20001449 Ver 1_Stormwater Info_20060110

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~~~~ urban. d~igfti plarorl~r?g ci~vk) en;~ineer~ing ~indse a~l~tect ure ~

TRANSMITTAL .y

223 North Graham Street, Charlotte, NC 28202
V: 704.333.0325 F: 704.332.3246
DATE: 1/9/2006 NUMBER OF PAGES: 1
PROJECT NAME: Catawba Hills Village D
PROJECT #:
1005018
TO: Ms. Cyndi Karoly BUS. PHONE: [phone]
NC Division Of Water Quality - 401 Permit U BUS. FAX: [phone]
2321 Crabtree Blvd. Bus. MOBILE:
Suite 250
Raleigh NC 27604 p ~~~~~~ D
CC:
JAN 1 0 2006
WE ARE SENDING: VIA: PURPOSE: DENR -WATER QUALITY
^x DRAWINGS ^ MAIL ®APPROVAL
^ SPECIFICATIONS ^ FAX ^ YOUR USE
^ APPLICATIONS ^ COURIER ^ YOUR INFORMATION
^ FEES ^FEDEX GROUND ^ REVIEW I COMMENT
^ REDLINES ~ FEDEX OVERNIGHT ^ YOUR REQUEST
^ DISK I CD ^ HAND DELIVERY ^ SIGNATURE
^ OTHER ^ PICK UP
^ EMAIL
QUANTITY: ITEM: DESCRIPTION:
2 Sets of Plans
1 Calculations
1 Wet Detention Basin Supplement Worksheets 8 for all three WQ Facilities
Maintenance Agreements
NOTES:
Ms. Karoly:
Please do not hesitate to contact me at 704.376.7777 should there be any questions or comments. Thank you.
FROM: Jeremy Pruett
JJP
If this document was delivered via FAX, the accompanying transmission contains confidential information intended only for the use of the individual of the entity named above.
If you are not the intended recipient, you are hereby notified that any disclosure, copying, distribution or the taking of any action in reliance on the contents of this facsimile
information is strictly prohibited. If you have received this FAX in error, please immediately notify us by telephone to arrange for disposition or return of the documents to us.
Charlotte NC
Washington DC Tampa FL Asheville NC Pinehurst NC Charlotte NC Nashville TN Beijing PRC

Permit No.
(to be provided by DWQ)
State of North Carolina
Department of Environment and Natural Resources
Division of Water Quality
STORMWATER MANAGEMENT PERMIT APPLICATION FORM ~ ~ ~ L~ ~~~
D
WET DETENTION BASIN SUPPLEMENT JAN 1 0 2p06
This form may 6e photocopied for use as an original DENR -WATER 4UALITY
SNETI.ANDS AND STORA,1VyATER BRANCk
DWQ Stormwater Management Plan Review:
A complete stormwater management plan submittal includes an application form, a wet detention basin
supplement for each basin, design calculations, and plans and specifications showing all basin and outlet
structure details.
I. PROJECT INFORMATION ~~II ~~~ 1 ~ V O C~ ~ ~ ~ 7 '7 7
~ 7
rod ect ame:
Contact Person: Robert B. Dienst Phone Number: (~-'t-~'~'a'1.2'3
For projects with multiple basins, specify which basin this worksheet applies to: wetland #~
elevations
Basin Bottom Elevation 622'5 ft. (floor of the basin)
Permanent Pool Elevation 624.0 ft. (elevation of the orifice)
Temporary Pool Elevation 6299 ft. (elevation of the discharge structure overflow)

areas
Permanent Pool Surface Area 9056 sq. ft. (water surface area at the orifice elevation)
Drainage Area 9.89 ac. (on-site and off-site drainage to the basin)
Impervious Area 4.45 ac. (on-site and off-site drainage to the basin)

volumes
Permanent Pool Volume NSA cu. ft. (combined volume of main basin and forebay)
Temporary Pool Volume 19,051 cu. ft. (volume detained above the permanent pool)
Forebay Volume NiA cu. ft. (approximately 20% of total volume)
Other parameters
SA/DA1 2.06 (surface area to drainage area ratio from DWQ table)
Diameter of Orifice 1.5 in. (2 to S day temporary pool draw-down required)
Design Rainfall 4.9 in.
Design TSS Removal 2 85 % (minimum 85% required)
Form SWU-102 Rev 3.99 Page 1 of 4

Fnntnntac
' When using the Division SA/DA tables, the correct SA/DA ratio for permanent pool sizing should be computed based upon the
actual impervious % and permanent pool depth. Linear interpolation should be employed to determine the correct value for non-
standard table entries.
2 In the 20 coastal counties, the requirement for a vegetative filter maybe waived if the wet detention basin is designed to provide
90%TSS removal. The NCDENR BMP manual provides design tables for both 85%TSS removal and 90%TSS removal.
II. REQUIRED ITEMS CHECKLIST
The following checklist outlines design requirements per the Stormwater Best Management Practices Manual
(N.C. Department of Environment, Health and Natural Resources, February 1999) and Administrative Code
Section: 15 A NCAC 2H .1008.
Initial in the space provided to indicate the following design requirements have been met and supporting
documentation is attached. If the applicant has designated an agent in the Stormwater Management Permit
Application Form, the agent may initial below. If a requirement has not been met, attach justification.
Applicants Initials
JP a. The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet).
JP b. The forebay volume is approximately equal to 20% of the basin volume.
JP c. The temporary pool controls runoff from the design storm event.
JP d. The temporary pool draws down in 2 to 5 days.
JP e. If required, a 30-foot vegetative filter is provided at the outlet (include non-erosive flow
calculations)
JP f. The basin length to width ratio is greater than 3:1.
JP g. The basin side slopes above the permanent pool are no steeper than 3:1.
N/A h. A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail).
JP i. Vegetative cover above the permanent pool elevation is specified.
N/A j. A trash rack or similar device is provided for both the overflow and orifice.
N/A k. A recorded drainage easement is provided for each basin including access to nearest right-
of-way.
JP 1. If the basin is used for sediment and erosion control during construction, clean out of the
basin is specified prior to use as a wet detention basin.
JP m. A mechanism is specified which will drain the basin for maintenance or an emergency.
III. WET DETENTION BASIN OPERATION AND MAINTENANCE AGREEMENT
The wet detention basin system is defined as the wet detention basin, pretreatment including forebays and the
vegetated filter if one is provided.
This system (check one) 0 does 0 does not incorporate a vegetated filter at the outlet.
This system (check one) 0 does 0 does not incorporate pretreatment other than a forebay.
Form SWU-102 Rev 3.99 Page 2 of 4

Maintenance activities shall be performed as follows:
After every significant runoff producing rainfall event and at least monthly:
a. Inspect the wet detention basin system for sediment accumulation, erosion, trash accumulation,
vegetated cover, and general condition.
b. Check and clear the orifice of any obstructions such that drawdown of the temporary pool occurs within
2 to 5 days as designed.
2. Repair eroded areas immediately, re-seed as necessary to maintain good vegetative cover, mow vegetative
cover to maintain a maximum height of six inches, and remove trash as needed.
3. Inspect and repair the collection system (i.e. catch basins, piping, swales, riprap, etc.) quarterly to maintain
proper functioning.
4. Remove accumulated sediment from the wet detention basin system semi-annually or when depth is
reduced to 75% of the original design depth (see diagram below). Removed sediment shall be disposed of
in an appropriate manner and shall be handled in a manner that will not adversely impact water quality (i.e.
stockpiling near a wet detention basin or stream, etc.).
The measuring device used to determine the sediment elevation shall be such that it will give an accurate
depth reading and not readily penetrate into accumulated sediments.
When the permanent pool depth reads N/A
When the permanent pool depth reads 1~5
feet in the main pond, the sediment shall be removed.
feet in the forebay, the sediment shall be removed.
BASIN DIAGRAM
(fill in the blanks)
Permanent Pool Elevation
Sediment Rertloval EI
-------------- ~ - Sediment Removal Elevation 75%
Bottom Ele ation % ---------------------------------------------- --o --
Bottom Elevation 25 /° ~
FOREBAY MAIN POND
5. ]E~emove cattails and other indigenous wetland plants when they cover 50% of the basin surface. These
plants shall be encouraged to grow along the vegetated shelf and forebay berm.
6. ][f the basin must be drained for an emergency or to perform maintenance, the flushing of sediment through
t:he emergency drain shall be minimized to the maximum extent practical.
Form SWU-102 Rev 3.99 Page 3 of 4

7. All components of the wet detention basin system shall be maintained in good working order.
I acl~:nowledge and agree by my signature below that I am responsible for the performance of the seven
maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any
changes to the system or responsible party.
Print name: Catawba Hills, LLC
Robert B. Dienst, Manager
Address: 125 Easton Drive, Mooresville, NC 28117
Phon°' [phone]
Sign,
Date;
NOte;: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a
resident of the subdivision has beef named the president.
!~ r
I `~-- a Nota Publi for th Sta of /Ii ~ f ~/
~ ~ C ~ ,
County of ~~~ , do h r by certi that ~~~'~ 1J
,_--.
personally appeared before me this ~ day of , ~~~, and acknowledge the due
execution of the forgoing wet detention basin maintenance requirements. Witness my hand and official seal,
_" _V
~~~
Form SWU-102 Rev 3.99 Page 4 of 4

Permit No.
State of North Carolina
Department of Environment and Natural Resources
Division of Water Quality
(to be provided by DWQ)
STORMWATER MANAGEMENT PERMIT APPLICATION ~~ ~ ~~ ~ D
WET DETENTION BASIN SUPPLEMENT JAN 1 0 2006
This form maybe photocopied for use as an original
DENR -WATER QUALITY
DWO Stonnwater Manal;ement Plan Review: WETLANDS AND S70RFAWATER 81iANCK
A complete stormwater management plan submittal includes an application form, a wet detention basin
supplement for each basin, design calculations, and plans and specifications showing all basin and outlet
structure details.
I. PROJECT INFORMATION
Catawba Hills Subdivision - Village D Townhomes
Proiect Name:
Contract Person: Robert B. Dienst Phone Number: (704 ) 309-0123
For projects with multiple basins, specify which basin this worksheet applies to: wetland #2
elevations
Basin Bottom Elevation 622'5 ft. (floor of the basin)
Permanent Pool Elevation 624.0 ft. (elevation of the orifice)
Temporary Pool Elevation 625.75 ft. (elevation of the discharge structure overflow)
areas
Permanent Pool Surface Area 3977.24 sq. ft. (water surface area at the orifice elevation)
Drainage Area 1'93 ac. (on-site and off-site drainage to the basin)
Impervious Area 089 ac. (on-site and off-site drainage to the basin)
volumes
Permanent Pool Volume tvtA cu. ft. (combined volume of main basin and forebay)
Temporary Pool Volume 5416 cu. ft. (volume detained above the permanent pool)
Forebay Volume NtA cu. ft. (approximately 20% of total volume)
Other parameters
2.13
SA/DA1 (surface area to drainage area ratio from DWQ table)
Diameter of Orifice 0.75 in. (2 to 5 day temporary pool draw-down required)
Design Rainfall 4'9 in.
Design TSS Removal 2 85 % (minimum 85% required)
Form SWU-102 Rev 3.99 Page 1 of 4

Footnotes:
When using the Division SA/DA tables, the correct SA/DA ratio for permanent pool sizing should be computed based upon the
actual impervious % and permanent pool depth. Linear interpolation should be employed to determine the correct value for non-
standard table entries.
In the 20 coastal counties, the requirement for a vegetative filter may be waived if the wet detention basin is designed to provide
90%TSS removal. The NCDENR BMP manual provides design tables for both 85%TSS removal and 90%TSS removal.
II. REQUIRED ITEMS CHECKLIST
The following checklist outlines design requirements per the Stormwater Best Management Practices Manual
(N.C. Department of Environment, Health and Natural Resources, February 1999) and Administrative Code
Section: 15 A NCAC 2H .1008.
Initial in the space provided to indicate the following design requirements have been met and supporting
documentation is attached. If the applicant has designated an agent in the Stormwater Management Permit
Application Form, the agent may initial below. If a requirement has not been met, attach justification.
Applicants Initials
JP a. The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet).
JP
JP
JP
N/A
JP
N/A
N/A
N/A
N/A
N/A
JP
JP
b. The forebay volume is approximately equal to 20% of the basin volume.
c. The temporary pool controls runoff from the design storm event.
d. The temporary pool draws down in 2 to 5 days.
e. If required, a 30-foot vegetative filter is provided at the outlet (include non-erosive flow
calculations)
f. The basin length to width ratio is greater than 3:1.
g. The basin side slopes above the permanent pool are no steeper than 3:1.
h. A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail).
i. Vegetative cover above the permanent pool elevation is specified.
j. A trash rack or similar device is provided for both the overflow and orifice.
k. A recorded drainage easement is provided for each basin including access to nearest right-
of-way.
1. If the basin is used for sediment and erosion control during construction, clean out of the
basin is specified prior to use as a wet detention basin.
m. A mechanism is specified which will drain the basin for maintenance or an emergency.
III. WET DETENTION BASIN OPERATION AND MAINTENANCE AGREEMENT
The wet detention basin system is defined as the wet detention basin, pretreatment including forebays and the
vegetated filter if one is provided.
This system (check one) 0 does 0 does not incorporate a vegetated filter at the outlet.
This system (check one) 0 does 0 does not incorporate pretreatment other than a forebay.
Form SWU-102 Rev 3.99 Page 2 of 4

Maintenance activities shall be performed as follows:
After every significant runoff producing rainfall event and at least monthly:
a. Inspect the wet detention basin system for sediment accumulation, erosion, trash accumulation,
vegetated cover, and general condition.
b. Check and clear the orifice of any obstructions such that drawdown of the temporary pool occurs within
2 to 5 days as designed.
2. Repair eroded areas immediately, re-seed as necessary to maintain good vegetative cover, mow vegetative
cover to maintain a maximum height of six inches, and remove trash as needed.
3. Inspect and repair the collection system (i.e. catch basins, piping, swales, riprap, etc.) quarterly to maintain
proper functioning.
4. Remove accumulated sediment from the wet detention basin system semi-annually or when depth is
reduced to 75% of the original design depth (see diagram below). Removed sediment shall be disposed of
in an appropriate manner and shall be handled in a manner that will not adversely impact water quality (i.e.
stockpiling near a wet detention basin or stream, etc.).
The measuring device used to determine the sediment elevation shall be such that it will give an accurate
depth reading and not readily penetrate into accumulated sediments.
When the permanent pool depth reads feet in the main pond, the sediment shall be removed.
When the permanent pool depth reads feet in the forebay, the sediment shall be removed.
BASIN DIAGRAM
ill in the blanks)
Permanent Pool Elevation
Sediment Re oval EI.
Bottom
FOREBAY
-_---Sediment Removal Elevation ___-----___- 75%
Bottom Elevation j 25%
MAIN POND
5. Remove cattails and other indigenous wetland plants when they cover 50% of the basin surface. These
plants shall be encouraged to grow along the vegetated shelf and forebay berm.
6. If the basin must be drained for an emergency or to perform maintenance, the flushing of sediment through
the emergency drain shall be minimized to the maximum extent practical.
Form SWU-102 Rev 3.99 Page 3 of 4

i
7. All components of the wet detention basin system shall be maintained in good working order.
I acknowledge and agree by my signature below that I am responsible for the performance of the seven
maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any
changes to the system or responsible party.
Print name: Catawba Hills, LLC
Title: Robert B. Dienst, Manager
Address: 125 Easton Drive, Mooresville, NC 28117
Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a
resident of the subdivision has been named the president.
I, ~~( ~ , , a Notary Public for th State of t~ ~a~-/c ,
County of I/~w~ , do her by certify that VJ~. ~'~
ersonall a eared before me this _~~ '~da of C-c'
p y pp y ~ ,and acknowledge the due
execution of the forgoing wet detention basin maintenance requirements. Witness my hand and official seal,
Form SWU-102 Rev 3.99 Page 4 of 4

Permit No.
(to be provided by DWQ)
State of North Carolina
Department of Environment and Natural Resources
Division of Water Quality D ~~~~n „~
STORMWATER MANAGEMENT PERMIT APPLICATION FOR `f ~D
JAN 1 ~ 2006
WET DETENTION BASIN SUPPLEMENT DENR w
- ATE
This form maybe photocopied for use as an original ~~~AND Sr~WA R BTMRANCy
DWQ Stormwater Management Plan Review:
A complete stormwater management plan submittal includes an application form, a wet detention basin
supplement for each basin, design calculations, and plans and specifications showing all basin and outlet
structure details.
I. PROJECT INFORMATION
Project Name:
Catawba Hills Subdivision - Village D Townhomes
Contact Person: Robert B. Dienst Phone Number: (704 ) 309-0123
For projects with multiple basins, specify which basin this worksheet applies to: Bioretention #1 (attached)
elevations
Basin Bottom Elevation
Permanent Pool Elevation
Temporary Pool Elevation
areas
Permanent Pool Surface Area
Drainage Area
Impervious Area
volumes
Permanent Pool Volume
Temporary Pool Volume
Forebay Volume
Other parameters
SA/DA~
Diameter of Orifice
Design Rainfall
Design TSS Removal 2
ft. (floor of the basin)
ft. (elevation of the orifice)
ft. (elevation of the discharge structure overflow)
sq. ft. (water surface area at the orifice elevation)
ac. (on-site and off-site drainage to the basin)
ac. (on-site and off-site drainage to the basin)
cu. ft. (combined volume of main basin and forebay)
cu. ft. (volume detained above the permanent pool)
cu. ft. (approximately 20% of total volume)
(surface area to drainage area ratio from DWQ table)
in. (2 to 5 day temporary pool draw-down required)
m.
(minimum 85% required)
Form SWU-102 Rev 3.99 Page 1 of 4

Footnotes:
When using the Division SA/DA tables, the correct SA/DA ratio for permanent pool sizing should be computed based upon the
actual impervious % and permanent pool depth. Linear interpolation should be employed to determine the correct value for non-
standard table entries.
In the 20 coastal counties, the requirement for a vegetative filter maybe waived if the wet detention basin is designed to provide
90%TSS removal. The NCDENR BMP manual provides design tables for both 85%TSS removal and 90% TSS removal.
II. REQUIRED ITEMS CHECKLIST
The following checklist outlines design requirements per the Stormwater Best Management Practices Manual
(N.C. Department of Environment, Health and Natural Resources, February 1999) and Administrative Code
Section: 15 A NCAC 2H .1008.
Initial in the space provided to indicate the following design requirements have been met and supporting
documentation is attached. If the applicant has designated an agent in the Stormwater Management Permit
Application Form, the agent may initial below. If a requirement has not been met, attach justification.
Applicants Initials
a. The permanent pool depth is between 3 and 6 feet (required minimum of 3 feet).
b. The forebay volume is approximately equal to 20% of the basin volume.
c. The temporary pool controls runoff from the design storm event.
d. The temporary pool draws down in 2 to 5 days.
e. If required, a 30-foot vegetative filter is provided at the outlet (include non-erosive flow
calculations)
f. The basin length to width ratio is greater than 3:1.
g. The basin side slopes above the permanent pool are no steeper than 3:1.
h. A submerged and vegetated perimeter shelf with a slope of 6:1 or less (show detail).
i. Vegetative cover above the permanent pool elevation is specified.
A trash rack or similar device is provided for both the overflow and orifice.
k. A recorded drainage easement is provided for each basin including access to nearest right-
of-way.
1. If the basin is used for sediment and erosion control during construction, clean out of the
basin is specified prior to use as a wet detention basin.
m. A mechanism is specified which will drain the basin for maintenance or an emergency.
III. WET DETENTION BASIN OPERATION AND MAINTENANCE AGREEMENT
The wet detention basin system is defined as the wet detention basin, pretreatment including forebays and the
vegetated filter if one is provided.
This system (check one) 0 does 0 does not incorporate a vegetated filter at the outlet.
This system (check one) 0 does 0 does not incorporate pretreatment other than a forebay.
Form SWU-102 Rev 3.99 Page 2 of 4

Maintenance activities shall be performed as follows:
1. After every significant runoff producing rainfall event and at least monthly:
a. Inspect the wet detention basin system for sediment accumulation, erosion, trash accumulation,
vegetated cover, and general condition.
b. Check and clear the orifice of any obstructions such that drawdown of the temporary pool occurs within
2 to 5 days as designed.
2. Repair eroded areas immediately, re-seed as necessary to maintain good vegetative cover, mow vegetative
cover to maintain a maximum height of six inches, and remove trash as needed.
3. Inspect and repair the collection system (i.e. catch basins, piping, swales, riprap, etc.) quarterly to maintain
proper functioning.
4. Remove accumulated sediment from the wet detention basin system semi-annually or when depth is
reduced to 75% of the original design depth (see diagram below). Removed sediment shall be disposed of
in an appropriate manner and shall be handled in a manner that will not adversely impact water quality (i.e.
stockpiling near a wet detention basin or stream, etc.).
The measuring device used to determine the sediment elevation shall be such that it will give an accurate
depth reading and not readily penetrate into accumulated sediments.
When the permanent pool depth reads NSA feet in the main pond, the sediment shall be removed.
When the permanent pool depth reads NSA feet in the forebay, the sediment shall be removed.
BASIN DIAGRAM
ill in the blanks)
Permanent Pool Elevation
Sediment Re oval EI. ----____-~ 75 0
_ _ _ _ _ Sediment Removal Elevation 75 /°
Bottom Ele ation T % ---------------------------------------------- -------
Bottom Elevation .ir 25%
FOREBAY MAIN POND
5. Remove cattails and other indigenous wetland plants when they cover 50% of the basin surface. These
plants shall be encouraged to grow along the vegetated shelf and forebay berm.
6. If the basin must be drained for an emergency or to perform maintenance, the flushing of sediment through
the emergency drain shall be minimized to the maximum extent practical.
Form SWU-102 Rev 3.99 Page 3 of 4

7. All components of the wet detention basin system shall be maintained in good working order.
I acknowledge and agree by my signature below that I am responsible for the performance of the seven
maintenance procedures listed above. I agree to notify DWQ of any problems with the system or prior to any
changes to the system or responsible party.
Print name: Catawba Hills, LLC
Title: Robert B. Dienst, Manager
Address: 125 Easton Drive, Mooresville, NC 28117
Phony
Signa
Date:
Note: The legally responsible party should not be a homeowners association unless more than 50% of the lots have been sold and a
resident of the subdivision has been named the president.
T
I, G/a ~l `~ ~G ~ a Nota Public or the Sta of v~
rY (~ 0 G ,
County of f ,doh by certif that ~ LJ 1/
personally appeared before me this _~~day of , ~~, and acknowledge the due
execution of the forgoing wet detention basin maintenance requirements. Witness my hand and official seal,
Form SWU-102 Rev 3.99 Page 4 of 4

DETENTION CALCULATIONS

1005018
1.0 INTRODUCTION
The purpose of the following documentation is to clearly describe two things: the methods
of calculating the storm water runoff and the mechanisms for routing and detaining that
runoff. Haestad Methods' PondPack v9.0 was used for the routing of the stormwater through
the proposed facilities. Before the establishment of stormwater facilities, it is important to
acknowledge the flood study prepared by LandDesign, Inc. entitled "Flood Study for
Catawba Hills Village D" dated September 6, 2005. Since these stormwater facilities are
located adjacent to the Catawba Creek, it is critical that the study is referenced for review.
Catawba Hills is a master planned residential community developed by Catawba Hills, LLC
located off Beatty Road (SR-2439) along the Catawba Creek. The development plan as
approved under a rezoning petition by the Gastonia City Council includes 250 single-family
residential homes and 228 residential town homes.
A vicinity map is attached as Figure 1.
2.0 EXISTING CONDITIONS
The proposed Catawba Hills Subdivision is located in the southeastern quadrant of Gastonia,
North Carolina, and is zoned for residential developments. The specific area of emphasis is
the Catawba Hills Village D town. homes located off of Catawba. Hills Drive directly. across
from Catawba Hills Phase 3 (See construction plans by LandDesign, Inc.) Village D will
consist of 75 town home units and has a total area of 19.33 acres. The Gastonia Unified
Development Ordinance (UDO) requires stormwater runoff from the. final build-out of a
subdivision to equal the pre-existing condition. That is to say that at a point near the
downstream limit of the subdivision, the stormwater flow resulting from the existing land use
should be greater than or equal to the stormwater runoff from the developed condition.
For the Village D town homes, .the point selected for calculating the stormwater was just
above the confluence of the Catawba Creek and the Unnamed Tributary bounding the parcel
on the south and west respectively. The drainage area used to calculate the pre-existing
runoff consists of land outside the "City of Gastonia Future Greenway" and encompasses
15.52 acres. The area is predominantly woods and has Type B with poor hydrologic
condition soils which affords a curve number (CN) of 66.
The time of concentration (Tc) for the pre-existing condition was calculated using WinTR-55
and can be found in the calculations accompanying this report. The total Tc of the pre-
existing condition was made up of the follow characteristics and was found to be 0.312
hours:
• 100' of sheet flow at an average slope of 4.50% and an average Manning's
n-value of 0.40. (Tc = 0.247 hr)
• 300' of shallow concentrated flow at an average slope of 4.67% over an
unpaved surface. (Tc = 0.024 hr)
• 500' of shallow concentrated flow at an average slope of 4.40% over an
unpaved surface. (Tc = 0.041 hr)
L:N 005018\DOCSIDETENTION-NARATIVE.DOClIMc108/20/05
1 LANDDESIGNINC.

1005018
3.0 PROPOSED CONDITIONS
As stated previously, the City of Gastonia UDO requires stormwater detention for this
project. The required detention will be accomplished by routing the stormwater from the site
through one of three facilities: Wetland #1, Wetland #2, and Bioretention #1. Please refer to
NCDENR's manual for BMP design for more detailed definitions of extended detention
wetlands and Bioretention areas. Please note that in this report, the required areas are
displayed along with the corresponding proposed areas.
3.1 Wetland #1
The flow for Wetland #1 was calculated using its drainage area of 9.89 acres, a curve number
(CN) number of 90, and a time of concentration of 5 minutes. Please note that the curve
number is conservative, based on the soil type of the site. The soils on this site are
predominantly B soils which would warrant a CN of 85; however a CN of 90 was used in the
detention routing to continue the conservative assumptions in the storm drainage
calculations. The 9.89 acres was found to contain 50% impervious area.
As seen in the accompanying. calculations, the.required surface area for the permanent pool
for Wetland #1 is 8,886.24 SF while 9,055.84 was provided. The required water quality
volume for the drainage area was 17,946.7 CF while the provided volume equals 19,051:'.0
CF. See calculations for detailed computation of the required areas and volumes.
The outlet structure is required to hold back the 2-year and 10-year storms to the pre-
- developed flows while allowing the 50-year storm to pass through without the wetland
overtopping. This structure consists of a 60 LF of 12" culvert laid at 1.00% with an invert in
of 622.0 and an invert out of 621.5. Please note that the 10-year flood elevation is below the
outfall therefore allowing the culvert to have a free outfall. The riser is a 3'x3' box with a
top elevation of 629.0 which captures the 10-year event and holds it to a crest of 629.72. The
riser also has a 12" round orifice with an invert of 627.0 which captures the 2-year event and
holds it to a crest of 627.84. The riser structure also includes a 1.5" water quality dewatering
pipe at elevation 624.0 and a 6" permanent pool dewatering pipe with a gate valve at 622.5 to
allow for maintenance. Also note that the water quality dewatering pipe has been designed to
drain this portion of the wetland in the required period of 2 to 5 days. Wetland #1 has been
designed with a 20' long spillway at 629.9 which allows the 50-year to reach a maximum
elevation of 630.66 and provides the sufficient freeboard with the top of dam at 631.5.
Please note that a calculation was completed to check the spillway and dam against the 50-
yearflood elevation from the creek. This was completed knowing that the 50-year flood
elevation for the Catawba Creek was above the culvert at 624.62 (XS 42250.0), therefore to
be as conservative as possible, all three storm events (2, 10, and 50) were routed through the
spillway and crested at an elevation of 630.8. Even with these conservative assumptions, the
dam did not overtop and still had the required 6 inches of freeboard.
L:110050181DOCS\DETENTION-NARATIVE.DOCUMc100/20/05 2 LANDDESIGN INC.

1005018
3.2 Wetland #2
The flow for Wetland #2 was calculated using its drainage area of 1.93 acres, a curve number
(CN) number of 90, and a time of concentration of S minutes. Please note that like the
previous wetland, the curve number is conservative for the soil type of the site. To recap, the
soils on this site are predominantly B soils which would warrant a CN of 85; however a CN
of 90 was used in the detention routing to continue the conservative assumptions in the storm
drainage calculations. The 1.93 acres was found to contain 52% impervious area.
As seen in the accompanying calculations, the required surface area for the permanent pool
for Wetland #2 is 1,790.71 SF while 3,977.24 SF was provided. The required water quality
volume for the drainage area was 3,502.95 CF while the provided volume equals 5,416.0 CF.
See calculations for detailed computation of the required areas and volumes.
As stated above, the outlet structure is required to hold back the 2-year and 10-year storms to
the pre-developed amounts while allowing the 50-year storm to pass through without the
wetland overtopping. This structure consists of 60 LF of 12" culvert laid at 1.00% with an
invert in of 620.1 and an invert out of 619.5. Please note that the 10-year flood elevation is
below the outfall therefore allowing the culvert to have a free outfall. The riser is a 3'x3'
box with a top elevation of 625.5 which captures the 10-year event and holds it to a crestof
625:52. The riser also has a 6" round orifice with ari invert of 624.5 which captures the 2-
year event and holds it to a crest of 624.76. The riser structure also includes a 0.75" water
quality dewatering pipe at elevation 624.0 and a 6" permanent pool dewatering pipe with a
gate valve at 622.5 to allow for maintenance. Please note that the water quality dewatering
pipe has been designed to drain this portion of the wetland in the required period of 2 to 5
days. Wetland #2 has been designed with a 10' long spillway at 625.75 which allows the
crest of the 50-year to reach a maximum elevation of 625.90 and provides the sufficient
freeboard with the top of dam at 628.0. As noted in the previous wetland calculation, a
calculation was completed to check the spillway and dam against the 50-year flood elevation
from the creek. This was completed knowing that the 50-year flood elevation for the
Catawba Creek was above the culvert at 623.50 (XS 41843.0), therefore to be as conservative
as possible, all three storm events (2, 10, and 50) were routed through the spillway and
crested at an elevation of 626.16. Even with these conservative assumptions, the dam did not
overtop and still had the required 6 inches of freeboard.
3.3 Bioretention #1
Bioretention areas are different from extended detention wetlands; however they accomplish
the same objective which is to match the post-developed stormwater flow release to the pre-
developed condition. Instead of, in the case of the wetland, digging out an area to store the
runoff and requiring it meander through aman-made wetland before reaching an outlet
structure which holds the flow back, the bioretention facility stores the runoff and requires it
to infiltrate through an amended soil column and then release through perforated pipes.
Please see NCDENR's BMP design manual for technical information and a more detailed
definition. The design was completed using a spreadsheet provided by NCDENR which is
provided in the calculations. The flow for Bioretention #1 was calculated using its drainage
L:11005018\DOCS\DETENTION-NARATIVE.DOCVMC\09/20105 ~ LANDDESIGN INC.

ioosois
area of 0.74 acres, a curve number (CN) number of 90, and a time of concentration of s
minutes. Please note that like the previous wetlands, the curve number is conservative for
the soil type of the site. To recap, the soils on this site are predominantly B soils which
would warrant a CN of 8s; however a CN of 90 was used in the detention routing to continue
the conservative assumptions in the storm drainage calculations. The 0.74 acres was found to
contain 62% impervious area.
As seen in the following calculations, the required surface area for the bioretention area is
769 SF while 1,861.59 SF was provided with a maximum depth of 6". The bottom elevation
of the bioretention area is 628.0.
The bioretention area does not have an outlet structure like the wetlands. The outlet consists
of a 70' railroad timber level spreader at elevation 628.5 and provides for the maximum
depth of 6". The corresponding crests of the 2-, 10-, and s0-year storms are 628.63, 628.66,
and 628.68 respectively. The top of dam elevation is 629.25.
4.0 CONCLUSION
As;stated above, the objective was to match the post-developed stormwateX runoff to.the; pre-
developed condition. The post-developed condition consisted of 9.89 acres to Wetland #1,
1.93 acres to Wetland #2, 0.74 acres to Bioretention #1, and 2.96 acres of undetained area.
The table below reports the pre-developed flows from these four drainage basins as well as
the resultant flows after the implementation of the stonnwater detention facilities for the l-
and 10-year storm.
2-year Storm
Drainage Area
Flows To
Area Pre-
developed
Flows (cfs) Post-Developed
Flow. Before
Detention (cfs)

Wetland #1 9.89 5.35 32.16

Wetland #2 1.93 1.04 6.28

Bioretention #1 0.74 0 4 2 39

Undetained 2.96 1.6 2.1
Totals 15.52 Ac. 8.39 42.93
Post-,
.`Developed ,'
Flow After
Detention (cfs)`
2.06
0.16
2.39
2.1
6.71
L:17005018\DOC5IDETE NTIO N-NARATIV E DOCUMC\09/20/05
4 LANDDESIGN INC.

1005018
10-year Storm
Drainage
Area Flows
To
Area Pre-
developed
Flows (cfs) Post-Developed
Flow Before
Detention (cfs) Post-
Developed
Flow After
Detention (cfs)

Wetland #1 9.89 16.53 55.08 g.22

Wetland #2 1.93 3.23 10.75 1.16

Bioretention
#1
0.74
1.24
4.1
4.1

Undetained 2.96 4.95 5.73 5.73
Totals 15.52 Ac. 25.95 75'.66 20.21
ok
The requirement for the 50-year storm is to simply be able to pass the through the emergency
spillway, not to .detain the flow. Please.note the 50-year. elevations in reference to the top of .
dam elevations in the above section of this report show that the.50-year event does comply
with the requirement for each of the facilities.
Fora detailed outline of each calculation for the stormwater detention facilities, please see
the calculations that follow this report.
L:\1005018\DOCSIDETENTION-NARATIVE.DOC\JMc109/20105 5 LANDDESIGN INC.

1005018
Figure 1
L:\7005010\DOCS\DETENTION-NARATIVE.DOCUMc\09/20/05 ~ LANDDESIGN INC.

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Type.... Master Network Summary Page 1.01
Name.... Watershed
File.... L:\1005018\CAD\Civil\PondPak\REVISED 9-2-OS\VILLAGE-D-PRE.PPW
MASTER DESIGN STORM SUMMARY
Network Storm Collection: Mecklenburg
Total
Depth Rainfall
Return Event
------------ in
------ Type
------ RNF ID

2
3.1200 ----------
Synthetic Curve ----------------
TypeII 24hr
10 4.8000 Synthetic Curve TypeII 29hr
50 6.4800 Synthetic Curve TypeII 24hr
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*NOde=Outfall; +Node=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Node ID
--------------
PRE-DEVEL
PRE-DEVEL
PRE-DEVEL
*PRE-DEVEL
*PRE-DEVEL
*PRE-DEVEL
Return HYG Vol
Type
---- Event
------ ac-ft Trun
------

AREA
2 ---- --
.780
AREA 10 2.060
AREA 50 3.623
JCT 2 .780
JCT 10 2.060
JCT 50 3.623
Max
Qpeak Qpeak Max WSEL Pond Storage
hrs
--------- cfs ft ac-ft
--------

12.1100 -------- ------------
8.39
12.1000 25.93
12.0700 47.03
12.1100 8.39
12.1000 25.93
.12.0700 -47.03
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 10:38 AM Date: 9/6/2005

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CATAWBA HILLS VILLAGE D WATER QUALITY WETLANDS #1
DESIGN: WATER QUALITY TO MEET 85% TSS REMOVAL
GIVEN:
DRAINAGE AREA TO FACILITY = 9.89 Ac.
LAND USE = Town Homes
ESTIMATED PERCENT IMPERVIOUS = 50%
PREDOMINANT SOIL TYPE = CeD, CeB
1) SA/DA RATIO:
AVERAGE POOL DEPTH= 3 FEET
PERCENT IMPERVIOUS = 50%
SA/DA = 2.06 % = 0.0206
SA REQUIRED = 9:89 Ac. X 0.0206
= 0.204 Ac.
= 8,875 SF
2) TEMPORARY WATER QUALITY POOL REQUIREMENTS
PROVIDE VOLUME TO DETAIN THE 1"STORM EVENT ABOVE THE ELEVATION.
ALLOCATED AS A PERMANENT POOL
THE VOLUME FOR THE 1"STORM EVENT CAN BE CALCULATED AS:
V~ _ (Design Rainfall)(Rv)(Drainage Area)
Design Rainfall = 1 Inch
Drainage Area = 9.89 Acres
Rv = 0.05 + 0.009(1)
I =Percent Impervious = 50%
Rv = 0.5 in./in.
V, _
0.412 acre-feet = 17,947 ft'
9/13/2005 9:29 AM Page 1 of 2

3) 4 DAY RELEASE OF TEMPORARY WATER QUALITY POOL
Required Q = (V1)/(345,600 seconds) = 0.05 cfs
Height Above Orifice (H) = 1.75 feet
Total Orifice Area Required = 0.012 sf
Average Q = 0.05 cfs
Number of Orifices = 1
Orifice Diameter = 1.45 inches .: use
H Q
0.00 0.00
0.05 0.01
0.10 0.02
0.15 0.02
0.20 0.02
0.25 0.03
0.30 0.03
0.35 0.03
0.40 .0.04
0.45 0.04
0.50. 0.04
0.55 0.04
0.60 0.04
0.65 0.04
0.70 0.05
0.75 0.05
0.80 0.05
0.85 0.05
0.90 0.05
0.95 0.05
1.00 0.06
1.05 0.06
1.10 0.06
1.15 0.06
1.20 0.06
1.25 0.06
1.30 0.06
1.35 0.06
1.40 0.07
1.45 0.07
1.50 0.07
1.55 0.07
1.60 0.07
1.65 0.07
1.70 0.07
1.75 0.07
1.5 Inches
0.= (2 x 32.2 x H)0~5 x 0.6 x A
9/13/2005 9:29 AM Page 2 of 2

Type.... Master Network Summary Page 2.01
Name.... Watershed
File.... L:\1005018\CAD\Civil\PondPak\REVISED 9-2-OS\VILLAGE-D-POST-WETLANDI.PPW
MASTER DESIGN STORM SUMMARY
Network Storm Collection: Mecklenburg
Total
Depth Rainfall
Return Event
------------ in
------ Type
----- RNF ID

2
3.1200 -----------
Synthetic Curve ----------------
TypeII 29hr
10 4.8000 Synthetic Curve TypeII 24hr
50 6.9800 Synthetic Curve TypeII 29hr
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*NOde=Outfall; +NOde=Diversion;)
(T run= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Mdx
Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage
Node ID -------- Type Event ---ac_ft-- Trun
-- hrs
---- cfs ft ac-ft

POST-DEV WET #1

AREA

2

1.726 -----

11.9200 -------- --------
------------
32.16
POST-DEV WET #1 AREA 10 3.036 11.9200 55.08
POST-DEV WET #i AREA 50 4.380 11.9200- ?7.81-
*PRE-DEVEL JCT 2 .497 12.1100 5.35
*PRE=DEVEL JCT 10 1.313 12.1000 16.53
*PRE-DEVEL- JCT 50 2.309 12.0700 29.97
PRE-DEVEL AREA 2 .497 12.1100 5.35
PRE-DEVEL AREA 10 1.313 12.1000 16.53
PRE-DEVEL AREA 50 2.309 12.0700 29.97
*WET #1 OUTFACE JCT 2 .69.7 R 12.7900 2.06
*WET #1 OUTFACE JCT 10 2.152 R 12.1400 9.22
*WET #1 OUTFACE JCT 50 3.979 R 12.0300 59.11
WETLAND #1 IN POND 2 1.726 11.9200 32.16
WETLAND #1 IN POND 10 3.036 11.9200 55.08
WETLAND #1 IN POND 50 9.380 11.9200 77.81
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 10:58 AM Date: 9/20/2005

Type.... Master Network Summary Page 2.02
Name.... Watershed
File.... L:\1005018\CAD\Civil\PondPak\REVISED 9-2-OS\VILLAGE-D-POST-WETLANDI.PPW
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*Node=Outfall; +Node=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Max
Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage
Node ID
-
---- Type
---- ---- Event
------ ac-ft
---------- Trun
-- hrs
-------- cfs ft ac-ft

WETLAND
#1
OUT POND
2
.897
R -
12.7400 --------
2.06 --------
627.89 ------------
1.035
WETLAND #1 OUT POND 10 2.152 R 12.1400 9.22 629.72 1.648
WETLAND #1 OUT POND 50 3.474 R 12.0300 59.11 630.66 1.961
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 10:58 AM Date: 9/20/2005

Type.... Outlet Input Data Page 13.01
Name.... Outlet 1
File.... L:\1005018\CAD\Civil\PondPak\REVISED 9-2-05\VILLAGE-D-POST-WETLANDI.PPW
REQUESTED POND WS ELEVATIONS:
Min. Elev.= 624.00 ft
Increment = .10 ft
Max. Elev.= 631.50 ft
OUTLET CONNECTIVITY
---> Forward Flow Only (Upstream to DnStream)
<--- Reverse Flow Only (DnStream to Upstream)
<---> Forward and Reverse Both Allowed
Structure No. Outfall E1, ft E2, ft
Orifice-Circular O1 ---> CO 627.000 631.500
Inlet Box RO ---> CO 629.000 631.500
Orifice-Circular 00 ---> CO 624.000 631.500
Culvert-Circular.. CO ---> TW 622.000 .631.500
weir-Rectangular w0 ---> TW 629.900 631.500
TW SETUP, DS Channel
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 10:59 AM Date: 9/20/20.05

Type.... Outlet Input Data
Name.... Outlet 1
Page 13.02
File.... L:\1005018\CAD\Civil\PondPak\REVISED 9-2-OS\VILLAGE-D-POST-WETLANDI.PPW
OUTLET STRUCTURE INPUT DATA
Structure ID = O1
Structure Type = Orifice-Circular
------------------------------------
# of Openings = 1
Invert Elev. = 627.00 ft
Diameter = 1.0000 ft
Orifice Coeff. _ .667
Structure ID = RO
Structure Type
------------- = Inlet Box
-----
# of Openings -----------
= 1 -------
Invert Elev. = 629.00 ft
Orifice Area = 9.0000 sq.ft
Orifice Coeff. _. .667
weir Length = 12.00 ft
Weir Coeff. = 3.333
K, Reverse = 1.000
Mannings n = .0000
Kev,Charged Riser = .000
Weir Submergence = No
Structure ID = 00
Structure Type = Orifice-Ci rcular
# of Openings = 1
Invert .Elev. = 629.00 ft
Diameter = .1250 ft
Orifice Coeff. _ .666
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 10:59 AM Date: 9/20/2005

Type.... Outlet Input Data Page 13.03
Name.... Outlet 1
File.... L:\1005018\CAD\Civil\POndPak\REVISED 9-2-OS\VILLAGE-D-POST-WETLANDI.PPW
OUTLET STRUCTURE INPUT DATA
Structure ID = CO
Structure Type =
------------------- Culvert-Circular
-

No. Barrels = ----------
1 ------
Barrel Diameter = 1.0000 ft
Upstream Invert = 622.00 ft
Dnstream Invert = 621.50 ft
Horiz. Length = 60.00 ft
Barrel Length = 60.00 ft
Barrel Slope = .00833 ft/ft
OUTLET CONTROL DATA ...
Mannings n = .0130
Ke = .5000 (forward entrance loss)
Kb = .031274 (per ft of full flow)
Kr = .5000 (reverse entrance loss)
HW Convergence = .001 +/- ft
INLET CONTROL DATA...
Equation form = 1
Inlet Control K = .0098
Inlet Control M = 2.0000
Inlet Control c = .03980
Inlet Control Y = .6700
T1 ratio (HW/D) = 1.156
T2 ratio (HW/D) = 1.303
Slope Factor = -.500.
Use unsubmerged inlet control Form l equ. below T1 elev.
Use submerged inlet control Form 1 equ. above T2 elev.
In transition zone between unsubmerged and submerged inlet control,
interpolate between flows at Tl & T2...
At T Elev = 623.16 ft ---> Flow = 2.75 cfs
At T2 Elev = 623.30 ft ---> Flow = 3.14 cfs
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 10:59 AM Date: 9/20/2005

Type.... Outlet Input Data
Name.... Outlet 1
Page 13.04
File.... L:\1005018\CAD\Civil\PondPak\REVISED 9-2-OS\VILLAGE-D-POST-WETLANDI.PPW
OUTLET STRUCTURE INPUT DATA
Structure ID
Structure Type
--------------
# of Openings
Crest Elev.
Weir Length
Weir Coeff.
WO
Weir-Rectangular
----------------
1
629.90 ft
20.00 ft
3.333000
weir Tw effects (Use adjustment equation)
Structure ID = TW
Structure Type = TW SETUP, DS Channel
------------------------------------
FREE OUTFACE CONDITIONS SPECIFIED
CONVERGENCE TOLERANCES...
Maximum Iterations= 90
Min. TW tolerance = .O1 ft
Max. TW tolerance = .O1 ft
Min. HW tolerance = .O1 ft
Max. HW tolerance = .O1 ft
Min. Q tolerance = .00 cfs
Max. Q tolerance = .00 cfs
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 10:59 AM Date: 9/20/2005

Type.... Master Network Summary Paqe 2.01
Name.... Watershed
File.... L:\1005018\CAD\Civil\POndPak\REVISED 9-2-OS\VILLAGE-D-POST-WETLANDI-TAILWATER.PPW
MASTER DESIGN STORM SUMMARY
Network Storm Collection: Mecklenburg
Total
Depth Rainfall
Return Event in Type RNF ID
------------ ------ ---------------- ----------------
50 6.9800 Synthetic Curve Typell 24hr
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*Node=outfall; +NOde=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Max
Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage
Node ID Type Event
------ ac-ft Trun
---------- -- hrs
--- cfs ft ac-ft

POST-DEV WET #1
AREA
50
4.380 ------
11.9200 --------
77.81 -------- ------------
*PRE-DEVEL JCT 50 3.623 12.0700 47.03
PRE-DEVEL AREA 50 3.623 12.0700 47.03
*WET #1 'WEIR ONLY JCT 50 2.665 R 12.0200 57.03
WETLAND #1 IN POND 50' 4.380. 11:9200 77.81
WETLAND #1 OUT POND 50 2.665 R 12.0200 57.03 630.80 2.033
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 1:37 PM Date: 9/8/2005

Type.... Master Network Summary Page 2.01
Name.... Watershed
File.... L:\1005018\CAD\Civil\POndPak\REVISED 9-2-OS\VILLAGE-D-POST-WETLAND2.PPW
MASTER DESIGN STORM SUMMARY
Network Storm Collection: Mecklenburg
Total
Depth Rainfall
Return Event
------------ in
------ Type
------ RNF ID

2
3.1200 ----------
Synthetic Curve ----------------
TypeII 24hr
10 9.8000 Synthetic Curve TypeII 24hr
50 6.9800 Synthetic Curve TypeII 29hr
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*NOde=Outfall; +NOde=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Max
Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage
Node ID
----------- Type
---- Event
------ ac-ft
---------- Trun
-- hrs
----- cfs ft ac-ft

POST-DEV WET #2
AREA
2
.337 ----
11.9200 -------- -------- ------------
6.28
POST-DEV WET #2 AREA 10 .592 11.9200 10.75
FOST-DEV WET #2 AREA 50 .855 11.9200 15.18
*PRE-DEVEL JCT 2 .097 12.1100 1.04
*PRE-DEVEL JCT 10 .256 12.1000 3.23
*PRE-.DEVEL JCT 50 ,451 12.0700 5.85
PRE-:DEVEL AREA 2 .097 12.1100 1.09
PRE-DEVEL AREA 10 .256 12.1000 3.23
PRE-DEVEL AREA 50 .951 12.0700 5.85
*WET #2 OUTFACE JCT 2 .109 R 14.97.00 .16
*WET #2:'OUTFALL JCT 10' .353 R 12.3500 1.16
*WET #2 'OUTFACE JCT 50 .610 R 12.0300 9.99
WETLAND #2 IN POND 2 .337 11.9200 6.28
WETLAND #2 IN POND 10 .592 11.9200 10.75
WETLAND #2 IN POND 50 .855 11.9200 15.18
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 11:03 AM Date: 9/20/2005

Type.... Master Network Summary Page 2.02
Name.... Watershed
File.... L:\1005018\CAD\Civil\PondPak\REVISED 9-2-05\VILLAGE-D-POST-WETLAND2.PPW
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*NOde=Outfall; +NOde=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Max
Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage
Node ID Type
---- Event
------ ac-ft
---------- Trun
-- hrs
--- cfs ft ac-ft

WETLAND #2
OUT POND
2
.109
R ------
19.8600 --------
.16 --------
624.76 ------------
.247
WETLAND #2 OUT POND 10 .353 R 12.3500 1.16 625.52 .350
WETLAND #2 OUT POND 50 .610 R 12.0300 9.99 625.90 .906
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 11:03 AM Date: 9/20/2005

Type.... Outlet Input Data
Name.... Outlet 2
Page 13.01
File.... L:\1005018\CAD\Civil\PondPak\REVISEb 9-2-OS\VILLAGE-D-POST-WETLAND2.PPW
REQUESTED POND WS ELEVATIONS:
Min. Elev.= 622.50 ft
Increment = .10 ft
Max. Elev.= 628.00 ft
OUTLET CONNECTIVITY
---> Forward Flow Only (Upstream to DnStream)
<--- Reverse Flow Only (DnStream to Upstream)
<---> Forward and Reverse Both Allowed
Structure No. Outfall E1, ft E2, ft
--- ------- --------
Orifice-Circular O1 ---> CO 624.500 628.000
Inlet Box RO ---> CO 625.500 628.000
Orifice-Circular 00 ---> CO 629.000 628.000
Culvert-Circular CO --->. TW 620.100 628.000
Weir-Rectangular WO ---> TW 625.750 628.000
TW SETUP, DS Channel
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 11:03 AM Date: 9/20/2005

Type.... Outlet Input Data Page 13.02
Name.... Outlet 2
File.... L:\1005018\CAD\Civil\PondPak\REVISED 9-2-OS\VILLAGE-D-POST-WETLAND2.PPW
OUTLET STRUCTURE INPUT DATA
Structure ID = O1
Structure Type = Orifice-Circular
------------------------------------
# of Openings = 1
Invert Elev. = 629.50 ft
Diameter = .5000 ft
Orifice Coeff. _ .667
Structure ID = RO
Structure Type = Inlet Box
# of Openings = 1
Invert Elev. = 625.50 ft
Orifice Area = 9.0000 sq.ft
Orifice Coeff. _ .667
Weir Length = 12.00 ft
Weir Coeff. = 3.333
K, Reverse = 1.000
Mannings n = .0000
Kev,Charged Riser = .000
Weir Submergence = No
Structure ID = 00
Structure Type Orifice-Circular
------------------------------------
# of Openings = 1
Invert Elev. = 629.00 ft
Diameter = .0625 ft
Orifice Coeff. _ .667
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 11:03 AM Date: 9/20/2005

Type.... Outlet Input Data Page 13.03
Name.... Outlet 2
File.... L:\1005018\CAD\Civil\PondPak\REVISED 9-2-OS\VILLAGE-D-POST-WETLAND2.PPW
OUTLET STRUCTURE INPUT DATA
Structure ID = CO
Structure Type = Culvert-Circular
------------------------------------
No. Barrels = 1
Barrel Diameter = 1.0000 ft
Upstream Invert = 620.10 ft
Dnstream Invert = 619.50 ft
Horiz. Length = 60.00 ft
Barrel Length = 60.00 ft
Barrel Slope = .01000 ft/ft
OUTLET CONTROL DATA...
Mannings n = .0130
Ke = .5000 (forward entrance loss)
Kb = .031279 (per ft of full flow)
Kr = .5000 (reverse entrance loss)
HW Convergence = .001 +/- ft
INLET CONTROL DATA...
Equation form = 1
Inlet Control K = .0098
Inlet Control M = 2.0000
Inlet Control c = .03980
Inlet Control Y = .6700
T1 ratio (HW/D) = 1.155
T2 ratio (HW/D) = 1.302
Slope Factor = -.500
Use unsubmerged inlet control Form 1 equ. below T1 elev.
Use submerged inlet control Form 1 equ. above'T2 elev.
In transition zone between unsubmerged and submerged inlet control,
interpolate between flows at T1 & T2...
At T1 Elev = 621.25 ft ---> Flow = 2.75 cfs
At T2 'Elev = 621.40 ft ---> Flow = 3.14 cfs
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 11:03 AM Date: 9/20/2005

Type.... Outlet Input Data Page 13.09
Name.... Outlet 2
File.... L:\1005018\CAD\Civil\POndPak\REVISED 9-2-OS\VILLAGE-D-POST-WETLAND2.PPW
OUTLET STRUCTURE INPUT DATA
Structure ZD
Structure Type
--------------
# of Openings
Crest Elev.
Weir Length
Weir Coeff.
WO
Weir-Rectangular
----------------
1
625.75 ft
10.00 ft
3.333000
Weir TW effects (Use adjustment equation)
Structure ID = TW
Structure Type = TW SETUP, DS Channel
------------------------------------
FREE OUTFACE CONDITIONS SPECIFIED
CONVERGENCE TOLERANCES ...
Maximum Iterations= 40
Min. TW tolerance = .O1 ft
Max. TW tolerance = .O1 ft
Min. HW tolerance = .O1 ft
Max. HW tolerance = .O1 ft
Min. Q tolerance = .00 cfs
Max. Q tolerance = .00 cfs
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 11:03 AM Date: 9/20/2005

Type.... Master Network Summary Page 1.01
Name.... Watershed
File.... L:\1005018\CAD\Civil\PondPak\REVISED 9-2-OS\VILLAGE-D-POST-BIOI.PPW
MASTER DESIGN STORM SUMMARY
Network Storm Collection: Mecklenburg
Total
Depth Rainfall
Return Event
------------ in
------ Type
------- RNF ID

2
3.1200 ---------
Synthetic Curve ----------------
TypeII 29hr
10 4.8000 Synthetic Curve TypeII 29hr
50 6.9800 Synthetic Curve TypeII 29hr
MASTER NETWORK SUMMARY
SC S. Unit Hydrograph Method
(*NOde=Outfall; +Node=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Max
Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage
Node ID
----------------- Type
---- Event
------ ac-ft Trun
---------- -- hrs
-- cfs ft ac-ft

*BIO #1 OUTFACE
JCT
2
.107 -------
11.9300 --------
2.39 -------- ------------
*BIO #1 OUTFACE JCT 10 .205 11.9300 9.10
*BIO #1 OUTFACE JCT 50 .305 11.9200 5:79.
BIO. #1 IN POND 2 .129 11.9200 2.91
BIO. #1 IN POND 10 .227 11.9200 9.12
BIO. #1 IN .POND 50 .328, .11.9200 5.82
BIO. #1 OUT POND 2 .107 11.9300 2.39 628.53 .029
BIO. #1 OUT POND 10 .205 11.9300 4.10 628.56 .025
BIO. #1 OUT POND 50 .305 11.9200 5.79 628.58 .026
POST-DEV BIO. #1 AREA 2 .129 11.9200 2.41
POST-DEV BIO. #1 AREA 10 .227 11.9200 9.12
POST-DEV BIO. #1 AREA 50 .328 11.9200 5.82
*PRE-DEVEL JCT 2 .037 12.1000 .40
*PRE-DEVEL JCT 10 .098 12.1000 1.29
*PRE-DEVEL JCT 50 .173 12.0700 2.29
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 11:06 AM Date: 9/20/2005

Type.... Master Network Summary Page 1.02
Name.... Watershed
File.... L:\1005018\CAD\Civil\PondPak\REVISED 9-2-OS\VILLAGE-D-POST-BIOI.PPW
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*Node=Outfall; +Node=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Max
Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage
Node ID Type Event ac-ft Trun hrs cfs ft ac-ft
----------------- ---- ------ ---------- -- --------- -------- -------- ------------
PRE-DEVEL AREA 2 .037 12.1000 .90
PRE-DEVEL AREA 10 .098 12.1000 1.24
PRE-DEVEL AREA 50 .173 12.0700 2.24
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 11:06 AM Date: 9/20/2005

Type.... Outlet Input Data
Name.... Outlet 3
Page 12.01
File.... L:\1005018\CAD\Civil\POndPak\REVISED 9-2-05\VILLAGE-D-POST-BIOI.PPW
REQUESTED POND WS ELEVATIONS:
Min. Elev.= 628.00 ft
Increment = .10 ft
Max. Elev.= 629.25 ft
OUTLET CONNECTIVITY
---> Forward Flow Only (Upstream to DnStream)
<--- Reverse Flow Only (DnStream to Upstream)
<---> Forward and Reverse Both Allowed
Structure No. Outfall E1, ft E2, ft
----------------- ---- ------- --------- ---------
Weir-Rectangular WO ---> TW 628.500 629.250
TW SETUP, DS Channel
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 11:06 AM Date: 9/20/2005

Type.... Outlet Input Data
Name.... Outlet 3
Page 12.02
File.... L:\1005018\CAD\Civil\PondPak\REVISED 9-2-OS\VILLAGE-D-POST-BIOl.PPW
OUTLET STRUCTURE INPUT DATA
Structure ID
Structure Type
--------------
# of Openings
Crest Elev.
Weir Length
weir Coeff.
WO
weir-Rectangular
----------------
1
628.50 ft
70.00 ft
3.333000
Weir TW effects (Use adjustment equation)
Structure ID = TW
Structure Type = TW SETUP, DS Channel
------------------------------------
FREE OUTFACE CONDITIONS SPECIFIED..
CONVERGENCE TOLERANCES ...
Maximum Iterations= 40
Min. TW tolerance = .O1 ft
Max. TW tolerance = .O1 ft
M>n. HW tolerance = .O1 ft
Max. HW tolerance = .O1 ft
Min. Q tolerance = .00 cfs
Max. Q tolerance = .00 cfs .
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 11:06 AM Date: 9/20/2005

_. _ __ _ _ ~_.____... ~_~ _ ._...___ __._. ~~..___ _.._.~..._ ._ ~__.. __ ___ _ ~ R_(~~os~ ~
~c-~N9~ Dec-~N~T~oN Wrc.T~NO ~2
~owN ~ D~ _ ~,93 ~~
t ~rlEav Ike CSF~ = 38, 61 c sF
°~b ~,~e~a.v .. sz
?~n~t~rY7 Qvo~ sc~Rt~c~ ~sLeA
S~lDA z ~ 13 Sn ~ ~- QESr MJ4NIbG~tF,~tT ~RA'C~CfS
C1~.NA ~Pril ~9~
Mtn . SW~F~C~. A~2£R _ 2.13
~~,, ~ 1.9 3 ~4c. = 0. o~ - ~ ac
oa 17Ra.7~ sF
(°~ -Et,rcv 62Z,5~ QRo~IAE.D S~~tc~ A~ = 3g7 7. Z4' SF
1
..
• -,moo ~ ems. e~~ _ ~z~.o
vt- Q~ACiT'Y vo~u~~ W ~. { S7aR~t.
pa = 1.°! 3 n~
ob {~PfG~1 a ~Z !.
0. aS ~- d. 0oq ~~
Rv = U. 5 Z `
Q~4l~L I R~.D V o l.Uli~t~ = C '~fS t 6 N QfN~-fhCt.\) `/ R y> p /q
l )CU,S /'n~` /iz ~;,,~ 1.93
R~G2. Veu~ME = D.0~8~ ~~-k ~ 3,SoZ.9~ C~
S/"~ ~ S7a~ ~ 1
~a2~ D S41 0
~a2 5 { 54~ a b4tG
~; PAoViOED VdLuw~~ 5'+}1~ ~~

Z
6ze. a' - -roi' of gActi
(~Z5,75~-~bP ol/ sP~uwl~1
dzr ~tS.52~ I~-yR ~'
--
G2~= G2s.5~ -~P aF RtSf~
3`X3' Qak j
(S~ •tFF
6Z~ ~ ~24.5~ 6„ ~~RtUt,n-R c2,fie~ ~ 6t(s.4s
.~ _... _~. ~ ,a - 0.75 D~.w~fzt~6 6~~ Fi GL4.7i
~,
Gz2 = ~
G2~ ~
G i8 ~- ~o.yR .4t) ~~r'ronti of
i'&.l~a. P~~
~~z.~
1~.N oar 1NV Irl,`aF
IL" RCP=bt1~5' 12" IZCP =62D.-~
i ~

CATAWBA HILS VILLAGE D WATER QUALITY WETLANDS #2 .
DESIGN: WATER QUALITY TO MEET 85% TSS REMOVAL
GIVEN:
DRAINAGE AREA TO FACILITY = 1.93 Ac.
LAND USE = Town Homes
ESTIMATED PERCENT IMPERVIOUS = 52%
PREDOMINANT SOIL TYPE = CeD, Ce6
1) SA/DA RATIO:
AVERAGE POOL DEPTH = 3 FEET
PERCENT IMPERVIOUS = 52%
SA/DA = 2.13 % = 0.0213
SA REQUIRED = 1.93 Ac. X 0:0213
_ .0.041. Ac.
= 1,791 SF
2) TEMPORARY WATER QUALITY POOL REQUIREMENTS
PROVIDE VOLUME TO DETAIN THE 1"STORM EVENT ABOVE THE ELEVATION
ALLOCATED AS A PERMANENT POOL
THE VOLUME FOR THE 1"STORM EVENT CAN BE CALCULATED AS:
V, _ (Design Rainfall)(Rv)(Drainage Area)
Design Rainfall = 1 Inch
Drainage Area = 1.93 Acres
Rv = 0.05 + 0.009(1)
=Percent Impervious = 52%
Rv = 0.52 in./in.
V~ = 0.084 acre-feet = 3,659 fts
9/13/2005 9:33 AM Page 1 of 2

3) 4 DAY RELEASE OF TEMPORARY WATER QUALITY POOL
Required O = (V1)/(345,600 seconds) = 0.01
Height Above Orifice (H) = 1 feet
Total Orifice Area Required = 0.003 sf
Average O = 0.01 cfs
Number of Orifices = 1
Orifice Diameter = 0.74 inches .: use
H Q
0.00 0.00
0.05 0'.00
0.10 0.00
0.15 0.01
0.20 0.01
0.25 0.01
0.30 0.01
.0.35. 0.01
0.40 0.01
0.45 0.01
.0.50 0.01
0.55 0.01
0.60 0.01
0.65 0.01
0.70 0.01
0.75 0.01
0.80 0.01
0.85 0.01
0.90 0.01
0.95 0.01
1.00 0.01
cfs
0.75 Inches
Q= (2x32.2xH)°'5x0.6xA
9/13/2005 9:33 AM Page 2 of 2

20 Width A~nroximate Size
39 Length
Water Draw Through Rate:
Darcy's Equation:
Q = (.0000232)*K*A*( HIL )
Where:
Q =Flow (Rate of Draw) through Bioretentioin Soil (cfs)
K =Hydraulic Conductivity of soil (Use 1 "/Hour)
A =Surface Area of Bio-Retention Area (SF)
H =Height of Water above Drainage Pipe (Underdrain)
L =Thickness of Soil Bed (Usually 4' )
Assume (H/L) --1
Q = 0.018 cfs
Time to Drawdown water from Inundation to Saturation at Surface:
Volume/Q: 21552 Seconds
6.0 Hours to Saturation
Time to lower Water Table to 2.0 feet below surface:
Assume'45% Porosity
Volume =..Area x 2' x 0.45
= 691.7 Cubic Feet
= 38793 Seconds
= 10.8 Hours to Lower Water 2' below surface .
SIZE UNDERDRAIN
As a rule of thumb, the length of underdrain is based on 10% of Af
Source: (NY State Stormwater Manual)
L = 26 Feet in 3' wide stone bed
Required Diameter 4.7 Inches (Minimum 6")
Source: (NCSU Rain Garden Design Worksheet, Bill Hunt)
~_~1 Or More Underdrains required

,1~~~~s
~t ~ R~~rcr~oN ~Rf~A ~-
t r~~v Mts~t CSF) I B, ?97 sF
~f.~~u e~to qua ~x ~.r~
Strom A~r~tc~ ~kCCutkn~NS
2fQ. ~ ~. 14t?.tr~i4 = 7&4 SF
~ SP~v sc~' P~v+aw t3~ NcOtµR ~ N ~~~ Ntrarroc` - S~t+u£c.~. ~ t'd?
N~D~+~ ~ ~4-~, n ~ ~~ 44
PR~~t~9 Su2~rK-+~ H Rs~.#k = l 86 ~ .39 S~
~z~ ~'
TbP of a~
(~2g,j~_ ~(+-o f,c6~
L~.V~I SP~~6.it
~.~~ (~ze.sa`~
i p-yF (628. s~ ~`s• - - - - - - - - - - - - - ~ -
2 _•~R Cbt~•53~)
i 2 . ~-
~ 6 8b
~ R a~~ tit o f
~% Ci l oRU~NTIoti1
/~
~ ~ b ~ pMn~Ea 4~p ~a+ tS;
i

BIORETENTION AREA #1
vesign storm attenuated by NGDENR required Surface Area
Rv =runoff coefficient (Runoff/Rainfall)
Rv = 0.05 + 0.009(1) Where "I" _ % Impervious
("Simple Method" - Schueler, 1987)
NGDENR April 1999
WQv = 1 "RvA
12
Formula:
Af = Qv) (Dfl
((k) (Hf+Df) (Tf))
From Georgia Design Manual
Section 3.2.3.6
(Based on Darcy's Law)
Fill in Values:
"1" _ ¢~ Percent Impervious of Site
"A" _ .Q.74 ' Acres
wer•
WQv = 0.037 , Ac. Ft.
Cubic Feet Required
RAW GARDEN AREA
Where:
Af = Surface area of Rain Garden (S.F.)
WQv = Water Quality Volume to be Captured
Df Filter Bed Depth (2 feet minimum)
k = permeability coefficient of filter media
(use 1.0 ft/day for sandy-loam)
Hf = Average height of water above filter bed
(use 3 inches, which is half of 6" ponding depth)
Tf = Design filter bed drain time in days
(2 Days or 48 hours )
Fill in Values:
"k" = 1 ft./day (1/2"/Hour)
Df = 4 Feet
Hf = 3 inches
Tf = 2 Days

Answer:
Af = ®Square Feet Required
For Rain Garden
Note: Area provided, 1860 SF, will capture and treat runoff from first 1.00 inch of rainfall

Type.... Master Network Summary Page 1.01
Name.... watershed
File.... L:\1005018\CAD\Civil\POndPak\REVISED 9-2-OS\VILLAGE-D-PRE-UNDETAINED.PPW
MASTER DESIGN STORM SUMMARY
Network Storm Collection: Mecklenburg
Total
Depth Rainfall
Return Event in Type RNF ID
------------ ------ ---------------- ----------------
2 3.1200 Synthetic Curve TypeII 29hr
10 4.8000 Synthetic Curve TypeII 29hr
50 6.9800 Synthetic Curve TypeII 24hr
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*Node=Outfall; +NOde=Diversion;)
(T run= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Return HYG Vol
Node ID
-------------- Type
--- ---- Event
---- ac-ft Trun

PRE-DEVEL
AREA --
2 ---------- --
.199
PRE-DEVEL AREA 10 .393
PRE-DEVEL - AREA 50 ~ :691
*PRE-DEVEL JCT 2 .149
*PRE-DEVEL JCT 10 .393
*PRE-DEVEL JGT. 50 .691
Qpeak
hrs
12.1100
12.1000
12.0700
12.1100
12.1000
12.0700
Max
Qpeak Max WSEL Pond Storage
cfs ft ac-ft
1.60
9.95
8.97
1.60
4.95
8.97
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 2:59 PM Date: 9/13/2005

Type.... Master Network Summary Page 1.01
Name.... Watershed
File.... L:\1005018\CAD\Civil\POndPak\REVISED 9-2-OS\VILLAGE-D-POST-UNDETAINED.PPW
MASTER DESIGN STORM SUMMARY
Network Storm Collection: Mecklenburg
Total
Depth Rainfall
Return Event in Type RNF ID
------------ ------ ---------------- ----------------
2 3.1200 Synthetic Curve TypeII 29hr
10 4.8000 Synthetic Curve TypeII 29hr
50 6.9800 Synthetic Curve TypeII 29hr
MASTER NETWORK SUMMARY
SCS Unit Hydrograph Method
(*Node=Outfall; +Node=Diversion;)
(Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt)
Max
Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage
Node-ID--------- Type Event ---ac-ft Trun hrs cfs ft ac-ft
------ -- ---------
-------- --------
------------
POST-DEVEL AREA 2 .181 12.1000 2.10
POST-DEVEL AREA 10 .447 12.1000 5.73
POST-DEVEL. AREA 50 .763 12:0700 9', 9g
*POST-DEVEL JCT 2 .181 12.1000 2.10
*POST-DEVEL JCT 10 .497 12.1000 5.73
*POST-DEVEL .JCT 50 ,,763, 12.0700 9,98,
S/N: A21305C2E1C5 LandDesign Incorporated
PondPack Ver. 09.00.077.00 Time: 10:50 AM Date: 9/20/2005