20041801 Ver 1_Stormwater Info_20050927

FhWK
LETTER OF TRANSMITTAL WDICKSON
community infrastructure consultants
3101 John Humphries Wynd Raleigh, North Carolina 27612 919.782.0495 tel. [phone] fax
TO: NC Division of Water Quality DATE: 9/26/05
Wetlands/401 Unit
1650 MSC
Raleigh, NC 27699-1650
ATTENTION: Mr. Sam ARhimien
RE: Ford's Colony at Rocky Mount
DWQ Project No. 04-1801
WKD# 40371.00.RA
We are sending via: ? Overnight ® Regular Mail ? Pick-up ? Hand Delivered
The following items: ? Correspondence ? Plans ? Specifications ® Other as listed below:
COPIES DATE NO. DESCRIPTION
1 9-14-05 NA Updated DWQ worksheets for BMP's.
1 9-14-05 NA Updated WK Dickson BMP Design Spreadsheets
1 9-23-05 NA Planting Plan
1 9-23-05 NA Updated report

THESE ARE TRANSMITTED as checked below:
? For Approval ® As Requested ? Approved as Submitted ? Returned for Corrections
? For Your Use ® For Review and Comment ? Approved as Noted ? Forward to Subcontractor
REMARKS:
Sam, Attached are the updates you requested. Let me know if you need anything else. The signed
Inspection agreements will be coming upon your review of my recent email.
COPY TO: SIGNED:
D
S F P 2 7 2005
?'?AWL sMo sroR?
LETTER OF TRANSMITTAL I&WK
WDICKSON
community infrastructure consultants
3101 John Humphries Wynd Raleigh, North Carolina 27612 919.782.0495 tel. [phone] fax
TO: NC Division of Water Quality
Wetlands/401 Unit
1650 MSC
Raleigh, NC 27699-1650
ATTENTION: Mr. Sam Aghimien
DATE: 9/14/05
RE: Ford's Colon at Rock Mount
DW Project No. 04-1801
WKD# 40371.00.RA
We are sending via: ? Overnight ? Regular Mail ? Pick-up ® Hand Delivered
The following items: ? Correspondence ? Plans ? Specifications ® Other as listed below:
COPIES DATE NO. DESCRIPTION
1 9-13-05 NA DWQ worksheets for BMP's.
1 9-13-05 NA Update report

of,

JF,e,ydiS?CRA.,,
Ai,' H
THESE ARE TRANSMITTED as checked below:
? For Approval ® As Requested ? Approved as Submitted ? Returned for Corrections
? For Your Use ® For Review and Comment ? Approved as Noted ? Forward to Subcontractor
REMARKS:
Sam, Attached are the DWQ worksheets that you requested. These now include anticipated elevations
for the proposed BMP's. The report now includes a Table 2 that provides an inventory of the BMP's. Let
me know if you need anvthinR else.
COPY TO:
G
SIGNED: I j k

DWQ 401 NARRATIVE
FORD'S COLONY AT ROCKY MOUNT
•
•
•
INTRODUCTION .......................................................................................................... 1
PROPOSESD IMPROVEMENTS ................................................................................................................ 3
DEVELOPMENT PHASING ..................................................................................................................... 4
PHYSIOGRAPHY, TOPOGRAPHY AND DRAINAGE ..................................................................................... 5
SOILS ................................................................................................................................................ 5
VEGETATION ...................................................................................................................................... 5
NATURAL RESOURCES OF SPECIAL CONCERN .......................................................................................... 6
STORMWATER QUALITY .............................................................................................. 9
DESIGN REQUIREMENTS & OBJECTIVES .................................................................................................. 9
SUMMARY OF STORMWATER QUALITY ................................................................................................... 9
EROSION CONTROL MEASURES ................................................................................ 10
PROPOSED MEASURES ....................................................................................................................... 10
CHANNEL STABILITY ANALYSIS ............................................................................................................ 10
INSPECTION AND MAINTENANCE PROCEDURES .................................................... 10
CONCLUSIONS ........................................................................................................... 10
Ford's Colony - Stormwater Quality
WK Dickson & Co., Inc.
TOC

DWQ 401 NARRATIVE
FORD'S COLONY AT ROCKY MOUNT
•
LIST OF FIGURES AND TABLES
FIGURE 1: VICINITY MAP ..................................................................................................................... 2
FIGURE 2: DRAINAGE MAP ................................................................................................................... 6
FIGURE 3: SOILS MAP .......................................................................................................................... 7
TABLE 1: SUMMARY OF TSS REMOVAL AT FOCUS AREAS ......................................................................... 3
TABLE 2: FEDERAL PROTECTED SPECIES FOR NASH COUNTY, NORTH CAROLINA ......................................... 3
TABLE 3: FEDERAL PROTECTED SPECIES FOR NASH COUNTY, NORTH CAROLINA ......................................... 8
TABLE 4: FEDERAL SPECIES OF CONCERN ............................................................................................... 8
TABLE 5: SUMMARY OF TSS REMOVAL .................................................................................................. 9
LIST OF APPENDICES
APPENDIX A: OVERVIEW MAP WITH LANDUSE & MAJOR DRAINAGE FEATURES
APPENDIX B: FOCUS AREA BMP DESIGN PLANS AND DETAILS
APPENDIX C: OVERVIEW MAP OF 5 FOCUS AREAS AND ADDITIONAL BMPS
APPENDIX D: USACE 404 REQUEST LETTER
APPENDIX E: WKD IN-HOUSE BMP SIZING SPREADSHEETS
APPENDIX F: DWQ WORKSHEETS
APPENDIX G: ENGINEERED SWALE DESIGN CRITERIA
APPENDIX H: DEVELOPMENT PHASING MAP
APPENDIX I: EXISTING CONDITIONS MAP
APPENDIX f : CONCEPTUAL PLAN VIEW OF PROPOSED OFFLINE POND & BMP'S FOR PHASE 1
APPENDIX K: INSPECTION AND MAINTENANCE AGREEMENTS
a
Ford's Colony - Stormwater Quality TOC
WK Dickson & Co., Inc.
DWQ 401 NARRATIVE
FORD'S COLONY AT ROCKY MOUNT
is Introduction
The following narrative supports the request for a 401 Water Quality permit from the NC Department of
Environment and Natural Resources (NCDENR) - Division of Water Quality (DWQ). The request is for
the Ford's Colony at Rocky Mount residential site development project located in Rocky Mount, North
Carolina. This report supports the design of the proposed best management practices (BMPs) that will
remove total suspended solids (TSS) to satisfy DWQ requirements for a residential development. The
project is located within the Tar-Pamlico River Basin and is subject to all City of Rocky Mount design
requirements for new development related to nutrient removal and water quantity. In addition, because
the project will disturb more than 5 acres of land, it will be subject to the NCDENR - Division of Land
Quality requirements for erosion control. Figure 1 shows a vicinity map for the Ford's Colony at Rocky
Mount project.
Ford's Colony at Rocky Mount is a nexus of opportunities, where economic growth and environmental
stewardship can succeed together. There is substantial demand in the marketplace for the quality of life
and recreation that this site will offer if the property's environmental values are conserved. While the
aesthetic value of these resources offer market appeal, the owners understand that what potential buyers
see is the result of interconnected environmental functions. In other words, the environmental values at
Ford's Colony are a major source of the market values: clean water sells, but streams and ponds stained
with sediments or covered with algae do not. The owners are committed to developing this special
mixture of forests, fields, and waters within the context of the site's ecological functions and values.
To protect their investment, the owners have charged the design team with developing land use products
that conserve and enhance their environmental principal. As a result, watershed conservation is an
integral component of the design process - not an afterthought. Ford's Colony could meet the letter of
stormwater quantity control regulations with large retention basins scattered across the site, but this
traditional approach is not likely to sustain the riparian forests and wetlands for the long term. A variety
of innovative and sophisticated design techniques will be implemented across the site to protect water
quality, sustain riparian woodlands, and conserve groundwater recharge to protect wetland hydrology
and baseflow in streams. The proposed 1125 acre development entails the following:
• 385 acres of V2-acre residential homes;
• 66 acres of 1/3-acre residential homes;
• 62 acres of '/4-acre residential homes;
• 30 acres of 1/8 acre (multi-family) residential homes;
• 189 acres for an 18 hole golf course with clubhouse;
• 96,700 linear feet of new roads that will require installing approximately 13 culvert or bridge
crossings over USGS blueline streams.
Appendix A shows the project site, including landuses, subbasin boundaries and the major drainage
features. Of the 1125 acres approximately 13% is managed open space (golf course), 34% V2-acre
residential, 6% 1/3-acre residential, 6% '/4-acre residential, 3% multi-family, 7% transportation
impervious (roads), and 2% commercial. The overall impervious percentage for the development is
23%. Although the impervious percentage for the overall project area was less than 30% BMP's are
being proposed at the following locations:
• At the eight locations of highly impervious development. These locations are shown in Appendix
B and will be referred to as the "focus areas" for the remainder of this report.
Ford's Colony at Rocky Mount Page 1
WK Dickson & Co., Inc.
DWQ 401 NARRATIVE
FORD'S COLONY AT ROCKY MOUNT
• Throughout the development at locations that "make sense" and help meet City of Rocky Mount
nutrient removal requirements for nitrogen and phosphorous. The identified BMPs shown in
Appendix C are conceptual and will require additional evaluation prior to meeting or exceeding
City of Rocky Mount nutrient requirements for the Tar-Pamlico River Basin.
As detailed in the Water Quality Section of this report, the proposed BMPs located at the eight focus
areas will remove the following amounts of TSS on an annual basis:
Table 1. Summary of TSS Removal at Focus Areas
Focus Area # Total TSS Supplied (lb) Total TSS Removed (lb)
1 5,068 4,308
2 1,299 1,104
3 3,702 3,147
4 3,599 3,059
5 1,459 1,241
6 2,792 2,373
7 15,863 13,154
8 7,654 6,506
The above table does not include the thousands of pounds of TSS removal that will occur at the "nutrient
removal" BMPs found throughout the development. The TSS benefits have not been quantified at this
time, but will become available in the near future. Because the Ford's Colony at Rocky Mount
residential site remains less than 30% impervious, it is our feeling that with the proposed BMPs in place
the project will exceed DWQ requirements for TSS removal.
An individual permit for the Section 404 stream and wetland impacts has been requested under a
separate request under USACE project number: 200121182. A copy of the USACE permit request and
transmittal letter has been included with this report as Appendix D.
Proposed Improvements
Stormwater runoff from impervious areas and managed landscapes is typically a source of water quality
impairment caused by development. At the Ford's Colony project, the efficiencies of treating
contaminated runoff close to the source will be realized. Advanced stormwater BMPs are proposed for
approximately 30 locations across the site as shown on the Stormwater BMP Location Map (Appendix Q.
The following table inventories the proposed stormwater BMPs for this project:
Table 2. Inventor of Proposed BMP's
Proposed BMP Number of Facilities
Grassed swales 1
Bioretention 1
Extended detention wetlands 10
Pocket wetlands 1
Wet Pond 3
Level Spreaders 25
BMPs shall be designed and sized to treat the first 1 inch of runoff, which transports the highest pollutant
concentrations. Design plans (Appendix B), design details (Appendix B), in-house design spreadsheets
(Appendix E) and DWQ worksheets (Appendix F) are provided in this report for focus area #lof the
project. For focus areas #2 through #5, the DWQ worksheets have not been filled out at this time.
Ford's Colony at Rocky Mount Page 3
WK Dickson & Co., Inc.
DWQ 401 NARRATIVE
FORD'S COLONY AT ROCKY MOUNT
• All collected runoff, including that from roadways and any appurtenant impervious surfaces, shall be
discharged via level spreaders to ensure diffuse surface flow to buffers. As shown on the plans, level
spreaders are located at the outfall of all areas of concentrated flow adjacent to roads. Because the
detailed design of roadside stormwater systems has not been performed, drainage areas are conceptual
and no DWQ worksheets have been filled out at this time. After roads have been designed a more
detailed approach to the design of the level spreaders will be performed. If diffuse flow cannot be
achieved, nutrient removal will be accomplished by treatment systems.
In addition to the eight focus areas, stormwater treatment is being provided throughout the project site
where feasible. These practices have been strategically placed at the following locations:
• Adjacent to existing wetlands to help diffuse flow entering the buffers.
• Within new lakes that will be used as water supply reservoirs for the golf course.
• Adjacent to roadways.
• Adjacent to golf course fairways and rear of residential lots.
Another stormwater treatment design concept presented herein is for an engineered swale to treat runoff
from parts of a spine road, residential area and/or golf fairway. This swale will typically drain to an
infiltration area adjacent to wetlands, with surface overflow capacity going to a level spreader.
Combining stormwater management techniques in this manner will likely occur at several locations
across the project in a holistic effort to conserve both water quality and wetland hydrology. The design
criteria for the engineered swale have been included in Appendix G of this report. Preliminary sizing of
the engineered swales adjacent to 4 golf course holes has been completed. Final design is currently
being coordinated with the golf course designer at the time of this May 2005 submission to DWQ. Upon
0 completion of the design, detailed plans, calculations and completed DWQ worksheets will be provided
prior to construction. An example of the worksheet that will be provided is included in Appendix F.
Development Phasing
Due to the size of the project, development will occur in multiple phases over a period of approximately
10 years. Appendix H shows the anticipated development phasing schedule for the project. Detailed
plans for many of the phases will not be developed for several years. For this original submittal, the
clubhouse area (focus area #1) is the only focus area that includes detailed drainage, stormwater and
erosion control plans. For this reason, a complete stormwater plan, erosion control plan, DWQ
checklists and necessary calculations have been prepared for only focus area #1. Calculations were
prepared to size BMPs for focus areas #2 through #5 based on conceptual level landuse and County GIS
topographic mapping. See the Stormwater Quality section of the report for additional details.
As a condition to receiving a 401 Water Quality Certification, Ford's Colony at Rocky Mount is
proposing that the following be submitted to DWQ for their review and approval prior to construction:
• Detailed design of the BMP's.
• Site development plans showing closed stormwater systems and detailed grading of roads and
lots.
• Completed DWQ worksheets supporting design of BMP's.
• Detailed summary of the water quantity calculations used to show that post-development peak
flows have not increased when compared to the pre-project peak flows.
• Detailed summary of culvert designs including outlet protection.
• A water quality improvement summary for the additional BMP's proposed to satisfy City of
Rocky Mount nitrogen and phosphorous requirements.
Ford's Colony at Rocky Mount Page 4
WK Dickson & Co., Inc.
DWQ 401 NARRATIVE
FORD'S COLONY AT ROCKY MOUNT
• Physiography, Topography and Drainage
Because of the large nature of the project, there are numerous swales, streams, wetlands and lakes that
drain the Ford's Colony watersheds. The Existing Conditions Map (Appendix 1) and USGS quadrangle
(Figure 2) show the drainage features, topography and planimetrics found in this area of Rocky Mount.
The Ford's Colony development is drained by three main streams:
Beech Branch - a FEMA identified stream that drains the largest portion of the project site. Beech
Branch drains the central areas of the project site through Belmont Lake, eventually outfalling
under US Highway 301.
Beech Branch Tributary - the northernmost stream that drains the clubhouse and multifamily
areas until its outfall with Beech Branch downstream of US Highway 301.
Indian Branch Tributary - this stream is located in the southern side of the project. This stream
outfalls through a 30" diameter RCP located at Cummings Road.
The proposed project focuses on limiting increases to peak flows in Indian Branch Tributary so that there
will not be adverse impacts to downstream flooding or stream stability.
Soils
Soils in the watershed consist mainly of Bibb, Rains, Norfolk and Goldsboro soil associations ranging
from poorly drained, moderately well drained, and well drained soils that have loamy or clayey subsoil
on uplands. As shown in Figure 3 and described in the Nash County Soil Survey (NRCS, 1989), the
Ford's Colony watershed is mapped within the following soils types:
• Rains fine sandy loam (Ra) - This nearly level soil is poorly drained and typically has a high water
table near or at the surface during most of the year. This soil has moderate permeability as well
as moderate available water capacity.
• Bibb loam (Bb) - This soil is frequently flooded, poorly drained and is at nearly level locations in
the landscape. Normally found on the bottom lands of the Coastal Plain, these soils are usually
found along strips near stream channels. The permeability is moderate and water capacity is high
for these loamy to clayey loam soils.
• Norfolk loamy sand, 2 to 6 percent slopes (NoB) - Found on convex ridges and side slopes of
Coastal Plain uplands, this gently sloping soil is considered well drained. With a moderate
surface runoff, this soil has moderate permeability and a high available water capacity.
• Bonneau loamy sand, 0 to 4 percent slopes (BoB) - Found on broad divides of Coastal Plain
uplands, this soil is well drained and nearly level to gently sloping. It has slow surface runoff,
and moderate permeability and available water capacity.
As described in more detail in the Mitigation Plan, soil samples were collected at various locations
(wetlands, dams, and culvert crossings) throughout the project and sent to an agricultural testing lab for
fertility analysis and soil amendment recommendations. The soil borings and analysis confirmed that
soils at the site should not present problems propagating vegetation proposed in the various proposed
BMPs. Additional soil testing will be required at many of the proposed BMP locations prior to final
design.
Vegetation
Native trees for Bibb loam soils are sweetgum, water oak, and blackgum. Understories consist of cedars,
American holly, sweetbay, sourwood, reeds, and wax myrtle. Typical dominant vegetation for Rains fine
sandy loam soils includes loblolly pine and sweetgum as well as greenbrier, galiberry, huckleberry, and
?16 Ford's Colony at Rocky Mount Page 5
WK Dickson & Co., Inc.
DWQ 401 NARRATIVE
FORDS COLONY AT ROCKY MOUNT
• vaccinium. An extensive planting plan has been provided in the Mitigation Plan to offset impacts from
the development (see the WK Dickson April 7, 2005, report for more details).
Natural Resources of Special Concern
Species with the federal classification of Endangered (E), Threatened (T), or officially Proposed (P) for
such listing, receive protection under the Endangered Species Act of 1973 (16 US 1531 et seq.) as
amended. The most recent list prepared by the United States Fish and Wildlife Service (USFWS) is dated
January 29, 2003. This list indicates that three endangered species have ranges considered to extend into
Nash County. Table 1 lists these three species. Records held by the North Carolina Natural Heritage
Program (NHP) were reviewed by Environmental Services, Inc., (ESI) in August 2004 to determine if any
federal protected species have been documented from the project study area or the surrounding vicinity.
Table 3. Federal Protected Species for Nash County, North Carolina
Common Name Scientific Name Federal Status Habitat Biological Conclusion
Present
Red-cockaded Picoides borealis Endangered No No Effect
woodpecker
Dwarf Alasmidonta Endangered Yes Unresolved
wedgemussel heterodon
Tar spinymussel Elliptio steinstansana Endangered Yes Unresolved
A more detailed description of the federally protected species is found in the WK Dickson Mitigation
Plan dated April 7, 2005. The January 29, 2003 USFWS list also includes a category of species
designated as "Federal Species of Concern" (FSC). The FSC designation provides no federal protection
under the ESA for the species listed. However, these species are listed because they may attain federally
protected status in the future. The presence of potential habitat within the project study area has been
evaluated in Table 2 for the FSC species listed for Nash County.
Table 4. Federal Species of Concern (FSC) (29 January 2003 USFWS list).
Common Name Scientific Name State
Designation A Potential Habitat B
Pinewoods shiner Lythrurus matutinus SR YES
"Carolina" madtom Noturus furiosus pop. 2 SR (PT) YES
Yellow lance Elliptio lanceolata E YES
Atlantic pigtoe Fusconaia masoni E YES
Yellow lampmussel Lampsilis cariosa E YES
Green floater Lasmigona subviridis E YES
Diana fritillary butterfly Speyeria diana SRC NO
Sandhills bog lily Lilium pyrophilum SR-L NO
Carolina least trillium Trillium pusillum var. pusillum E NO
t-Endangered, SR-Signiticantly Rare, L-The range of the species is limited to N.C. and adjacent states, T-
Threatened, PT-Proposed Threatened. Updated April 2003 (NCNHP 2003).
B Proposed habitat based extensively on Amoroso and Finnegan (2002), LeGrand et al. (2001), and other literature
previously cited.
C Historic record
Ford's Colony at Rocky Mount Page 8
WK Dickson & Co., Inc.
DWQ 401 NARRATIVE
FORD'S COLONY AT ROCKY MOUNT
• Stormwater Quality
Design Requirements & Objectives
The following design requirements were used to size and place the best management practices (BMPs)
within the Ford's Colony project:
• DWQ 401 Stormwater - remove 85% of the total suspended solids (TSS).
• City of Rocky Mount - limit nutrient loadings for nitrogen to 4.0 Ib/ac/yr for total nitrogen (TN) for
the proposed conditions.
• City of Rocky Mount - limit nutrient loadings for phosphorus to 0.4 Ib/ac/yr for total phosphorus
(TP) for the proposed conditions.
• City of Rocky Mount - provide control for peak stormwater flows from new development lands to
ensure that the nutrient processing functions of existing riparian buffers and streams are not
compromised by channel erosion.
As briefly described in the introduction, the site was evaluated in the following manners to confirm that
the project meets all DWQ requirements for TSS removal:
• Evaluate project as a whole - The entire development area of 1125 acres has an impervious
percentage of 23%; therefore, it is not subject to DWQ requirements for TSS removal.
• Evaluate major onsite hydrologic subbasins - Each of the three onsite hydrologic subbasins was
evaluated individually for impervious percentages. Because all three subbasins have landuse
impervious percentages less than 30%, BMPs are not required using this rational.
• Eight Focus Areas - Treat the eight focus areas as individual projects that need to meet all DWQ
• requirements for TSS removal. The eight focus areas are those areas which will result in higher
than 30% impervious surface (see Appendix B). These focus areas include the golf course
clubhouse golf, course maintenance facility, and three multi-family residential areas.
Summary of Stormwater Quality
BMPs were designed at the eight focus areas to reduce TSS by approximately 85% in the post-project
conditions. These focus areas were selected due to the high levels of development proposed. The
following table shows that if these "sub-project" developments were required to meet DWQ's TSS
removal requirements, then they would be in compliance:
Table 5. Summary of TSS Removal
•

Focus Area Proposed TSS
Loading Without
BMP (Ib)
Proposed BMP Proposed TSS
Loading With
BMP (Ib) % Reduction
to TSS
1 5,068 Wet pond 760 85%
2 1,299 Extended detention wetland 195 85%
3 3,702 Extended detention wetland,
Bioretention
555 85%
4 3,599 Extended detention wetland 540 85%
5 1,459 Extended detention wetland 219 85%
6 2,792 Extended detention wetland 419 85%
7 15,863 Extended detention wetland,
wet pond, grass swale
2,709 85%
8 7,654 Wet pond 1,148 85%
Ford's Colony at Rocky Mount
WK Dickson & Co., Inc.
Page 9
DWQ 401 NARRATIVE
FORD'S COLONY AT ROCKY MOUNT
• The wet pond proposed for Focus Area #1 is based on the surface area to drainage area (SA/DA)
relationship found in the DWQ BMP manual for the Piedmont. Although the project area is located in
the Coastal Plain the soil types found onsite at Focus Area #1 were clayey in nature. For this reason, it
was more appropriate to use the SA/DA relationship for the Piedmont in sizing the permanent pool for
the proposed pond.
BMP's shown outside the eight focus areas are proposed to meet City of Rocky Mount nutrient
requirements for nitrogen and phosphorous. As final design progresses additional BMP's may be needed
to satisfy City of Rocky Mount nutrient requirements.
Erosion Control Measures
Proposed Measures
Erosion control plans and details are being prepared as each phase of the development progresses.
Because the City of Rocky Mount has local jurisdiction over erosion control, these plans are being
submitted to the City of Rocky Mount for their review and approval. For this reason only a summary is
being provided with this narrative. The proposed measures to control erosion will include: silt fence,
check dams, vegetative grass channels designed appropriately, level spreaders, rip-rap placed for outlet
control of culverts, inlet protection at drop inlets and catch basins, temporary sediment traps, and rock
check dams.
Grassed lined channels will be evaluated for both a temporary and permanent liner. Allowable velocities
and shear stress as described in the NC DENR erosion control manual will be used to determine the
appropriate liner and slopes for grass lined channels. Because of the clayed-silt-sand nature of soils
• velocities will be limited to approximately 3.5 feet per second using a 10-year design storm.
Channel Stability Analysis
Modifications have been proposed to the Belmont Lake spillway to reduce post-project flows down to the
pre-project conditions flows. These improvements to the spillway result in no downstream increases to
peak flows as a result of the Ford's Colony development. The spillway improvements at Belmont Lake
should limit any potential for downstream instability in Beech Branch.
Outfalling downstream of Belmont Lake are several of the focus areas. Focus Area #1 is being routed
through a wet pond that will perform both water quality and quantity. This pond exceeds the size
needed to remove 85% TSS. Although the peak flows in the 1-year and 10-year events have increased
slightly from pre-project conditions, these increases should not affect channel stability do to the size of
Beech Branch. Beech Branch is a FEMA designated stream that has a drainage area of 5.5 square miles
and should not have any channel stability issues with the relatively minor increases to peak flows (1-year
increase less than 1 cfs and 2-year peak flow increase less
An offline regional detention facility is proposed just south of Subdivision M as shown in Appendix J.
This facility will provide both water quality and quantity benefits. This BMP will be sized to attenuate
the 1-, 10-, and 25-year frequency, 24-hour duration storm so that post project flows in the Tributary to
Indian Branch do not increase relative to existing conditions. These improvements will help reduce the
potential for channel instability downstream of Ford's Colony along Tributary to Indian Branch.
Inspection and Maintenance Agreements
• Examples of the inspection and maintenance agreements are shown in Appendix K that will be provided
in the future. As each phase of the subdivision is built, the agreement form will be signed, dated and
notarized for the BMP practices that are located within that phase of the project.
Ford's Colony at Rocky Mount Page 10
WK Dickson & Co., Inc.
DWQ 401 NARRATIVE
FORD'S COLONY AT ROCKY MOUNT
• Conclusions
The innovative and sophisticated design techniques presented in this report and attached plans show that
extensive measures have been taken by the Ford's Colony design team to protect the natural
environment. Protecting water quality, sustaining riparian woodlands, and conserving groundwater
recharge to protect wetland hydrology and baseflow in streams was a priority to the design team. A
review of the supporting data and calculations shows that the Ford's Colony of Rocky Mount site
development project meets DWQ and City of Rocky Mount design requirements for water quality and
quantity. In addition, this report provides all the necessary data to support approval for an erosion
control permit from NCDENR - Division of Land Quality.
is
•
Ford's Colony at Rocky Mount Page 11
WK Dickson & Co., Inc.
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN. 5 REQUIRED DESIGN:
9/14/2005
elevations
Permanent Pool (ft) 104
Temporary Pool (ft) 106 2 ft. depth ok
areas
Permanent Pool SA (sq ft) 3963 3958 sq. ft. ok
Drainage Area (ac) 6.42
Impervious Area (ac) 2.05 31.9 % -
Forebay (ft2) 594 14.988645 % ok
High Marsh (ft2) 1387 35.0 % ok
Low Marsh (ft2) 1387 35.0 % ok
Micropool (ft2) 594 14.988645 % ok
99.97477 %
volumes
Temporary Pool (cu ft) 7872 7863 cu. ft. ok
other parameters
SA/DA 1.418 1.42 -
Orifice Diameter (in) 2 0.10 cfs drawdown -
Design Rainfall (in) 1 0.9 day drawdown check drawG
Linear Interpolation of Correct SAIDA
Impervious
Next Lowest 30
Project Impervious 31.9
Next Highest 40
0 ft. Permanent Pool Depth
SA/DA from Table
1.34
1.42
1.73
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 5 REQUIRED DESIGN.
9/14/2005
elevations
Permanent Pool (ft) 104
Temporary Pool (ft) 106 2 ft. depth
areas
Permanent Pool SA (sq ft) 3963 3958 sq. ft.
Drainage Area (ac) 6.42
Impervious Area (ac) 2.05 31.9 %
Forebay (ft2) 594 14.988645 %
High Marsh (ft2) 1387 35.0 %
Low Marsh (ft2) 1387 35.0 %
Micropool (ft2) 595 15.013878 %
100 %
volumes
Temporary Pool (cu ft) 7872 7863 cu. ft.
other parameters
SA/DA 1.418 1.42
Orifice Diameter (in) 1.25 0.04 cfs drawdown
Design Rainfall (in) 1 2.2 day drawdown
Linear Interpolation of Correct SAIDA * * *
Impervious
Next Lowest 30
Project Impervious 31.9
Next Highest 40
0 ft. Permanent Pool Depth
SA/DA from Table
1.34
1.42
1.73
ok
ok
ok
ok
ok
ok
ok
ok
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 6 REQUIRED DESIGN:
9/14/2005
elevations
Permanent Pool (ft) 105
Temporary Pool (ft) 107 2 ft. depth ok
areas
Permanent Pool SA (sq ft) 1618 1625 sq. ft. check surfac
Drainage Area (ac) 3.83
Impervious Area (ac) 0.77 20.1 % -
Forebay (ft2) 243 15.018541 % ok
High Marsh (ft2) 566 35.0 % ok
Low Marsh (ft2) 566 35.0 % ok
Micropool (ft2) 243 15.018541 % ok
100 %
volumes
Temporary Pool (cu ft) 3198 3211 cu. ft. check tempo
other parameters
SA/DA 0.98 0.97 -
Orifice Diameter (in) 3 0.24 cfs drawdown -
Design Rainfall (in) 1 0.2 day drawdown check draws
Linear Interpolation of Correct SAIDA***
% Impervious
Next Lowest 20
Project Impervious 20.1
Next Highest 30
0 ft. Permanent Pool Depth
SA/DA from Table
0.97
0.97
1.34
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 6 REQUIRED DESIGN.
9/14/2005
elevations
Permanent Pool (ft) 105
Temporary Pool (ft) 107 2 ft. depth
areas
Permanent Pool SA (sq ft) 1630 1625 sq. ft.
Drainage Area (ac) 3.83
Impervious Area (ac) 0.77 20.1 %
Forebay (ft2) 243 14.907975 %
High Marsh (ft2) 566 34.7 %
Low Marsh (ft2) 566 34.7 %
Micropool (ft2) 243 14.907975 %
99.2638 %
volumes
Temporary Pool (cu ft) 3300 3211 cu. ft.
other parameters
SA/DA 0.98 0.97
Orifice Diameter (in) 0.75
E 0.01 cfs drawdown
Design Rainfall (in) 1 2.6 day drawdown
Linear Interpolation of Correct SAIDA * * *
% Impervious
Next Lowest 20
Project Impervious 20.1
Next Highest 30
0 ft. Permanent Pool Depth
SA/DA from Table
0.97
0.97
1.34
ok
ok
ok
ok
ok
ok
ok
ok
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN. 7 REQUIRED DESIGN:
9/14/2005
elevations
Permanent Pool (ft) 96
Temporary Pool (ft) 98.1 2.1 ft. depth ok
areas
Permanent Pool SA (sq ft) 3374 3382 sq. ft. check surfac
Drainage Area (ac) 3.76
Impervious Area (ac) 1.88 50.0 % -
Forebay (ft2) 506 14.997036 % ok
High Marsh (ft2) 1181 , 35.0 % ok
Low Marsh (ft2) 1181 35.0 % ok
Micropool (ft2) 506 14.997036 % ok
100 %
volumes
Temporary Pool (cu ft) 6824 6824 cu. ft. check tempo
other parameters
SA/DA 2.06 2.07 -
Orifice Diameter (in) 2 0.11 cfs drawdown -
Design Rainfall (in) 1 0.7 day drawdown check draws
Linear Interpolation of Correct SA/DA * * *
% Impervious
Next Lowest 40
Project Impervious 50.0
Next Highest 60
0 ft. Permanent Pool Depth
SA/DA from Table
1.73
2.07
2.4
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 7 REQUIRED DESIGN.
9/14/2005
elevations
Permanent Pool (ft) 96
Temporary Pool (ft) 98.1 2.1 ft. depth
areas
Permanent Pool SA (sq ft) 3384 3382 sq. ft.
Drainage Area (ac) 3.76
Impervious Area (ac) 1.88 50.0 %
Forebay (ft2) 511 15.100473 %
High Marsh (ft2) 1181 34.9 %
Low Marsh (ft2) 1181 34.9 %
Micropool (ft2) 511 15.100473 %
100 %
volumes
Temporary Pool (cu ft) 6826 6824 cu. ft.
other parameters
SA/DA 2.06 2.07
Orifice Diameter (in) 1 0.03 cfs drawdown
Design Rainfall (in) 1 2.9 day drawdown
Linear Interpolation of CorrectSAIDA***
% Impervious
Next Lowest 40
Project Impervious 50.0
Next Highest 60
0 ft. Permanent Pool Depth
SA/DA from Table
1.73
2.07
2.4
ok
ok
ok
ok
ok
ok
ok
ok
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 8 REQUIRED DESIGN:
9/14/2005
elevations
Permanent Pool (ft) 104.5
Temporary Pool (ft) 106.5 2 ft. depth ok
areas
Permanent Pool SA (sq ft) 4427 4422 sq. ft. ok
Drainage Area (ac) 3.85
Impervious Area (ac) 2.5 64.9 % -
Forebay (ft2) 664 14.998871 % ok
High Marsh (ft2) 1550 35.0 % ok
Low Marsh (ft2) 1550 35.0 % ok
Micropool (ft2) 664 14.998871 % ok
100.0226 %
volumes
Temporary Pool (cu ft) 8874 8866 cu. ft. ok
other parameters
SA/DA 2.64 2.64 -
Orifice Diameter (in) 2 0.10 cfs drawdown -
Design Rainfall (in) 1 1.0 day drawdown check draws
Linear Interpolation of Correct SAIDA***
0 ft. Permanent Pool Depth
% Impervious SA/DA from Table
Next Lowest 60 2.4
Project Impervious 64.9 2.64
Next Highest 70 2.88
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 8 REQUIRED DESIGN:
9/14/2005
elevations
Permanent Pool (ft) 104.5
Temporary Pool (ft) 106.5 2 ft. depth
areas
Permanent Pool SA (sq ft) 4427 4422 sq. ft.
Drainage Area (ac) 3.85
Impervious Area (ac) 2.5 64.9 %
Forebay (ft2) 664 14.998871 %
High Marsh (ft2) 1550 35.0 %
Low Marsh (ft2) 1550 35.0 %
Micropool (ft2) 664 14.998871 %
100.0226 %
volumes
Temporary Pool (cu ft) 8874 8866 cu. ft.
other parameters
SA/DA 2.64 2.64
Orifice Diameter (in) 1.25 0.04 cfs drawdown
Design Rainfall (in) 1 2.5 day drawdown
Linear Interpolation of Correct SAIDA * * *
Impervious
Next Lowest 60
Project Impervious 64.9
Next Highest 70
0 ft. Permanent Pool Depth
SA/DA from Table
2.4
2.64
2.88
ok
ok
ok
ok
ok
ok
ok
ok
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 9 REQUIRED DESIGN:
9/14/2005
elevations
Permanent Pool (ft) 105
Temporary Pool (ft) 107.1 2.1 ft. depth ok
areas
Permanent Pool SA (sq ft) 5506 5575 sq. ft. check surfac
Drainage Area (ac) 5.42
Impervious Area (ac) 3.14 57.9 % -
Forebay (ft2) 826 15.001816 % ok
High Marsh (ft2) 1927 35.0 % ok
Low Marsh (ft2) 1927 35.0 % ok
Micropool (ft2) 826 15.001816 % ok
100%
volumes
Temporary Pool (cu ft) 11254 11242 cu. ft. ok
other parameters
SA/DA 2.33 2.36 -
Orifice Diameter (in) 2 0.11 cfs drawdown -
Design Rainfall (in) 1 1.2 day drawdown check draw6
Linear Interpolation of Correct SAIDA***
Impervious
Next Lowest 50
Project Impervious 57.9
Next Highest 60
0 ft. Permanent Pool Depth
SA/DA from Table
2.06
2.36
2.44
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 9 REQUIRED DESIGN.
9/14/2005
elevations
Permanent Pool (ft) 105
Temporary Pool (ft) 107.1 2.1 ft. depth
areas
Permanent Pool SA (sq ft) 5580 5575 sq. ft.
Drainage Area (ac) 5.42
Impervious Area (ac) 3.14 57.9 %
Forebay (ft2) 826 14.802867 %
High Marsh (ft2) 1927 34.5 %
Low Marsh (ft2) 1927 34.5 %
Micropool (ft2) 826 14.802867 %
98.67384 %
volumes
Temporary Pool (cu ft) 11254 11242 cu. ft.
other parameters
SA/DA 2.33 2.36
Orifice Diameter (in) 1.5 0.06 cfs drawdown
Design Rainfall (in) 1 2.2 day drawdown
Linear Interpolation of Correct SAIDA * * *
% Impervious
Next Lowest 50
Project Impervious 57.9
Next Highest 60
0 ft. Permanent Pool Depth
SA/DA from Table
2.06
2.36
2.44
ok
ok
ok
ok
ok
ok
ok
ok
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 10 REQUIRED DESIGN
9/14/2005
elevations
Permanent Pool (ft) 109
Temporary Pool (ft) 111.1 2.1 ft. depth ok
areas
Permanent Pool SA (sq ft) 5408 5459 sq. ft. check surfac
Drainage Area (ac) 4.88
Impervious Area (ac) 3.07 62.9 % -
Forebay (ft2) 811 14.996302 % ok
High Marsh (ft2) 1893, 35.0 % ok
Low Marsh (ft2) 1893 35.0 % ok
Micropool (ft2) 811 14.996302 % ok
100 %
volumes
Temporary Pool (cu ft) 10930 10915 cu. ft. ok
other parameters
SA/DA 2.54 2.57 -
Orifice Diameter (in) 2 0.11 cfs drawdown -
Design Rainfall (in) 1 1.2 day drawdown check drawc,
Linear Interpolation of Correct SAIDA***
0 ft. Permanent Pool Depth
% Impervious SA/DA from Table
Next Lowest 60 2.44
Project Impervious 62.9 2.57
Next Highest 70 2.88
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN. 10 REQUIRED DESIGN:
9/14/2005
elevations
Permanent Pool (ft) 109
Temporary Pool (ft) 111.1 2.1 ft. depth
areas
Permanent Pool SA (sq ft) 5460 5459 sq. ft.
Drainage Area (ac) 4.88
Impervious Area (ac) 3.07 62.9 %
Forebay (ft2) 837 15.32967 %
High Marsh (ft2) 1893 34.7 %
Low Marsh (ft2) 1893 34.7 %
Micropool (ft2) 837 15.32967 %
100 %
volumes
Temporary Pool (cu ft) 10930 10915 cu. ft.
other parameters
SA/DA 2.54 2.57
Orifice Diameter (in) 1.5 0.06 cfs drawdown
Design Rainfall (in) 1 2.1 day drawdown
Linear Interpolation of Correct SA/DA * * *
°/U Im ervious
Next Lowest 60
Project Impervious 62.9
Next Highest 70
0 ft. Permanent Pool Depth
SA/DA from Table
2.44
2.57
2.88
ok
ok
ok
ok
ok
ok
ok
ok
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 11 REQUIRED DESIGN:
9/14/2005
elevations
Permanent Pool (ft) 117
Temporary Pool (ft) 119.1 2.1 ft. depth ok
areas
Permanent Pool SA (sq ft) 4571 4634 sq. ft. check surfac
Drainage Area (ac) 4.5
Impervious Area (ac) 2.61 58.0 % -
Forebay(ft2) 685 14.98578 % ok
High Marsh (ft2) 1600 , 35.0 % ok
Low Marsh (ft2) 1600 35.0 % ok
Micropool (ft2) 685 14.98578 % ok
99.97812 %
volumes
Temporary Pool (cu ft) 9344 9344 cu. ft. ok
other parameters
SA/DA 2.33 2.36 -
Orifice Diameter (in) 2 0.11 cfs drawdown -
Design Rainfall (in) 1 1.0 day drawdown check drawc,
Linear Interpolation of CorrectSAIDA***
% Impervious
Next Lowest 50
Project Impervious 58.0
Next Highest 60
0 ft. Permanent Pool Depth
SA/DA from Table
2.06
2.36
2.44
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 11 REQUIRED DESIGN.
9/14/2005
elevations
Permanent Pool (ft) 117
Temporary Pool (ft) 119.1 2.1 ft. depth
areas
Permanent Pool SA (sq ft) 4660 4634 sq. ft.
Drainage Area (ac) 4.5
Impervious Area (ac) 2.61 58.0 %
Forebay (ft2) 730 15.665236 %
High Marsh (ft2) 1600 34.3 %
Low Marsh (ft2) 1600 34.3 %
Micropool (ft2) 730 15.665236 %
100 %
volumes
Temporary Pool (cu ft) 9344 9344 cu. ft.
other parameters
SA/DA 2.33 2.36
Orifice Diameter (in) 1.25 0.04 cfs drawdown
Design Rainfall (in) 1 2.6 day drawdown
Linear Interpolation of Correct SAIDA***
% Impervious
Next Lowest 50
Project Impervious 58.0
Next Highest 60
0 ft. Permanent Pool Depth
SA/DA from Table
2.06
2.36
2.44
ok
ok
ok
ok
ok
ok
ok
ok
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN 12 REQUIRED DESIGN.
9/14/2005
elevations
Permanent Pool (ft) 116
Temporary Pool (ft) 118.1 2.1 ft. depth ok
areas
Permanent Pool SA (sq ft) 5658 5735 sq. ft. check surfac
Drainage Area (ac) 5.57
Impervious Area (ac) 3.23 58.0 % -
Forebay (ft2) 848 14.987628 % ok
High Marsh (ft2) 1980 35.0 % ok
Low Marsh (ft2) 1980 35.0 % ok
Micropool (ft2) 848 14.987628 % ok
99.96465 %
volumes
Temporary Pool (cu ft) 7-11715-6-31 11563 cu. ft. check tempo
other parameters
SA/DA 2.33 2.36 -
Orifice Diameter (in) 2 0.11 cfs drawdown -
Design Rainfall (in) 1 1.2 day drawdown check draws
Linear Interpolation of Correct SAIDA * * *
% Impervious
Next Lowest 50
Project Impervious 58.0
Next Highest 60
0 ft. Permanent Pool Depth
SA/DA from Table
2.06
2.36
2.44
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 12 REQUIRED DESIGN.
9/14/2005
elevations
Permanent Pool (ft) 116
Temporary Pool (ft) 118.1 2.1 ft. depth
areas
Permanent Pool SA (sq ft) 5740 5735 sq. ft.
Drainage Area (ac) 5.57
Impervious Area (ac) 3.23 58.0 %
Forebay (ft2) 890 15.505226 %
High Marsh (ft2) 1980 34.5 %
Low Marsh (ft2) 1980 34.5 %
Micropool (ft2) 890 15.505226 %
100 %
volumes
Temporary Pool (cu ft) 11564 11563 cu. ft.
other parameters
SAIDA 2.33 2.36
Orifice Diameter (in) 1.5 0.06 cfs drawdown
Design Rainfall (in) 1 2.2 day drawdown
Linear Interpolation of CorrectSAIDA***
0 ft. Permanent Pool Depth
% Impervious SAIDA from Table
Next Lowest 50 2.06
Project Impervious 58.0 2.36
ok
ok
ok
ok
ok
ok
ok
ok
Next Highest 60 2.44
Project Name: Ford Colony
Project No. DWQ 04-1801
Pond No.
SUBMITTED DESIGN. 13 REQUIRED DESIGN:
9/14/2005
elevations •4.0, average depth status
Bottom of Basin (ft) 129
Permanent Pool (ft) 133 4 ft. depth ok
Temporary Pool (ft) 135.5 2.5 ft. depth ok
areas
Permanent Pool SA (sq ft) 22154 19642 sq. ft. ok
Drainage Area (ac) 41.45 22161 based on avg depth check surfac
Impervious Area (ac) 14.18 34.2 % -
volumes
Permanent Pool (cu ft) 88617
Temporary Pool (cu ft) 53836 53849 cu. ft. check tempo
Forebay (cu ft) 0 0.0 % check forebc

other parameters
SA/DA 1.23 1.09 -
Orifice Diameter (in) 2 0.12 cfs drawdown -
Design Rainfall (in) 1 5.3 day drawdown check drawc,
Linear Interpolation of Correct SAIDA * * *
4 ft. Permanent Pool Depth
% Impervious SA/DA fron (Avg. Depth)
Next Lowest 30 0.97 1.080004965 1.08
Project Impervious 34.2 1.09 1,23; 1.23
Next Highest 40 1.25 1.430008125 1.43
3 ft 4
Project Name: Ford Colony
Project No. DWQ 04-1801
Pond No.
SUBMITTED DESIGN: 13 REQUIRED DESIGN:
9/14/2005
elevations 3.9 average depth status
Bottom of Basin (ft) 129
Permanent Pool (ft) 133 4 ft. depth ok
Temporary Pool (ft) 135.5 2.5 ft. depth ok

areas
Permanent Pool SA (sq ft) 22800 19642 sq. ft. ok
Drainage Area (ac) 41.45 21875, based on avg depth ok
Impervious Area (ac) 14.18 34.2 % -
volumes
Permanent Pool (cu ft) 88617
Temporary Pool (cu ft) 54000 53849 cu. ft. ok
Forebay (cu ft) 16000 18.1 % ok
other parameters
SA/DA 1.23 1.09 -
Orifice Diameter (in) 3 0.26 cfs drawdown -
Design Rainfall (in) 1 2.4 day drawdown ok
Linear Interpolation of Correct SA/DA***
4 ft. Permanent Pool Depth
% Impervious SA/DA fron (Avg. Depth)
Next Lowest 30 0.97 1.067538158 1.08
Project Impervious 34.2 1.09 1.21" 1.23
Next Highest 40 1.25 1.4096U7895 1.43
3ft 4
Project Name: Ford Colony
Project No. DWQ 04-1801
Pond No.
SUBMITTED DESIGN: 14 REQUIRED DESIGN:
9/14/2005
elevations 4.0' average depth status
Bottom of Basin (ft) 129
Permanent Pool (ft) 133 4 ft. depth ok
Temporary Pool (ft) 135.5 2.5 ft. depth ok

areas
Permanent Pool SA (sq ft) 16311 16313 sq. ft. check surfac
Drainage Area (ac) 23.52 13005 based on avg depth ok
Impervious Area (ac) 10.68 45.4 % -
volumes
Permanent Pool (cu ft) 65242
Temporary Pool (cu ft) 39154 39160 cu. ft. check tempo
Forebay(cu ft) 13048 20.0 % ok
other parameters
SA/DA 1.59 1.59 -
Orifice Diameter (in) 2 0.12 cfs drawdown -
Design Rainfall (in) 1 3.9 day drawdown ok
Linear Interpolation of Correct SAIDA * * *
4 ft. Permanent Pool Depth
% Impervious SA/DA fron (Avg. Depth)
Next Lowest 40 1.43 1.080042916 1.08
Project Impervious 45.4 1.59 11 1:27 1.27
Next Highest 50 1.73 1.430036785 1.43
3ft 4
Project Name: Ford Colony
Project No. DWQ 04-1801
Pond No.
SUBMITTED DESIGN: 14 REQUIRED DESIGN:
9/14/2005
elevations 4.0 average depth status
Bottom of Basin (ft) 129
Permanent Pool (ft) 133 4 ft. depth ok
Temporary Pool (ft) 135.5 2.5 ft. depth ok

areas
Permanent Pool SA (sq ft) 16400 16313 sq. ft. ok
Drainage Area (ac) 23.52 1307¢ based on avg depth ok
Impervious Area (ac) 10.68 45.4 % -
volumes
Permanent Pool (cu ft) 65242
Temporary Pool (cu ft) 39800 39160 cu. ft. ok
Forebay(cu ft) 13048 20.0 % ok
other parameters
SA/DA 1.59 1.59 -
Orifice Diameter (in) 2 0.12 cfs drawdown -
Design Rainfall (in) 1 3.9 day drawdown ok
Linear Interpolation of Correct SAIDA * * *
4 ft. Permanent Pool Depth
% Impervious SA/DA fron (Avg. Depth)
Next Lowest 40 1.43 1.087640244 1.08
Project Impervious 45.4 1.59 1:25 1.27
Next Highest 50 1.73 1.43654878 1.43
3 ft 4
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN. 16 REQUIRED DESIGN:
9/14/2005
elevations

Permanent Pool (ft) 128
Temporary Pool (ft) 131.8 3.8 ft. depth ok
areas
Permanent Pool SA (sq ft) 4306 8281 sq. ft. check surfac
Drainage Area (ac) 13.18
Impervious Area (ac) 4.3 32.6 % -
Forebay(ft2) 574 13.330237 % ok
High Marsh (ft2) 1579 36.7 % ok
Low Marsh (ft2) 1579 36.7 % ok
Micropool (ft2) 574 13.330237 % ok
100 %
volumes
Temporary Pool (cu ft) 16429 16440 cu. ft. check tempo
other parameters
SA/DA 0.75 1.44 -
Orifice Diameter (in) 2 0.14 cfs drawdown -
Design Rainfall (in) 1 1.3 day drawdown check drawc,
Linear Interpolation of Correct SA/DA * * *
% Impervious
Next Lowest 30
Project Impervious 32.6
Next Highest 40
0 ft. Permanent Pool Depth
SA/DA from Table
1.34
1.44
1.73
Project Name: Ford colony
Project No. DWQ 04-1801
SUBMITTED DESIGN: 16 REQUIRED DESIGN:
9/14/2005
elevations
Permanent Pool (ft) 128
Temporary Pool (ft) 131.8 3.8 ft. depth
areas
Permanent Pool SA (sq ft) 8300 8281 sq. ft.
Drainage Area (ac) 13.18
Impervious Area (ac) 4.3 32.6 %
Forebay (ft2) 1150 13.855422 %
High Marsh (ft2) 3000 36.1 %
Low Marsh (ft2) 3000 36.1 %
Micropool (ft2) 1150 13.855422 %
100 %
volumes
Temporary Pool (cu ft) 16500 16440 cu. ft.
other parameters
SA/DA 0.75 1.44
Orifice Diameter (in) 1.5 0.08 cfs drawdown
Design Rainfall (in) 1 2.3 day drawdown
Linear Interpolation of Correct SAIDA***
% Impervious
Next Lowest 30
Project Impervious 32.6
Next Highest 40
0 ft. Permanent Pool Depth
SA/DA from Table
1.34
1.44
1.73
ok
ok
ok
ok
ok
ok
ok
ok
Project Name: Ford Colony
Project No. DWQ 04-1801
Pond No.
SUBMITTED DESIGN: 17 REQUIRED DESIGN
9/14/2005
elevations 4.0 average depth status
Bottom of Basin (ft) 128
Permanent Pool (ft) 132 4 ft. depth ok
Temporary Pool (ft) 134.4 2.4 ft. depth ok

areas
Permanent Pool SA (sq ft) 3896 3892 sq. ft. ok
Drainage Area (ac) 14.18 7679 based on avg depth check surfac
Impervious Area (ac) 2.08 14.7 % -
volumes
Permanent Pool (cu ft) 15583
Temporary Pool (cu ft) 9397 9369 cu. ft. ok
Forebay (cu ft) 3117 20.0 % ok
other parameters
SA/DA 0.63 0.63 -
Orifice Diameter (in) 2 0.12 cfs drawdown -
Design Rainfall (in) 1 0.9 day drawdown check drawn
Linear Interpolation of Correct SAIDA***
4 ft. Permanent Pool Depth
% Impervious SA/DA fron (Avg. Depth)
Next Lowest 10 0.49 1.079848563 1.08
Project Impervious 14.7 0.63 1.24 1.24
Next Highest 20 0.79 1.429835729 1.43
3ft 4
Project Name: Ford Colony
Project No. DWQ 04-1801
Pond No.
SUBMITTED DESIGN: 17
9/14/2005
elevations
Bottom of Basin (ft) 128
Permanent Pool (ft) 132
Temporary Pool (ft) 134.4
areas
Permanent Pool SA (sq ft) 5000
Drainage Area (ac) 14.18
Impervious Area (ac) 2.08
volumes
Permanent Pool (cu ft) 15583
Temporary Pool (cu ft) 9397
Forebay (cu ft) 3117
other parameters
SA/DA 0.63
Orifice Diameter (in) 1
Design Rainfall (in) 1
Linear Interpolation of Correct SAIDA***
% Impervious
Next Lowest 10
Project Impervious 14.7
Next Highest 20
REQUIRED DESIGN:
3. PIS average depth status
4 ft. depth ok
2.4 ft. depth ok
3892 sq. ft. ok
4333 based on avg depth ok
14.7 % -
9369 cu. ft. ok
20.0% ok
0.63 -
0.03 cfs drawdown -
3.8 day drawdown ok
4 ft. Permanent Pool Depth
SA/DA fron (Avg. Depth)
0.49 0.558794 1.08
0.63 0.70 1.24
0.79 0.864624 1.43
3 ft 4