20180399 Ver 1_Stormwater- 3/20/2018_20180320

March 19, 2018
NC DWQ, WBSCP Unit
1650 Mail Service Center
Raleigh, NC 27699-1650
RE: Staybridge Suites DWQ Buffer Permit
To Whom It May Concern,
Please see online application PCN Form for the proposed Staybridge Suites Hotel located at 8001 ACC
Boulevard, Raleigh, NC 27617. We are seeking written Buffer Rule approval only.
Please let us know if you have any questions or concerns.
Sincerely,
;Jonwry, P.E.
Lowry Engineering
[e-mail]
701.235.0199

Preliminary Stormwater
Management Plan
Staybridge Suites
107 Units/4.5 Story
8001 ACC Bouelvard
Raleigh, NC 27617
Developer Information:
Dakota Legacy Group
1202 Westrac Drive, 3rd Floor
Fargo, ND 58103
LE Project # 16009.4
44
Lover
ENGINEERING
1111 Westrac Drive Suite 108 . Fargo, ND • 58103
Prepared by:
Jonathan Lowry, P.E.
January 2018

Table of Contents
Cover..............................................................................................................................1
Tableof Contents..........................................................................................................2
1 Location and Introduction.........................................................................................3
2 Summary of Raleigh, NC Requirements...................................................................3
3 Proposed Drainage Improvements...........................................................................3
4 Hydrology...................................................................................................................4
5 Water Quality..............................................................................................................4
6 Hydraulics and Pond Sizing......................................................................................4
7 Additional Stormwater Management.........................................................................5
Appendix A
Project Site Information Map
Appendix B
Hydrology Table
Appendix C
Proposed Drainage Areas Map
Appendix D
Time of Concentration Calculations
Appendix E
Water Quality Calculations
Appendix F
Hydraulics
Appendix G
Pipe Map
Appendix H
HydroCAD Report
Appendix I
Hydrologic Soil Group
Appendix J
NOAA Precipitation Data
Appendix K
Stormwater Details
Appendix L
Aerial Sewer Crossing
21Page

Location and Introduction
The Staybridge Suites site is located in Raleigh, North Carolina at 8001 ACC Boulevard.
The project vicinity map can be seen in Appendix A. The lot has a total area of 6.99
acres. Design calculations for water quality and detention will include the right-of-way
area of the adjacent street to the east, ACC Boulevard, and up to the back of the existing
curb on T.W. Alexander to the south which makes the total area analyzed 7.93 acres.
ACC Boulevard is not currently built out however, the design for this site considers the
built -out conditions as ACC Boulevard construction will occur prior to site improvements.
Site improvements will consist of building construction, concrete driveway, asphalt
parking lot, sanitary sewer service connection, domestic, fire, and irrigation water service
connection, storm water quality and detention system, and an outlet control structure.
2 Summary of Raleigh, NC Requirements
North Carolina's Department of Environment and Natural Resources (NCDENR)
Stormwater BMP Manual provides water quality requirements for the City of Raleigh.
The Archived Stormwater Design Manual 2009 — 2016 was used per the direction of
Kevin Kidd from the City of Raleigh. The post -development nitrogen load must be
reduced to 3.6 Ib/ac/yr by installing a nitrogen -reducing BMP and/or through offset
payments to the Ecosystem Enhancement Program (EEP).
Per the City of Raleigh Stormwater Management Design Manual, the site must detain
the difference between the existing and proposed flows after development in the 2 -year
and 10 -year storm events. The Rational method was used to determine the pre- and
post- construction runoff rates for the 2 -year and 10 -year storm events. The Kirpich
Equation was used to calculate the time of concentration.
3 Proposed Drainage Improvements
Stormwater from the developed portion of the site will drain to the storage chambers
beneath the parking lot through a series of inlets and discharge through an orifice into a
level spreader and engineered filter strip. The stormwater from ACC Boulevard will not
be routed through the storage chambers and filter strip however storage chambers and
filter strip on our site are sized to account for and include this area for quality and
quantity. The inlets and storm sewer were designed to the 10 -year storm event using
Manning's Equation and the Continuity Equation. Appendix F includes sizing
calculations for the storm sewer. An orifice structure will be included in ST -5 and will
consist of a metal plate or concrete wall with holes cut in a manner so that peak flow
rates at the 2 -year and 10 -year storm will be controlled. Hydraulics are discussed in
further detail in Section 6 below.
4 Hydrology
Per the City of Raleigh Stormwater Management Design Manual, the time of
concentration was calculated using the Kirpich Equation. Per the Rational Method
calculations that can be found in Appendix B, the 2 -year storm event flow rate under
existing conditions is 11.35 cfs. The 10 -year flow rate for the existing site is 14.36 cfs.
The proposed site was split into two main drainage basins: A and B. Basin A flows into
the storage chambers and filter strip while Basin B flows directly off site. See Appendix
31Page

C. Basin A was split into three sub -basins based on the path the water in these areas
will take to the pond. Basin Al will flow into the roof drain connection ST -9. The water in
Basin A2 will flow into inlet ST -3 where it will combine with the water from Basin Al and
flow to ST -4. Basin A3 will flow into inlet ST -12 and flow to ST -4. In ST -4, all of the water
from Basins Al, A2, and A3 will combine and flow to ST -5 and be directed to the storage
chambers. Basin B was split into two sub -basins: B1 and B2. B1 flows from the site and
into ACC Boulevard. From ACC Boulevard this water will flow back through our site
through a street inlet and into the existing creek. Basin B2 covers the area that flow
directly in the adjacent creek. A large portion of Basin B includes areas where the
existing drainage patterns will not be disturbed.
As stated above, Basin B1 flows directly into ACC Boulevard. As shown in Appendix B,
this area produces a total runoff of 0.78 cfs in the 10 -year event. This will be allowed by
The City because it is less than 3 cfs. A catch basin will not be required to be installed to
capture this flow.
The post developed calculated flow from Basin B1 & B2 for the 2 -year event is 9.42 cfs
and for the 10 -year event is 11.91 cfs. The runoff from this area was subtracted from the
existing 2 -year and 10 -year release rates to calculate the allowable release rate from the
detention pond. Therefore, to not exceed the existing release rate for the entire site, the
pond shall release water at a rate of 1.93 cfs or less in the 2 -year rainfall event (11.35 —
9.42 = 1.93 cfs) and 2.45 cfs or less in the 10 -year rainfall event (14.36 — 11.91 = 2.45
cfs).
5 Water Quality
The site will utilize a level spreader with engineered filter strip to discharge the runoff
through the existing riparian buffer as well as pay an offset fee for the excess nitrogen
load that the filter strip cannot remove. According to the NCDENR Manual, filter strips
provided 30% Total Nitrogen removal. Water from the orifice structure will discharge
through a pipe into the forebay prior to entering the level spreader. The required length
of the level spreader is 24.5' long because the site releases 2.45 cfs from the 10 -year
event. To be conservative, we designed a 30' level spreader for the site. On the
downstream side of the level spreader will be 3' of #57 stone followed by 30' of grass at
an 8% grade or less.
Per the Exhibit 3-2 from the City of Raleigh Stormwater Design Manual, the total TN
export from our site is 7.3 lbs/ac/yr. This includes the future improvements planned for
ACC Boulevard. The installation of the filter strip will reduce the export by 30%. To
remove the remaining TN, an offset payment of $6,202.05 will be provided to the City.
See Appendix E.
6 Hydraulics and Pond Sizinq
The roof leader pipes (ST -1 to ST -2, and ST -8 to ST -11) on this site were sized to
handle 2 cfs. All other pipes on site were sized to the 10 -year storm event using
Manning's Equation. The pipes were sized for only the drainage areas that flow through
them. The SCS TR -20 method with a Type II 24 -hr storm event was used in the
51Page

HydroCAD modeling software to calculate the runoff volume. These calculations may be
found in Appendix H.
The storage chambers were designed so that all stormwater up to and including the 10 -
year event can be properly controlled by the orifice structure located in ST -5. The orifice
structure will include a metal plate or concrete wall with orifice holes cut in a manner so
that peak flow rates at the 2 -year and 10 -year will not exceed existing discharge rates.
Per Section 15A of the North Carolina Administrative Code Subchapter 2B.0233, when a
stormwater management facility is installed to control nitrogen and attenuate flow before
the conveyance discharges through the riparian buffer an exemption of the diffuse flow
requirement may be allowed. The filter strip on our site provides 30% TN removal.
Because there are no practical alternatives we will be discharging through the riparian
buffer. See Appendix K for outlet structure and orifice plate detail. When peak flow rates
are experience above the 10 -year levels, water will flow over the top of the orifice
structure and into the outlet pipe.
In the 2 -year event, the peak runoff release rate from the storage chamber is 1.81 cfs
and the water reaches an elevation of 373.13 feet. In the 10 -year event, the peak runoff
release rate from the storage chamber is 2.45 cfs and the water reaches an elevation of
376.01 feet. The top of the storage chamber is set at an elevation of 376.18' resulting in
0.17' of freeboard. The orifice that controls the 2 -year and 10 -year events is 5.4 inches
wide and 5.3 inches high.
As shown in Table 1 below, under proposed conditions the site generates 18.23 cfs of
runoff in the 2 -year event, and 23.05 cfs of runoff in the 10 -year event. The orifice control
structure holds back water in the storage chambers in order to only release it at or less
than the rate that water flows from the site under existing conditions.
Table 1. Summary of Existing and Proposed Flows leaving the
site. For full calculations see Appendix B and H
Site
Flow
Flow Destination
Event
(cfs)
2 YRT
10
YR
Existing
Generated
Offsite
11.35
14.36
Proposed
Generated
Offsite
9.42
11.91
To Orifice
8.81
11.14
Total
18.23
23.05
Allowed
Offsite
9.42
11.91
Through Orifice
1.81
2.45
Total
11.23
14.36
7 Additional Stormwater Management
All disturbed areas will be seeded. Silt fence will be used along the tree conservation
area to prevent any sediment from getting offsite and to protect the existing vegetation.
Inlet protection devices will be used in all inlets that could receive stormwater discharge
from our construction site.
51Page

OWNER: CREEKWOOD HIGHWAY 70 ALEXANDER LLC
LAND USE: COMMERICAL
DURHAM, NC
PROJECT SITE INFORMATION
\ \ 1
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OWNER: EAGLES ENTERPRISE LLC \
LAND USE: VACANT
4
LO W RY
ENGINEERING
1111 WESTRAC DRIVE -SUITE 108
FARGO, NORTH DAKOTA 58103
A
/
NT \ \
OWNER: WAKEMED PROPERTY SERVICES \
LAND USE: CHARITABLE HOSPITAL \
NOTES:
1. TOTAL AREA OF LOT - 6.99 ACRES
2. TOTAL AREA INCLUDED IN STORMWATER
MANAGEMENT REPORT = 7.93 ACRES
3. ZONING = CX -7 -CU
LOT BOUNDARY
STAYBRIDGE SUITES
107 UNITS/4.5 STORY
8001 ACC BOULEVARD
IGH, NORTH CAROLINA 27617
VICINITY MAP
RALEIGH, NORTH CAROLINA DEL WEBS
ARBORS DR
SITE
ACC
BOULEVARD
T.W. ALEXANDER DR
GLENWOOD AVE
r=i000
PRELIMINARY
NOT FOR
CONSTRUCTION
LE JOB # 16009.4
PROJECT DATE: 06/22/2017
DRAWN BY: DJK
APPROVED BY: JML
SHEET: 1 OF 1
APPENDIX
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OWNER- PULTE
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CORPORATION
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LAND USE: VACANT
OWNER: PULTE HOME CORPORATION
RESIDENTIAL
LANDUSE: RESIDENTIAL
DURHAM, NC
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DURHAM. NC ....:......................................
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1 OWNER: BRIER CREEK ARBORS DRIVE RETAIL LLC
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LAND USE: VACANT
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OWNER: WAKEMED PROPERTY SERVICES \
LAND USE: CHARITABLE HOSPITAL \
NOTES:
1. TOTAL AREA OF LOT - 6.99 ACRES
2. TOTAL AREA INCLUDED IN STORMWATER
MANAGEMENT REPORT = 7.93 ACRES
3. ZONING = CX -7 -CU
LOT BOUNDARY
STAYBRIDGE SUITES
107 UNITS/4.5 STORY
8001 ACC BOULEVARD
IGH, NORTH CAROLINA 27617
VICINITY MAP
RALEIGH, NORTH CAROLINA DEL WEBS
ARBORS DR
SITE
ACC
BOULEVARD
T.W. ALEXANDER DR
GLENWOOD AVE
r=i000
PRELIMINARY
NOT FOR
CONSTRUCTION
LE JOB # 16009.4
PROJECT DATE: 06/22/2017
DRAWN BY: DJK
APPROVED BY: JML
SHEET: 1 OF 1
APPENDIX
A

PROPERTY LEGAL DESCRIPTION:
LOT NO. 121
PLAN NO.T W Alexander PARCEL ID: 0768398793
Place PH 16
STREET ADDRESS: 8001 ACC Boulevard, Raleigh, NC 27617
Please print:
Property Owner:
Property Owner:
Heritage Inn of Raleigh, LLC
The undersigned, registered property owners of the above noted property, do hereby authorize
Jonathan Lowry
(Contractor / Agent)
of Lowry Engineering
(Name of consulting firm)
to act on my behalf and take all actions necessary for the processing, issuance and acceptance of
this permit or certification and any and all standard and special conditions attached.
Property Owner's Address (if different than property above):
1202 Westrac Drive, 3rd Floor, Fargo, ND 58103
Telephone: [phone]
We hereby certify the above information submitted in this application is true and accurate to the
best of our knowledge.
w r
Authorized gnature Authorized Signature
Date:t 'r` %' ?`tf Date:

3 Hydrologic Soil Group—Wake County, North Carolina
(8001 ACC Boulevard)
699890 699910 699930 699950 699970 699990
0
35° 55'14'N
0
c°3+
M
_o
c°3
0
O_
35° 55'7'N
699890 699910 699930 6999550 659970 699990
3
v
v Map Scale: 1:1,020 if printed on A portrait (8.5" x 11") sheet.
rs
N Mete
0 15 30 60 90
Feet
0 45 90 180 270
Map projection: Web Mercator Comer coordinates: WGS84 Edge tics: UTM Zone 17N WGS84
usDA Natural Resources Web Soil Survey
1 Conservation Service National Cooperative Soil Survey
700010
3
700030
35° 5514" N
0
93
0
0p�
M
o_
93
0
M
O
M
O
m
M
35° 557 N
700030
3
700010
6/6/2017
Page 1 of 4

Hydrologic Soil Group—Wake County, North Carolina
(8001 ACC Boulevard)
MAP LEGEND
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Rating Polygons
0 A
0 A/D
0 B
0 B/D
C
0 C/D
0 D
Not rated or not available
Soil Rating Lines
r r A
r r
A/D
r B
B/D
r r C
0 C/D
r r D
r r Not rated or not available
Soil Rating Points
0 A
0 A/D
■ B
■ B/D
MAP INFORMATION
p C
The soil surveys that comprise your AOI were mapped at
1:15,800.
0 C/D
0 D
Warning: Soil Map may not be valid at this scale.
p Not rated or not available
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
Water Features
line placement. The maps do not show the small areas of
Streams and Canals
contrasting soils that could have been shown at a more detailed
scale.
Transportation
§_§_+ Rails
Please rely on the bar scale on each map sheet for map
#%-0 Interstate Highways
measurements.
US Routes
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Major Roads
Coordinate System: Web Mercator (EPSG:3857)
Local Roads
Maps from the Web Soil Survey are based on the Web Mercator
Background
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
® Aerial Photography
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Wake County, North Carolina
Survey Area Data: Version 15, Sep 19, 2016
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Apr 27, 2014—May
6, 2014
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
UUP Natural Resources Web Soil Survey 6/6/2017
� Conservation Service National Cooperative Soil Survey Page 2 of 4

Hydrologic Soil Group—Wake County, North Carolina
Hydrologic Soil Group
8001 ACC Boulevard
Hydrologic Soil Group— Summary by Map Unit — Wake County, North Carolina (NC183)
Map unit symbol
Map unit name
Rating
Acres in AOI
Percent of AOI
CmA
Chewacla sandy loam, 0
B/D
1.1
25.5%
to 2 percent slopes,
frequently flooded
CrB
Creedmoor sandy loam,
D
0.9
19.9%
2 to 6 percent slopes
CrC
Creedmoor sandy loam,
D
1.6
36.6%
6 to 10 percent slopes
CrC2
Creedmoor sandy loam,
D
0.8
18.0%
6 to 10 percent
slopes, moderately
eroded
Totals for Area of Interest
4.4
100.0%
usDA Natural Resources Web Soil Survey 6/6/2017
Conservation Service National Cooperative Soil Survey Page 3 of 4

Hydrologic Soil Group—Wake County, North Carolina
Description
Hydrologic soil groups are based on estimates of runoff potential. Soils are
assigned to one of four groups according to the rate of water infiltration when the
soils are not protected by vegetation, are thoroughly wet, and receive
precipitation from long -duration storms.
The soils in the United States are assigned to four groups (A, B, C, and D) and
three dual classes (A/D, B/D, and C/D). The groups are defined as follows:
Group A. Soils having a high infiltration rate (low runoff potential) when
thoroughly wet. These consist mainly of deep, well drained to excessively
drained sands or gravelly sands. These soils have a high rate of water
transmission.
Group B. Soils having a moderate infiltration rate when thoroughly wet. These
consist chiefly of moderately deep or deep, moderately well drained or well
drained soils that have moderately fine texture to moderately coarse texture.
These soils have a moderate rate of water transmission.
Group C. Soils having a slow infiltration rate when thoroughly wet. These consist
chiefly of soils having a layer that impedes the downward movement of water or
soils of moderately fine texture or fine texture. These soils have a slow rate of
water transmission.
Group D. Soils having a very slow infiltration rate (high runoff potential) when
thoroughly wet. These consist chiefly of clays that have a high shrink -swell
potential, soils that have a high water table, soils that have a claypan or clay
layer at or near the surface, and soils that are shallow over nearly impervious
material. These soils have a very slow rate of water transmission.
If a soil is assigned to a dual hydrologic group (A/D, B/D, or C/D), the first letter is
for drained areas and the second is for undrained areas. Only the soils that in
their natural condition are in group D are assigned to dual classes.
Rating Options
Aggregation Method: Dominant Condition
Component Percent Cutoff. None Specified
Tie-break Rule: Higher
8001 ACC Boulevard
uSDA Natural Resources Web Soil Survey 6/6/2017
Conservation Service National Cooperative Soil Survey Page 4 of 4