20100434 Ver 2_SW Impact Analysis_20150930

,O�, consultants LAND DEVELOPMENT CONSULTANTS
STORMWATER IMPACT ANALYSIS
for
CAROLINA FRIENDS SCHOOL
MASTERPLAN IMPROVEMENTS
Orange County, NC
April 29, 2014
Revised February 12, 2015
Project #15010
Prepared for:
Carolina Friends School
4809 Friends School Rd.
Durham, NC 27705
e -15
LAND PLANNERS + CIVIL ENGINEERS
3708 LYCKAN PARKWAY, SUITE 201 DURHAM, NC 27707, PHONE: 919,490,1645
WWW.CIVIL- CONSULTANTS.COM LIC. C -1030

Stormwater Impact Analysis
Carolina Friends School
Masterplan Improvements
Orange County, NC
Purpose
The purpose of this report is to present a stonnwater management analysis and a
corresponding management strategy for the subject Carolina Friends School property, in
support of proposed Campus Masterplan improvements.
General Site Description
The subject property consists of two parcels (Orange County PINS 9892 -31 -0306 and
9892 -22 -7326) comprising approximately 87 acres of partially- developed land located on
the west side of Friends School Road (SR 1719) in eastern Orange County (shown as
Parcels 2 and 3 in Exhibit 1).
The subject property lies within an unincorporated portion of Orange County, and is
subject to Orange County planning jurisdiction. All stormwater runoff from the property
drains to Piney Mountain Creek, which drains to New Hope Creek (Exhibit 2). The
property is therefore located entirely within the Jordan Lake drainage basin.
According to published soil survey data, the dominant onsite and upslope soils are
classified as Appling, Cecil, Georgeville, and Herndon series (Exhibit 3), all of which are
in SCS Hydrologic Soil Group B.
The property contains several stream features (Exhibit 4) with associated Jordan Lake
riparian buffers, as well as Orange County stream buffers. Orange County stream buffers
for this property are wider than the riparian buffers imposed by Jordan Lake regulations.
Develonment Summary
The property has a vested zoning right and a Special Use Permit (SUP) for a school
campus serving approximately 500 students. The first school facilities were built in the
1960s, and the facilities have been slowly expanded and improved since that time. The
most recent SUP modification covering Campus Masterplan Improvements (Exhibit 5)
was approved in February, 2012. Proposed improvements include a Performing Arts
Facility, a Shop building, additions to several campus buildings, new athletic facilities, a
new driveway from Mt. Sinai Road, and replacement of the onsite wastewater system.

Phasing Summary
Proposed development will occur in phases over a period of several years. This report
will present a stormwater management strategy reflecting the entire scope of site
improvements covered by the approved Masterplan. The elements of this strategy will be
logically integrated with the anticipated phasing scope and sequence.
The first phase of work, currently in process, is installation of a new wastewater system
and construction of a new gravel access driveway from Mt. Sinai Road to serve the new
treatment facilities. This driveway will also serve future building and athletic facilities.
Due to the size of the overall site, and the relatively small amount of additional
impervious surface, this phase of work results in no exceedance of maximum nutrient
thresholds or pre - development runoff rates.
The second phase of work included renovations and building additions to the "Quaker
Dome" (completed) and the Middle School (currently in process). This work added
building roof area to areas that were mostly impervious already, also resulting in no
exceedance of maximum nutrient thresholds or pre - development runoff rates.
The next phase of work will include construction of a new tennis facility on the site of the
existing baseball field, with a small adjacent parking area that will also serve the adjacent
Campus Early School; and construction of a new baseball facility on the western side of
campus, with a small parking area. This work is scheduled for construction in mid -2014.
Other near -tern projects include a building addition to the Lower School and a very
small addition to one of the Upper School buildings. Neither of these would be expected
to require any new driveway or parking areas.
The largest future phase of work will include a new Performing Arts Facility on the
western side of campus. The timing of this phase is uncertain, but probably would begin
within the next three years. This work could take the form of several buildings in
separate sub - phases, or a single building or cluster of buildings in a single phase. In any
case, the first such building will require some refinement of the existing gravel drive
(recently constructed for the new wastewater system) to provide adequate access for
emergency services, and some limited parking to minimally support the new facility. A
pedestrian connector is anticipated to support foot traffic and cart traffic from the east
side of campus to the new facility. The work associated with the Performing Arts Facility
is also expected to include a new connecting driveway from the Upper School area to the
new driveway on the west side of campus, to provide intra - campus vehicular flow. Both
the connecting pedestrian path and the connecting driveway will require stream and
stream buffer crossings. These several Masterplan components (Performing Arts Facility
and various access improvements) are very inter- dependent; and therefore likely to be
constructed as a single phase of work.

Other smaller future projects are anticipated, including a building addition to the Campus
Early School and a new Shop Facility. The timing of these projects is uncertain, both in
absolute terms, and relative to construction of the larger Performing Arts Facility.
Reaulatory Requirements
The property is subject to Orange County requirements for stormwater runoff
management in the Jordan Lake Basin (Unprotected Watershed), Upper New Hope Creek
Arm. Specific performance requirements include the following:
1. Limit the Post - development Total Nitrogen export to 2.2 lb /ac /yr.
2. Limit the Post - development Total Phosphorus export to 0.82 lb /ac /yr.
3. Limit the Post - development Peak Flowrate for the 1 -year 24 -hour storm (Qi) to
the Pre - development level
Defmitions and Assumutions
Point of Interest: The "point of interest" used for hydrologic analysis purposes requires
explanation. The subject property receives substantial runoff from offsite parcels, in both
concentrated and unconcentrated flow patterns. Almost all of this drainage winds through
the site in a manner that mingles directly with runoff from developed (or future
developed) areas of the site. All of this upstream area, as well as the subject parcel area,
drains to Piney Mountain Creek located along the northern property border. A very small
amount of parcel area exists on the north side of the stream. The creek channel in this
location receives a very much larger drainage area upstream from the west, but this
drainage is bypassed through the site along the northern property line. Considering these
characteristics, the "point of interest" for this analysis has been defined essentially as an
"edge of interest ". Specifically, this edge is the southern bank of Piney Mountain Creek
along the northern property boundary, except where the creek diverges from the property
line, the actual property line is used.
Site Area: Based on the foregoing definition, the amount of land area used for nutrient
export accounting purposes, and the total drainage area used for hydrologic analysis, is
defined as the sum of the subject parcel area and the several upstream (offsite) drainage
areas, which collectively drain to the "edge of interest" from the south. This "Total Site
Area" consists of approximately 231 acres, and is shown graphically in Exhibit 6.
Pre - development: For both nutrient export analysis and hydrologic analysis, the "pre -
development" condition is defined as the condition (land uses and development
intensities, other ground -cover characteristics, etc.) that existed just prior to the time of
SUP approval in February, 2012.

Post - develonment: For both nutrient export analysis and hydrologic analysis, the "post -
development" condition is defined as the condition that is anticipated upon full buildout
of the Masterplan improvements covered by the SUP approval in February, 2012; plus
allocations for slight increases in development intensity to account for other additions
that may reasonably be expected.
Post - development land uses and intensities are graphically depicted on site maps in
Exhibits 6 and 7. Pre - development and allocated post - development land use values are
tabulated in Exhibit 10.
Nutrient Exnort Accountine Land Cover Cateeories: Since the Site Area doesn't include
any significant small -lot residential area, nutrient export analysis utilized only "Column
1" categories on the approved Nutrient Accounting Tool. Additionally, for nutrient
analysis, the following logic has been used, which is consistent with discussions held
with Orange County Stormwater review staff as documented in Exhibit 9:
• "Parking Lot" includes vehicular areas such as parking, loading, and service
zones; and driveways and aisles adjacent to these areas.
• "Roof' includes the horizontal area of building and shed roofs, and
appropriate non -roof areas. These non -roof areas include large impervious
courtyards adjacent to buildings, and the proposed tennis courts, which will
not generally be subject to fertilization or vehicle - generated nutrients, and
therefore act like roof areas for nutrient accounting purposes.
• "Open / Landscaped" includes pervious non - fertilized areas such as non -
"Forest" woods and similar areas.
• "Low Density Transportation" includes the pavement area of Mt. Sinai Road.
• "Rural Transportation" includes the pavement area of Friends School Road,
and longer sections of private driveways that don't have adjacent parking,
loading, or service zones.
• "Sidewalk" includes impervious pedestrian areas such as walkways, the
walking trail around the soccer fields, and similar areas.
• "Managed Pervious" includes pervious non - "Forest" area that is potentially
fertilized, grazed, thinned, or managed in any way; such as soccer and
baseball fields, landscaped areas around buildings and other features, lawns,
actively grazed pasture, crop production fields, and similar areas.
• "Unmanaged / Pasture" includes unmanaged pervious areas such as meadows
with broom -straw or similar cover, but not actively grazed areas.
• "Forest" includes wooded portions of offsite Duke Forest property, and
undeveloped vegetated portions of stream buffers. (Also see discussion near
the end of this report under "Alternate Nutrient Strategy".)
• "Open Water" includes stream channels, lakes, and ponds.
• `BMP Area" includes only the anticipated impoundment area of proposed
stormwater management pond(s).

Dedication of Conservation Area
In order to take full advantage of the subject property's unique resources, the landowner
is willing to dedicate a portion of the property as conservation area, allowing the
conserved area to essentially act as a non - structural stormwater management measure.
This strategy is based on a concept embedded in the nutrient accounting methodology
that assigns the lowest contributions of nutrients from wooded areas that are
"permanently protected" from future development. The most easily acceptable way of
securing this status is to legally place a conservation easement, with strong language
requiring tree preservation, on the affected area. In this way, wooded land that would
otherwise be considered in a higher nutrient - producing category could be re- assessed as
"forest" with a lower nutrient export rate, thereby reducing the allocated total nutrient
load from the overall site.
This "forest" status is also used herein for wooded stream buffer areas, since these areas
are already highly protected by State and local ordinances; and for wooded portions of
the offsite Duke Forest property.
This analysis is based on dedication of approximately 470,000 square feet of
conservation area that is not already included as protected stream buffer. Exhibit 7
indicates this area near the northern edge of the property. Including the stream buffer
areas contained in the conservation zone, approximately 16 acres of land is proposed to
be dedicated. Some of this area contains an onsite wastewater drip irrigation system,
which was specifically designed and installed to preserve the forested condition. The drip
lines are installed on the ground surface just under the leaf litter, and not trenched into the
soil. This type of wastewater system is compatible with forest conservation principles.
Nutrient Exuort Results
Using the accepted Nutrient Accounting Tool with the foregoing logic, the resulting
nutrient export from the Total Site Area, without any BMP, is 2.20 lb /ac /yr for Nitrogen
and 0.58 lb /ac /yr for Phosphorus. These data and results are shown in more detail in
Exhibit 11.
Initial Peak Flowrate Analvsis
For initial peak flowrate analysis purposes, the Total Site Area was considered as a single
large drainage area with an identical "time of concentration" for both development
conditions. Existing and proposed land cover characteristics were evaluated in a detailed
manner, and each type of area was assigned an appropriate runoff curve number (Exhibit
12). A composite runoff curve number was then tabulated for each of the development
conditions. This analysis utilized standard SCS curve number methodology to account for
Gi

land cover conditions, and the SCS TR -55 method to determine the time of concentration
using flow path characteristics.
For this initial simplified analysis, the only difference in hydrologic parameters between
the pre- and post - development conditions is the SCS runoff curve number, which is
higher for the post - development condition, as expected.
The resulting one -year peak flowrate (Q I) for the post - development condition was
calculated to be 53.9 cubic feet per second (cfs), which is about 13% higher than the pre -
development Q1 value of 47.5 cfs (Exhibit 13). This Q, increase requires mitigation in
order to lower the post - development value to a level that is no larger than the pre -
development value.
Refined Flowrate Analvsis
For a more refined Qi analysis, the site was divided into logical sub - watersheds that
allow for proper accounting of the flow time along each flow path for each sub - watershed
element. This subdivision is necessary in order to properly model travel time along flow
paths, to account for timing differences in each hydrograph from sub - watershed areas,
and to especially account for runoff rate delays provided by the proposed detention
devices. Essentially, the sub - watersheds are (a) the discrete drainage areas to each pond,
and (b) the resulting balance of the larger watershed area. The pond drainage area
boundaries and acreages are shown in Exhibit 8.
The existing lake on the subject property was not considered as having any detention
effect because (a) it has so little available detention volume relative to its drainage area as
to be negligible for peak flowrate reduction purposes, and (b) any attributable detention
effect will be equivalent (net neutral) in both the pre- and post- development scenarios.
For each identified subwatershed, the contributing drainage area, flow path, time of
concentration, land cover characteristics, and composite runoff curve number (Exhibit
12) were evaluated for both pre - development and post - development conditions. For most
of the drainage area, no modification of drainage flowpaths and stream channels will
occur, due to the very limited scope of proposed site development and storm drainage
piping. For these areas therefore, the only difference in hydrologic parameters between
the pre- and post - development conditions is the runoff curve number.
Drainage area and flow path conditions are slightly different for the drainage areas to the
ponds in pre- and post - development conditions. Where flow paths will be altered by new
construction, these adjustments are reflected in the hydrologic analysis, with resulting
changes in the time of concentration. Where drainage area limits will be altered by new
construction, the post - development drainage area is used for both conditions. This
simplification is acceptable because the affected areas are small, and these small
differences are offset by the same amount of area in the respective `Balance of Area"

subwatershed for both pre- and post - development conditions. In other words, there is no
net gain or loss of total land area being evaluated for runoff in each case.
This more - refined hydrologic information was used to generate one -year runoff
hydrographs for each subwatershed. These hydrographs were then routed and combined
to obtain a comprehensive Q1 value for the Total Site Area. This modelling process was
performed for both pre - development and post - development conditions.
Prouosed Mana¢ement Measures
Several iterations of detention pond locations, sizes, and combinations were evaluated.
Limited suitable locations exist on the subject property for detention facilities, or for any
structural management measure in general. This is because much of the existing campus
infrastructure occurs in low -lying areas adjacent to or within stream buffer areas.
Structural runoff control measures need to be located at a lower elevation than the area
being served, but these types of devices are not generally permitted within stream buffers.
This site therefore offers very little opportunity to capture and detain runoff from existing
developed areas. Also, where existing (or proposed) facilities are (or will be) located on
higher ground, it is difficult to find suitable downslope locations that will capture enough
runoff volume to have any meaningful detention effect. For these reasons, the subject
property is unusually challenging in this regard.
However, three viable stormwater detention locations have been identified for the subject
property. These locations are depicted schematically in Exhibit 8 and are described as
follows:
Pond 1
Location: In the mostly wooded area north of the Lower School, adjacent to the
grassed play field.
Advantages: Will capture runoff from the largest amount of drainage area of any
identified location, including most of the soccer fields, much of the Lower School,
some driveway and parking area, etc.
Disadvantages: Does not receive enough runoff to fulfill all of the site's detention
requirements; requires substantial tree removal and grading; adjacent to Lower
School; not perceived as having a rational nexus to larger campus improvements.
Pond 2
Location: In the partially- wooded low -lying area west of the existing baseball field
(future tennis courts); adjacent to, and south of, the future connecting driveway.
Advantages: Will capture runoff from a significant amount of new impervious area
(tennis courts), and a small portion of the future driveway.
Disadvantages: Does not receive enough runoff to fulfill all of the site's detention
requirements.

Pond 3
Location: In the partially- wooded side -slope area south of the future Performing
Arts Facility, and west of the existing stream.
Advantages: Will capture runoff from a significant amount of new development
area, including most or all of the Performing Arts buildings, parking, portions of the
access driveway, baseball field, etc.
Disadvantages: Does not receive enough runoff to fulfill all of the site's detention
requirements; requires some slight, but reasonable, adjustment in natural drainage
patterns from both the baseball field and the Performing Arts area in order to capture
sufficient runoff volume.
Based on evaluation of several options, the recommended management strategy is to
construct both Pond 2 and Pond 3, which will combine to meet the mitigation
requirement. These ponds are not physically or logistically linked in any way; they could
just as well be constructed separately or at the same time. They will each serve to meet
approximately half of the mitigation requirement, and neither can apparently be
configured to solely meet the full requirement.
These ponds should be logically linked with corresponding future site and building
improvement projects on the property. Probably the largest component of future work,
and a large contributor to the increased runoff, will be the Performing Arts Center and the
associated access and parking infrastructure. This report therefore recommends that Pond
2 be constructed along with the driveway that will connect the eastern and western areas
of campus, and that Pond 3 be constructed along with the Performing Arts Center project.
In the likely event that both of these project elements are developed together, both ponds
should be constructed at the same time.
Alternately, at the Owner's option, Pond 1 could be simply substituted for either Pond 2
or Pond 3. Using Pond 1 as one of the detention devices would achieve equal or better
results than the recommended combination. Although Pond 1 would be in a location that
may be less desirable for operational and aesthetic reasons, it is a viable technical
solution if used in combination with one of the other ponds.
Peak Flowrate Results
Using the recommended combination of Pond 2 and Pond 3, the calculated post -
development Q1 from the Total Site Area is 39.5 cfs, which is slightly lower than the
calculated pre - development Qi of 40.1 cfs. The storage volume provided by these two
ponds sufficiently reduces the peak rate of stormwater runoff from the Total Site Area to
meet the regulatory requirement. These data and results are shown in Exhibits 14 and 15.

Effect on Nutrient Export
The detention pond data was also entered into the Nutrient Accounting Tool as Best
Management Practices (BMPs), to determine the ponds' effect on nutrient export values.
Dry detention ponds are considered to provide a very small amount of nutrient reduction,
even though this is not their primary function. With these two ponds, the post -
development nutrient export from the Total Site Area is 2.16 lb /ac /yr for Nitrogen and
0.57 lb /ac /yr for Phosphorus. These data and results are shown in Exhibit 11.
Final Desi2n
This analysis includes a viable, but preliminary, design model of the two recommended
ponds. Each pond will require a finalized design prior to construction, to evaluate the
land cover characteristics and contributing drainage patterns associated with the detailed
design of upslope site improvements, to establish more exact dimensional details and
construction specifications, and to configure the ponds to properly withstand rainfall
events larger than the one -year storm.
Limitations
The analysis and recommendations outlined in this report are based on current plans,
regulations, policies, and interpretations pertaining to stormwater management for the
subject property. While the intent of this report is to identify a durable management
strategy that will satisfy relevant stormwater- related requirements for all approved
Campus Masterplan elements, it is conceivable that additional or alternate measures may
be required under some circumstances. These circumstances include, but may not be
limited to, future changes in regulatory requirements and/or Masterplan elements.
For example, the strategies outlined herein do not require or include installation of any
structural devices that provide 85% Total Suspended Solids (TSS) removal, such as
"wet" detention ponds or bio- retention devices (rain gardens). Changing future
conditions, regulations, or interpretations could possibly result in the need to comply with
such a requirement. Also, changes in adopted methodologies for nutrient export
accounting, or interpretations thereof, have potential for a similar outcome.
Practically, the future stream crossings may represent the largest potential for additional
or unanticipated types of runoff management measures to be required, based on the
potential involvement of State and/or Federal review agencies for this work.
If additional requirements are imposed for any reason, the pond strategy outlined herein
is expected to remain viable and sufficient for peak flowrate management purposes. The
primary risk is simply that additional nutrient management strategies may be
superimposed, which may include structural devices and/or non - structural measures such
as described below.
10

Summary Conclusion
Stormwater runoff impacts associated with the Campus Masterplan for Carolina Friends
School may be fully mitigated in compliance with applicable State and local regulations,
by constructing two onsite stormwater detention ponds and dedicating forested
conservation area as outlined herein.
End
List of Exhibits
1 - Boundary Survey of subject property (I page)
2 - Excerpt from USGS Topographic Map showing subject property (1 page)
3 - Excerpt from Soil Conservation Service Soil Map showing subject property (1 page)
4 - Orange County Surface Water Identification (SWID) letter (4 pages)
5 - Site Plan from 2012 Special Use Permit drawing set (1 page)
6 - Site Area Plan (1 page) (Revised)
7 - Nutrient Export Land Use Plan (1 page) {Revised}
8 - Pond Location Plan (1 page)
9 - Email documentation regarding analysis methodology (2 pages)
10 -Land Use and Development Intensity Summary (2 pages) {Revised}
11 - Nutrient Accounting Tool (4 pages) {Revised}
12 - Runoff Curve Number Analysis (2 pages)
13 - Runoff Hydrographs — Initial Simple Analysis (6 pages)
14 - Runoff Hydrographs — Refined Pre - Development Analysis (13 pages)
15 - Runoff Hydrographs — Refined Post - Development Analysis (17 pages)
11

RECOMBINATION SURVEY
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Project No. Figure 2 NKC5
I I339.W County Soil Survey
Project Mgr.: Carolina FrlencI5 5Ghool Soil & Environmental Consultants, PA
JP 11010 Raven Ridge Rd • Raleigh, NC 27614
Orange County, NC (919)8465900 °(919)8469467
Scale: I Web Page www SandEC com
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1 1/04/09 Sheet 23

EXHIS IT 4
Page 1 or 3
ORANGE COUNTY PLANNING & INSPECTIONS DEPARTMENT
Craig N. Benedict, AICP, Director
Administration 245 -2575
LpuN[ o[ Or
Erosion Control Division d` P 306E Revere Road
(919) 245 -2586 g P O Box 8181
(919) 644 -3002 (FAX) 4a Hillsborough, NC 27278
www.co.oranae.nc.us
rutt
September 10, 2009
Ellen Weinstein
601 -A West Main Street
Carrboro, NC 27701
Re: Orange County Zoning Ordinance Surface Water Identification
Jordan Lake Unprotected Watershed
PIN / TMBL: 9891 -29 -1739 / 7.7..26E
PIN / TMBL: 9892 -21 -1486 / 7.7..19
PIN / TMBL: 9892 -22 -7252 / 7.7..20
PIN / TMBL: 9892 -31 -5318 / 7.7..26A
PIN / TMBL: 9892 -33 -5224 / 7.5..20
PIN / TMBL: 9892 -32 -3662 / 7.6..2
PIN / TMBL: 9892 -21 -6594 / 7.7..206
PIN / TMBL: 9892 -31 -0894 / 7.7..20A
To Whom It May Concern:
This letter serves as confirmation of an on -site surface water identification made by Orange
County Erosion Control Division staff for the referenced parcel. Orange County enforces a
stream buffer along streams and water features in the County per the Orange County
Zoning Ordinance (see Section 6.24.1 Additional Requirements for Lots Outside of
Watershed Protection Areas, as amended on May 20, 2003).
The evaluation showed that there are (4) water features on the parcels in question that
are subject to buffer regulations. The water features are approximately referenced on
the attached aerial photograph / map. The subject water feature will require a 65' or 80'
undisturbed buffer along both sides, calculated per the referenced Zoning regulations.
These undisturbed buffer areas shall be measured from the top of the stream bank,
outer edge of wet, marshy areas, or outer edge of the floodplain where applicable (see
below):
S:\\ErosionControlDivision\2009 \Cape Fear\ 091009. TMBL7 .7..26E.CarolinaFriendsSchool

Page 2 of 3
1 — s, fyy y wiat]l
1
m
_1
1
1 Top of str�arn barilc
5B
1 _ Buii'er VJiath 1
S: \ \ErosionControlDivision\2009 \Cape Fear\ 091009. TMBL7 .7..26E.CarolinaFriendsSchool

Page 3 of 3
The following is a description of how the buffers affect the property:
1. Feature A, a previously mapped stream segment, is present in the field and subject
to buffer regulations. The beginning point has been flagged in the field for reference.
2. Feature B, a previously mapped stream segment, is present in the field and subject
to buffer regulations.
3. Feature C, a previously mapped stream segment, is present in the field and subject
to buffer regulations.
4. Feature D, a previously mapped stream segment, is present in the field and subject
to buffer regulations. The beginning point has been flagged in the field for reference.
If you have questions about this determination, please contact me at (919) 245 -2587.
However, if you have further questions about the application of the Zoning Ordinance to
these parcels, how to calculate the buffer lengths, or possible restoration requirements,
please contact Michael Harvey, Zoning Enforcement Officer at 919- 245 -2607.
Sincerely,
�4/�
Wesley Poole
Erosion Control Officer I
Attachments: Aerial Photograph / Map
Relevant Text from Zoning Ordinance
cc: File
S:\\ErosionControlDivision\2009 \Cape Fear\ 091009. TMBL7 .7..26E.CarolinaFriendsSchooI

Orange County f,
'Surface Water Identification
NR
g
>e f y Feature C:
Subject
�✓. t� .t L, aY .d!
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Feature D ,.
Subject
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Cato shown an this map is obtained from Orange County
v CIS and is for reference only
5 8 0 114 809 FRIENDS SCHOOL RD v/ J '\ % t Exact iarations entl boundaries shows be hem vornied
DURHAM, NC 27705 -8193 /�/ 1/ r� < a y crap prepared by Bring. County planning B lnspocUons.
�rY. -co USGSWatbr FeaWta �parcel zoning 100 YR Floodplaln(Effective 02=07) Peter Klopfer Property/
'' cn Limus Floadway (Edeawe ovov¢7) Carolina Friends School
Soils Survey Water Feature E : Tmvnship r.r' Y
l
OC Updated Water Feature School System Boundary r f ETJ L �!! 500 Year Flood bans ( ERectva 0&02107 ) 0 275 550
.. Water Bodies �N, Contours Conservatlon Eosemants Buildinge FEE F
Held by Others
C3 River Easlns - - -- County ., orange County Streams (Deleted) 1 inch = 50G feet "
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. Solis Conservation Easements -
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SITE AREA PLAN
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LAND PLANNERS + CIVIL ENGINEERS
3206 HERITAGE TRADE DRIVE - SUITE 100 - WAKE FOREST, NC 27587
919.453.2386 PHONE
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SITE AREA PLAN
civil consul.tants
LAND PLANNERS + CIVIL ENGINEERS
3206 HERITAGE TRADE DRIVE - SUITE 100 - WAKE FOREST, NC 27587
919.453.2386 PHONE

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Tony Whitaker WOW Q
From: Wesley Poole <wpoole @orangecountync.gov>
Sent: Friday, March 21, 2014 9:15 AM
To: 'Tony Whitaker'; Steve J Kaltenbach
Cc: 'McGovern, John'; 'Hanas, Mike'
Subject: RE: Carolina Friends School - Stormwater Masterplan
Looks good other than one item in 44 ... the Phosphorus load threshold of 0.83 Ibs /ac /year should be 0.82 Ibs /ac /year.
Wesley Poole
Orange County Planning & Inspections Dept.
Erosion Control Division
(919) 245 -2587
From: Tony Whitaker [mailto:tony.whitaker @civil- consultants.com]
Sent: Thursday, March 20, 2014 2:05 PM
To: Steve J Kaltenbach; Wesley Poole
Cc: 'McGovern, John'; 'Hanas, Mike'
Subject: Carolina Friends School - Stormwater Masterplan
Gentlemen,
Thank you for your time and energy to meet with John and me yesterday about the referenced project. In the meeting,
we discussed the need to prepare a campus -wide stormwater management strategy that correlates to the current
approved Masterplan, which is covered by a Special Use Permit (SUP) that was approved a couple of years ago. Some of
the work covered by this SUP is in progress, but most of it remains as future work, and will be implemented in phases.
In our meeting, we discussed and agreed as follows:
1. The upstream offsite drainage area, which is considerable in this case, will be included as part of the "site" for
analysis purposes.
2. For hydrologic modelling, the "pre- development" condition is defined as the condition that existed at the time
of SUP approval ( February, 2012).
3. For nutrient loading analysis, the following logic will be used:
• Wooded portions of offsite Duke Forest areas will be considered "Forest" (Conservation);
• The school has the option of dedicating additional Conservation area onsite, including the forested portions
of the new wastewater drip area, if needed to keep nutrient loading levels below thresholds. If so, these
areas must be legally protected from future clearing and development by a formal conservation easement;
• For nutrient loading purposes, tennis courts are more like roof areas, and will be considered as such;
• Only the vegetated portions of stream buffers will be considered "Forest ";
• Driveways without adjoining parking or loading areas will be classified as "Transportation - Rural ";
otherwise vehicular parking and adjoining drive aisles will be classified as "Parking ";
• "Managed Pervious" areas will include any pervious non - conservation area that is potentially fertilized,
grazed, thinned, or managed in any way. Other pervious non - conservation areas may be generally
considered as "Open / Landscaped ".
• Meadow or "broom- straw" areas will be considered "Pasture "; and

• An additional allowance will be made for future unspecified development (roof area), to allow future
flexibility.
4. Preliminary analysis indicates that in the fully -built condition, impacts will be as follows:
• Phosphorous loading will be well below the 0.83 Ib /ac /yr threshold, and will therefore not require any
mitigation;
• Nitrogen loading will be approximately at the 2.2 Ib /ac /yr threshold, which may require a small amount of
mitigation; and
• The one -year peak flowrate will increase, and will require some onsite detention storage for mitigation.
5. A simple "dry pond" will be proposed for detention storage, and only two reasonable areas exist on campus for
this kind of device. The superior location is in the low area north of the Lower School, below the current grassed
play area. The inferior location is in the low area just west of the existing ball field, which may not receive
enough runoff to be effective in any case. The actual location of the detention area must be approved by school
administration / directors.
6. A dry pond will provide a very small amount of mitigation for nutrient loading. In this case, if any nitrogen
mitigation is required at all, the dry pond should provide a sufficient amount. Therefore, it is expected that
construction of a dry pond will be the only structural measure required for stormwater management on the
campus.
7. 1 will prepare final stormwater analysis calculations and preliminary pond design parameters to validate the
above. I will also prepare a written report containing this information, with detailed documentation of the
assumptions made and conditions modelled.
8. The report will also discuss probable phasing of campus improvements, including construction of the dry
pond. We agreed that is seems reasonable for the pond to be constructed just before, or in conjunction with,
construction of the future performing arts facility.
9. After the Stormwater Report is submitted for review, we expect to move ahead with design of site
improvements for the new tennis courts and baseball field, including the grading and appropriate erosion
control measures for each. With this application, we will need to pay the $500 Stormwater Plan review fee,
along with the applicable erosion control fees. We should also identify and include any other site disturbance
work that is anticipated within the upcoming two -year period, so all of this work will be covered by a
consolidated new grading permit. The current grading permit, covering the wastewater system work and
associated driveway, will expire on November 5, 2014. We expect all of the work covered by the current permit
to be completed by then.
If any of the above information needs clarification or correction, please let me know.
Thank you,
Tony M. Whitaker, P.E.
(919) 490 -1645 (office)
(919) 943 -8418 (cell)
htti)://www,civil-consultants.com
civil consultants
IiuO Di V[LOIU {AI [DM {U �li�tl

Carolina Friends School - Master Stormwater Plan 7f Revised Feb. 12, 2015
Land Use and Development Intensity Summary
Offsite Area
Offsite Area
Offsite Area
Offsite Area
Onsite Pre-
Total Pre-
Onsite Amount
Onsite New
Onshe Post-
Grand Total
Post.
Map
Nutrient Export Accounting Land
"A" Amount
"B" Amount
"C" Amount
"D" Amount
Development
Development
tube Removed
Amount(SF)
Development
Development
Key
Use Category
(SF)
(SF)
(SF)
(SF)
Amount (SF)
Amount (SF)
(SF)
3
Amount (SF)
Amount (SF)
A
Parking
1,000
13,327
19,163
1,512
130,846
165,848
3,600
60,947
188,193
223,195
B
Building Roof '
1,788
44,642
26,512
8,741
94,581
176,264
729
76,326
170,178
251,861
C
Open /Landscaped
75,000
1,025,000
5501000
324,730
1,699,872
3,674,602
753,483
0
946,389
2,921,119
D
Low - Density Transportation
0
15,000
0
0
0
15,000
0
0
0
15,000
Z
E
Rural Transportation
25,480
32,735
37,915
0
56,333
152,463
0
69,473
125,806
221,936
F
Sidewalk z
0
3,000
1,000
2,000
50,645
56,645
0
17,594
68,239
74,239
G
Managed Pervious
191,000
440,000
769,010
267,785
500,000
2,167,795
55,000
148,472
593,472
2,261,267
H
Unmanaged / Pasture
92,535
649,175
500,000
0
500,000
1,741,710
25,000
0
475,000
1,716,710
I
Forest
0
1,051,000
0
0
0
11051,000
0
470,000
470,000
1,521,000
J
Wetland (outside buffer)
0
0
0
0
1,400
1,400
0
0
1,400
1,400
_
K
Vegetated Stream Buffer
0
30,000
3,000
0
687,000
720,000
15,000
0
672,000
705,000
O
L
Open Water
0
16,645
48,800
0
85,000
150,445
0
0
85,000
150,445
M
BMP surface area
0
0
0
0
0
0
0
10,000
10,000
10,000
Totals:
386,803
3,320,524
1,955,400
604,768
3,805,677
10,073,172
852,812
852,812
3,805,677
10,073,172
These values must be equal
Notes
1. Also includes paved recreational equipment,
pads, courts; and Impervious plazas not subject to fertilization impacts.
2. Includes Impervious porches, stoops, walks, etc. that
could reasonably be subject to adjacent fertilization
impacts.
3. Includes allowances for unspecified
future additions
as listed elsewhere.

Carolina Friends School - Master Stormwater Plan Revised Feb. 12, 2015
Land Use and Development Intensity Summary - Onsite Only
Parking Roof/ Patio Open LS Rural Trans. Sidewalk Man, Perv. water
A -Pre A -New B -Pre B -New C -Post E -Pre E -New F -Pre F -New G -Post L
2,000 384 1,000 1,018 10,000
1,217 2,500 13,381 443 100,000 75,000
12,730 480 10,000 1,142 145,000 85,000
28,000 192 108,000 33,000 552 3,942
9,103 800 217,000 6,865 9,200 2,500
17,161 1,488 30,000 4,608 4,919 160,000
1,596 1,150 40,000 8,200 1,522 26,504
91000 480 80,000 9,200 746 44,000
31,624 240 20,000 14,000 146 8,537
2,331 240 451,389 5,000 1,300 11,264
67,031 300 946,389 5,000 320 85,000
Allowance 10,000 300 5,552 198 6,725
130,846 60,947 800 Allowance 10,000 459 593,472
Subtotal = 191,793 44,000 56,333 69,473 112
Demo= 3600 806 E -Post= 125,806 56
A -P05t= 188,193 300 2,621
253 3,353
1,673 165
400 3,647
400 2,112
11900 1,784
224 2,305
3,200 2,383
17,032 1,000
284 1,893
1,000 5,578
1,000 1,271
2,664 705
2,133 854
3,767 203
8,835 2,151
1,320 2,666
3,000 36
900 181
7,835 228
2,101 970
1,550 Allowance 10,000
4,035 50,645 17,594
1,633 F -Post= 68,239
10,764
4,103
2,110
3,282
3,373
2,396
2,000
5,448
632
100
100
Allowance 15,000
94,581 76,326
Subtotal = 170,907
Demo = 729
B -Post= 170,178

I AIBI
22
23
24
26
51
52
53
54
F 55
56
57
58
59
C I D. I E I F I G IHIIIJIKI L I M I N I O 1 P I Q I R IS
COLUMN 1 -- NON- RESIDENTIAL LAND USES
TN EMC
TP EMC
Pre-
Post -
(mg/L)
(mg/L)
Development
Development
IR'1
(ft°)
COMMERCIAL
Parking lot
' .44
0.16
Roof
1.08
I
0.15
Open /Landscaped
2.24
0.44
INDUSTRIAL
I Parking lot
1.44 IrII
0.39
I Roof
I L08
0.15
Open /Landscaped
214 I
0.44
(TRANSPORTATION
High Density (interstate, main)
3.67
0.43
Low Density (secondary, feeder)
1.4
0.52
Rural
1.14
I
0.47
(Sidewalk
1.4
1.16
PERVIOUS
- -- "
Managed pervious
3.06 J
0.59
Unmanaged (pasture)
I
3.61
1.56
Forest
1.47 I
0.25
lURiSDICiiDMAL (ANDS'
Natural wetlantl
Riparian buffer
Open water
(AND TAKEN UP BY BMPS
LOB
0.35
'W5,11odonal land uses are not ind uded In nutrient/flow calculations.
Total Development Area (ft'):
Development Name:
Model Prepared By:
�I
PARTA
X- aclots
Xaclots
X-aclots
lac lots
2 -ac lots
Multi- family
Townhomes
Custom Lot Size
PART
Roadway
Driveway
Parking lot
Roof
Sidewalk/Patio
Lawn
Managed pervious
Forest
Natural wetland'
Riparian buffer'
Open water'
LAND TAKEN UP BY BMPS
10,073,172
Carolina Friends School,
Tony M. WhitakeG=
COLUMN 2 -- RESIDENTIAL LAND USES
Custom Pre- post-
Lot Age TN EMC TP EMC Development Development
(Yrs) (mgQ) (mg/L)
(a` Iftal (it')
1.08 0.15
L4 1.16
224 0.44
3.06 0.59
1.47 0.25
1.08 0.15
LANDUSEAREACHEp('_.__._._
Total Development Area Entered (ft): 10,073,172
Total Pre-Development Calculated Area (k'): 10,073,172.
bV

Vu CdichmentI
Camhment2
Ca"hment3
Cal h eot4
Cat nment5
fLt M1meel6:
Drainage Area Land Use
-
-
-
no
n0
no
no
-
no
Be
- no
221.538
INDUSTRIAL _ _ -
he
_— e
h p
nu
no
Ile
No
r10
_ - - -e
ne
no
r10
110
no
nei i
Ar¢a2that1
..
Area treated
.a no
ne
Aleatlthat1
n
Area treated
no
Area irea[¢tl
byeMP82yWRnot
by BMP #3 that Is not
Area Treated
not
bye Mad
by BMP 03 that lF not
Area Treated
by BMP
treated by BMP pl
treated by War 91
by BMP
by INtls
V¢aletl byBMP pl
treated by BMPS#1
by BMP
1 v)
IN
In'I
ortlx
Inv[
(it')
or N2
NO
Iny
11ESIDENTIAL
2-nc lots Nw wl
In'1
2 -ac lots lBUilt aNer ]9951
COMMERCIAL
Parking lot
0
21.500 _ 1
Roof _
45,106
22 \000
_Ope /Lan =-aped __
_146:0]9 _ _ _ _ _ _ _ _
221.538
INDUSTRIAL _ _ -
_ Parking b0
Roal
_0pen0.andsaped__
TRANSPORTATION
High y state, main)
uric
Law Death, lse<nnaarv,faeaerl
5.e22
14,247
IRural
Sudswrlk
2.911
MISC. PERVIOUS
Managed pervious
105,000
200,000
_
�
forest
Forest
11ESIDENTIAL
2-nc lots Nw wl
2 -ac lots lBUilt aNer ]9951
r
PaC lots leuiltbefore 1995
—
-- _—
1— hu[Bilt
o9
_ let, [Built hot .. 19951
4 a lots lN.) _
Rae lots iBullt alter 195�
-
R- ac lots lBYllt belore1 15)
-
XaFletsINew)
_ ac lets(Built aner199
% n
Mar Ia15(Built befa 1999 5)
% -ac lots l New) _
[
% -ac lots Built after 1995
R-ac lots I Built before 19951
i0wnh0mes New)_
T PwnM1Oms Built al ter 1995
'Burt,
Twnhe he fore 19 5)
omes
Multi fair ily(New)___
Multi-fan lBUdI r.
19951
o,e 1_9_95_1
♦- -
Crain. Los Sao (-New)
CustomLOtiim)New)
Custom Wt SIN, Dart afti, 1995)
Cu..t,S (Bill before 19951
-
Read.,
Driveway_ _
Parking let
- - - - - --
_ Roof
sidewalk
- --
_
_—
Managed permous
Forest
Imo_
LAND TAKEN UP BY BMP
5000
5,000
TOTAL AREA TREATED BYBMPIn
812 0539,1
301,812 0
8 6 I 0 0 0
�',
TOTAL AREA TREATED BY SERIES I1
307,812
537,196

WATERSHED SUMMARY Ver2.0
REGION:
TOTPL DEV ELOPMENT AREA (N'I:
Percent impervious
I %)
Annual Runoff Volume
(c.f.)
Total Nitrogen EMC
(mg/L)
Total Nitrogen trading
(lb /ac /yr)
Total PhasphorusEM[
(Ral
Total Phosphorus trading
(b /ab/n)
Percent DIJJerence Between:
3. Development Summary
Development
Prepared Bv:
Date:
Pm -0evelopment[ aditions
5.7%
3,886,325
Les
1.97
0.49
0.52
Piedmont
10,073,172
Post - Development Candle...
8.0%
4.686.246
1.71
2.20
0.48
0.58
Pon47evelopment w/ BM Ps
8.196
4,688,178
L68
2,16
0.44
0.57
PoxbDev withoutBMPS&
Post -Onerwith BMPS
0%
0%
-2%
-2%
-7%
-2%
h lina Friends School
Tany M. Whitaker
February 12, 2015 .
13MP VOLUME
Bivretention with
IWS
Iloretendon without
ws
Dry Detention Pond
Grassed Swale
Green Roof
Waal Spdr, FlIter
Strip
Permeable
Pavement'
Sand Filter
Water Harvesting
Wet Detention Pand
Wetland
e ftreating wane erria
Prb0ea.&
Pre - Development&
Post -Dev. without BMPS
Port - Development wRh BMPs
Percent Impervious ( %)
2%
2%
Nmaal Runoff Volume (cf.)
n%
21%
Total Nitrogen FMC (mg/L)
-A6
-9%
Total Nitrogen Wading(lb /ac /yr)
12%
10%
Total Phosphorus EMC(mg/L)
'2%
-9%
Total Phosphorus Watling(lb /ac /yr)
12%
1D%
'Negadve percent difference values indicate a decrease in runoff volume, pollutant wncenuzdon or pollutant loading Positive values indicate an increase.
Pon47evelopment w/ BM Ps
8.196
4,688,178
L68
2,16
0.44
0.57
PoxbDev withoutBMPS&
Post -Onerwith BMPS
0%
0%
-2%
-2%
-7%
-2%
h lina Friends School
Tany M. Whitaker
February 12, 2015 .
13MP VOLUME
Bivretention with
IWS
Iloretendon without
ws
Dry Detention Pond
Grassed Swale
Green Roof
Waal Spdr, FlIter
Strip
Permeable
Pavement'
Sand Filter
Water Harvesting
Wet Detention Pand
Wetland
e ftreating wane erria

UrollnafNBnd35thnol
mem 5ummary Toms M. Wnitakar �
3, Develop paBNa 122015
peVC18P[nene CA WMEW 4
p{ are AY'
amp3 BMP2
BMP1
�fATRIMEN[� I eMP3
BM4Z
' BMP1 I
CATdMEN72 BMP3 ^
BMP2 1 ^
1
BMP SUMMARYVeT2. -„� pA3piMENT ) BMP3
"P2 VgDe � POnd
�,pNenBdaPOnd 12.33 '
1
...........
333,899
7.07
laQ 25A,959
Total MBPw' 168 - -
PestentVaBn^a Bedutan _
lY)
1.37 2.69
N1Vagen EMC _ _ `
inpbw imKi1) 0332 2'
3A9
TWal inibw NWOBen _ - �- __. ... -
(IhladVd
EMC 0.144
�'�m[Law PlrosPh°cus 055
3 mRjE1
4 zo9
Taml{nflow sPnonls -
(Ib1ac7Yd
1.74 8.36
BMP OUdInw _
MweenP�ac(y[) 134
096
BMP putBaw {
Phosph °s °s Obs7adYt)
1.71 2,nO ,,....
MaaBan EMClmEtt) 23% _
��,hment OUxBow 1.74
c. _f'- -�
Wo'' nt OUtOOw ,.
11% - 0.213
tm hb(atjY4 ._..
iaxal Ni 8a^ ., .. .,.._.. _
in Nitm8VnlPatl l %) -' J 0.3`v9
t BedutBan0.1p4
Pmcan
tPZEMCImsltl 7% •.
wpBOSP1w 0.459
eatshmentput0o _
UtthmantOodw I6%
Total PhosPhon`s llb(atlYt)
Pastan[BanutVOnin PhesPh °^ts t^adl %)

Curve Number Analysis
Project: Carolina Friends School Calculated By: TMW
Slormwater Masterplan 2014
Location: 4809 Friends School Road, Durham, NC
Notes
1 Soils are primarily Appling and Herndon, per the Orange County Soil Survey. Both are classified by SCS as Hydrologic Soil Group B.
Date: 3124/2014
Z
M
N
Total Drainage Area - 231 Acres
Soils Data
Pre - Development
Post - Development
Soil
Group I Cover Description I
CN
Area
I CN: Area
Area I
CN x Area
All Impervious Cover
RGravel
I / Pavement
I
98
I 389.956
38,215,688
I I
530,770
52,015,460
Open Water
lPervious/Semi-Pery
98
150,445
14,743,610
150,445 I
14,743,6110
I
B Cover I
I
l
Lawn, Good Condition
61
, 300,000
I I
18,300,000
350,000
21,350,000
Lawn, Fair Condition
69
300,000
20,700,000
300,000
20,700,000
Lawn, Poor Condition
79
300,000
23,700,000
300,000
23,700,000
Woods, Good Condition
55
2,200,000
121,000,000
2,000,000
110,000,000
Woods, Fair Condition
60
2,356,505
141,390,300
2,335,823
140,149,380
Woods, Poor Condition
66
1,500,000
99,000,000
1,500,000
99,000,000
Brush, Good Condition
48
200,000
9,600,000
200,000
9,600,000
Brush, Fair Condition
56
100,ODD
5,600,000
70,000
3,92D,000
Brush, Poor Condition
67
250,000
16,750,000
250,000 l
_
16,750,000
Meadow /Pasture
58
850,000
49,300,000
730,000 I
42,340,000
Landscape
58
1,000,000
58,000,000 I
1,100,000 1
63,800,000
(Total
1
10,073,170
633,573,470
I
10,073,170 1
643,169,366
lWeighted Curve N
1
1 62.9 I
1
63.8
Notes
1 Soils are primarily Appling and Herndon, per the Orange County Soil Survey. Both are classified by SCS as Hydrologic Soil Group B.
Date: 3124/2014
Z
M
N

Project: Carolina Friends School
Slonnwater Mastemlan 2014
Location: 4809 Friends School Road, Durham, NC
CN
98
98
98
61
69
79
55
60
66
48
56
67
58
58
Drainaqe Area to
Pre - Development
Area CN x Area
806 78,988
5,827 571,046
0
90,000 5,490,000
20,000 1,380,000
0
0
141,179 .8,470,740
0
0
0
0
35,000 2,030,000
15,000 870,000
307,812 18,890,774
61.4
Curve Number Analysis
Pond 2 - 7.07 Acres
Post - Development
Area CN x Arez
45,106 4,420,38E
5,827 571,046
0
50,000 3,050,000
20,000 1 380,000
0
0
126,879 7012.740
0
0
0
0
35,000 2,030,000
25,000 1,450,000
307,812 20,514,174
66.6
Drainage Area to
Pre - Development
Area CN x Area
0
0
0
Calculated By: TMW
pond 3 - 12.33 Acres
Post -Development
Area CN x Area
22,000 2,156,000
38,658 3,788,484
0
0 0
0 90,000
0 20,000
0 0
337,196 20,231,760 236,538
0 0
0 0
0 0
0 0
200,000 11.600,000 90,000
0 40,000
537,196 31,831,760 537,196
59.3
Notes
1 Soils are primarily Appling and Herndon, per the Orange County Soil Survey. Both are classified by SCS as Hydrologic Soil Group B.
Date: 3131/2014
Balance of Drainage Area - 211.85 Acres
Pre - Development I Post- Development
Area CN x Area Area CN x Area
175,458 17,194,884 189,026 18,524,54E
384,129 37,644,642 486,285 47,655,93(
150,445 150,445
210,000
6,210,000 280,000
1,580,000 300,000
2,200,000
14,192,280 1,878,130
1,500,000
200,000
100,000
250,000
5,220,000 615,000
2,320,000 985,000
35,466,764 9,228,162
66.0
12,810,000 300,000 18300,000
19,320,000 190,000 13,110,000
23,700,000 280,000 22.120,000
121,000,000 2,000,000 110,000,000
112,687,800 1,972.406 118,344,360
99,000,000 1,500,000 99,000,000
9,600.000 200,000 9,600,000
5,600,000 70,000 3,920,000
16,750,000 250,000 16,750,000
35,670,000 605.000 35,090,000
57.130,000 1,035,000 60,030,000
568,107,326 9,228,162 572,444,838
61,6 62.0
Soils Data
Soil
Group
Cover Description
All
Impervious Cover
Roof, Tennis. Patios
Gravel / Pavement
Open Water
B
Pervious /Semi -Pery Cover
Lawn, Good Condition
Lawn, Fair Condition
Lawn, Poor Condition
Woods, Good Condition
Woods, Fair Condition
Woods. Poor Condition
Brush, Good Condition
Brush, Fair Condition
Brush, Poor Condition
Meadow / Pasture
Landscape
Total
Weighted Curve Number
CN
98
98
98
61
69
79
55
60
66
48
56
67
58
58
Drainaqe Area to
Pre - Development
Area CN x Area
806 78,988
5,827 571,046
0
90,000 5,490,000
20,000 1,380,000
0
0
141,179 .8,470,740
0
0
0
0
35,000 2,030,000
15,000 870,000
307,812 18,890,774
61.4
Curve Number Analysis
Pond 2 - 7.07 Acres
Post - Development
Area CN x Arez
45,106 4,420,38E
5,827 571,046
0
50,000 3,050,000
20,000 1 380,000
0
0
126,879 7012.740
0
0
0
0
35,000 2,030,000
25,000 1,450,000
307,812 20,514,174
66.6
Drainage Area to
Pre - Development
Area CN x Area
0
0
0
Calculated By: TMW
pond 3 - 12.33 Acres
Post -Development
Area CN x Area
22,000 2,156,000
38,658 3,788,484
0
0 0
0 90,000
0 20,000
0 0
337,196 20,231,760 236,538
0 0
0 0
0 0
0 0
200,000 11.600,000 90,000
0 40,000
537,196 31,831,760 537,196
59.3
Notes
1 Soils are primarily Appling and Herndon, per the Orange County Soil Survey. Both are classified by SCS as Hydrologic Soil Group B.
Date: 3131/2014
Balance of Drainage Area - 211.85 Acres
Pre - Development I Post- Development
Area CN x Area Area CN x Area
175,458 17,194,884 189,026 18,524,54E
384,129 37,644,642 486,285 47,655,93(
150,445 150,445
210,000
6,210,000 280,000
1,580,000 300,000
2,200,000
14,192,280 1,878,130
1,500,000
200,000
100,000
250,000
5,220,000 615,000
2,320,000 985,000
35,466,764 9,228,162
66.0
12,810,000 300,000 18300,000
19,320,000 190,000 13,110,000
23,700,000 280,000 22.120,000
121,000,000 2,000,000 110,000,000
112,687,800 1,972.406 118,344,360
99,000,000 1,500,000 99,000,000
9,600.000 200,000 9,600,000
5,600,000 70,000 3,920,000
16,750,000 250,000 16,750,000
35,670,000 605.000 35,090,000
57.130,000 1,035,000 60,030,000
568,107,326 9,228,162 572,444,838
61,6 62.0

Table of Contents EXH181T 13 15010 SWM Simple Analysis 4- 27- 14.gpw.
Hydra low Hydrographs by Intelisolve
1 - Year
Sunday, Apr 27 2014, 3:31 PM
SummaryReport .................................................................................. ............................... 1
HydrographReports ............................................................................ ............................... 2
Hydrograph No. 1, SCS Runoff, Total Site Area - Pre ....................... ............................... 2
TR -55 Tc Worksheet ..................................................................... ............................... 3
Hydrograph No. 2, SCS Runoff, Total Site Area - Post ..................... ............................... 4
TR -55 Tic Worksheet ..................................................................... ............................... 5

Hydrograph Summary Report
Hyd. Hydrograph I Peak T", Time to Volume
No. type flow interval peak
j (origin) (cfs) (min) (min) (cuft)
fl I
1 SCS Runoff 47.47 6 7381 369,816
2 SCS Runoff 1 53.92 6 738 1 398.672
Inflow Maximum Maximum Hydrograph
hyd(s) elevation storage description
(ft) (cult)
Total Site Area - Pre
Total Site Area - Post
1
I
j I
I
i
- -- - - -- - -- - -- - - - - -- - - - - -- L -- —. 1. _- ' -- --- - -y - -- - - - -- --- - - -- -- -
15010 SWM Simple Analysis 4 -27 -1 Vurn Period: 1 Year Sunday, Apr 27 2014, 3:31 PM
HydraFlow Hydrographs by Intelisolve

Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 1
Total Site Area - Pre
Hydrograph type
= SCS Runoff
Storm frequency
= 1 yrs
Drainage area
= 231.25 ac
Basin Slope
= 0.0%
Tc method
= TR55
Total precip.
= 3.00 in
Storm duration
= 24 hrs
Q (cfs)
50.00
40.00
30.00
20.00
10.00
Sunday, Apr 27 2014, 3:31 PM
Peak discharge
Time interval
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
47.47 cfs
6 min
62.9
Oft
32.4 min
Type II
484
Hydrograph Volume = 369,816 cult
Total Site Area - Pre
Hyd. No. 1 -- 1 Yr
2 4
Hyd Na 1
C:l
Q (cfs)
50.00
!1811P,
30.00
20.00
10.00
0.00
10 12 14 16 18 20 22 24 26
Time (hrs)

TR55 Tc Worksheet
Hydraflow Hydrographs by Intehsolve
Hyd. No. 1
Total Site Area - Pre
Description
A
B
C
Sheet Flow
Manning's n -value
= 0.060
0.011
0.011
Flow length (ft)
= 300.0
0.0
0.0
Two -year 24 -hr precip. (in)
= 3.60
0.00
0.00
Land slope ( %)
= 2.00
0.00
0.00
Travel Time (min)
= 10.69 +
0.00 +
0.00 =
Shallow Concentrated Flow
Flow length (ft)
= 300.00
0.00
0.00
Watercourse slope ( %)
= 3.00
0.00
0.00
Surface description
= Unpaved
Unpaved
Paved
Average velocity (ft /s)
= 2.79
0.00
0.00
Travel Time (min)
= 1.79 +
0.00 +
0.00 =
Channel Flow
X sectional flow area (sqft)
= 3.00
9.00
15.00
Wetted perimeter (ft)
= 12.00
12.00
12.00
Channel slope ( %)
= 2.00
1.60
0.50
Manning's n -value
= 0.040
0.030
0.025
Velocity (ft/s)
= 2.08
5.18
4.89
Flow length (ft)
= 1300.0
850.0
2000.0
Travel Time (min)
= 10.41 +
2.73 +
6.81 =
TotalTravel Time, Tc ...............................................
...............................
Totals
10.69
1.79
19.96
32.40 min

Hydrograph Plot
Hydraflow Hydrographs by Inlelisolve
Hyd. No. 2
Total Site Area - Post
Hydrograph type
Storm frequency
Drainage area
Basin Slope
Tc method
Total precip.
Storm duration
Q (cfs)
60.00
50.00
40.00
30.00
20.00
10,00
0.00
0 2 4 6 8
— Hyd No. 2
SCS Runoff
1 yrs
231.25 ac
0.0%
TR55
3.00 in
24 hrs
Total Site Area - Post
Hyd. No 2 -- 1 Yr
Sunday, Apr 27 2014, 3:31 PM
Peak discharge = 53.92 cfs
Time interval =
6 min
Curve number =
63.8
Hydraulic length =
0 ft
Time of conc. (Tc) =
32.4 min
Distribution =
Type II
Shape factor =
484
Hydrograph Volume = 398,672 cuff
Q (cfs)
60.00
I M
40.00
30.00
20.00
10.00
0.00
10 12 14 16 18 20 22 24 26
Time (hrs)
L

TR55 Tc Worksheet
Hydraflow Hydrographs by Infelisolve
Hyd. No. 2
Total Site Area - Post
Description
A
B
C
Totals
Sheet Flow
Manning's n -value
= 0.060
0.011
0.011
Flow length (ft)
= 300.0
0.0
0.0
Two -year 24 -hr precip. (in)
= 3.60
0.00
0.00
Land slope ( %)
= 2.00
0.00
0.00
Travel Time (min)
= 10.69 +
0.00 +
0.00 =
10.69
Shallow Concentrated Flow
Flow length (ft)
= 300.00
0.00
0.00
Watercourse slope ( %)
= 3.00
0.00
0.00
Surface description
= Unpaved
Unpaved
Paved
Average velocity (ft/s)
= 2.79
0.00
0.00
Travel Time (min)
= 1.79 +
0.00 +
0.00 =
1.79
Channel Flow
X sectional flow area (sqft)
= 3.00
9.00
15.00
Wetted perimeter (ft)
= 12.00
12.00
12.00
Channel slope ( %)
= 2.00
1.60
0.50
Manning's n -value
= 0.040
0.030
0.025
Velocity (ft/s)
= 2.08
5.18
4.89
Flow length (ft)
= 1300.0
850.0
2000.0
Travel Time (min)
= 10.41 +
2.73 +
6.81 =
19.96
Total Travel Time, Tc ...............................................
...............................
32.40 min
G

Legend
Hyd• Origin Description
7
SCS Runoff
Area to Pond 2 - Pre
3
Reach
Route to Stream Confluence
4
SCS Runoff
Area to Pond 3 - Pre
6
Combine
Combined Sub -areas at Confluence
7
Reach
Route to Lake
8
SCS Runoff
Balance of Area - Pre
9
Combine
Total Area - Pre
Hydraflow Hydrographs Model
1
3 4
6 y
7 1 8
!RV14 CD
Project: 15010 SWM With Ponds 2 & 3 PRE -DEV 3- 31 -1Iay, Mar 31 2014, 7:36 PM
_J,

Table of Contents 15010 SWM With Ponds 2 & 3 PRE-DEV 3-31-14.gpw
Hydraflow Hydrographs by Intelisolve Monday, Mar 31 2014, 7,14 PM
1 - Year
SummaryReport .................................................................................. ...............................
1
HydrographReports ............................................................................ ...............................
2
2
Hydrograph No. 1, SCS Runoff, Area to Pond 2 - Pre ....................... ...............................
TR -55 Tc Worksheet ..................................................................... ...............................
3
Hydrograph No. 3, Reach, Route to Stream Confluence ................... ...............................
4
Hydrograph No. 4, SCS Runoff, Area to Pond 3 - Pre ....................... ...............................
5
TR -55 Tc Worksheet ..................................................................... ...............................
6
Hydrograph No. 6, Combine, Combined Sub -areas at Confluence ... ...............................
7
Hydrograph No. 7, Reach, Route to Lake .......................................... ...............................
8
Hydrograph No. 8, SCS Runoff, Balance of Area - Pre ..................... ...............................
9
TR -55 Tc Worksheet ................................................................... ...............................
10
Hydrograph No. 9, Combine, Total Area - Pre ................................. ...............................
11

Hydrograph Summary Report
Hydrograph
description
Area to Pond 2 - Pre
Route to Stream Confluence
Area to Pond 3 - Pre
Combined Sub -areas at Confluence
Route to Lake
Balance of Area - Pre
Total Area - Pre
1
I
15010 SWM With Ponds 2 & 3 PRE - L t8r81P&icujhW Year Monday, Mar 31 2014, 7:14 PM 1
Hydragow Hydrographs by Intelisolve
T
Hyd.
Hydrograph
Peak
Time
Time to
Volume
Inflow
Maximum
Maximum
No-
type
flow
I interval'
peak
hyd(s)
elevation
storage
(origin)
(cfs)
(min)
(min)
(cuft)
(ft)
(cult)
1
SCS Runoff
1.93
6
726
9,096
- - --
- - - --
3
Reach
1.84
6
732
9,095
2
- - ---
- - - --
4
SCS Runoff
2.32
6
726
13,047
- - --
- - - - --
- - - - --
6
Combine
3.81
6
732
22,142
3, 4,
- --
- - --
7
Reach
3.65
6
738
22,139
6
- - - --
- - - --
8
SCS Runoff
36.48
6
738
304,950
- --
- - - --
- -- --
9
Combine
40.13
6
738
327,089
7,8
- - --
- - --
Hydrograph
description
Area to Pond 2 - Pre
Route to Stream Confluence
Area to Pond 3 - Pre
Combined Sub -areas at Confluence
Route to Lake
Balance of Area - Pre
Total Area - Pre
1
I
15010 SWM With Ponds 2 & 3 PRE - L t8r81P&icujhW Year Monday, Mar 31 2014, 7:14 PM 1
Hydragow Hydrographs by Intelisolve

Hydrograph Mot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 1
Area to Pond 2 - Pre
Hydrograph type
Storm frequency
Drainage area
Basin Slope
Tc method
Total precip.
Storm duration
Q (cfs)
2.00
1.00
SCS Runoff
1 yrs
7.07 ac
0.0%
TR55
3.00 in
24 hrs
Area to Pond 2 - Pre
Hyd. No. 1 -- 1 Yr
Monday, Mar 31 2014, 7:14 PM
Peak discharge = 1.93 cfs
Time interval =
6 min
Curve number =
61.4
Hydraulic length =
0 ft
Time of conc. (Tc) =
11.1 min
Distribution =
Type II
Shape factor =
484
Hydrograph Volume = 9,096 cult
i
i
I v I
2 4
- Hyd No. 1
6 8 10 12 14 16 18 20 22 24
Q (cfs)
2.00
1.00
-- 0.00
26
Time (hrs)
e

TR55 Tc Worksheet
Hydraflow Hydrographs by Inlelisolve
Hyd. No. 1
Area to Pond 2 - Pre
Description
A
B
C Totals
Sheet Flow
Manning's n -value
= 0.050
0.011
0.011
Flow length (ft)
= 300.0
0.0
0.0
Two -year 24 -hr precip. (in)
= 3.60
0.00
0.00
Land slope ( %)
= 4.00
0.00
0.00
Travel Time (min)
= 7.00 +
0.00 +
0.00 = 7.00
Shallow Concentrated Flow
Flow length (ft)
= 600.00
0.00
0.00
Watercourse slope ( %)
= 2.30
0.00
0.00
Surface description
= Unpaved
Unpaved
Paved
Average velocity (ft/s)
= 2.45
0.00
0.00
Travel Time (min)
= 4.09 +
0.00 +
0.00 = 4.09
Channel Flow
X sectional flow area (sqft)
= 0.00
0.00
0.00
Wetted perimeter (ft)
= 0.00
0.00
0.00
Channel slope ( %)
= 0.00
0.00
0.00
Manning's n -value
= 0.040
0.030
0.025
Velocity (ft/s)
= 0.00
0.00
0.00
Flow length (ft)
= 0.0
0.0
0.0
Travel Time (min) = 0.00 + 0.00 + 0.00 = 0.00
TotalTravel Time, Tc ............................................... ............................... 11.10 min

Hydrograph KDt
Hydraflow Hydrographs by Intelisolve
Hyd. No. 3
Route to Stream Confluence
Hydrograph type = Reach
Storm frequency = 1 yrs
Inflow hyd. No.
= 2
Reach length
= 700.0 ft
Manning's n
= 0.030
Side slope
= 1.0:1
Rating curve x
= 2.194
Ave-. velocity
= 2.11 ft/s
Modified Att -Kin routing method used
0 (cfs)
0.10 —
0.09
0.08
0.07
0.06
0.05
0.04
0.03 -
0.02
0.01 -
0.00 -
0 2 4
- -- Hyd No. 3
Monday, Mar 31 2014, 7:14 PM
Peak discharge = 1.84 cfs
Time interval
= 6 min
Section type
= Trapezoidal
Channel slope
= 1.7 %
Bottom width
= 5.0 ft
Max. depth
= 2.0 ft
Roating curve = 1.431
m uting coeff. = 0.8740
Hydrograph Volume = 9,095 cult
Route to S':ream Confluence \
Hyd. No. 3 -- 1 Yr 0 (cfs)
0.10
- 0.09
- 1 0.08
I
� 0.07
- 0.06
0.05
0.04
-- 0.03
- 0.02
I
- - —}-- T 0.01
0.00
8 10 12 14 16 18 20 22 24 26
Time (hrs)
-- Hyd No. 2
lrl
I

Hydrograph Mot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 4
Area to Pond 3 - Pre
Hydrograph type
= SCS Runoff
Storm frequency
= 1 yrs
Drainage area
= 12.33 ac
Basin Slope
= 0.0%
Tc method
= TR55
Total precip.
= 3.00 in
Storm duration
= 24 hrs
Q (cfs)
3.00
2.00
1.00
Area to Pond 3 - Pre
Hyd. No. 4 -- 1 Yr
Monday, Mar 31 2014. 7:14 PM
Peak discharge = 2.32 cfs
Time interval
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
6 min
59.3
Oft
13 min
Type II
484
Hydrograph Volume = 13,047 cuff
0.00 i I — i -
0 2 4 6 8
- - -- Hyd No. 4
Q (cfs)
3.00
2.00
1.00
I i --L 1 -- ' I — 1 -- 0.00
10 12 14 16 18 20 22 24 26
Time (hrs)
4

TR55 Tc Worksheet
Hyd. No. 4
Area to Pond 3 - Pre
Description
A B C
Hydraflow Hydrographs by Intelisolve
Totals
Sheet Flow
= 0.00
0.00
0.00
Manning's n -value
= 0.050
0.011
0.011
Flow length (ft)
= 300.0
0.0
0.0
Two -year 24 -hr precip. (in)
= 3.60
0.00
0.00
Land slope ( %)
= 4.00
0.00
0.00
Travel Time (min)
= 7.00 +
0.00 +
0.00 = 7.00
Shallow Concentrated Flow
= 0.00
+ 0.00 +
0.00 = 0.00
Flow length (ft)
= 400.00
450.00
0.00
Watercourse slope ( %)
= 1.00
6.00
0.00
Surface description
= Unpaved
Unpaved
Paved
Average velocity (ft/s)
= 1.61
3.95
0.00
Travel Time (min)
= 4.13 +
1.90 +
0.00 = 6.03
Channel Flow
X sectional flow area (sqft)
= 0.00
0.00
0.00
Wetted perimeter (ft)
= 0.00
0.00
0.00
Channel slope ( %)
= 0.00
0.00
0.00
Manning's n -value
= 0.015
0.015
0.050
Velocity (ft/s)
= 0.00
0.00
0.00
Flow length (ft)
= 0.0
0.0
0.0
Travel Time (min)
= 0.00
+ 0.00 +
0.00 = 0.00
TotalTravel Time, Tc ...............................................
...............................
13.00 min

Hydvograph Mot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 6
Combined Sub -areas at Confluence
Hydrograph type = Combine
Storm frequency = 1 yrs
Inflow hyds. = 3, 4
Q (cfs)
4.00 —
K m
2.00
1.00
Monday, Mar 31 2014, 7:14 PM
Peak discharge = 3.81 cfs
Time interval = 6 min
Hydrograph Volume = 22,142 cull
Combined Sub -areas at Confluence
Hyd. No. 6 -- 1 Yr
Q (cfs)
4.00
3.00
2.00
1.00
0.00 _— L_! -_ � -N-- 1 0.00
0 2 4 6 8 10 12 14 16 18 20 22 24 26
-- Hyd No. 6 -- Hyd No. 3 —Hyd No. 4 Time (hrs)
7

H y ®drrograph Mot
Hydraflow Hydrographs by Intalisolve
Hyd. No. 7
Route to Lake
Hydrograph type
= Reach
Storm frequency
= 1 yrs
Inflow hyd. No.
= 6
Reach length
= 800.0 ft
Manning's n
= 0.025
Side slope
= 1.0:1
Rating curve x
= 1.441
Ave. velocity
= 1.93 ft/s
Modified Att -kin routing method used
Q (cfs)
4.00
3.00
2.00
1.00
0.00
0 2 4
— -- Hyd No. 7
Monday, Mar 31 2014, 7:14 PM
Peak discharge = 3.65 cfs
Time interval
Section type
Channel slope
Bottom width
Max. depth
Rating curve m
Routing coeff.
6 min
Trapezoidal
0.5%
5.0 ft
3.0 ft
1.429
0.7656
Hydrograph Volume = 22,139 cuff
Route to Lake
Hyd. No. 7 -- 1 Yr
ll
Q (cfs)
4.00
3.00
2.00
1.00
0.00
8 10 12 14 16 18 20 22 24 26
Hyd No. 6 Time (hrs)

Hydrograph Pk)t
Hydraflow Hydrographs by Intelisolve
Hyd. No. 8
Balance of Area - Pre
Hydrograph type
= SCS Runoff
Storm frequency
= 1 yrs
Drainage area
= 211.85 ac
Basin Slope
= 0.0%
Tc method
= TR55
Total precip.
= 3.00 in
Storm duration
= 24 hrs
Q (cfs)
40.00
30.00
r0 1I,
10.00
0.00
0 2 4
-- - Hyd No. 8
Monday, Mar 31 2014, 7,14 PM
Peak discharge = 36.48 cfs
Time interval
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
6 min
61.6
Oft
32.4 min
Type II
484
Hydrograph Volume = 304,950 cult
Balance of Area - Pre
Hyd. No. 8 -- 1 Yr
6 8 10 12 14 16
Q (cfs)
40.00
30.00
/ 1 11
10.00
0.00
18 20 22 24 26
Time (hrs)
F

TR55 Tc Worksheet
Hydraflow Hydrographs by Intelisolve
Hyd. No. 8
Balance of Area - Pre
Description
A
B
C
Sheet Flow
Manning's n -value
= 0.060
0.011
0.011
Flow length (ft)
= 300.0
0.0
0.0
Two -year 24 -hr precip. (in)
= 3.60
0.00
0.00
Land slope ( %)
= 2.00
0.00
0.00
Travel Time (min)
= 10.69 +
0.00 +
0.00 =
Shallow Concentrated Flow
Flow length (ft)
= 300.00
0.00
0.00
Watercourse slope ( %)
= 3.00
0.00
0.00
Surface description
= Unpaved
Unpaved
Paved
Average velocity (f /s)
= 2.79
0.00
0.00
Travel Time (min)
= 1.79 +
0.00 +
0.00 =
Channel Flow
X sectional flow area (sqft)
= 3.00
9.00
15.00
Wetted perimeter (ft)
= 12.00
12.00
12.00
Channel slope ( %)
= 2.00
1.60
0.50
Manning's n -value
= 0.040
0.030
0.025
Velocity (fYs)
= 2.08
5.18
4.89
Flow length (ft)
= 1300.0
850.0
2000.0
Travel Time (min)
= 10.41 +
2.73 +
6.81 =
Total Travel Time, Tc ...............................................
...............................
Totals
i to) M. $
1.79
19.96
32.40 min
1(

Hydrrogrraph P o4
Hydraflow Hydrographs by Intelisolve
Hyd. No. 9
Total Area - Pre
Hydrograph type = Combine
Storm frequency = 1 yrs
Inflow hyds. = 7, 8
Q (cfs)
50.00
40.00
30.00
20.00
10.00 --
0.00 ------ I-- I
0 2 4
- Hyd No. 9
2
Total Area - Pre
Hyd. No. 9 -- 1 Yr
Monday, Mar 31 2014, 7:14 PM
Peak discharge = 40.13 cis
Time interval = 6 min
Hydrograph Volume = 327,089 cuff
Q (cfs)
50.00
40.00
30.00
20.00
- - -- - I -- - - -- - -- -- 10.00
--�
0.00
8 10 12 14 16 18 20 22 24 26
-- Hyd No. 7 —Hyd No. 8 Time (hrs)
I.

WAR
21
4
CD
7 $
CD
Legend
Hyd• Origin Description V9
1 SCS Runoff Area to Pond 2 - Post
2 Reservoir Outflow from Pond #2
3 Reach Route to Stream Confluence
4 SCS Runoff Area to Pond 3 - Post
5 Reservoir Outflow from Pond #3
6 Combine Combined Sub -areas at Confluence
7 Reach Route to Lake
8 SCS Runoff Balance of Area - Post
9 Combine Total Area - Post
Hydraflow Hydrographs Model I Project: 15010 SWIM With Ponds 2 & 3 POST -DEV 3- 31 }Utgplliiiiiy, Mar 31 2014, 7:31 PM
4ti

Table of Contents 15010 SWM With Ponds 2 & 3 POST -DEV 3- 31- 14.gpw
Hydraflow Hydrographs by Intelisolve Monday, Mar 31 2014, 7:29 PM
1 - Year
SummaryReport
.................................................................................. ...............................
1
HydrographReports ............................................................................ ...............................
2
2
Hydrograph No.
1, SCS Runoff, Area to Pond 2 - Post ..................... ...............................
TR-55 Tc Worksheet ..................................................................... ...............................
3
Hydrograph No.
2, Reservoir, Outflow from Pond #2 ........................ ...............................
4
PondReport
.................................................................................. ...............................
5
Hydrograph No.
3, Reach, Route to Stream Confluence ................... ...............................
6
Hydrograph No.
4, SCS Runoff, Area to Pond 3 - Post ..................... ...............................
7
TR -55 Tc Worksheet ..................................................................... ...............................
8
Hydrograph No.
5, Reservoir, Outflow from Pond #3 ....................... ...............................
9
PondReport
................................................................................ ...............................
10
Hydrograph No.
6, Combine, Combined Sub -areas at Confluence . ...............................
11
Hydrograph No.
7, Reach, Route to Lake ........................................ ...............................
12
Hydrograph No.
8, SCS Runoff, Balance of Area - Post ................. ...............................
13
TR -55 Tc Worksheet ................................................................... ......:........................
14
Hydrograph No.
9, Combine, Total Area - Post ............................... ...............................
15

Hydrograph Summary Report
Hyd.
Hydrograph
Peak
Time
Time to 1
Volume
Inflow
No.
type
flow
interval
peak
hyd(s)
(origin)
(cfs)
(min)
(min)
(cuft)
i
1
SCS Runoff
3.65
6
726
13,667
- - --
2
Reservoir
0.55
6
774
I
13,666
1
3
r Reach
0.55
6
780
13,660
2
4
SCS Runoff
5.99
6
726
22,852
--
5
Reservoir
0.60
6
828
22,851
4
6
Combine
1.15
6
798
36,511
3.5
7
Reach
1.15
6
810
36,502
6
8
SCS Runoff
38.62
6
738
315,297
- --
9
Combine
39.51
6
738
351,799
T8
i
Maximum Maximum I Hydrograph
elevation storage description
(ft) (cuft)
104.39 4,081
105.34 8,270
I
I
15010 SWM With Ponds 2 & 3 P0S1- i0IeW6vPbA4cb0kWear
Area to Pond 2 - Post
Outflow from Pond #2
Route to Stream Confluence
Area to Pond 3 - Post
Outflow from Pond #3
Combined Sub -areas at Confluence
Route to Lake
Balance of Area - Post
Total Area - Post
Monday, Mar 31 2014, 7:29 PM___ J
Hydraffow Hydrographs by Intelisolve

Hydrograph No4
Hydraflow Hydrographs by Intelisolve
Hyd. No. 1
Area to Pond 2 - Post
Hydrograph type
= SCS Runoff
Storm frequency
= 1 yrs
Drainage area
= 7.07 ac
Basin Slope
= 0.0%
Tc method
= TR55
Total precip.
= 3.00 in
Storm duration
= 24 hrs
Q (cfs)
4.00
3.00
2.00
1.00
0.00
0
Monday, Mar 31 2014, 7:29 PM
Peak discharge = 3.65 cfs
Time interval
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
6 min
66.6
Oft
11.1 min
Type II
484
Hydrograph Volume = 13,667 cuff
Area to Pond 2 - Post
Hyd. No. 1 -- 1 Yr
2 4
Hyd No 1
6 8 10 12 14 16 18 20 22 24
Q (cfs)
4.00
i 11
2.00
1.00
0.00
26
Time (hrs)

TR55 Tc Worksheet
Hydraflow Hydrographs by Intelisolve
Hyd. No. 1
Area to Pond 2 - Post
Description
A
B
C
Totals
Sheet Flow
Manning's n -value
= 0.050
0.011
0.011
Flow length (ft)
= 300.0
0.0
0.0
Two -year 24 -hr precip. (in)
= 3.60
0.00
0.00
Land slope ( %)
= 4.00
0.00
0.00
Travel Time (min)
= 7.00 +
0.00 +
0.00 =
7.00
Shallow Concentrated Flow
Flow length (ft)
= 600.00
0.00
0.00
Watercourse slope ( %)
= 2.30
0.00
0.00
Surface description
= Unpaved
Unpaved
Paved
Average velocity (ft/s)
= 2.45
0.00
0.00
Travel Time (min)
= 4.09 +
0.00 +
0.00 =
4.09
Channel Flow
X sectional flow area (sqft)
= 0.00
0.00
0.00
Wetted perimeter (ft)
= 0.00
0.00
0.00
Channel slope ( %)
= 0.00
0.00
0.00
Manning's n -value
= 0.040
0.030
0.025
Velocity (ft/s)
= 0.00
0.00
0.00
Flow length (ft)
= 0.0
0.0
0.0
Travel Time (min)
= 0.00 +
0.00 +
0.00
= 0.00
TotalTravel Time, Tc ............................................... ............................... 11.10 min

Hydrr®giyap h Not
Hydraflow Hydrographs by Inteltsolve
Hyd. No. 2
Outflow from Pond #2
Hydrograph type = Reservoir
Storm frequency = 1 yrs
Inflow hyd. No. = 1
Reservoir name = Detention Pond 2
Storage Indication method used
Q (cfs)
4.00
3.00
2.00
1.00 — -
2 4
Hyd No. 2
Outflow from Pond #2
Hyd. No. 2 -- 1 Yr
-r - - - -- —
I
6 8 10 12 14
- Hyd No 1
Monday, Mar 31 2014. 7:29 PM
Peak discharge = 0.55 cfs
Time interval = 6 min
Max. Elevation = 104.39 ft
Max. Storage = 4,081 cuft
Hydrograph Volume = 13,666 cuff
16 18 20
Q (cfs)
4.00
3.00
2.00
1.00
0.00
22 24 26
Time (hrs)
I

- e! III r, 1 0 tom. lei
Hydrallow Hydrographs by Intelisolve Monday, Mar 31 2014, 729 PM
Pond No. 1 • Detention Pond 2
Pond Data
Pond storage is based on known contour areas. Average end area method used.
Stage / Storage Table
Stage (ft)
Elevation (ft)
Contour area (sgft)
Incr. Storage (cult)
Total storage (cuft)
0.00
100.00
00
0
0
1.00
101.00
300
150
150
2.00
102.00
600
450
600
3.00
103.00
1,200
900
1,500
4.00
104.00
2,000
1,600
3,100
5.00
105.00
3,000
2,500
5,600
6.00
106.00
5,000
4,000
9,600
Culvert I Orifice
Structures
Weir Structures
[A]
[B]
[C]
[D]
[A] IB]
[C]
[D]
Rise (in)
= 4.00
0.00
0.00
0.00
Crest Len (ft)
= 10.00 0.00
0.00
0.00
Span (in)
= 4.00
0.00
0.00
0.00
Crest El. (ft)
= 104.50 0.00
0.00
0.00
No. Barrels
= 1
0
0
0
Weir Coen.
= 2.60 0.00
0.00
0.00
Invert El. (ft)
= 100.00
0.00
0.00
0.00
Weir Type
= Broad --
--
- --
Length (ft)
= 50.00
0.00
0.00
0.00
Multi -Stage
= No No
No
No
Slope ( %)
= 2.00
0.00
0.00
0.00
N -Value
= .013
.000
.000
.000
Orif. Coeff.
= 0.60
0.00
0.00
0.00
Multi -Stage = n/a No No No Exfiltration = 0.000 in /hr (Contour) Tailwater Elev. = 0.00 It
Note. C.WerttOrlke w lows have been analyzed under inlet and outlet control
Stage (ft)
6.00
5.00
4.00
3.00
2.00
1.00
Stage / Discharge
Stage (ft)
6.00
5.00
4.00
3.00
2.00
1.00
j
0.00 __. ..1 __ _. __ _ !__ - __ -. ._. __'___.. __ J_.. - _. __ �.- - 0.00
0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00 50.00
Discharge (cfs)
Total 0

Hydrograph Plot
Hydrallow Hydrographs by Inlelisolve
Hyd. No. 3
Route to Stream Confluence
Hydrograph type
= Reach
Storm frequency
= 1 yrs
Inflow hyd. No.
= 2
Reach length
= 700.0 ft
Manning's n
= 0.030
Side slope
= 1.0:1
Rating curve x
= 2.194
Ave. velocity
= 1.45 fUs
Modified Att -Kin routing method used
Q (cfs)
1.00
T
0.90
I
0.80 } - --}
0.70 -_
0.60 -
0.50 -
0.40
0.30 --
0.20 -
0.10T - -I
� I
0.00 ____ -__
0 2 4
Hyd No. 3
11
Monday, Mar 31 2014, 729 PM
Peak discharge = 0.55 cfs
Time interval
Section type
Channel slope
Bottom width
Max. depth
Rating curve m
Routing coeff.
6 min
Trapezoidal
1.7%
5.0 ft
2.0 ft
1.431
0.6949
Hydrograph Volume = 13,660 cult
Route to Stream Confluence
Hyd. No. 3 -- 1 Yr Q (cfs)
---T . -_ _ _ 1.00
- - 0.90
I I
�- - - -- - 0.80
- -� 0.70
0.60
J-4 - 0.50
+ - 0.40
- - -- - 0.30
-- - - -� -- - -- - -- - -- -- 0.20
I
114 0.00
8 10 12 14 16 18 20 22 24 26
Hyd No. 2 Time (hrs)
- - - --

Hydrograph Not
Hydraflow Hydrographs by Intelisolve
Hyd. No. 4
Area to Pond 3 - Post
Hydrograph type
= SCS Runoff
Storm frequency
= 1 yrs
Drainage area
= 12.33 ac
Basin Slope
= 0.0%
Tc method
= TR55
Total precip.
= 3.00 in
Storm duration
= 24 hrs
Q (cfs)
6.00
5.00
I
4.00
3.00
2.00 —�— -
i
1.00 — -- - -1 . — - -- -
i
I �
0.00 - -- -- - - --
0 2 4 6 8
- Hyd No. 4
Area to Pond 3 - Post
Hyd. No. 4 -- 1 Yr
Monday, Mar 31 2014, 7:29 PM
Peak discharge = 5.99 cfs
Time interval
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
6 min
66
Oft
15.3 min
Type II
484
Hydrograph Volume = 22,852 cult
Q (cfs)
6.00
5.00
4.00
3.00
2.00
1.00
- — - -- - ! -� — -- �— 0.00
10 12 14 16 18 20 22 24 26
Time (hrs)

TR55 Tc Worksheet
Hydraflow Hydrographs by Intelisolve
Hyd. No. 4
Area to Pond 3 - Post
Description
A
B
C
Totals
Sheet Flow
Manning's n -value
= 0.050
0.011
0.011
Flow length (ft)
= 300.0
0.0
0.0
Two -year 24 -hr precip. (in)
= 3.60
0.00
0.00
Land slope ( %)
= 4.00
0.00
0.00
Travel Time (min)
= 7.00 +
0.00 +
0.00 =
7.00
Shallow Concentrated Flow
Flow length (ft)
= 400.00
550.00
0.00
Watercourse slope ( %)
= 2.00
1.50
0.00
Surface description
= Unpaved
Unpaved
Paved
Average velocity (ft/s)
= 2.28
1.98
0.00
Travel Time (min)
= 2.92 +
4.64 +
0.00 =
7.56
Channel Flow
X sectional flow area (sqft)
= 3.00
0.00
0.00
Wetted perimeter (ft)
= 6.30
0.00
0.00
Channel slope ( %)
= 1.50
0.00
0.00
Manning's n -value
= 0.015
0.050
0.050
Velocity (ft/s)
= 7.40
0.00
0.00
Flow length (ft)
= 350.0
0.0
0.0
Travel Time (min)
= 0.79 +
0.00 +
0.00 =
0.79
TotalTravel Time, Tc ...............................................
...............................
15.30 min
E

Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 5
Outflow from Pond #3
Hydrograph type = Reservoir
Storm frequency = 1 yrs
Inflow hyd. No. = 4
Reservoir name = Detention Pond 3
Storage Indication method used
Q (cfs)
6.00
5.00
4.00
3.00
2.00
1.00
0.00 —
0
Outflow from Pond #3
Hyd. No. 5 -- 1 Yr
Monday. Mar 31 2014, 7,29 PM
Peak discharge = 0.60 cfs
Time interval = 6 min
Max. Elevation = 105.34 ft
Max. Storage = 8,270 cuft
Hydrograph Volume = 22,851 cuft
2 4
Hyd No. 5
ty
Q (cfs)
6.00
. W
4.00
3.00
2.00
1.00
0.00
8 10 12 14 16 18 20 22 24 26
Time (hrs)
— - Hyd No. 4
■

Pond Report
Hydraflow Hydrographs by Intelisolve
Monday, Mar 31 2014, 7:29 PM
Pond No. 2 - Detention Pond 3
Pond Data
Pond storage is based on known contour areas.
Average end area method used.
Stage / Storage Table
Stage (ft) Elevation (ft) Contour
area (sgft)
Incr. Storage (cuft)
Total storage (cult)
0.00 100.00
00
0
0
1.00 101.00
500
250
250
2.00 102.00
800
650
900
3.00 103.00
1,500
1,150
2,050
4.00 104.00
2,400
1,950
4,000
5.00 105.00
3,300
2,850
6,850
6.00 106.00
5,000
4,150
11,000
Culvert I Orifice Structures
Weir Structures
[A] IB]
IC]
[D]
[A] [B)
[C]
[P]
Rise (in) = 4.00 0.00
0.00
0.00
Crest Len (ft)
= 10.00 0.00
0.00
0.00
Span (in) = 4.00 0.00
0.00
0.00
Crest El. (ft)
= 105.50 0.00
0.00
0.00
No. Barrels = 1 0
0
0
Weir Coeff.
= 2.60 0.00
0.00
0,00
Invert El. (ft) = 100.00 0.00
0.00
0.00
Weir Type
= Broad -
-
- --
Length (ft) = 50.00 0.00
0.00
0.00
Multi -Stage
= No No
No
No
Slope ( %) = 2.00 0.00
0.00
0.00
N -Value = .013 .000
.000
.000
Crif. Coeff. = 0.60 0.00
0.00
0.00
Multi -Stage = n/a No No No Extiltration = 0.000 in /hr (Contour) Tailwater Elev. = 0.00 it
Note CulveWOrifice outflows have been analyzed under inlet and outlet control
Stage (ft)
6.00
5.00
4.00
3.00
2.00
Stage / Discharge
1.00 - --- - --
j0.00 - '
0.00 1.00 2.00
Total 0
300 4.00 5.00
6.00 7.00 8.00 9.00
Stage (ft)
6.00
5.00
4.00
3.00
2.00
1.00
0.00
10.00
Discharge (cfs)
1(

Hydrograph Mot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 6
Combined Sub -areas at Confluence
Hydrograph type = Combine
Storm frequency = 1 yrs
Inflow hyds. = 3, 5
Q (cfs)
2.00 — -
1.00
Monday. Mar 31 2014. 7:29 PM
Peak discharge = 1.15 cfs
Time interval = 6 min
Hydrograph Volume = 36,511 cuff
Combined Sub -areas at Confluence
Hyd. No. 6 -- 1 Yr
0.00 - -- - -=
0 2 4
Hyd No. 6
6 8 10
- Hyd No. 3
12 14
16
Hyd No. 5
18 20 22 24
Q (cfs)
2.00
1.00
- 1 0.00
26
Time (hrs)
11

Hydrograph Not
Hydraflow Hydrographs by Intelisolve
Hyd. No. 7
Route to Lake
Hydrograph type = Reach
Storm frequency = 1 yrs
Inflow hyd. No. = 6
Reach length
= 800.0 ft
Manning's n
= 0.025
Side slope
= 1.0:1
Rating curve x
= 1.441
Ave. velocity
= 1.35 ft/s
Modified Att -Kin routing method used.
Q (cfs)
2.00
1.00
0.00 i - - ----
0 2
Monday, Mar 31 2014, 7:29 PM
Peak discharge
Time interval
Section type
Channel slope
Bottom width
Max. depth
Rating curve m
Routing coeff.
= 1.15 cfs
= 6 min
= Trapezoidal
= 0.5%
= 5.0 ft
= 3.0 ft
= 1.429
= 0.6040
Hydrograph Volume = 36.502 cuff
Route to Lake
Hyd. No. 7 -- 1 Yr
Hyd No. 7 - -- Hyd No. 6
14 16 18 20 22 24
Q (cfs)
2.00
1.00
0.00
26
Time (hrs)
1:
0
it
i
i
I
i�
6
8
10
12
Hyd No. 7 - -- Hyd No. 6
14 16 18 20 22 24
Q (cfs)
2.00
1.00
0.00
26
Time (hrs)
1:

Hydrograph Blot
HydraOow Hydrographs by Intelisolve
Hyd. No. 8
Balance of Area - Post
Hydrograph type
= SCS Runoff
Storm frequency
= 1 yrs
Drainage area
= 211.85 ac
Basin Slope
= 0.0%
Tc method
= TR55
Total precip.
= 3.00 in
Storm duration
= 24 hrs
Q (cfs)
40.00
30.00
20.00
10.00
Monday, Mar 31 2014, 7:29 PM
Peak discharge = 38.62 cfs
Time interval
Curve number
Hydraulic length
Time of conc. (Tc)
Distribution
Shape factor
6 min
62
Oft
32.4 min
Type II
484
Hydrograph Volume = 315,297 cuff
Balance of Area - Post
Hyd. No. 8 -- 1 Yr
0.00 --
0 2 4 6
Hyd No. 8
8 10 12 14 16 18 20 22 24
Q (cfs)
40.00
30,00
rMI
10.00
0.00
26
Time (hrs)
1:

1r
TR55 Tc Worksheet
Hydraflow Hydrographs by Intelisolve
Hyd. No. 8
Balance of Area - Post
Description
A
B
C
Totals
Sheet Flow
Manning's n -value
= 0.060
0.011
0.011
Flow length (ft)
= 300.0
0.0
0.0
Two -year 24 -hr precip. (in)
= 3.60
0.00
0.00
Land slope ( %)
= 2.00
0.00
0.00
Travel Time (min)
= 10.69 +
0.00 +
0.00 =
10.69
Shallow Concentrated Flow
Flow length (ft)
= 300.00
0.00
0.00
Watercourse slope ( %)
= 3.00
0.00
0.00
Surface description
= Unpaved
Unpaved
Paved
Average velocity (ft/s)
= 2.79
0.00
0.00
Travel Time (min)
= 1.79 +
0.00 +
0.00 =
1.79
Channel Flow
X sectional flow area (sqft)
= 3.00
9.00
15.00
Wetted perimeter (ft)
= 12.00
12.00
12.00
Channel slope ( %)
= 2.00
1.60
0.50
Manning's n -value
= 0.040
0.030
0.025
Velocity (ft/s)
= 2.08
5.18
4.89
Flow length (ft)
= 1300.0
850.0
2000.0
Travel Time (min)
= 10.41 +
2.73 +
6.81 =
19.96
Total Travel Time, Tc ...............................................
...............................
32.40 min

Hydrograph Plot
Hydraflow Hydrographs by Intelisolve
Hyd. No. 9
Total Area - Post
Hydrograph type = Combine
Storm frequency = 1 yrs
Inflow hyds. = 7, 8
Q (cfs)
40.00
30.00
20.00
10.00
Monday, Mar 312014, 7:29 PM
Peak discharge = 39.51 cfs
Time interval = 6 min
Hydrograph Volume = 351,799 cuh
Total Area - Post
Hyd. No. 9 -- 1 Yr
2 4
Hyd No. 9
6 8 10
- — Hyd No. 7
12 14
16
Hyd No. 8
18 20
Q (cfs)
40.00
30.00
20.00
10.00
- 0.00
22 24 26
Time (hrs)
1;