
4.83 61 Open, good, HSG B
1.91 80 Open, good, HSG D
9.83 98 Parking, good, HSG B
1.32 98 Roof, good, HSG B
0.01 98 Offsite Impervious, good, HSG B
0.53 100 BMP, good, HSG B
0.58 55 Forest, good, HSG B
23.26 86 Weighted Average
8.97 68 38.55% Pervious Area
14.29 98 61.45% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 39HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcatchment WDB#2: Subcat WDB#2
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Type II 24-hr
10-Year Rainfall=5.10"
Runoff Area=23.26 ac
Runoff Volume=7.244 af
Runoff Depth>3.74"
Tc=5.0 min
CN=68/98
136.08 cfs
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 40HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Pond 1P: WDB#1
Inflow Area = 18.39 ac, 79.42% Impervious, Inflow Depth > 4.18" for 10-Year event
Inflow = 117.53 cfs @ 11.95 hrs, Volume= 6.410 af
Outflow = 25.80 cfs @ 12.11 hrs, Volume= 4.264 af, Atten= 78%, Lag= 9.7 min
Primary = 25.80 cfs @ 12.11 hrs, Volume= 4.264 af
Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 347.25' @ 12.11 hrs Surf.Area= 34,425 sf Storage= 156,070 cf
Plug-Flow detention time= 252.1 min calculated for 4.255 af (66% of inflow)
Center-of-Mass det. time= 148.1 min ( 899.5 - 751.4 )
Volume Invert Avail.Storage Storage Description
#1 342.00' 256,908 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
342.00 22,247 0 0
342.50 25,486 11,933 11,933
343.00 26,567 13,013 24,947
344.00 28,777 27,672 52,619
344.01 29,241 290 52,909
345.00 30,835 29,738 82,646
346.00 32,417 31,626 114,272
347.00 34,018 33,218 147,490
348.00 35,641 34,830 182,319
349.00 37,288 36,465 218,784
350.00 38,961 38,125 256,908
Device Routing Invert Outlet Devices
#1 Primary 340.40'36.0" Round Culvert
L= 165.0' RCP, square edge headwall, Ke= 0.5?
Inlet / Outlet Invert= 340.40' / 339.50' S= 0.0055 '/' Cc= 0.900
n= 0.013, Flow Area= 7.07 sf
#2 Device 1 342.00'3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 344.00'6.0" W x 6.0" H Vert. Orifice/Grate C= 0.600
#4 Device 1 345.80'30.0" W x 12.0" H Vert. Orifice/Grate X 2.00 C= 0.600
#5 Device 1 347.40'60.0" x 60.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#6 Primary 347.50'50.0' long x 40.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63
Primary OutFlow Max=25.68 cfs @ 12.11 hrs HW=347.24' (Free Discharge)
1=Culvert (Passes 25.68 cfs of 75.20 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.53 cfs @ 10.9 fps)
3=Orifice/Grate (Orifice Controls 2.08 cfs @ 8.3 fps)
4=Orifice/Grate (Orifice Controls 23.07 cfs @ 4.6 fps)
5=Orifice/Grate ( Controls 0.00 cfs)
6=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 41HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Pond 1P: WDB#1
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)130
120
110
100
90
80
70
60
50
40
30
20
10
0
Inflow Area=18.39 ac
Peak Elev=347.25'
Storage=156,070 cf
117.53 cfs
25.80 cfs
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 42HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Pond 2P: WDB#2
Inflow Area = 23.26 ac, 61.45% Impervious, Inflow Depth > 3.74" for 10-Year event
Inflow = 136.08 cfs @ 11.95 hrs, Volume= 7.244 af
Outflow = 11.27 cfs @ 12.47 hrs, Volume= 5.309 af, Atten= 92%, Lag= 31.0 min
Primary = 11.27 cfs @ 12.47 hrs, Volume= 5.309 af
Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 347.09' @ 12.47 hrs Surf.Area= 35,270 sf Storage= 184,035 cf
Plug-Flow detention time= 284.3 min calculated for 5.309 af (73% of inflow)
Center-of-Mass det. time= 187.4 min ( 950.6 - 763.3 )
Volume Invert Avail.Storage Storage Description
#1 341.00' 292,968 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
341.00 22,011 0 0
341.50 25,135 11,787 11,787
342.00 26,278 12,853 24,640
343.00 28,660 27,469 52,109
344.00 30,938 29,799 81,908
345.00 32,321 31,630 113,537
346.00 33,723 33,022 146,559
347.00 35,146 34,435 180,994
348.00 36,587 35,867 216,860
349.00 38,049 37,318 254,178
350.00 39,530 38,790 292,968
Device Routing Invert Outlet Devices
#1 Primary 337.20'30.0" Round Culvert
L= 90.0' RCP, square edge headwall, Ke= 0.5?
Inlet / Outlet Invert= 337.20' / 336.70' S= 0.0056 '/' Cc= 0.900
n= 0.013, Flow Area= 4.91 sf
#2 Device 1 341.00'3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 343.00'8.0" W x 8.0" H Vert. Orifice/Grate C= 0.600
#4 Device 1 344.90'18.0" W x 8.0" H Vert. Orifice/Grate C= 0.600
#5 Device 1 347.30'60.0" x 60.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#6 Primary 347.30'60.0' long x 25.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63
Primary OutFlow Max=11.27 cfs @ 12.47 hrs HW=347.09' (Free Discharge)
1=Culvert (Passes 11.27 cfs of 69.46 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.58 cfs @ 11.8 fps)
3=Orifice/Grate (Orifice Controls 4.14 cfs @ 9.3 fps)
4=Orifice/Grate (Orifice Controls 6.54 cfs @ 6.5 fps)
5=Orifice/Grate ( Controls 0.00 cfs)
6=Broad-Crested Rectangular Weir ( Controls 0.00 cfs)
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 43HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Pond 2P: WDB#2
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Inflow Area=23.26 ac
Peak Elev=347.09'
Storage=184,035 cf
136.08 cfs
11.27 cfs
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 44HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Link 1L: DP#1
Inflow Area = 50.51 ac, 60.61% Impervious, Inflow Depth > 2.63" for 10-Year event
Inflow = 58.72 cfs @ 12.07 hrs, Volume= 11.087 af
Primary = 58.72 cfs @ 12.07 hrs, Volume= 11.087 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Link 1L: DP#1
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)65
60
55
50
45
40
35
30
25
20
15
10
5
0
Inflow Area=50.51 ac
58.72 cfs58.72 cfs
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 45HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Link 2L: DP#2
Inflow Area = 18.39 ac, 79.42% Impervious, Inflow Depth > 2.78" for 10-Year event
Inflow = 25.80 cfs @ 12.11 hrs, Volume= 4.264 af
Primary = 25.80 cfs @ 12.11 hrs, Volume= 4.264 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Link 2L: DP#2
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
Inflow Area=18.39 ac
25.80 cfs25.80 cfs
Type II 24-hr 10-Year Rainfall=5.10"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 46HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Link 3L: DP#3
Inflow Area = 23.26 ac, 61.45% Impervious, Inflow Depth > 2.74" for 10-Year event
Inflow = 11.27 cfs @ 12.47 hrs, Volume= 5.309 af
Primary = 11.27 cfs @ 12.47 hrs, Volume= 5.309 af, Atten= 0%, Lag= 0.0 min
Primary outflow = Inflow, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Link 3L: DP#3
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)12
11
10
9
8
7
6
5
4
3
2
1
0
Inflow Area=23.26 ac
11.27 cfs11.27 cfs
WDB#1
Subcat WDB#1
WDB#2
Subcat WDB#2
4P
WDB#1-100 YR
5P
WDB#2-100 YR
Routing Diagram for 1915_SIA_POST
Prepared by Horvath Associates, PA, Printed 3/4/2020
HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcat Reach Pond Link
Type II 24-hr 100-Year Rainfall=7.40"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 2HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv.
Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method
Runoff Area=18.39 ac 79.42% Impervious Runoff Depth>6.34"Subcatchment WDB#1: Subcat WDB#1
Tc=5.0 min CN=63/98 Runoff=177.62 cfs 9.718 af
Runoff Area=23.26 ac 61.45% Impervious Runoff Depth>5.84"Subcatchment WDB#2: Subcat WDB#2
Tc=5.0 min CN=68/98 Runoff=212.59 cfs 11.311 af
Peak Elev=348.21' Storage=28,440 cf Inflow=177.62 cfs 9.718 afPond 4P: WDB#1-100 YR
Outflow=161.66 cfs 9.717 af
Peak Elev=348.18' Storage=31,791 cf Inflow=212.59 cfs 11.311 afPond 5P: WDB#2-100 YR
Outflow=197.19 cfs 11.308 af
Total Runoff Area = 41.64 ac Runoff Volume = 21.030 af Average Runoff Depth = 6.06"
30.62% Pervious = 12.75 ac 69.38% Impervious = 28.89 ac
Type II 24-hr 100-Year Rainfall=7.40"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 3HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment WDB#1: Subcat WDB#1
Runoff = 177.62 cfs @ 11.95 hrs, Volume= 9.718 af, Depth> 6.34"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 100-Year Rainfall=7.40"
Area (ac) CN Description
2.27 61 Open, good, HSG B
0.38 80 Open, good, HSG D
0.31 77 Forest, good, HSG D
0.14 100 BMP, good, HSG D
0.05 98 Roof, good, HSG D
9.33 98 Parking, good, HSG B
3.82 98 Parking, good, HSG D
0.82 98 Roof, good, HSG B
0.44 100 BMP, good, HSG B
0.81 55 Forest, good, HSG B
18.39 91 Weighted Average
3.78 63 20.58% Pervious Area
14.60 98 79.42% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Subcatchment WDB#1: Subcat WDB#1
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Type II 24-hr
100-Year Rainfall=7.40"
Runoff Area=18.39 ac
Runoff Volume=9.718 af
Runoff Depth>6.34"
Tc=5.0 min
CN=63/98
177.62 cfs
Type II 24-hr 100-Year Rainfall=7.40"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 4HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Subcatchment WDB#2: Subcat WDB#2
Runoff = 212.59 cfs @ 11.95 hrs, Volume= 11.311 af, Depth> 5.84"
Runoff by SCS TR-20 method, UH=SCS, Split Pervious/Imperv., Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Type II 24-hr 100-Year Rainfall=7.40"
Area (ac) CN Description
1.65 77 Forest, good, HSG D
0.20 98 Offsite Impervious, good, HSG D
0.94 98 Roadway, good, HSG B
0.21 98 Roadway, good, HSG D
0.15 98 Sidewalk, good, HSG D
0.31 98 Sidewalk, good, HSG B
0.80 98 Parking, good, HSG D
4.83 61 Open, good, HSG B
1.91 80 Open, good, HSG D
9.83 98 Parking, good, HSG B
1.32 98 Roof, good, HSG B
0.01 98 Offsite Impervious, good, HSG B
0.53 100 BMP, good, HSG B
0.58 55 Forest, good, HSG B
23.26 86 Weighted Average
8.97 68 38.55% Pervious Area
14.29 98 61.45% Impervious Area
Tc Length Slope Velocity Capacity Description
(min) (feet) (ft/ft) (ft/sec) (cfs)
5.0 Direct Entry,
Type II 24-hr 100-Year Rainfall=7.40"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 5HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Subcatchment WDB#2: Subcat WDB#2
Runoff
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)230
220
210
200
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Type II 24-hr
100-Year Rainfall=7.40"
Runoff Area=23.26 ac
Runoff Volume=11.311 af
Runoff Depth>5.84"
Tc=5.0 min
CN=68/98
212.59 cfs
Type II 24-hr 100-Year Rainfall=7.40"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 6HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Pond 4P: WDB#1-100 YR
Inflow Area = 18.39 ac, 79.42% Impervious, Inflow Depth > 6.34" for 100-Year event
Inflow = 177.62 cfs @ 11.95 hrs, Volume= 9.718 af
Outflow = 161.66 cfs @ 11.99 hrs, Volume= 9.717 af, Atten= 9%, Lag= 2.1 min
Primary = 161.66 cfs @ 11.99 hrs, Volume= 9.717 af
Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 348.21' @ 11.99 hrs Surf.Area= 35,979 sf Storage= 28,440 cf
Plug-Flow detention time= 1.5 min calculated for 9.697 af (100% of inflow)
Center-of-Mass det. time= 1.5 min ( 748.7 - 747.2 )
Volume Invert Avail.Storage Storage Description
#1 347.40' 95,681 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
347.40 34,667 0 0
348.00 35,641 21,092 21,092
349.00 37,288 36,465 57,557
350.00 38,961 38,125 95,681
Device Routing Invert Outlet Devices
#1 Primary 340.40'36.0" Round Culvert
L= 165.0' RCP, square edge headwall, Ke= 0.5?
Inlet / Outlet Invert= 340.40' / 339.50' S= 0.0055 '/' Cc= 0.900
n= 0.013, Flow Area= 7.07 sf
#2 Device 1 342.00'3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 344.00'6.0" W x 6.0" H Vert. Orifice/Grate C= 0.600
#4 Device 1 345.80'30.0" W x 12.0" H Vert. Orifice/Grate X 2.00 C= 0.600
#5 Device 1 347.40'60.0" x 60.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#6 Primary 347.50'50.0' long x 40.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63
Primary OutFlow Max=157.69 cfs @ 11.99 hrs HW=348.19' (Free Discharge)
1=Culvert (Passes 81.59 cfs of 82.36 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.58 cfs @ 11.9 fps)
3=Orifice/Grate (Orifice Controls 2.39 cfs @ 9.6 fps)
4=Orifice/Grate (Orifice Controls 32.97 cfs @ 6.6 fps)
5=Orifice/Grate (Weir Controls 45.65 cfs @ 2.9 fps)
6=Broad-Crested Rectangular Weir (Weir Controls 76.10 cfs @ 2.2 fps)
Type II 24-hr 100-Year Rainfall=7.40"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 7HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Pond 4P: WDB#1-100 YR
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Inflow Area=18.39 ac
Peak Elev=348.21'
Storage=28,440 cf
177.62 cfs
161.66 cfs
Type II 24-hr 100-Year Rainfall=7.40"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 8HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Summary for Pond 5P: WDB#2-100 YR
Inflow Area = 23.26 ac, 61.45% Impervious, Inflow Depth > 5.84" for 100-Year event
Inflow = 212.59 cfs @ 11.95 hrs, Volume= 11.311 af
Outflow = 197.19 cfs @ 11.98 hrs, Volume= 11.308 af, Atten= 7%, Lag= 1.9 min
Primary = 197.19 cfs @ 11.98 hrs, Volume= 11.308 af
Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs
Peak Elev= 348.18' @ 11.98 hrs Surf.Area= 36,847 sf Storage= 31,791 cf
Plug-Flow detention time= 2.2 min calculated for 11.285 af (100% of inflow)
Center-of-Mass det. time= 2.0 min ( 761.1 - 759.2 )
Volume Invert Avail.Storage Storage Description
#1 347.30' 101,365 cf Custom Stage Data (Prismatic) Listed below (Recalc)
Elevation Surf.Area Inc.Store Cum.Store
(feet) (sq-ft) (cubic-feet) (cubic-feet)
347.30 35,578 0 0
348.00 36,587 25,258 25,258
349.00 38,049 37,318 62,576
350.00 39,530 38,790 101,365
Device Routing Invert Outlet Devices
#1 Primary 337.20'30.0" Round Culvert
L= 90.0' RCP, square edge headwall, Ke= 0.5?
Inlet / Outlet Invert= 337.20' / 336.70' S= 0.0056 '/' Cc= 0.900
n= 0.013, Flow Area= 4.91 sf
#2 Device 1 341.00'3.0" Vert. Orifice/Grate C= 0.600
#3 Device 1 343.00'8.0" W x 8.0" H Vert. Orifice/Grate C= 0.600
#4 Device 1 344.90'18.0" W x 8.0" H Vert. Orifice/Grate C= 0.600
#5 Device 1 347.30'60.0" x 60.0" Horiz. Orifice/Grate C= 0.600
Limited to weir flow at low heads
#6 Primary 347.30'60.0' long x 25.0' breadth Broad-Crested Rectangular Weir
Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60
Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63
Primary OutFlow Max=190.95 cfs @ 11.98 hrs HW=348.16' (Free Discharge)
1=Culvert (Passes 65.43 cfs of 73.64 cfs potential flow)
2=Orifice/Grate (Orifice Controls 0.63 cfs @ 12.8 fps)
3=Orifice/Grate (Orifice Controls 4.70 cfs @ 10.6 fps)
4=Orifice/Grate (Orifice Controls 8.23 cfs @ 8.2 fps)
5=Orifice/Grate (Weir Controls 51.88 cfs @ 3.0 fps)
6=Broad-Crested Rectangular Weir (Weir Controls 125.52 cfs @ 2.4 fps)
Type II 24-hr 100-Year Rainfall=7.40"1915_SIA_POST
Printed 3/4/2020Prepared by Horvath Associates, PA
Page 9HydroCAD® 10.00-24 s/n 03736 © 2018 HydroCAD Software Solutions LLC
Pond 5P: WDB#2-100 YR
Inflow
Primary
Hydrograph
Time (hours)
2423222120191817161514131211109876543210Flow (cfs)230
220
210
200
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Inflow Area=23.26 ac
Peak Elev=348.18'
Storage=31,791 cf
212.59 cfs
197.19 cfs
SCM Sizing Calculations
FedEx Freight N/A
0748-91-06-3841, 91-73-3991 D1900260
Matt Jones, PE
Setzer Properties
490919 4990
919 669 6295Scott Bender
354 Walker Ave, STE 200, Lexington, KY, 40504
TBD TBD TBD TBD
X X X
10.5 N/A
335.5
342.0
344.0
344.0
345.7
345.8
346.1
345.8
347.3
347.5
**349.5 "settled"350.0
348.2
22,247
20,988
34,425
18.4
10
N/A
WDB#1
64.63
1.88
64.63
3.97
1.88
22.42
169.51
15.96
65.88
269.85
58.72
4.40
76.96
25.80
117.53
84,340
52,619
240,410
156,070
341,248
16,861
3.8
4.8
2.62
3
81
0.5
2.5
100 20
36
5'x5' Riser
50
2.5
DP#2 DP#1 DP#1
MJ
MJ
MJ
MJ
MJ
N/A
MJ 1.5:1 Per 2009 NC BMP
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
1915_WDB#1.xls
Surface Area Calcs (85% TSS)
Matt Jones, PE
3/4/2020
1915 - FedEx Freight
WDB#1 Surface Area
Drainage Area to Basin = 18.39 acres
Impervious Area to Basin = 14.02 acres
Impervious Percentage = 78%
Avereage Depth (Volume/SA) = 4.20 ft
Average Depth (Vol/SA) (ft)
% Impervious 4.0 4.2 5.0
Lower Boundary 70%2.40 2.07 <- from table below
Site % impervious 78%2.70 2.62 2.32 <- interpolated
Upper Boundary 80%2.78 2.38 <- from table below
SA/DA = 2.62
Surface Area Required = 20,988 sf
Surface Area Provided = 22,247 sf
3.0 4.0 5.0 6.0 7.0 8.0 9.0
10% 0.59 0.49 0.43 0.35 0.31 0.29 0.26
20% 0.97 0.79 0.70 0.59 0.51 0.46 0.44
30% 1.34 1.08 0.97 0.83 0.70 0.64 0.62
40% 1.73 1.43 1.25 1.05 0.90 0.82 0.77
50% 2.06 1.73 1.50 1.30 1.09 1.00 0.92
60% 2.40 2.03 1.71 1.51 1.29 1.18 1.10
70% 2.88 2.40 2.07 1.79 1.54 1.35 1.26
80% 3.36 2.78 2.38 2.10 1.86 1.60 1.42
90% 3.74 3.10 2.66 2.34 2.11 1.83 1.67
Percent
Impervious
Cover
Permanent Pool Average Depth (ft)
Surface Area (SA) to Drainage Area (DA) Ratio for Permanent Pool Sizing to
Achieve 85 Percent TSS Pollutant Removal Efficiency in the Piedmont
(From NCDWQ Stormwater BMP Manual , July 2007)
Interpolation to Determine SA/DA Ratio
1915_WDB#1.xls
Below NP Volumes
Matt Jones, PE
3/4/2020
1915 - FedEx Freight
Below Normal Pool Volumes
Forebay Volume
Stage/Storage Calculations
Contour
Elevation Stage Contour
Surface Area
Average
Contour
Surface Area
Incremental
Volume
Cumulative
Volume
(ft) (ft) (sf) (sf) (cf) (cf)
Forebay Bottom 336.5 0.0 1894 0 0 0
Bottom of Aquatic Shelf 341.5 5.0 3942 2918 14590 14590
Permanent Pool 342.0 5.5 5141 4542 2271 16861
Forebay Volume = 16861 cf
Main Pool Volume
Stage/Storage Calculations
Contour
Elevation Stage Contour
Surface Area
Average
Contour
Surface Area
Incremental
Volume
Cumulative
Volume
(ft) (ft) (sf) (sf) (cf) (cf)
Main Pool Bottom 336.5 0.0 9213 0 0 0
Bottom of Aquatic Shelf 341.5 5.0 14607 11910 59550 59550
Permanent Pool 342.0 5.5 17106 15857 7929 67479
Main Pool Volume = 67479 cf
Total Pond Volume
Forebay Volume = 16861 cf
Main Pool Volume = 67479 cf
Total Pond Volume = 84340 cf
Forebay Percentage of Total Volume = 19.99%
1915_WDB#1.xls
Average Depth
Matt Jones, PE
3/4/2020
1915 - FedEx Freight
Average Depth Calculation
Abot_shelf = 18549 sf
Aperm_pool=22247 sf
Abot_pond=9213 sf
Depth= 5.0 ft
18549 sf 18549 sf + 9213 sf 5.0 ft
22247 sf 2 18549 sf
Avearage Depth = 4.20 ft
1915_WDB#1.xls
WQ Volume
Matt Jones, PE
3/4/2020
1915 - FedEx Freight
Water Quality Volume
Runoff Volume
Simple Method
Drainage Area (A) = 18.39 Acres
Impervious Area = 14.02 Acres
Impervious Fraction (I A) = 0.76
Rainfall Depth (RD) = 1.00 Inch
RV = 0.73 (RV = 0.05+0.9*IA)
Runoff Volume (V) = 48732 cf (V = 3630*RD*RV*A)
Normal Pool Elevation = 342.00
Temporary Pool Elevation = 344.00
Temporary Pool Volume = 52619 cf (From HydroCAD Report)
Temporary Pool Surface Area = 28777 sf (From HydroCAD Report)
1915_WDB#1.xls
Drawdown Orifice Sizing
Matt Jones, PE
3/4/2020
1915 - FedEx Freight
Drawdown Orifice Sizing
Water Quality Drawdown Orifice Sizing
3in(Orifice Size)
A1= 28,777 sf (Area of pond at the beginning of drawdown)
A0= 22,247 sf (Area of pond at the orifice outlet elevation)
Cd= 0.6 (Orifice Coefficient of Discharge)
a=0.049 sf Orifice Area (calculated)
g=32.2 ft/s2 Acceleration of Gravity (constant)
H1= 2.00 ft (Maximum head (t=0))
T=3.39 days (Time for water level to fall from H1 to Permanent Pool Elevation)
1915_WDB#1.xls
Anti-flotation
Matt Jones, PE
3/4/2020
1915 - FedEx Freight
Riser Anti-Flotation Calculations
Input Data ==>
Invert of Extended Base = 337.60 feet
Riser Top Elevation = 347.40 feet
Invert of Outlet Barrel = 340.40
Inside Dimension of Riser =5.0 feet
Wall thickness of Riser =0.5 feet
Height of Base =0.50 feet
Inside Barrel diameter = 2.5 feet
Area of Weir Openings =5.25 sf
Weight of Structure ==>
Volume of Riser Walls = 102.30 cf
Volume of Base = 18.00 cf
Total Volume of Concrete = 120.30 cf
Opening for barrel = 2.454 cf
Total Volume of Openings in Concrete = 5.079 cf
Total Concrete in Riser Section Minus Openings = 115.22 cf
Depth of Concrete Fill Layer = 2.30 ft
Volume of Concrete in Fill Layer = 57.50 cf
Total Volume of Concrete Present in Riser = 172.72 cf
Concrete unit weight =150 lb/cf (From National Precast Concrete Assoc.)
Total Weight of Concrete = 25908 lbs
Amount of water displaced ==>
Volume of Water Displaced by Riser Structure = 352.8 cf
Unit Weight of water = 62.4 lb/cf
Weight of water displaced =22015 lbs
Determine if Anti-Flotation Block is Required ==>
Desired Saftey Factor =1.15 (recommend 1.15 or higher)
Safety Factor =1.18
1915 - FedEx Freight
Dam Settlement Calculation
Top of Dam Elevation = 350.0 ft
Inv Down of PSP = 339.5 ft
Dam Height = 10.5 ft
Settlement Factor = 5%
Settled top of Dam = 349.5
100-Year WSE = 348.2
Freeboard Provided = 1.3
1915 - FedEx Freight
Riprap Outlet Protection
WDB #1 Outfall
Pipe Diameter (D0)= 36 inch
Number of Barrels = 1
Use D = 3ft(D0)
Q10 = 26.00 cfs
V10 = 6.55 ft/s
Apron Slope > 10%?No
Zone From Chart = 2
Use Recommendations for Zone 3
Apron Length = 24 feet
Upstream Apron Width = 9 feet (3*D)
Downstream Apron Width = 13
Stone Class = Class '1'
Stone Layer Thickness = 24
Design procedure explained in Chapter 8 (Section 8.06) of North Carolina Erosion and
Sediment Control Planning and Design Manual
FedEx Freight N/A
0748-91-06-3841, 91-73-3991 D1900260
Matt Jones, PE
Setzer Properties
490919 4990
919 669 6295Scott Bender
354 Walker Ave, STE 200, Lexington, KY, 40504
TBD TBD TBD TBD
X X X
13.3 N/A
334.5
341.0
343.0
343.0
344.7
344.9
345.3
344.9
347.1
347.3
**349.3 "settled"350.0
348.1
22,011
19,614
35,270
23.3
10
N/A
WDB#2
70.11
2.94
70.11
3.42
2.94
22.42
169.51
15.96
65.88
269.85
58.72
4.60
85.25
11.27
136.08
84,174
52,109
268,209
184,035
377,142
19,048
3.8
4.8
1.94
3
81
0.67
1.5
100 20
30
5'x5' Riser
60
1.5
MJ
MJ
MJ
MJ
MJ
N/A
MJ 1.5:1 Per 2009 NC BMP
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
MJ
1915_WDB#2.xls
Surface Area Calcs (85% TSS)
Matt Jones, PE
3/4/2020
1915 - FedEx Freight
WDB#2 Surface Area
Drainage Area to Basin = 23.26 acres
Impervious Area to Basin = 13.77 acres
Impervious Percentage = 59%
Avereage Depth (Volume/SA) = 4.22 ft
Average Depth (Vol/SA) (ft)
% Impervious 4.0 4.2 5.0
Lower Boundary 50%1.73 1.50 <- from table below
Site % impervious 59%2.01 1.94 1.69 <- interpolated
Upper Boundary 60%2.03 1.71 <- from table below
SA/DA = 1.94
Surface Area Required = 19,614 sf
Surface Area Provided = 22,011 sf
3.0 4.0 5.0 6.0 7.0 8.0 9.0
10% 0.59 0.49 0.43 0.35 0.31 0.29 0.26
20% 0.97 0.79 0.70 0.59 0.51 0.46 0.44
30% 1.34 1.08 0.97 0.83 0.70 0.64 0.62
40% 1.73 1.43 1.25 1.05 0.90 0.82 0.77
50% 2.06 1.73 1.50 1.30 1.09 1.00 0.92
60% 2.40 2.03 1.71 1.51 1.29 1.18 1.10
70% 2.88 2.40 2.07 1.79 1.54 1.35 1.26
80% 3.36 2.78 2.38 2.10 1.86 1.60 1.42
90% 3.74 3.10 2.66 2.34 2.11 1.83 1.67
Percent
Impervious
Cover
Permanent Pool Average Depth (ft)
Surface Area (SA) to Drainage Area (DA) Ratio for Permanent Pool Sizing to
Achieve 85 Percent TSS Pollutant Removal Efficiency in the Piedmont
(From NCDWQ Stormwater BMP Manual , July 2007)
Interpolation to Determine SA/DA Ratio
1915_WDB#2.xls
Below NP Volumes
Matt Jones, PE
3/4/2020
1915 - FedEx Freight
Below Normal Pool Volumes
Forebay Volume
Stage/Storage Calculations
Contour
Elevation Stage Contour
Surface Area
Average
Contour
Surface Area
Incremental
Volume
Cumulative
Volume
(ft) (ft) (sf) (sf) (cf) (cf)
Forebay Bottom 336.0 0.0 2348 0 0 0
Bottom of Aquatic Shelf 340.5 4.5 4879 3614 16261 16261
Permanent Pool 341.0 5.0 6271 5575 2788 19048
Forebay Volume = 19048 cf
Main Pool Volume
Stage/Storage Calculations
Contour
Elevation Stage Contour
Surface Area
Average
Contour
Surface Area
Incremental
Volume
Cumulative
Volume
(ft) (ft) (sf) (sf) (cf) (cf)
Main Pool Bottom 335.5 0.0 9394 0 0 0
Bottom of Aquatic Shelf 340.5 5.0 13711 11553 57763 57763
Permanent Pool 341.0 5.5 15740 14726 7363 65125
Main Pool Volume = 65125 cf
Total Pond Volume
Forebay Volume = 19048 cf
Main Pool Volume = 65125 cf
Total Pond Volume = 84174 cf
Forebay Percentage of Total Volume = 22.63%
1915_WDB#2.xls
Average Depth
Matt Jones, PE
3/4/2020
1915 - FedEx Freight
Average Depth Calculation
Abot_shelf = 18590 sf
Aperm_pool=22011 sf
Abot_pond=9394 sf
Depth= 5.0 ft
18590 sf 18590 sf + 9394 sf 5.0 ft
22011 sf 2 18590 sf
Avearage Depth = 4.22 ft
1915_WDB#2.xls
WQ Volume
Matt Jones, PE
3/4/2020
1915 - FedEx Freight
Water Quality Volume
Runoff Volume
Simple Method
Drainage Area (A) = 23.26 Acres
Impervious Area = 13.77 Acres
Impervious Fraction (I A) = 0.59
Rainfall Depth (RD) = 1.00 Inch
RV = 0.58 (RV = 0.05+0.9*IA)
Runoff Volume (V) = 49208 cf (V = 3630*RD*RV*A)
Normal Pool Elevation = 341.00
Temporary Pool Elevation = 343.00
Temporary Pool Volume = 52109 cf (From HydroCAD Report)
Temporary Pool Surface Area = 28660 sf (From HydroCAD Report)
1915_WDB#2.xls
Drawdown Orifice Sizing
Matt Jones, PE
3/4/2020
1915 - FedEx Freight
Drawdown Orifice Sizing
Water Quality Drawdown Orifice Sizing
3in(Orifice Size)
A1= 28,660 sf (Area of pond at the beginning of drawdown)
A0= 22,011 sf (Area of pond at the orifice outlet elevation)
Cd= 0.6 (Orifice Coefficient of Discharge)
a=0.049 sf Orifice Area (calculated)
g=32.2 ft/s2 Acceleration of Gravity (constant)
H1= 2.00 ft (Maximum head (t=0))
T=3.36 days (Time for water level to fall from H1 to Permanent Pool Elevation)
1915_WDB#2.xls
Anti-flotation
Matt Jones, PE
3/4/2020
1915 - FedEx Freight
Riser Anti-Flotation Calculations
Input Data ==>
Invert of Extended Base = 333.70 feet
Riser Top Elevation = 347.30 feet
Invert of Outlet Barrel = 337.20
Inside Dimension of Riser =5.0 feet
Wall thickness of Riser =0.5 feet
Height of Base =0.50 feet
Inside Barrel diameter = 2.5 feet
Area of Weir Openings =1.45 SF
Weight of Structure ==>
Volume of Riser Walls = 144.10 cf
Volume of Base = 18.00 cf
Total Volume of Concrete = 162.10 cf
Opening for barrel = 2.454 cf
Total Volume of Openings in Concrete = 3.181 cf
Total Concrete in Riser Section Minus Openings = 158.92 cf
Depth of Concrete Fill Layer = 3.00 ft
Volume of Concrete in Fill Layer = 75.00 cf
Total Volume of Concrete Present in Riser = 233.92 cf
Concrete unit weight =150 lb/cf (From National Precast Concrete Assoc.)
Total Weight of Concrete = 35088 lbs
Amount of water displaced ==>
Volume of Water Displaced by Riser Structure = 489.6 cf
Unit Weight of water = 62.4 lb/cf
Weight of water displaced =30551 lbs
Determine if Anti-Flotation Block is Required ==>
Desired Saftey Factor =1.15 (recommend 1.15 or higher)
Safety Factor =1.15
1915 - FedEx Freight
Dam Settlement Calculation
Top of Dam Elevation = 350.0 ft
Inv Down of PSP = 336.7 ft
Dam Height = 13.3 ft
Settlement Factor = 5%
Settled top of Dam = 349.3
100-Year WSE = 348.1
Freeboard Provided = 1.2
1915 - FedEx Freight
Riprap Outlet Protection
WDB#2 Outfall
Pipe Diameter (D0)= 30 inch
Number of Barrels = 1
Use D = 2.5 ft (D0)
Q10 = 20.00 cfs
V10 = 8.95 ft/s
Apron Slope > 10%?No
Zone From Chart = 2
Use Recommendations for Zone 3
Apron Length = 20 feet
Upstream Apron Width = 8 feet (3*D)
Downstream Apron Width = 11
Stone Class = Class '1'
Stone Layer Thickness = 24
Design procedure explained in Chapter 8 (Section 8.06) of North Carolina Erosion and
Sediment Control Planning and Design Manual

Nutrient Loading Calculations

nutrient offset intro
Is this Redevelopment? Yes No
Development Type (Please check all that apply)
Commercial Duplex Residential
Industrial Single-Family Residential
Institutional Multi-Family Residential
Mixed Use
WATERSHED INFORMATION (See online map or alternative source for 12-digit and 6-digit IDs)
Upper Falls Basin, 12-digit Watershed ID:
Lower Falls Basin, 12-digit Watershed ID:
Neuse/Outside of Falls Basin, 03020201
Jordan Lake (Upper New Hope) 6-digit Small
Watershed ID:
Neuse/Falls Lake Delivery Factors: There are no delivery factors, so the Delivery Factor = 1.
N: P: N:YES P:N/A
NUTRIENT OFFSET REQUEST (Must meet the offsite thresholds – see above)
Nitrogen Loading / Offset Needs (For the Jordan, Falls, and Neuse/Outside of Falls Watershed areas)
Phosphorus Loading / Offset Needs (For the Jordan and Falls Watershed areas)
FedEx Freight
___________________
(J)
(H)
State Buy Down
Amount Delivered
(lbs)
D * E * F * G
3354.08
(H)
Offset
Duration
(yrs)
30
(F)
Impervious Cover (%) Pre-Construction:
0.8
(D)
Name of Bank
Off-site treatment threshold (%):
Impervious Cover (%) Post-Construction:
55.2
Offset
Duration
(yrs)
(E)
Project Size
(square feet)
2,265,174
(E)
30
(F)
-78.8833 0748-91-06-3841, 0748-91-73-3991
State Buy Down
Amount Delivered
(lbs)
D * E * F * G
N/A
(G)
Site Delivery
Factor
1.00
(G)
Site Delivery
Factor
1.00
Nutrient loading limits and on-site treatment minimum (Sections 70-740(a) and Sections 70-741(a))
Responsible Professional Engineer’s Name: PE #:
Staff Name: Staff e-mail:
Project Size
(square feet)
2,265,174
Phone #:
Matt Jones, PE
Site:
39170
Total Delivered
(lbs)
H + I
Name of Bank
N/A
Additional
5% if bank
not in City
limits (lbs)
167.70
(I) (Where
Applicable)
Additional
5% if bank
not in City
limits (lbs)
N/A
(J)
Total Delivered
(lbs)
H + I
3521.78
(I) (Where
Applicable)
Required on-site reduction achieved?
Bank:
Phosphorus
Site: Bank:
Applicant Name : Setzer Properties Prepared by : Matt Jones, PE
Project Name (& Previous name, if applicable): Site Plan #:
D1900260
Project
Locatn:
Lat: (dec. degrees)Long: (dec. degrees)PIN/PID #s:
35.897518
Reduction
Needed
(lbs/ac/yr)
(from Compl.
Worksheet)
Untreated
Loading
Rate
(lbs/ac/yr)
Treated
Loading
Rate
(lbs/ac/yr)
CITY OF DURHAM Neuse, Falls Lake and Jordan Lake Developer Nutrient Reporting Form
Please complete and submit the following information to the City of Durham Stormwater Services to
characterize your project and assess the need to purchase nutrient offsets. See the
City Stormwater Performance Standards.For nutrient offset information, see
Jordan Lake Delivery Factors (%)
Nitrogen
PROJECT INFORMATION
0.79 0.82
8.01
(B)
5.75 2.20
NONE
Project Address (if available): Street: City/Town: County:
5203 Chin Page Road Durham Durha
Date: (mo/d/yr)
10/23/2019
2.15
Load Rate
Target
(lbs/ac/yr)
2.14
(D)(C)

Untreated
Loading
Rate
(lbs/ac/yr)
Treated
Loading
Rate
(lbs/ac/yr)
Load Rate
Target
(lbs/ac/yr)
(A)
Reduction
Needed
(lbs/ac/yr)
(from Compl.
Worksheet)
(A) (B)
DURHAM STORMWATER PERFORMANCE STANDARDS FOR DEVELOPMENT COMPLIANCE ALTERNATIVE
(C)
Version 2, July 10, 2013
Watershed (Select from Menu)
3 Falls Lake Basin
Jordan Lake Basin
Lower Neuse Basin
Compliance Alternative (Pick one alternative, see descriptions and calculations below)
1 Nutrient loading limits and on-site treatment minimum (Sections 70-740(a) and Sections 70-741(a))
0
0
0 Alternative for low impact development in Falls Basin.
Exempt from Stormwater Pollutant standards (Section 70-739)
Project Area Disturbance (Fill in yellow cell below)
1,753,290 square feet 40.250 acres
The Project is Located Outside the Downtown Area (select from menu list)
The Project Type is (select from menu list)
Other key definitions from Section 70-736:
Alternative percentage reduction option for Redevelopment that does not increase impervious area
(Section 70-740(c))
Redevelopment means Development on a site where structures or impervious surface
already exists. It is a category of new development.
Per Section 70-736,
Limited Residential means single family and duplex residential and recreational development.
Multifamily and Other Development means development not included in Limited Resdiential, and
includes but is not limited to multifamily and townhomes, and office, industrial, institutional (including local
government institutional), and commercial development.
Note that if a nutrient bank is used to buy offset credits
in order to achieve compliance with the alternative
selected below, the bank must be located in the same
watershed as the project site.
Multifamily & Other
Land DisturbanceProject Location
Alternative percentage reduction option for Redevelopment that increases impervious area (Section 70-
740(b))
Multifamily and Other
Falls Basin
Jordan Basin 1 acre
0.5 acres
1 acre
0.5 acres
12,000 square feet
0.5 acres
Limited Residential
TABLE 1 THRESHOLDS FOR APPLICATION OF STORMWATER
POLLUTANT REQUIREMENTS
Lower Neuse Basin
Per Section 70-736, Downtown Area means the Downtown Tier, Compact Neighborhoods,
and Suburban Transit Zones as shown on the Durham Comprehensive Land Use Plan most
recently approved by the Durham City Council.
Note: Thresholds are based upon land disturbance since the
applicable basin Baseline date.
Development means Land Disturbance which increases impervious surface on a property, or
alters its location, or results in an increase in runoff from a property or a decrease in infiltration
of precipitation into the soil. It includes both existing development and new development. It
does not include agriculture, mining, or forestry activities.
COMPLIANCE WORKSHEET
Version 2 DRAFT, April 5,2013
Nutrient Loading Limits and On-Site Treatment Minimum
ORDINANCE REQUIREMENTS
Sec. 70-740.
(a) Nutrient Loading Rate Limits. Development not exempt under subsection 70-739 shall
construct and implement SCMs so as to limit the post construction loading rate of nitrogen
and phosphorus from the project area to the limits set forth in Table 2 below, or shall
comply with an allowed alternative as set forth in (b) through (d) below. A portion of the
reduction requirements for nitrogen and phosphorus may be met through off site
measures or payments as set forth in 70-741.
Sec. 70-741
(a) On site nutrient treatment requirements. Nitrogen and phosphorus reduction
requirements may be met, in part, through offsite management measures or the
purchase of nutrient credits. At a minimum, however, in the Jordan and Falls Basins a
percentage of the required nitrogen and phosphorus reductions must be achieved through
onsite treatment, in the amount shown in Table 4 below. In addition to meeting the
percentage reductions below, in the Jordan and Lower Neuse Basins, nitrogen export
load from the site must not exceed 6 lbs. per acre per year for Limited Residential, and
and 10 lbs per acre per year for Multifamily and Other.
(Note: offsite credit purchases do not meet TSS removal requirements, which must be
met onsite.)
Phosphorus
2.2
2.2
0.82
Jordan - General *40% of required
reduction
TABLE 2 NUTRIENT EXPORT LOADING RATE LIMITS
Nitrogen
Minimum Onsite Nutrient TreatmentProject
not required
Project Location Export Limit lbs/acre/year
Jordan Basin
Falls Basin
Phosphorus
TABLE 4 ONSITE NUTRIENT TREATMENT REQUIREMENTS
3.6
0.33
Nitrogen
Lower Neuse Basin
*40% of required
reduction
Falls - General *50% of required
reduction
*50% of required
reduction
*30% of required
reduction
*30% of required
reduction
Falls and Jordan within
Downtown Area
Version 2 DRAFT, April 5,2013
*The “required reduction” is the difference between the post development loading in
pounds per acre per year multiplied by the site area in acres before treatment minus the
loading target, in pounds per acre per year multiplied by the acres. The percentage shown in
the chart above is applied to that difference and the resulting number is the amount in
pounds/year of nutrient reduction that must be achieved onsite.
CALCULATIONS - ENTER VALUES IN YELLOW CELLS
TRUE
Required Onsite Reduction Achieved?
Nitrogen Phosphorus
0 YES N/A
Onsite Reduction
Required (%)
Lower Neuse
No percentage
reductions apply, but
the 6/10 nitrogen
export limit described
in paragraph (a)
above must be met
No percentage
reductions apply, but
the 6/10 nitrogen
export limit described
in paragraph (a)
above must be met
Treated Loading Rate
(lbs/ac/yr)
Load Rate Target
(lbs/ac/yr)
Reduction Needed
(lbs/ac/yr)
5.75
*30% of required
reduction
*30% of required
reduction
Nitrogen
2.15
Untreated Loading
Rate (lbs/ac/yr)
Falls and Jordan exceeding
thresholds but with less than 1
acre land disturbance
Phosphorus
Untreated Loading
Rate (lbs/ac/yr)
Treated Loading Rate
(lbs/ac/yr)
Load Rate Target
(lbs/ac/yr)
Reduction Needed
(lbs/ac/yr)
3.68.01
2.14 0.79 NONE NONE
ONSITE CALCULATIONS - ENTER VALUE IN YELLOW CELLS BASED ON TABLE 4
In the Jordan and Lower Neuse Basins, the nitrogen export loading rate from the
site does not exceed 6 lb/ac/yr for Limited Residential, or 10 lb/ac/yr for Multifamily
and Other.
Version 2 DRAFT, April 5,2013
12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061AB C D E F G HIJK L M N O P Q R S T UWatershed Characteristics Ver2.0PART A     Parking lot 1.44 0.16     ⅛‐ac lots‐‐ ‐‐ ‐‐     Roof 1.08 0.15     ¼‐ac lots ‐‐ ‐‐‐‐     Open/Landscaped 2.24 0.44     ½‐ac lots‐‐ ‐‐ ‐‐     1‐ac lots‐‐ ‐‐ ‐‐     Parking lot 1.44 0.39 1,035,736     2‐ac lots‐‐ ‐‐ ‐‐     Roof 1.08 0.15 95,620     Multi‐family‐‐ ‐‐ ‐‐     Open/Landscaped 2.24 0.44 868,409     Townhomes‐‐ ‐‐ ‐‐     Custom Lot Size‐‐ ‐‐     High Density (interstate, main)3.67 0.43 PART B     Low Density (secondary, feeder)1.4 0.52 49,836‐‐1.4 0.52     Rural 1.14 0.471.0 1.44 0.39 8,201     Sidewalk 1.4 1.16 19,810‐‐1.44 0.39‐‐1.08 0.15 9,874     Managed pervious 3.06 0.59‐‐1.4 1.16     Unmanaged (pasture) 3.61 1.56‐‐2.24 0.44 202,734     Forest 1.47 0.25 150,715‐‐3.06 0.59‐‐1.47 0.25 2,044,365     Natural wetland‐‐ ‐‐‐‐ ‐‐ ‐‐     Riparian buffer‐‐ ‐‐‐‐ ‐‐ ‐‐     Open water‐‐ ‐‐‐‐ ‐‐ ‐‐LAND TAKEN UP BY BMPs 1.08 0.15 45,048‐‐1.08 0.15*Jurisdictional land uses are not included in nutrient/flow calculations.Total Post‐Development Calculated Area (ft2):2,265,1742,265,1742,265,174Custom Lot Size (ac)     Forest     Managed perviousTotal Development Area Entered (ft2):LAND USE AREA CHECKLAND TAKEN UP BY BMPs     Lawn     Sidewalk/Patio     Roof     Natural wetland*     Riparian buffer*     Open water*INDUSTRIALTRANSPORTATIONCOMMERCIAL     Parking lot     Driveway     RoadwayPERVIOUSJURISDICTIONAL LANDS*Total Pre‐Development Calculated Area (ft2):InstructionsAdditional Guidelines     1. Select your physiographic/geologic region. (see map on 'instructions' page)Physiographic/Geologic Region:TP EMC(mg/L)Pre‐Development(ft2)     2. Enter the area of the entire development in square feet (ft2).     4. For each applicable land use, enter the total area of that land use that lies within the development under pre‐development conditions.     5. For each applicable land use, enter the total area of that land use that lies within the development under post‐development conditions, before BMP implementation.     ‐ Unless runoff flowing onto the development from offsite is routed separately around or through the site, the offsite catchment area draining in must be included in the acreage        values of the appropriate land use(s) and treated.     6. Ensure that the sum of pre‐ and post‐development areas entered equal the orginal development area. Post‐Development(ft2)Matt Jones, PEPost‐Development(ft2)RaleighTotal Development Area (ft2): 2,265,174Soil Hydrologic GroupBPrecipitation location:Age(yrs)TN EMC(mg/L)TN EMC(mg/L)TP EMC(mg/L)Pre‐Development(ft2)COLUMN 2 -- RESIDENTIAL LAND USESCOLUMN 1 -- NON-RESIDENTIAL LAND USESModel Prepared By:      7. Continue to "BMP Characteristics" tab.     3. Select the location that is most representative of the site's precipitation characteristics. (see map on 'instructions' page)FeEx FreightTriassic Basin     ‐ Residential areas may be entered by average lot size (column, part A), or may be separated into individual land uses (column 2, part B) ‐‐ do NOT list out individual land uses within an         area already described by lot size.      ‐ For non‐residential watersheds, indicate acreages of each land use type in Column 1 for both pre‐ and post‐development conditions.     ‐ For residential watersheds, complete the required information in Column 2 for both pre‐ and post‐development conditions.      ‐ If a given land use is not present in the given watershed, leave the cell blank or enter a zero.     ‐ Ensure that land use areas entered for both pre‐ and post‐development conditions match the total development area entered in cell O21.Development Name:Clear All ValuesReturn to InstructionsProceed to BMP CharacteristicsSkip to Development SummaryClear All ValuesReturnto InstructionsProceed to BMP CharacteristicsSkip to Development SummaryClear All ValuesReturn to InstructionsProceed to BMP CharacteristicsSkip to Development Summary
BMP Characteristics Ver2.0Instructions     1. Select the type of BMP for each catchment.     2. Enter the area of each land use type in the contributing drainage area for each BMP. 0.12     3. Continue to "Development Summary" tab.0.120.20Additional Guidelines0.26     ‐ This spreadsheet allows the development to be divided into as many as 6 smaller catchments. 0.15     ‐ BMPs 1, 2, and 3 for a given catchment are assumed to operate in series, with the outflow from 1 serving as the inflow to 2, etc. 0.150.39     ‐ Not all BMP or catchments must be utilized. Simply leave fields blank in the columns not needed.0.14     ‐ Leave cells blank or insert zeroes if a land use is not present in the area draining to the BMP.0.15     ‐ For water harvesting BMPs, be sure to enter the percent volume reduction that will be achieved by your system.  Volume detention (catch‐and‐release mechanisms) will not be considered ‐ only proven volume reductions are valid inputs. 0.11     ‐ The BMP undersizing option should only be used for existing development or retrofit sites.0.12*if treating commercial parking lot, TP effluent concentration = 0.16 mg/L     ‐ IMPORTANT: for the land area calculation checks to occur, you MUST press enter after entering a value for area to be treated by a BMP (not just click on the next cell).     ‐ See User's Manual for instructions on modeling oversized BMPs.BMP #1 BMP #2 BMP #3 BMP #1 BMP #2 BMP #3 BMP #1 BMP #2 BMP #3 BMP #1 BMP #2 BMP #3 BMP #1 BMP #2 BMP #3 BMP #1 BMP #2 BMP #3Type of BMP:Wet Detention PondWet Detention PondIf BMP is undersized, indicate the BMP's size relative to the design size required to capture the designated water quality depth (i.e. 0.75 = BMP is 75% of required design size):*For water harvesting BMP, enter percent volume reduction in decimal form.Catchment 1:‐‐ ‐‐ ‐‐no no no no no no no no no no no no no no noCatchment 2:no no no‐‐ ‐‐ ‐‐no no no no no no no no no no no noCatchment 3:no no no no no no‐‐ ‐‐ ‐‐no no no no no no no no noCatchment 4:no no no no no no no no no‐‐ ‐‐ ‐‐no no no no no noCatchment 5:no no no no no no no no no no no no‐‐ ‐‐ ‐‐no no noCatchment 6:no no no no no no no no no no no no no no no‐‐ ‐‐ ‐‐COMMERCIAL     Parking lot00     Roof00     Open/Landscaped00INDUSTRIAL     Parking lot 572,711 463,0251,035,736 1,035,736     Roof 38,083 57,53795,620 95,620     Open/Landscaped 151,181 258,766409,947 868,409TRANSPORTATION     High Density (interstate, main)00     Low Density (secondary, feeder)49,83649,836 49,836     Rural00     Sidewalk19,81019,810 19,810MISC. PERVIOUS     Managed pervious00     Unmanaged (pasture)00     Forest6,6156,615 150,715RESIDENTIAL     2‐ac lots (New)00     2‐ac lots (Built after 1995)00     2‐ac lots (Built before 1995)00     1‐ac lots (New)00     1‐ac lots (Built after 1995)00     1‐ac lots (Built before 1995)00     ½‐ac lots (New)00     ½‐ac lots (Built after 1995)00     ½‐ac lots (Built before 1995)00     ¼‐ac lots (New)00     ¼‐ac lots (Built after 1995)00     ¼‐ac lots (Built before 1995)00     ⅛‐ac lots (New)00     ⅛‐ac lots (Built aŌer 1995)00     ⅛‐ac lots (Built before 1995)00     Townhomes (New)00     Townhomes (Built after 1995)00     Townhomes (Built before 1995)00     Multi‐family (New)00     Multi‐family (Built after 1995)00     Multi‐family (Built before 1995)00     Custom Lot Size (New)00     Custom Lot Size (Built after 1995)00     Custom Lot Size (Built before 1995)00     Roadway00     Driveway00     Parking lot00     Roof00     Sidewalk00     Lawn00     Managed pervious00     Forest00LAND TAKEN UP BY BMP 23,037 22,01145,048 45,048TOTAL AREA TREATED BY BMP (ft2):785,012 0 0 877,600 0 0 0 0 0 0 0 0 0 0 0 0 0 0TOTAL AREA TREATED BY SERIES (ft2):Drainage Area Land UseArea treatedby BMP #2 that is not treated by BMP #1(ft2)Area treatedby BMP #3 that is not treated by BMPs #1 or #2(ft2)Area Treatedby BMP(ft2)‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐    CATCHMENT 1    ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐Total Land Use Area Treated By All BMPs(ft2)Allowable Total Land Use Area to be Treated Based on Post‐Dev. Areas(ft2)Does BMP accept the outflow from another Catchment? If so, indicate which one(s). (Land use areas entered below are in addition to the watershed areas treated by contributing catchment(s).)Area treatedby BMP #2 that is not treated by BMP #1(ft2)Area treatedby BMP #3 that is not treated by BMPs #1 or #2(ft2)Area Treatedby BMP(ft2)Area Treatedby BMP(ft2)Area treatedby BMP #2 that is not treated by BMP #1(ft2)Area treatedby BMP #3 that is not treated by BMPs #1 or #2(ft2)Area Treatedby BMP(ft2)Area treatedby BMP #2 that is not treated by BMP #1(ft2)Area treatedby BMP #3 that is not treated by BMPs #1 or #2(ft2)Area treatedby BMP #2 that is not treated by BMP #1(ft2)785,012000877,600‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐    CATCHMENT 2    ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐Area Treatedby BMP(ft2)‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐    CATCHMENT 3    ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐    CATCHMENT 6    ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐    CATCHMENT 5    ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐Area treatedby BMP #3 that is not treated by BMPs #1 or #2(ft2)Area treatedby BMP #3 that is not treated by BMPs #1 or #2(ft2)Area Treatedby BMP(ft2)Area treatedby BMP #2 that is not treated by BMP #1(ft2)‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐    CATCHMENT 4    ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐BMP DETAILSTP Effluent Concen. (mg/L)BMPTN Effluent Concen. (mg/L)Volume Reduction (%)0Grassed SwaleGreen RoofLevel Spreader, Filter StripPermeable Pavement*Sand Filter1.441.211.081.200%20%50%35%1.081.01Water HarvestingWet Detention Pond0%user definedDry Detention Pond0% 1.201.0015%0.95Bioretention without IWSBioretention with IWS     ‐ Volume reduction efficiencies for undersized BMPs are calculated based on a 1:1 ratio (a BMP that is 60% smaller than the required design size is assigned a removal efficiency equal to 60% of the standard efficiency       value). Effluent concentrations remain the same as full‐sized BMPs.0.92     ‐ If the outflow from an entire catchment (including outflow from selected BMPs) drains to another BMP, indicate this in the drop down menu below the BMP type and leave all cells for individual land uses blank. 5%5%Wetland15% 1.08Clear All ValuesReturn to InstructionsReturn to Watershed CharacteristicsProceed to Development Summary
3. Development SummaryWATERSHED SUMMARY Ver2.0Bioretention with IWS35% 0.95 0.12Bioretention without IWS15% 1.00 0.12Dry Detention Pond0% 1.20 0.20Grassed Swale0% 1.21 0.26Green Roof50% 1.08 0.15Level Spdr, Filter Strip20% 1.20 0.15Percent Difference Between:Sand Filter5% 0.92 0.14 *Negative percent difference values indicate a decrease in runoff volume, pollutant concentration or pollutant loading. Positive values indicate an increase. *if treating commercial parking lot, TP effluent concentration = 0.16 mg/LBMP SUMMARY Ver2.0BMP 1BMP 2BMP 3BMP 1BMP 2BMP 3BMP 1BMP 2BMP 3BMP 1BMP 2BMP 3BMP 1BMP 2BMP 3BMP 1BMP 2BMP 3Wet Detention Pond‐‐ ‐‐Wet Detention Pond‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐18.02‐‐ ‐‐20.15‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐2,311,560‐‐ ‐‐2,255,279‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐5%‐‐ ‐‐5%‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐1.42‐‐ ‐‐1.41‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐11.33‐‐ ‐‐9.83‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐0.367‐‐ ‐‐0.395‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐2.94‐‐ ‐‐2.76‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐7.99‐‐ ‐‐6.97‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐1.06‐‐ ‐‐0.95‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐ ‐‐0.390.150.110.12Permeable Pavement*Water HarvestingWet Detention PondWetland0%user defined5%15%1.441.081.011.08551%‐44%403%Pre‐Dev. &Post‐Dev. without BMPsPost‐Dev without BMPs &Post‐Dev with BMPs‐5%‐24%‐28%‐61%‐63%0%54%853%‐5%807%43%1267%Pre‐Development &Post‐Development with BMPs54%808%‐‐‐‐‐‐‐‐‐‐CATCHMENT 6‐‐ ‐‐‐‐‐‐‐‐‐‐ ‐‐‐‐ ‐‐‐‐ ‐‐‐‐ ‐‐‐‐0.9451.06164%‐‐‐‐29%0.1402.14FeEx FreightMatt Jones, PENovember 26, 2019Development:Prepared By:Date:Post‐Development w/ BMPs55.0%4,452,5061.085.750.150.79REGION:TOTAL DEVELOPMENT AREA (ft2):Triassic Basin29%Catchment Outflow Phosphorus EMC (mg/L)Percent Reduction in Nitrogen Load (%)CATCHMENT 1Total Nitrogen EMC (mg/L)Total Nitrogen Loading (lb/ac/yr)Total Phosphorus EMC(mg/L)Total Phosphorus Loading(lb/ac/yr)Total Nitrogen Loading (lb/ac/yr)Total Phosphorus EMC (mg/L)Total Phosphorus Loading (lb/ac/yr)Percent Impervious (%)Annual Runoff Volume (c.f.)Total Nitrogen EMC (mg/L)18%‐‐Total Inflow Phosphorus(lb/ac/yr)BMP OutflowNitrogen (lbs/ac/yr)Total Area Treated(ac)Percent Reduction in Phosphorus Load (%)6.97CATCHMENT 2CATCHMENT 31.05 1.05Catchment OutflowTotal Nitrogen (lb/ac/yr)7.99Percent Volume Reduced(%)BMP OutflowPhosphorus (lbs/ac/yr)Total Inflow Volume(c.f.)Total Inflow Nitrogen(lb/ac/yr)Inflow Phosphorus EMC(mg/L)Catchment Outflow Nitrogen EMC (mg/L)CATCHMENT 40.143‐‐‐‐Catchment OutflowTotal Phosphorus (lb/ac/yr)Volume Reduction (%)TN Effluent Concen. (mg/L)1.500.880.270.16TP Effluent Concen. (mg/L)BMP VOLUME REDUCTIONS/EFFLUENT CONCENTRATIONSInflow Nitrogen EMC(mg/L)CATCHMENT 5Percent Impervious(%)Annual Runoff Volume (c.f.)490,149Post‐Development Conditions55.0%4,672,3251.438.010.382,265,174Pre‐Development Conditions0.8%‐28%Return to Watershed CharacteristicsReturn to BMP CharacteristicsPrint SummaryReturn to Instructions

Maps

STIRRUP IRON CREEKTRIBUTARY CCHIN PAG
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TO DP#1
AREA=19.93 AC
DRAINAGE AREA
BOUNDARY (TYP)
PROPERTY LINE (TYP)
TC PATH
SHEET FLOW=75'
TC PATH
SHALLOW FLOW=843'
TC PATH
CHANNEL FLOW=430'
TEST TC PATH
DP#1
TEST TC PATH
TC PATH
SHEET FLOW=75'
TC PATH
SHALLOW FLOW=618'
DP#3
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AREA=19.68 AC
TO DP#3
AREA=6.19 AC
TC PATH
CHANNEL FLOW=642'
TC PATH
CHANNEL FLOW=648'
TC PATH
SHEET FLOW=75'
TC PATH
SHALLOW FLOW=802'
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CHANNEL FLOW=642'
©
DRAWN BY: CHECKED BY:
DATE
SCALE
PROJECT NO.
SHEET NO.
16 CONSULTANT PLACE, SUITE 201
DURHAM, NORTH CAROLINA 27707
P 919.490.4990 F 919.490.8953
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HORVATH
A S S O C I A T E S
5203 CHIN PAGE ROADDURHAM, NORTH CAROLINATJS
JULY 31, 2019
1915
<SITE PLAN>
PIN: 0748-91-73-3991
PID: 157676
FEDEX FREIGHTOCTOBER 1, 2019
PER 1ST CITY
REVIEW COMMENTS
JC1
PIN: 0748-91-06-3841
PID: 157785
MJ
AS NOTED
SW1
PRE-
DEVELOPMENT
DRAINAGE MAP
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TO WDB#2
AREA=23.26 AC
TO WDB#1
AREA=18.39 AC
TO DP#1
AREA=6.45 AC
DRAINAGE AREA
BOUNDARY (TYP)
PROPERTY LINE (TYP)
TC PATH
SHEET FLOW=75'
TC PATH
SHALLOW FLOW=341'
TC PATH
PIPE FLOW=186'
TC PATH
SHALLOW FLOW=187'
TC PATH
CHANNEL FLOW=112'
TO DP#3
AREA=2.42 AC
DP#1
DP#3
STREAM BUFFER (TYP)
TC PATH
SHEET FLOW=75'DP#2
COPYRIGHT 2020 THIS DOCUMENT AND THE DESIGN ARE THE PROPERTY OF HORVATH ASSOCIATES, P.A. ANY REPRODUCTION WITHOUT PRIOR WRITTEN CONSENT IS PROHIBITED©
DRAWN BY: CHECKED BY:
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1 6 C O N S U L T A N T P L A C E , S U I T E 2 0 1
D U R H A M , N O R T H C A R O L I N A 2 7 7 0 7
P 9 1 9 .4 9 0 .4 9 9 0 F 9 1 9 .4 9 0 .8 9 5 3
NORTH CAROLINA BOARD OF
EXAMINERS FOR ENGINEERS AND
SURVEYORS LICENSE NO.: C-0676
www.horvathassociates.com
HORVATH
A S S O C I A T E S
CIVIL ENGINEERING
LAND PLANNING
LANDSCAPE ARCHITECTURE
STORMWATER MANAGEMENT
TJS
November 27, 2019
1915
PUBLIC WORKS DEPARTMENT
APPROVED
CITY OF DURHAM
TRANSPORTATION
STORM WATER
ENGINEERING
CONSTRUCTION DRAWINGS
MARCH 6, 2020
1ST CD REVIEW AND
OWNER REVISIONS
MJ1
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N5203 CHIN PAGE ROADDURHAM, NORTH CAROLINAFEDEX FREIGHTPIN: 0748-91-73-3991
PID: 157676
PIN: 0748-91-06-3841
PID: 157785
TS
JC
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DRAINAGE MAP
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PROPERTY LINE (TYP)PROPERTY LINE (TYP)
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DRAINAGE AREA
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PRE-DEVELOPMENT LAND USE MAP
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N
DRIVEWAY
ROOF
LAWN
FOREST
TOTAL
8,201 SF
9,874 SF
202,734 SF
2,044,365 SF
2,265,174 SF
LAND USE AREAS
PARKING LOT
ROOF
OPEN/LANDSCAPED
ROADWAY
SIDEWALK
FOREST
LAND TAKEN UP BY BMPS
TOTAL
ENTIRE SITE
1,035,736 SF
95,620 SF
868,409 SF
49,836 SF
19,810 SF
150,715 SF
45,048 SF
2,265,174 SF
LAND USE AREAS
TO WDB#1
572,711 SF
38,083 SF
151,181 SF
0 SF
0 SF
0 SF
23,037 SF
785,012 SF
TO WDB#2
463,025 SF
57,537 SF
258,766 SF
49,836 SF
19,810 SF
6,615 SF
22,011 SF
877,600 SF
POST-DEVELOPMENT LAND USE MAP
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