20171409 Ver 3_08_2020-01-06 SW Impact Analysis_20200131

STORMWATER IMPACT ANALYSIS
LINDEN – LOT 22 / DRB-19010 / JANUARY 2020
NARRATIVE > DRB-19010
2905 Meridian Parkway, Durham, NC 27713 / 919. 361. 5000 creating experiences through experience
LINDEN – LOT 22
Stormwater Impact Analysis

GENERAL DESCRIPTION

The proposed residential development includes 11 single-family units which shall front Pricewood Lane (to
be renamed Linden Grove Lane with the first Phase of the Linden Subdivision Plat). Utilities will be served by
the infrastructure installed with the Linden Subdivision. There is a potential that the front portion of this site
will be carved out for a non-residential use along Olive Chapel Road. One stormwater control measure (SCM)
device will be used to serve the development.

The proposed development is located within the Cape Fear River basin with all stormwater runoff draining
into Reedy Branch (WS-IV; NSW), which is located in the Jordan Lake Watershed. Per the Town of Apex
regulations, stormwater management on this site shall meet the stormwater management performance
standards for development set forth in the Town Unified Development Ordinance (UDO). These are as
follows:

6.1.4 General

A) Development Review
All development within the Watershed Protection Overlay Districts shall comply with the watershed protection
standards of this Sec. 6.1 Watershed Protection Overlay Districts, and shall demonstrate compliance
concurrent with the submission for approval of a site plan (major or minor) (Sec. 2.3.6), master plan for
subdivision (Sec. 2.3.7(D)) or development plan for MEC-CZ, PUD-CZ or TND-CZ (Sec. 2.3.4), whichever occurs
first.

B) Compliance Prior to Approval of Certificate of Occupancy
Prior to approval of a final plat (with respect to a subdivision), issuance of a certificate of occupancy (with
respect to a site plan), or commencement of a use, in addition to meeting all other requirements of this
ordinance, all of the watershed protection standards required by Sec. 6.1 must be met, all required facilities
must be in place, be operational, and be approved by the Environmental Programs Manager.

C) Definitions
Certain words in this Section have meanings that are specific for the purposes of Sec. 6.1 Watershed Protection
Overlay Districts. Such words shall be defined in Article 12, Definitions.

6.1.7 High-Density Development Option
Developers wishing to exceed the built-upon limitations for low-density development within either the Primary
Watershed Protection District or the Secondary Watershed Protection District, as set forth in Sec. 6.1.6(B) Standards,
shall submit an appropriate development plan per Section 2.3 Development Approvals, which shall meet the
following standards:

NARRATIVE > DRB-19010
creating experiences through experience 2 of 4
A) Within the Primary Watershed Protection District

1) Built-Upon Area
Within the Primary Watershed Protection District, all development shall comply with the built-upon
area limitations for the underlying district found in Sec. 5.1 Table of Intensity and Dimensional
Standards.

2) Vegetated Conveyances
Stormwater runoff from the development may be transported from the development by vegetated
conveyances to the maximum extent practicable provided that the standards of Article 7.5.4(B)(4)
are met.

3) Structural BMPs
Within the Primary Watershed Protection District, structural BMPs shall be used to collect and hold
the runoff from the first one-inch of rainfall. These stormwater control structures shall meet the
requirements in Sec. 6.1.12 Structural BMPs. In addition, the post-development peak runoff rate shall
be limited to the pre-development peak runoff rate for the 1-year, 24-hour and the 10-year, 24-hour
storms. Detention volumes stored to reduce peak flows shall drain within seventy-two (72) hours to
allow for subsequent storms. A storm water impact statement shall be prepared by a qualified
professional engineer registered to practice in North Carolina and submitted with the initial
application for any development or activity that is not exempt from the requirements of Sec. 6.1
Watershed Protection Overlay Districts showing the impacts from the development site to the
confluence point downstream where the area of the proposed development is less than 10% of the
total drainage area (the “10% point”). The impact statement shall verify the effects of detention on
the downstream hydrographs to ensure that the peaks do not increase for a given storm. The impact
statement shall list the infrastructure (ditches, culverts, etc.) and indicate all the adverse effects and
impacts (to roads, culverts, businesses, homes, lawns, etc.) from the development to the 10% point. If
backwater from detention appears to be a problem, then the impact statement shall also consider
potential effects on upstream properties for the 100-year, 24-hour storm.

4) Riparian Buffers for Perennial Streams
Within the Primary Watershed Protection District, a vegetative buffer of not less than 100 feet shall
be maintained along each side of a perennial stream. All buffers shall meet the requirements in Sec.
6.1.11 Riparian Buffers.

5) Riparian Buffers for Intermittent Streams
Within the Primary Watershed Protection District, a vegetative buffer with a
width of not less than fifty (50) feet shall be maintained along each side of an
NARRATIVE > DRB-19010
creating experiences through experience 3 of 4
intermittent stream. All buffers shall meet the requirements in Sec. 6.1.11
Riparian Buffers.

This report contains calculations detailing the expected stormwater impacts as a result of the proposed
development, along with design calculations for the stormwater control measure that will be used to alleviate
those impacts and meet the requirements of the Town of Apex. Please refer to the appropriate sections of
this report for additional information.

CALCULATION METHODOLOGY

 Rainfall data for the Apex, NC region is from NOAA Atlas 14. This data describes a depth-duration-
frequency (DDF) table describing rainfall depth versus time for varying return periods in the Apex, NC
area. These rainfall depths are input into the meteorological model within PondPack for peak flow
rate calculations. Please reference the rainfall data section within this report for additional
information.

 The on-site topography used in the analysis is from a field survey performed by Bass, Nixon, &
Kennedy, Inc. The offsite topography used in the analysis is from Wake County GIS data.

 Using maps from the NRCS Web Soil Survey, the on- and off-site soils were determined to be from
hydrologic soil group (HSG) ‘D’ soils. Since the method chosen to compute both pre- and post-
development peak flow rates and runoff volumes is dependent upon the soil type, care was taken
when selecting the appropriate Soil Conservation Number (SCS CN).

Within the site boundary, an approximate proportion of each soil group was determined using NRCS
Soil Survey Maps. Once an approximate proportion was determined, a composite SCS CN was
computed for each cover condition.

 Land cover conditions for the pre-development condition were taken from site aerial. Land cover
conditions for the post-development condition were taken from the proposed development plan.
Please refer to the pre- and post-development watershed maps for additional information.

 The times of concentration are calculated using the SCS TR-55 Segmental Approach. The Tc flow
paths are divided into three segments: overland flow, concentrated flow, and channel flow. The
travel time is then computed for each segment, from which the overall time of concentration is
determined by taking the sum of each segmental time.

 The post-development times of concentration to the proposed stormwater management facility is
assumed to be 5 minutes. This provides a conservative estimate of facility size for design purposes.

 PondPack Version V8i, by Bentley Systems, Inc., was used in determining the pre- & post-development
peak flow rates for the 1- and 10-year storm events, as well as routing calculations for the proposed
stormwater control measure.

 For 100- year storm routing calculations, a “worst case condition” was modeled in order to insure the
proposed SCMs would safely pass the 100-year storm event. The assumption used in this scenario is
as follows:
o The starting water surface elevation in each facility, just prior to the 100-year storm event, is
at the secondary spillway elevation. This scenario could occur as a result of a clogged water
NARRATIVE > DRB-19010
creating experiences through experience 4 of 4
quality siphon or a rainfall event that lingers for several days. This could also occur as a result
of several rainfall events in a series, before the siphon has an opportunity to draw down the
storage pool.
o Approximately 1-foot of freeboard is provided between the peak elevation during the “worst-
case” scenario and the top of the dam for the proposed facilities.

 Impervious area is captured to the maximum extent practicable. The northern most half of the offsite
road is being captured and treated by our onsite SCM, in lieu of the three southern most lots on the
site. The impervious area related to the offsite road represents nearly twice as much as impervious
area treatment than that related to the three lots being bypassed onsite.

DISCUSSION OF RESULTS

PEAK RUNOFF CONTROL REQUIREMENTS

The proposed project will result in an increase in peak flow rates. To mitigate this impact, the proposed facilities have
been designed such that post-development peak flow rates resulting from on-site development are no greater than
pre-development levels in the 1- and 10-year storm events.

POLLUTANT AND NUTRIENT CONTROL REQUIREMENTS

The site is treated for water quality per 6.1.7 (A) (3) and 6.1.12, using a stormwater wetland to capture runoff from the
developed areas of the site and aforementioned portion of offsite road. The SCM meets the design requirements of
the Town of Apex and the North Carolina Department of Environmental Quality Minimum Design Criteria.

CONCLUSION

If the development on this tract is built as proposed within this report, then the requirements set forth in the Town of
Apex Unified Development Ordinance will be met with the proposed stormwater management facilities. However,
modifications to the proposed development may require that this analysis be revised. Some modifications that would
require this analysis to be revised include:

1. The proposed site impervious surface exceeds the amount accounted for in this report.
2. The post-development watershed breaks change significantly from those used to prepare this report.

The above modifications may result in the assumptions within this report becoming invalid. The computations within
this report will need to be revisited if any of the above conditions become apparent as development of the proposed
site moves forward.

LINDEN - LOT 22
DRB-19010
SUMMARY OF RESULTS N. BOHORQUEZ, EI
12/23/2019
RELEASE RATE MANAGEMENT RESULTS
Return Period Pre-Dev Post-Dev % Increase
[cfs][cfs][%]
1-Year 9.38 8.86 -6%
10-Year 20.35 19.04 -6%
POINT OF ANALYSIS #1
LINDEN - LOT 22
DRB-19010
SUMMARY OF RESULTS N. BOHORQUEZ, EI
12/23/2019
STORMWATER CONTROL MEASURE SUMMARY
Design Drainage Area =3.27 ac
Design Impervious Area =1.53 ac
% Impervious =46.8%
Top of Dam =320.00 ft
NWSE =315.00 ft
WQv Ponding Elevation = 316.21 ft
Required Surface Area at NWSE =4,469 sf
Provided Surface Area at NWSE =4,618 sf
WQv Orifice Diameter =1.00 in
WQv Orifice Invert Elevation =315.00 ft
Riser Size =4' x 4'
Riser Crest =319.00 ft
Number of Orifices =1
Orifice Bottom Elevation =316.00 ft
Orifice Dimensions 3' W x 1' H
Barrel Diameter =24 in
# of Barrels =1
Upstream Invert =314.50 ft
Downstream Invert =313.00 ft
Length =32.4 ft
Slope =0.0463 ft/ft
STORMWATER CONTROL MEASURE ROUTING RESULTS
Return Period Inflow Outflow Max. WSE Freeboard
[cfs][cfs][ft][ft]
1-Year 10.57 5.81 316.77 3.23
10-Year 18.88 12.34 317.30 2.70
25-Year 21.52 13.23 317.51 2.49
100-Year 25.04 14.39 317.78 2.22
100-Year - Worst Case***25.04 14.39 317.78 2.22
*** See narrative for explanation of the modeled worst case scenario
DRAINAGE AREAS
1 Is this a high density project?Yes
2 If so, number of drainage areas/SCMs 1
3
Is all/part of this project subject to previous rule
versions?No
FORMS LOADED
Entire Site 1
4 Type of SCM N/A
Stormwater
Wetland
5 Total BUA in project (sq ft)79095 sf 66585 sf
6
New BUA on subdivided lots (subject to permitting)
(sq ft)45870 sf 33360 sf
7
New BUA outside of subdivided lots (subject to
permitting) (sf)11981 sf 11981 sf
8 Offsite - total area (sq ft)35383 sf 35383 sf
9 Offsite BUA (sq ft)21244 sf 21244 sf
10 Breakdown of new BUA outside subdivided lots:
- Parking (sq ft)
- Sidewalk (sq ft)2831 sf 2831 sf
- Roof (sq ft)
- Roadway (sq ft)9150 sf 9150 sf
- Future (sq ft)

- Other, please specify in the comment box
below (sq ft)
11
New infiltrating permeable pavement on
subdivided lots (sq ft)
12
New infiltrating permeable pavement outside of
subdivided lots (sq ft)
13
Exisitng BUA that will remain (not subject to
permitting) (sq ft)21244 sf 21244 sf
14 Existing BUA that is already permitted (sq ft)
15 Existing BUA that will be removed (sq ft)
16 Percent BUA 34%29%
17 Design storm (inches)1 in
18 Design volume of SCM (cu ft)28773 cf
19 Calculation method for design volume SA/DA
20
DRAINAGE AREA INFORMATION
ADDITIONAL INFORMATION
Please see pre- and post- development hydrology sheets for further
information.
Please use this space to provide any additional information about the
drainage area(s):
STORMWATER WETLAND
1 Drainage area number 1 to SCM
2 Design volume of SCM (cu ft)28773 cf
3 Is the SCM sized to treat the SW from all surfaces at build-out?Yes
4 Is the SCM located away from contaminated soils?Yes
5 What are the side slopes of the SCM (H:V)?3:1
6
Does the SCM have retaining walls, gabion walls or other engineered side
slopes? Yes
7
Are the inlets, outlets, and receiving stream protected from erosion (10-year
storm)?Yes
8 Is there an overflow or bypass for inflow volume in excess of the design volume?Yes
9 What is the method for dewatering the SCM for maintenance?\Pump (preferred)
10 If applicable, will the SCM be cleaned out after construction?Yes
11 Does the maintenance access comply with General MDC (8)?Yes
12 Does the drainage easement comply with General MDC (9)?Yes
13
If the SCM is on a single family lot, does (will?) the plat comply with General MDC
(10)?No
14 Is there an O&M Agreement that complies with General MDC (11)?Yes
15 Is there an O&M Plan that complies with General MDC (12)?Yes
16 Does the SCM follow the device specific MDC?
17 Was the SCM designed by an NC licensed professional?
18 Are the inlet(s) and outlet located in a manner that avoids short-circuiting?Yes
19 Are berms or baffles provided to improve the flow path?No
20 Does the orifice drawdown from below the top surface of the permanent pool?Yes
21
Does the wetland minimize impacts to the receiving channel from the 1-yr, 24-hr
storm?Yes
22 Is a trash rack or other device provided to protect the outlet system?Yes
23 Elevation, peak attenuation above temporary pool (if applicable) (fmsl)320.00
24 Elevation, temporary pool (top of the temporary inundation zone) (fmsl)316.25
25 Elevation, permanent pool (top of the shallow water zone) (fmsl)315.00
26 Elevation, bottom of shallow water zone (fmsl)314.50
27
Elevation, bottom of forebay deep pool at deepest point (at forebay entrance)
(fmsl)311.67
28 Elevation, bottom of forebay deep pool at shallowest point (at forebay exit) (fmsl)314.50
29 Elevation, bottom of non-forebay deep pool at deepest point (fmsl)311.67
30 Area, total surface area of the SW wetland at temporary pool elev. (sq ft)4,618.00
31 Area, temporary inundation zone at temporary pool elev. (sq ft)1,697.00
32 Area, shallow water zone at temporary pool elev. (sq ft)1,874.00
33 Area, forebay at temporary pool elev. (sq ft)591.00
34 Area, non-forebay deep pool at temporary pool elev .(sq ft)456.00
35 Percent area provided, temporary inundation zone (should be 30-45%)37%
36 Percent area provided, shallow water zone (should be 35-45%)41%
37 Percent area provided, deep pool (forebay) (should be 10-15%)13%
38 Percent area provided, deep pool (non-forebay) (should be 5-15%)10%
39 Peak attenuation depth above temporary inundation zone (inches)45 in
40 Temporary inundation zone depth (temporary pool to permanent pool) (inches)15 in
41 Shallow water zone depth (permanent pool to bottom of wetland) (inches)6 in
42
Depth, forebay at entrance (permanent pool to bottom of forebay entrance)
(inches)40 in
43 Depth, forebay at exit (permanent pool to bottom of forebay exit) (inches)6 in
44 Depth, non-forebay deep pools (permanent pool to deep pool bottom) (inches)40 in
45 If there is an orifice, diameter (inches)1 in
46 If there is a weir, weir height (inches)12 in
47 If there is a weir, weir length (inches)36 in
48 Drawdown time for the temporary pool (days)2.27
49 Soil amendment depth (inches)12 in
50 Has a soil amendment specification been provided?Yes
51 Has a landscaping plan that meets SW Wetland MDC (12) been provided?Yes
52 Number of plants per 200 square feet (#) in the shallow water zone:
53
Does the temporary inundation zone planting comply with SW Wetland MDC
(14)?Yes
54 Are the dam structure and temporary fill slopes planted in non-clumping turfgrass?Yes
55 Will cattails be planted in the wetland?No
56
Please use this space to provide any additional information about the stormwater
wetland(s):
ADDITIONAL INFORMATION
Item #52 cannot be filled out due to data restrictions on the vell. However, the SCM is
planted at a ratio of 1 stem per 4 sf (i.e. 50 plants per 200 sf). The shallow water zone
has 470 stems proposed.
GENERAL MDC FROM 02H .1050
STORMWATER WETLAND MDC FROM 02H .1054
Elevations
Planting Zones
Soil and Plants
Depths and Outlet
Wetland 3 4:00 PM 1/6/2020
1 STORMWATER IMPACT STATEMENT
2 MISCELLANEOUS SITE INFORMATION
5 DESIGN OF STORMWATER CONTROL
MEASURE
3 PRE-DEVELOPMENT HYDROLOGIC
CALCULATIONS
4 POST-DEVELOPMENT HYDROLOGIC
CALCULATIONS
Linden – Lot 22
DRB-19010

STORMWATER IMPACT STATEMENT

Linden – Lot 22
Stormwater Impact Statement

Stormwater Impact Statement

Per Town of Apex UDO section 6.1.7 (A) (3), a downstream Stormwater Impact Statement (SIS) is
required documenting any adverse impacts to downstream areas that may result as a “by-
product” of on-site detention. The SIS is to extend from the site discharge point downstream to
a point at which the area of the proposed development is 10% or less of the overall total
drainage area to that point.

This site has one 10% analysis point which drains the entirety of the site. The drainage area
consists of 1744.66 acres, of which 4.46 acres is onsite, roughly 0.26% of the total area. It is
made up of mixed zoning districts, mainly single-family residential and is located on Reedy
Branch just upstream of Olive Chapel Road.

To determine each basin’s hydrograph and peak flows, current zoning was used to generate SCS
Curve Numbers in accordance with the underlying soils obtained from Web Soil Survey. Time of
concentrations for each basin was estimated using Kirpich’s equation and the resulting data
input into PondPack. Hydrographs generated for each basin was then overlaid with on-site pre-
development and post-development hydrographs to confirm no adverse impacts.

At the Point of Analysis, post-development flow rates were held below their pre-development
flow rates and was shown to not adversely impact the overall watershed hydrograph for the 1
Year 24 Hour and 10 Year 24 storms.

Please refer to the calculations in this section in the Stormwater Impact Analysis for additional
information.

LINDEN - LOT 22
DRB-16010
POST-DEVELOPMENT HYDROLOGY
Subbasin SIS
N. BOHORQUEZ, EI
8/30/2019
I. SCS CURVE NUMBERS
HSG Commercial Industrial Open Area ROW 1/8 acre 1/6 acre 1/3 acre 1 acre 2 acre
A 89 81 68 83 77 72 57 51 46
B 92 88 79 89 85 82 72 68 65
C 94 91 86 92 90 88 81 79 77
D 95 93 89 93 92 90 86 84 82
Assume:HSG 'A' =0.0%
HSG 'B' =15.5%
HSG 'C' =0.4%
HSG 'D' =84.1%
Cover Condition SCS CN
Commercial 95
Industrial 92
Open Area 87
ROW 92
1/8 acre 91
1/6 acre 89
1/3 acre 84
1 acre 82
2 acre 79
II. POST-DEVELOPMENT
C. Watershed Breakdown
Contributing Area SCS CN Area [acres]
Planned Unit Development 84 472.05
Neighborhood Business 95 5.56
Conservation Buffer 87 10.07
High Density Multi-family 91 33.52
Light Industrial 92 13.29
Planned Commercial 95 59.62
Tech/Flex 95 19.43
Residential Agricultural 79 2.61
Rural Residential 82 399.85
Medium Density Residential 89 498.70
Highway Residential District 79 1.83
Residential 40W District 82 0.91
Office and Institutional 95 6.26
ROW 92 220.96
Total area =1744.66 acres
75,997,390 sq. ft.
Composite SCS CN =86
III. Time of Concentration Information
Time of concentration is calculated using the Kirpich Equation.
Length =18,316 ft
Top Elev =438 ft
Bot Elev =256 ft
Height =182 ft
Slope =0.0099 ft/ft
Surface Roughness Factor =1.00
Segment Time =88.21 minutes
Time of Concentration =88.21 minutes
SCS Lag Time =52.93 minutes (SCS Lag = 0.6* Tc)
Time Increment =15.35 minutes (= 0.29*SCS Lag)
-
Residential
Comments
-
-
-
-
-
Assume good condition
-
-
Assume good condition
-
-
-
-
Assume good condition
-
-
Assume good condition
-
Comments
Assume good condition
-
Assume good condition
-
POINT OF ANALYSIS #11 YEAR - 24 HOUR STORMX:\Projects\DRB\DRB-19010\Storm\Site Plan - Construction Drawings\SIS\CRS16000-SIS-EXHIBITS.dwg, 8/30/2019 1:29:42 PM, Bohorquez, NatalieLINDEN - LOT 22MASTER SUBDIVISIONAPEX, NCThe John R. McAdams Company, Inc.2905 Meridian ParkwayDurham, NC 27713phone [phone]fax [phone]license number: C-0293, C-187www.mcadamsco.comPROJECT NO.DRB-19010FILENAMEDRB19010-SISCHECKED BYDCWDRAWN BYNBSCALENTSDATE08.30. 2019PLAN INFORMATION
POINT OF ANALYSIS #110 YEAR - 24 HOUR STORMX:\Projects\DRB\DRB-19010\Storm\Site Plan - Construction Drawings\SIS\CRS16000-SIS-EXHIBITS.dwg, 8/30/2019 1:31:02 PM, Bohorquez, NatalieLINDEN - LOT 22MASTER SUBDIVISIONAPEX, NCThe John R. McAdams Company, Inc.2905 Meridian ParkwayDurham, NC 27713phone [phone]fax [phone]license number: C-0293, C-187www.mcadamsco.comPROJECT NO.DRB-19010FILENAMEDRB19010-SISCHECKED BYDCWDRAWN BYNBSCALENTSDATE08.30. 2019PLAN INFORMATION
GRAPHIC SCALE
0 100 200 400
1 inch = 200 ft.
CLIENT
REVISIONS
PROJECT NO.DRB-19010
FILENAME
CHECKED BY
DRAWN BY
SCALE
DATE 09. 03. 2019
N0.DATE
X:\Projects\DRB\DRB-19010\Storm\Site Plan - Construction Drawings\SIS\DRB19010-SIS.dwg, 8/30/2019 1:50:44 PM, Bohorquez, NatalieThe John R. McAdams Company, Inc.
2905 Meridian Parkway
Durham, NC 27713
phone [phone]
fax [phone]
license number: C-0293
www.mcadamsco.com
LINDEN - LOT 22MASTER SUBDIVISION PLANAPEX, NORTH CAROLINASHEET
PLAN INFORMATION
FIELDING HOMES
3000 RDU CENTER DRIVE, SUITE 202
MORRISVILLE, NORTH CAROLINA 27560
PHONE: [phone]
PRELIMINARY DRAWING - NOT RELEASED FOR CONSTRUCTION
DRB19010-SIS
DCW
NB
1" = 200'
SIS
Linden – Lot 22
DRB-19010

STORMWATER CONTROL MEASURE
DESIGN CALCULATIONS

LINDEN - LOT 22
DRB-19010
STORMWATER CONTROL MEASURE
SSFxn Above NP
L. KABRICH, EI
12/23/2019
STAGE-STORAGE FUNCTION - ABOVE NORMAL POOL
Average Incremental Accumulated Estimated
Contour Contour Contour Contour Stage
Contour Stage Area Area Volume Volume w/ S-S Fxn
(feet)(feet)(SF)(SF)(CF)(CF)(feet)
315.00 0.00 2,921
316.25 1.25 4,618 3770 4712 4712 1.26
318.00 3.00 6,267 5443 9524 14236 2.94
320.00 5.00 8,270 7269 14537 28773 5.06
1.300610629 8.158749223
3493.813888
KS =3494
b =1.301
y = 3493.8x1.3006
R² = 0.9995
0
5000
10000
15000
20000
25000
30000
35000
0.00 1.00 2.00 3.00 4.00 5.00 6.00Storage (CF)Stage (feet)
Storage vs. Stage
LINDEN - LOT 22
DRB-19010
STORMWATER CONTROL MEASURE
SSFxn Below NP
L. KABRICH, EI
12/23/2019
WETLAND ZONE TABULATION
Per NCDEQ "Stormwater Design Manual" Minimum Design Criteria
Deep Pool - Forebay 6 to 40 21 to 55 10 - 15%
Deep Pool - Non Forebay 6 to 40 21 to 55 5 - 15%
Shallow Water 0 to 6 15 to 21 35 - 45%
Shallow Land -to -0 to 15 30 - 45%
Permanent Pool Elevation =
Temporary Pool Elevation =
Wetland Surface Area at Temporary Pool =
Deep Pool - Forebay 314.50 to 311.67 12.8%
Deep Pool - Non Forebay 314.50 to 311.67 9.9%
Shallow Water 315.00 to 314.50 40.6%
Shallow Land 316.25 to 315.00 36.7%
Zone
591
1,874
Zone Depth at Temp Pool
(inches)
1,697
456
316.25
Portion of Wetland
Surface Area
315.00
4,618
Depth at Normal Pool
(inches)
Elevation (ft)Measured Area
(sf)
Portion of Wetland
Surface Area
LINDEN - LOT 22
DRB-19010
STORMWATER CONTROL MEASURE
WQV Calculation - MDC
L. KABRICH, EI
12/23/2019
DETERMINATION OF WATER QUALITY VOLUME
WQ V = (P)(R V )(A)/12
where,
WQV = water quality volume (in acre-ft)
RV = 0.05+0.009(I) where I is percent impervious cover
A = area in acres
P = rainfall (in inches)
Input data:
Total area, A =3.27 acres
Impervious area =1.53 acres
Percent impervious cover, I =46.8 %
Rainfall, P =1.00 inches
Calculated values:
RV =0.47
WQV =0.13 acre-ft
=5587 cf.
SURFACE AREA CALCULATION
Per NCDEQ "Stormwater Design Manual" Wetland MDC 3. Surface Area
WQV =5587 cf.
Max. ponding depth =15 inches
Min. surface area (at temp. pool) =4469 sf.
Surface area provided at temp. pool =4618 sf.
Approximate ponding depth =1.21 feet
=14.52 inches
LINDEN - LOT 22
DRB-19010
STORMWATER CONTROL MEASURE
WQV Drawdown Calculation
L. KABRICH, EI
12/23/2019
DRAWDOWN ORIFICE DESIGN
D orifice =1 inch
# orifices =1
Ks =3494
b =1.301
Cd orifice =0.60
Normal Pool Elevation =315.00 feet
Volume @ Normal Pool =0 cf
Orifice Invert =315.00 feet
WSEL @ 1" Runoff Volume =316.21 feet
WSEL Vol. Stored Orifice Flow Avg. Flow Incr. Vol.Incr. Time
(feet)(cf)(cfs)(cfs)(cf)(sec)
316.21 4476 0.028
316.11 4017 0.027 0.028 459 16542
316.02 3570 0.026 0.027 447 16860
315.92 3135 0.025 0.025 434 17219
315.82 2714 0.023 0.024 421 17628
315.73 2308 0.022 0.022 406 18104
315.63 1917 0.020 0.021 390 18668
315.53 1545 0.018 0.019 373 19358
315.44 1192 0.016 0.017 353 20234
315.34 862 0.014 0.015 330 21415
315.24 559 0.012 0.013 303 23173
Drawdown Time =2.19 days
By comparison, if calculated by the average head over the orifice
(assuming average head is one-third the total depth), the result would be:
Average driving head on orifice = 0.389 feet
Orifice composite loss coefficient = 0.600
Cross-sectional area of siphon = 0.005 sf
Q =0.0164 cfs
Drawdown Time = Volume / Flowrate / 86400 (sec/day)
Drawdown Time = 3.16 days
LINDEN - LOT 22
DRB-19010
STORMWATER CONTROL MEASURE
Temp Pool Drawdown Calculation
L. KABRICH, EI
12/23/2019
DRAWDOWN ORIFICE DESIGN
D orifice =1 inch
# orifices =1
Ks =3494
b =1.301
Cd orifice =0.60
Normal Pool Elevation =315.00 feet
Volume @ Normal Pool =0 cf
Orifice Invert =315.00 feet
Temp Pool Elevation Volume =316.25 feet
WSEL Vol. Stored Orifice Flow Avg. Flow Incr. Vol.Incr. Time
(feet)(cf)(cfs)(cfs)(cf)(sec)
316.25 4670 0.029
316.15 4188 0.028 0.028 483 17111
316.05 3717 0.026 0.027 470 17442
315.95 3261 0.025 0.026 457 17815
315.85 2818 0.024 0.024 442 18242
315.75 2391 0.022 0.023 427 18738
315.65 1981 0.020 0.021 410 19329
315.55 1590 0.019 0.020 391 20051
315.45 1220 0.017 0.018 370 20972
315.34 875 0.014 0.016 346 22221
315.24 559 0.012 0.013 316 24099
Drawdown Time =2.27 days
By comparison, if calculated by the average head over the orifice
(assuming average head is one-third the total depth), the result would be:
Average driving head on orifice = 0.403 feet
Orifice composite loss coefficient = 0.600
Cross-sectional area of siphon = 0.005 sf
Q =0.0167 cfs
Drawdown Time = Volume / Flowrate / 86400 (sec/day)
Drawdown Time = 3.24 days
Storm Event: 1-yrLabel: SCM
Return Event: 1 yearsSubsection: Elevation-Area Volume Curve
Volume (Total)
(ft³)
Volume
(ft³)
A1+A2+sqr
(A1*A2)
(ft²)
Area
(ft²)
Planimeter
(ft²)
Elevation
(ft)
0002,9210.0315.00
4,6724,67211,2124,6180.0316.25
14,1599,48816,2656,2670.0318.00
28,65014,49121,7368,2700.0320.00
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 1-yrLabel: SCM
Return Event: 1 yearsSubsection: Outlet Input Data
Requested Pond Water Surface Elevations
ft315.00Minimum (Headwater)
ft0.10Increment (Headwater)
ft321.00Maximum (Headwater)
Outlet Connectivity
E2
(ft)
E1
(ft)
OutfallDirectionOutlet IDStructure Type
317.00316.00CulvertForwardWeirRectangular Weir
320.00317.00CulvertForwardOrificeOrifice-Area
320.00319.00CulvertForwardRiserInlet Box
320.00315.00CulvertForwardWQ OrificeOrifice-Circular
320.00314.50TWForwardCulvertCulvert-Circular
(N/A)(N/A)TailwaterTailwater Settings
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 1-yrLabel: SCM
Return Event: 1 yearsSubsection: Outlet Input Data
Structure ID: Culvert
Structure Type: Culvert-Circular
1Number of Barrels
in24.0Diameter
ft32.40Length
ft32.43Length (Computed Barrel)
ft/ft0.046Slope (Computed)
Outlet Control Data
0.013Manning's n
0.5Ke
0.0Kb
0.0Kr
ft0.00Convergence Tolerance
Inlet Control Data
Form 1Equation Form
0.0098K
2.0000M
0.0398C
0.6700Y
0.0T1 ratio (HW/D)
1.3T2 ratio (HW/D)
-0.5Slope Correction Factor
Use unsubmerged inlet control 0 equation below T1 elevation.
Use submerged inlet control 0 equation above T2 elevation
In transition zone between unsubmerged and submerged inlet
control,
interpolate between flows at T1 & T2...
ft314.50T1 Elevation ft³/s15.55T1 Flow
ft317.07T2 Elevation ft³/s17.77T2 Flow
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 1-yrLabel: SCM
Return Event: 1 yearsSubsection: Outlet Input Data
Structure ID: Riser
Structure Type: Inlet Box
1Number of Openings
ft319.00Elevation
ft²16.0Orifice Area
0.6Orifice Coefficient
ft16.00Weir Length
(ft^0.5)/s3.00Weir Coefficient
1.0K Reverse
0.0Manning's n
0.0Kev, Charged Riser
FalseWeir Submergence
FalseOrifice H to crest
Structure ID: WQ Orifice
Structure Type: Orifice-Circular
1Number of Openings
ft315.00Elevation
in1.0Orifice Diameter
0.6Orifice Coefficient
Structure ID: Orifice
Structure Type: Orifice-Area
1Number of Openings
ft316.00Elevation
ft²3.0Orifice Area
ft317.00Top Elevation
ft316.50Datum Elevation
0.6Orifice Coefficient
Structure ID: Weir
Structure Type: Rectangular Weir
1Number of Openings
ft316.00Elevation
ft3.00Weir Length
(ft^0.5)/s3.00Weir Coefficient
Structure ID: TW
Structure Type: TW Setup, DS Channel
Free OutfallTailwater Type
Convergence Tolerances
30Maximum Iterations
ft0.01Tailwater Tolerance
(Minimum)
ft0.50Tailwater Tolerance
(Maximum)
ft0.01Headwater Tolerance
(Minimum)
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 1-yrLabel: SCM
Return Event: 1 yearsSubsection: Outlet Input Data
Convergence Tolerances
ft0.50Headwater Tolerance
(Maximum)
ft³/s0.001Flow Tolerance (Minimum)
ft³/s10.000Flow Tolerance (Maximum)
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 1-yrLabel: SCM
Return Event: 1 yearsSubsection: Composite Rating Curve
Composite Outflow Summary
Contributing StructuresConvergence Error
(ft)
Tailwater Elevation
(ft)
Flow
(ft³/s)
Water Surface
Elevation
(ft)
(no Q:
Weir,Orifice,Riser,WQ
Orifice,Culvert)
0.00(N/A)0.00315.00
WQ Orifice,Culvert (no
Q: Weir,Orifice,Riser)
0.00(N/A)0.01315.10
WQ Orifice,Culvert (no
Q: Weir,Orifice,Riser)
0.00(N/A)0.01315.20
WQ Orifice,Culvert (no
Q: Weir,Orifice,Riser)
0.00(N/A)0.01315.30
WQ Orifice,Culvert (no
Q: Weir,Orifice,Riser)
0.00(N/A)0.02315.40
WQ Orifice,Culvert (no
Q: Weir,Orifice,Riser)
0.00(N/A)0.02315.50
WQ Orifice,Culvert (no
Q: Weir,Orifice,Riser)
0.00(N/A)0.02315.60
WQ Orifice,Culvert (no
Q: Weir,Orifice,Riser)
0.00(N/A)0.02315.70
WQ Orifice,Culvert (no
Q: Weir,Orifice,Riser)
0.00(N/A)0.02315.80
WQ Orifice,Culvert (no
Q: Weir,Orifice,Riser)
0.00(N/A)0.02315.90
WQ Orifice,Culvert (no
Q: Weir,Orifice,Riser)
0.00(N/A)0.03316.00
Weir,WQ Orifice,Culvert
(no Q: Orifice,Riser)
0.00(N/A)0.31316.10
Weir,WQ Orifice,Culvert
(no Q: Orifice,Riser)
0.00(N/A)0.82316.20
Weir,WQ Orifice,Culvert
(no Q: Orifice,Riser)
0.00(N/A)1.48316.30
Weir,WQ Orifice,Culvert
(no Q: Orifice,Riser)
0.00(N/A)2.24316.40
Weir,WQ Orifice,Culvert
(no Q: Orifice,Riser)
0.00(N/A)3.10316.50
Weir,WQ Orifice,Culvert
(no Q: Orifice,Riser)
0.00(N/A)4.04316.60
Weir,WQ Orifice,Culvert
(no Q: Orifice,Riser)
0.00(N/A)5.05316.70
Weir,WQ Orifice,Culvert
(no Q: Orifice,Riser)
0.00(N/A)6.12316.80
Weir,WQ Orifice,Culvert
(no Q: Orifice,Riser)
0.00(N/A)7.24316.90
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)10.22317.00
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)11.21317.10
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)11.87317.20
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)12.32317.30
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)12.77317.40
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)13.21317.50
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 1-yrLabel: SCM
Return Event: 1 yearsSubsection: Composite Rating Curve
Composite Outflow Summary
Contributing StructuresConvergence Error
(ft)
Tailwater Elevation
(ft)
Flow
(ft³/s)
Water Surface
Elevation
(ft)
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)13.63317.60
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)14.07317.70
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)14.47317.80
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)14.88317.90
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)15.29318.00
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)15.68318.10
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)16.08318.20
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)16.45318.30
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)16.83318.40
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)17.22318.50
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)17.58318.60
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)17.94318.70
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)18.30318.80
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)18.65318.90
Orifice,WQ Orifice,Culvert
(no Q: Weir,Riser)
0.00(N/A)19.01319.00
Orifice,Riser,WQ
Orifice,Culvert (no Q:
Weir)
0.00(N/A)20.15319.10
Orifice,Riser,WQ
Orifice,Culvert (no Q:
Weir)
0.00(N/A)21.87319.20
Orifice,Riser,WQ
Orifice,Culvert (no Q:
Weir)
0.00(N/A)23.84319.30
Orifice,Riser,WQ
Orifice,Culvert (no Q:
Weir)
0.00(N/A)25.86319.40
Orifice,Riser,WQ
Orifice,Culvert (no Q:
Weir)
0.00(N/A)27.86319.50
Orifice,Riser,WQ
Orifice,Culvert (no Q:
Weir)
0.00(N/A)29.66319.60
Orifice,Riser,WQ
Orifice,Culvert (no Q:
Weir)
0.00(N/A)30.96319.70
Riser,Culvert (no Q:
Weir,Orifice,WQ Orifice)
0.00(N/A)31.52319.80
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 1-yrLabel: SCM
Return Event: 1 yearsSubsection: Composite Rating Curve
Composite Outflow Summary
Contributing StructuresConvergence Error
(ft)
Tailwater Elevation
(ft)
Flow
(ft³/s)
Water Surface
Elevation
(ft)
Riser,Culvert (no Q:
Weir,Orifice,WQ Orifice)
0.00(N/A)31.91319.90
Riser,Culvert (no Q:
Weir,Orifice,WQ Orifice)
0.00(N/A)32.29320.00
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 1-yrLabel: SCM (IN)
Return Event: 1 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft315.00Elevation (Water Surface,
Initial)
ft³0Volume (Initial)
ft³/s0.00Flow (Initial Outlet)
ft³/s0.00Flow (Initial Infiltration)
ft³/s0.00Flow (Initial, Total)
min1.00Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s10.57Flow (Peak In) min721.00Time to Peak (Flow, In)
ft³/s5.81Flow (Peak Outlet) min727.00Time to Peak (Flow, Outlet)
ft316.77Elevation (Water Surface,
Peak)
ft³7,197Volume (Peak)
Mass Balance (ft³)
ft³0Volume (Initial)
ft³21,213Volume (Total Inflow)
ft³0Volume (Total Infiltration)
ft³17,526Volume (Total Outlet
Outflow)
ft³3,679Volume (Retained)
ft³-8Volume (Unrouted)
%0.0Error (Mass Balance)
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 10-yrLabel: SCM (IN)
Return Event: 10 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft315.00Elevation (Water Surface,
Initial)
ft³0Volume (Initial)
ft³/s0.00Flow (Initial Outlet)
ft³/s0.00Flow (Initial Infiltration)
ft³/s0.00Flow (Initial, Total)
min1.00Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s18.88Flow (Peak In) min721.00Time to Peak (Flow, In)
ft³/s12.34Flow (Peak Outlet) min726.00Time to Peak (Flow, Outlet)
ft317.30Elevation (Water Surface,
Peak)
ft³10,035Volume (Peak)
Mass Balance (ft³)
ft³0Volume (Initial)
ft³45,232Volume (Total Inflow)
ft³0Volume (Total Infiltration)
ft³41,398Volume (Total Outlet
Outflow)
ft³3,821Volume (Retained)
ft³-14Volume (Unrouted)
%0.0Error (Mass Balance)
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 25-yrLabel: SCM (IN)
Return Event: 25 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft315.00Elevation (Water Surface,
Initial)
ft³0Volume (Initial)
ft³/s0.00Flow (Initial Outlet)
ft³/s0.00Flow (Initial Infiltration)
ft³/s0.00Flow (Initial, Total)
min1.00Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s21.52Flow (Peak In) min721.00Time to Peak (Flow, In)
ft³/s13.23Flow (Peak Outlet) min726.00Time to Peak (Flow, Outlet)
ft317.51Elevation (Water Surface,
Peak)
ft³11,185Volume (Peak)
Mass Balance (ft³)
ft³0Volume (Initial)
ft³56,077Volume (Total Inflow)
ft³0Volume (Total Infiltration)
ft³52,191Volume (Total Outlet
Outflow)
ft³3,871Volume (Retained)
ft³-15Volume (Unrouted)
%0.0Error (Mass Balance)
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 100-yrLabel: SCM (IN)
Return Event: 100 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft315.00Elevation (Water Surface,
Initial)
ft³0Volume (Initial)
ft³/s0.00Flow (Initial Outlet)
ft³/s0.00Flow (Initial Infiltration)
ft³/s0.00Flow (Initial, Total)
min1.00Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s25.04Flow (Peak In) min721.00Time to Peak (Flow, In)
ft³/s14.39Flow (Peak Outlet) min727.00Time to Peak (Flow, Outlet)
ft317.78Elevation (Water Surface,
Peak)
ft³12,802Volume (Peak)
Mass Balance (ft³)
ft³0Volume (Initial)
ft³73,507Volume (Total Inflow)
ft³0Volume (Total Infiltration)
ft³69,588Volume (Total Outlet
Outflow)
ft³3,903Volume (Retained)
ft³-16Volume (Unrouted)
%0.0Error (Mass Balance)
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 100-yrLabel: SCM WC
Return Event: 100 yearsSubsection: Outlet Input Data
Requested Pond Water Surface Elevations
ft314.00Minimum (Headwater)
ft0.10Increment (Headwater)
ft320.00Maximum (Headwater)
Outlet Connectivity
E2
(ft)
E1
(ft)
OutfallDirectionOutlet IDStructure Type
320.00317.00CulvertForwardOrificeOrifice-Area
320.00319.00CulvertForwardRiserInlet Box
317.00316.00CulvertForwardWeirRectangular Weir
320.00314.50TWForwardCulvertCulvert-Circular
(N/A)(N/A)TailwaterTailwater Settings
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 100-yrLabel: SCM WC
Return Event: 100 yearsSubsection: Outlet Input Data
Structure ID: Culvert
Structure Type: Culvert-Circular
1Number of Barrels
in24.0Diameter
ft32.40Length
ft32.43Length (Computed Barrel)
ft/ft0.046Slope (Computed)
Outlet Control Data
0.013Manning's n
0.5Ke
0.0Kb
0.0Kr
ft0.00Convergence Tolerance
Inlet Control Data
Form 1Equation Form
0.0098K
2.0000M
0.0398C
0.6700Y
1.1T1 ratio (HW/D)
1.3T2 ratio (HW/D)
-0.5Slope Correction Factor
Use unsubmerged inlet control 0 equation below T1 elevation.
Use submerged inlet control 0 equation above T2 elevation
In transition zone between unsubmerged and submerged inlet
control,
interpolate between flows at T1 & T2...
ft316.77T1 Elevation ft³/s15.55T1 Flow
ft317.07T2 Elevation ft³/s17.77T2 Flow
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 100-yrLabel: SCM WC
Return Event: 100 yearsSubsection: Outlet Input Data
Structure ID: Riser
Structure Type: Inlet Box
1Number of Openings
ft319.00Elevation
ft²16.0Orifice Area
0.6Orifice Coefficient
ft16.00Weir Length
(ft^0.5)/s3.00Weir Coefficient
1.0K Reverse
0.0Manning's n
0.0Kev, Charged Riser
FalseWeir Submergence
FalseOrifice H to crest
Structure ID: Orifice
Structure Type: Orifice-Area
1Number of Openings
ft316.00Elevation
ft²3.0Orifice Area
ft317.00Top Elevation
ft316.50Datum Elevation
0.6Orifice Coefficient
Structure ID: Weir
Structure Type: Rectangular Weir
1Number of Openings
ft316.00Elevation
ft3.00Weir Length
(ft^0.5)/s3.00Weir Coefficient
Structure ID: TW
Structure Type: TW Setup, DS Channel
Free OutfallTailwater Type
Convergence Tolerances
30Maximum Iterations
ft0.01Tailwater Tolerance
(Minimum)
ft0.50Tailwater Tolerance
(Maximum)
ft0.01Headwater Tolerance
(Minimum)
ft0.50Headwater Tolerance
(Maximum)
ft³/s0.001Flow Tolerance (Minimum)
ft³/s10.000Flow Tolerance (Maximum)
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 100-yrLabel: SCM WC
Return Event: 100 yearsSubsection: Composite Rating Curve
Composite Outflow Summary
Contributing StructuresConvergence Error
(ft)
Tailwater Elevation
(ft)
Flow
(ft³/s)
Water Surface
Elevation
(ft)
(no Q:
Orifice,Riser,Weir,Culvert)
0.00(N/A)0.00315.00
(no Q:
Orifice,Riser,Weir,Culvert)
0.00(N/A)0.00315.10
(no Q:
Orifice,Riser,Weir,Culvert)
0.00(N/A)0.00315.20
(no Q:
Orifice,Riser,Weir,Culvert)
0.00(N/A)0.00315.30
(no Q:
Orifice,Riser,Weir,Culvert)
0.00(N/A)0.00315.40
(no Q:
Orifice,Riser,Weir,Culvert)
0.00(N/A)0.00315.50
(no Q:
Orifice,Riser,Weir,Culvert)
0.00(N/A)0.00315.60
(no Q:
Orifice,Riser,Weir,Culvert)
0.00(N/A)0.00315.70
(no Q:
Orifice,Riser,Weir,Culvert)
0.00(N/A)0.00315.80
(no Q:
Orifice,Riser,Weir,Culvert)
0.00(N/A)0.00315.90
(no Q:
Orifice,Riser,Weir,Culvert)
0.00(N/A)0.00316.00
Weir,Culvert (no Q:
Orifice,Riser)
0.00(N/A)0.28316.10
Weir,Culvert (no Q:
Orifice,Riser)
0.00(N/A)0.79316.20
Weir,Culvert (no Q:
Orifice,Riser)
0.00(N/A)1.45316.30
Weir,Culvert (no Q:
Orifice,Riser)
0.00(N/A)2.22316.40
Weir,Culvert (no Q:
Orifice,Riser)
0.00(N/A)3.08316.50
Weir,Culvert (no Q:
Orifice,Riser)
0.00(N/A)4.02316.60
Weir,Culvert (no Q:
Orifice,Riser)
0.00(N/A)5.03316.70
Weir,Culvert (no Q:
Orifice,Riser)
0.00(N/A)6.10316.80
Weir,Culvert (no Q:
Orifice,Riser)
0.00(N/A)7.21316.90
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)10.21317.00
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)11.19317.10
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)11.86317.20
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)12.31317.30
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)12.76317.40
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)13.19317.50
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)13.62317.60
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 100-yrLabel: SCM WC
Return Event: 100 yearsSubsection: Composite Rating Curve
Composite Outflow Summary
Contributing StructuresConvergence Error
(ft)
Tailwater Elevation
(ft)
Flow
(ft³/s)
Water Surface
Elevation
(ft)
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)14.06317.70
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)14.47317.80
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)14.87317.90
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)15.28318.00
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)15.66318.10
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)16.05318.20
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)16.45318.30
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)16.82318.40
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)17.21318.50
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)17.56318.60
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)17.94318.70
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)18.28318.80
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)18.65318.90
Orifice,Culvert (no Q:
Riser,Weir)
0.00(N/A)19.00319.00
Orifice,Riser,Culvert (no
Q: Weir)
0.00(N/A)20.13319.10
Orifice,Riser,Culvert (no
Q: Weir)
0.00(N/A)21.85319.20
Orifice,Riser,Culvert (no
Q: Weir)
0.00(N/A)23.83319.30
Orifice,Riser,Culvert (no
Q: Weir)
0.00(N/A)25.85319.40
Orifice,Riser,Culvert (no
Q: Weir)
0.00(N/A)27.86319.50
Orifice,Riser,Culvert (no
Q: Weir)
0.00(N/A)29.66319.60
Orifice,Riser,Culvert (no
Q: Weir)
0.00(N/A)30.96319.70
Riser,Culvert (no Q:
Orifice,Weir)
0.00(N/A)31.52319.80
Riser,Culvert (no Q:
Orifice,Weir)
0.00(N/A)31.91319.90
Riser,Culvert (no Q:
Orifice,Weir)
0.00(N/A)32.29320.00
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
Storm Event: 100-yrLabel: SCM (IN)
Return Event: 100 yearsSubsection: Level Pool Pond Routing Summary
Infiltration
No InfiltrationInfiltration Method
(Computed)
Initial Conditions
ft315.50Elevation (Water Surface,
Initial)
ft³1,616Volume (Initial)
ft³/s0.00Flow (Initial Outlet)
ft³/s0.00Flow (Initial Infiltration)
ft³/s0.00Flow (Initial, Total)
min1.00Time Increment
Inflow/Outflow Hydrograph Summary
ft³/s25.04Flow (Peak In) min721.00Time to Peak (Flow, In)
ft³/s14.39Flow (Peak Outlet) min727.00Time to Peak (Flow, Outlet)
ft317.78Elevation (Water Surface,
Peak)
ft³12,812Volume (Peak)
Mass Balance (ft³)
ft³1,616Volume (Initial)
ft³73,507Volume (Total Inflow)
ft³0Volume (Total Infiltration)
ft³71,164Volume (Total Outlet
Outflow)
ft³3,944Volume (Retained)
ft³-16Volume (Unrouted)
%0.0Error (Mass Balance)
12/23/2019DRB19010.ppc
N. Bohorquez, EILinden - Lot 22
LINDEN - LOT 22
DRB-19010
STORMWATER CONTROL MEASURE
Anti-Flotation Block Calculations
N. BOHORQUEZ, EI
12/22/2019
RISER ANTI-FLOTATION CALCULATION
Input Data ==>
Safety Factor:
Safety factor to use =1.15 (recommend 1.15 or higher)
Concrete:
Concrete unit weight =142.0 PCF Note: NC Products lists unit wt. of
manhole concrete at 142 PCF.
Riser:
Inside height of Riser =4.50 feet
Inside length of riser =4.00 feet
Inside width of riser =4.00 feet
Wall thickness of riser =6.00 inches
Base thickness of riser =6.00 inches
Base length of riser =5.00 feet
Base width of riser =5.00 feet
Openings:
Total Orifice Area = 3.087 SF
OD of barrel exiting manhole =30.00 inches
Size of drain pipe (if present) =6.0 inches
Trash Rack:
Bottom Length = 7.00 feet
Bottom Width = 7.00 feet
Top Length = 1.00 feet
Top Width = 1.00 feet
Height = 2.00 feet
Trash Rack water displacement =38.00 CF
Concrete Present in Riser Structure ==>
Total amount of concrete:
Base of Riser =12.50 CF
Riser Walls =40.50 CF
Adjust for openings:
Opening for Orifices = 1.54 CF
Opening for barrel =2.45 CF
Opening for drain pipe =0.10 CF
Total Concrete present, adjusted for openings =48.904 CF
Weight of concrete present =6,944 lbs
LINDEN - LOT 22
DRB-19010
STORMWATER CONTROL MEASURE
Anti-Flotation Block Calculations
N. BOHORQUEZ, EI
12/22/2019
Amount of water displaced by Riser Structure ==>
Displacement by concrete =48.90 CF
Displacement by open air in riser =72.00 CF
Displacement by trash rack =38.00 CF
Total water displaced by riser/barrel structure =158.90 CF
Weight of water displaced =9,916 lbs
Calculate size of base for riser assembly ==>
Length =8.00 feet
Width =8.00 feet
Thickness =12 inches
Concrete Present =64.00 CF
Check validity of base as designed ==>
Total Water Displaced =210.40 CF
Total Concrete Present =112.90 CF
Total Water Displaced =13,129 lbs
Total Concrete Present =16,032 lbs
Actual safety factor =1.22 OK
Results of design ==>
Base length =8.00 feet
Base width =8.00 feet
Base Thickness =12.00 inches
CY of concrete total in base =2.37 CY
Concrete unit weight in added base >=142.0 PCF
LINDEN - LOT 22
DRB-19010
STORMWATER CONTROL MEASURE
Steel Calculations
N. BOHORQUEZ, EI
12/22/2019
II. CALCULATION FOR RISER ANTI-FLOTATION STEEL
Input Data ==>
Anti-Floatation Block Length =8.0 feet
Anti-Floatation Block Width =8.0 feet
Anti-Floatation Block Thickness =12 inches
Asteel to Aconcrete Ratio =0.0020 (recommend 0.0018 or higher)
Cross-Section Calculations==>
Cross-Section Area* =8.00 SF
Minimum Steel Area Required =0.016 SF
2.30 SI
*Note: Assumes a "square" x-sec (L and W same)
Rebar Calculations ==>
Bar Size 4 5 6 7 8
Diameter (inches)0.500 0.625 0.750 0.875 1.000
X-Sec Area (SI)0.196 0.307 0.442 0.601 0.785
Minimum Number of Bars Each X-Sec 12 8 6 4 3
Project Date 12/23/2019
Project No.Designer LK
Outlet ID
Flow, Q10-yr 12.34 cfs
Slope, S 4.63 %
Pipe Diameter, Do 24 inches
Pipe Diameter, Do 2.0 feet
Number of pipes 1
Pipe separation 0 feet
Manning's n 0.013
Zone from graph above =3
Outlet pipe diameter 24 in.Length =16.0 ft.
Outlet flowrate 12.3 cfs Width =6.0 ft.
Outlet velocity 13.0 ft/sec Stone diameter =13 in.
Material =Class I Thickness =22 in.
Zone Material Diameter Thickness Length Width
1 Class A 3 9 4 x D(o)3 x D(o)
2 Class B 6 22 6 x D(o)3 x D(o)
3 Class I 13 22 8 x D(o)3 x D(o)
4 Class I 13 22 8 x D(o)3 x D(o)
5 Class II 23 27 10 x D(o)3 x D(o)
6 Class II 23 27 10 x D(o)3 x D(o)
7
1. Calculations based on NY DOT method - Pages 8.06.05 through 8.06.06 in NC Erosion Control Manual
2. Outlet velocity based on full-flow velocity
DESIGN OF RIPRAP OUTLET PROTECTION WORKSHEET
Linden - Lot 22
DRB-19010
SCM
Special study required
13.0 ft/sec
0
5
10
15
20
25
0 1 2 3 4 5 6 7 8 9 10Velocity (ft/sec)Pipe diameter (ft)
Figure 8.06.b.1
Zone 1 Zone 2
Zone 3
Zone 4
Zone 5
Zone 6 Zone 7
SCM - Rip Rap Outlet Protection Design12/23/2019