20150320 Ver 1_Stormwater Info_20150330

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Robertson's Mill Pond Park
Stormwater Impact Analysis
January 7, 2015
2 0 1 5 0 3 2 0
For:
Wake County Facilities Design & Construction
Wake County Office Building
PO Box 550
Raleigh, North Carolina 27602
Prepared by:
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Ward Consulting Engineers, P.C.
4805 Green Road, Suite 100
Raleigh, North Carolina 27616 -2848
Phone: [phone]
Fax: [phone]
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Robertson's Mill Pond Park
Stormwater Impact Analysis
Table of Contents
10 Background .................... ...................................... ..............................3
2.0 Wake County Hybrid Stormwater Design Tool Analysis ...... ..............................3
2 1 Pre and Post Project Peak Discharge .. ................. .4
2 2 Stormwater Volume Control for Drainage Area DA-2.... . ............. .4
2 3 Water Quality Impact Analysis ............... .................. .................... 5
30
Driveway Culvert Sizing .......................... ...............................
4.0
Buffer Impacts .................................. ...............................
50
Open Water Impacts ..... . ................... .... . ............... .. .......
60
Wetland Impacts .... ............................... ....................... .
70
FEMA Impacts ....................... ............................... ..........
80
Conclusion ..................................... ...............................
Appendices
Appendix A. Project Soils and Location Maps
Appendix B - Construction Plans
Appendix C Wake County Stormwater Design Tool
• Pre- project Drainage Area Map
• Post - project Drainage Area Map
• Wake County Stormwater Design Tool
a. Site Data
b. Drainage Area 1 Stormwater Pre -Post Calculations
c Drainage Area 2 Stormwater Pre -Post Calculations
d Drainage Area 3 Stormwater Pre -post Calculations
e. DA Site Summary Stormwater Pre -Post Calculations
f. Drainage Area 2 BMP Calculations
g. DA Site Summary BMP Calculations
Appendix D• Detention Basin Design
• Dry Detention Pond — Ks & b Relationships
• Dry Detention Pond— Routing Calculations 1 -yr
• Dry Detention Pond —Routing Calculations 10 -yr
• Dry Detention Pond — Routing Calculations 100 -yr
• Infiltration and Dewatering Calculations
Appendix E. Driveway Culvert Calculations
• Weighted Rational Runoff Coefficient
• Time of Concentration — Kirpich Equation
• Storm Drainage Design Discharge
• Pipe System Capacity — Manning's Equation
• Pipe System Entrance Capacity — Orifice Equation
• Hydraulic Grade Line
Appendix F. Soils Report
Ward Consulting Engineers, P C 2
Robertson's Mill Pond Park
Stormeater Impact Analisis
January 7, 2015

Ir
Robertson's Mill Pond Preserve
Stormwater Impact Analysis
1.0 Background
Wake County purchased the Robertson's Mill Pond property located on the north side of
Robertson Pond Road between East Wake High School and Old Mill Farm Drive for use as
future park. The site comprises 8171 acres of open water, farmland, and managed open space
Robertson Pond Park is a nature preserve and will serve as limited access passive recreation for
residents in the area of Kmghtdale, Wendell, and Zebulon. The proposed park improvements will
include minor modifications to an existing picnic shelter, a proposed floating dock, a launch for
small boats and canoes, and a gravel parking lot Entrance to the site will be maintained on
Robertson Pond Road at the existing location and improved Improvements will be located on
2 24 acres of land in the south east comer of the parcel The remaining 79.47 acres of land will
remain undisturbed
Robertson's Mill Pond consists of a portion of Buffalo Creek that has been impounded above an
existing dam just north of Robertson Pond Road A concrete block structure exists on site that
will be used only for unmanned storage. The existing covered picnic area will remain with only
improvements being made to the roof structure and access.
2.0 Wake County Hybrid Stormwater Design Tool Analysis
The Wake County Department of Water Quality Hybrid Stormwater Design Tool was used to
determine the pre- and post - project peak flow and nitrogen loading for the 1 -year 24 -hour storm
event Data entered into the tool was delineated from GIS and survey information for land use,
impervious area, soil types, hydrologic soil group, and the area of open water. A soils map is
included in Appendix C
The 2.24 acre project area delineated for this study receives drainage from onsite areas only.
Offsite drainage from properties to the east of the project site enter into a roadway ditch on
Robertson Pond Road which was excluded from this study. The water in the ditch is carried in
the right -of -way to Buffalo Creek. Offsite drainage conveyed by Buffalo Creek which passes
through Robertson's Mill Pond. The project area and improvements, excluding the boat dock, are
above the normal water pool elevation of Robertson's Mill Pond and the FEMA 100 year
floodplain of Buffalo Creek and are therefore not affected by stormwater flows from this portion
of the watershed.
The onsite stormwater runoff from the project area is directed in two primary directions on site
due to a ridge that runs east to southwest through the project area. The south side of the site, 1.3
acres, discharges south to the roadway ditch on Robertson Pond Road (DA -1) The north side of
the site, 0.93 acres, discharges north as sheet flow into Robertson's Mill Pond (DA -2). The site
is comprised of managed open space, wooded area, and some existing impervious surfaces
(block structure roof, covered picnic area roof, and exposed bedrock). The remainder of the
Ward Consulting Engineers, P C
Robertson's Mill Pond Park
Storm\Valer Impact Analysis
January 7, 2015

project property, 79.48 acres that will not be disturbed with this project, is identified as DA -3 for
this study The pre - project drainage area map is included in Appendix C.
The proposed development of the 2.24 acre project site includes impervious areas for a driveway,
gravel parking area, and walkways. The site was graded for the improvements and the
delineation of the post drainage areas 1 and 2 changed. The post area for DA -1 decreased from
1.3 acres to 0.5 acres and the post area DA -2 increased from 0.93 acres to 1.74 acres. The post -
project drainage area map is included in Appendix C
2.1 Pre and Post Project Peak Discharge
The pre and post discharges were obtained through the Stormwater Design Tool Due to the
change in drainage area configurations and the proposed additional impervious area the pre and
post discharges changed for drainage areas 1 and 2 No changes are proposed for drainage area 3
and therefore no changes occurred for this area. The changes that occurred in DA -1 included an
increase in curve number reflecting higher impervious area and a decrease in drainage area due
to site grading for the improvements Therefore the post project discharge decreased for this area
and no post stormwater volume control is necessary Drainage area DA -2 had an increase in
curve number reflecting a higher impervious area and a significant increase in drainage area,
therefore stormwater volume control is regwred for DA -2 Table 1.0 below summarizes the
changes for drainage areas DA -1 and DA -2. The site data, stormwater pre -post calculations for
drainage areas 1, 2, and 3, and the DA site summary stormwater tool data sheets are included in
Appendix C
Table 10 Drains a Area 1 and 2 Pre and Post Com arisons
2.2 Stormwater Volume Control for Drainage Area DA -2
The increase in discharge from DA -2 proposed to be controlled by a detention pond is 129 cfs,
the difference in the pre - project discharge of 0.22 and post - project discharge of 1 509 cfs
The detention pond is proposed to be located to the north and downstream of the proposed
parking lot. The drainage area to the pond is 1.27 acres that generates a peak discharge of 129
cfs and therefor the pond has been designed to detain the 1 -yr 24 -hr storm discharge for the
entire drainage area. The remaining 0.47 acres of drainage area DA -2 sheet flows into
Robertson's Mill Pond The bottom elevation of the pond was set at 292 and the 1 -yr 24 -hr storm
elevation was set at 294 The water that is detained in the pond will infiltrate into the soil. The
infiltration rate is predicted to be 0 5 -1.0 inches per hour based on the onsite soils obtained in the
soils report included in Appendix F With a 2 -foot water column, the predicted time to fully
infiltrate is 24-48 hours. Larger storm events are designed to discharge as diffuse flow over a 50-
foot long stone protected weir. It is predicted that the detention pond will be capable of handling
Ward Consulting Engmem, P C
Robertson's Miff Pond Park
Storm«ater Impact Analysis
January 7, 2015
Curve Number CN
Drama e Area ac
Peak Dischar a cfs
Drainage
Area
Pre - Project
Post - Project
Pre - Project
Post - Project
Pre- Project
Post - Project
DA -1
61
67
1.30
0.50
0.467
0 465
DA -2
60
70
0.93
1.74
0.220
1509
2.2 Stormwater Volume Control for Drainage Area DA -2
The increase in discharge from DA -2 proposed to be controlled by a detention pond is 129 cfs,
the difference in the pre - project discharge of 0.22 and post - project discharge of 1 509 cfs
The detention pond is proposed to be located to the north and downstream of the proposed
parking lot. The drainage area to the pond is 1.27 acres that generates a peak discharge of 129
cfs and therefor the pond has been designed to detain the 1 -yr 24 -hr storm discharge for the
entire drainage area. The remaining 0.47 acres of drainage area DA -2 sheet flows into
Robertson's Mill Pond The bottom elevation of the pond was set at 292 and the 1 -yr 24 -hr storm
elevation was set at 294 The water that is detained in the pond will infiltrate into the soil. The
infiltration rate is predicted to be 0 5 -1.0 inches per hour based on the onsite soils obtained in the
soils report included in Appendix F With a 2 -foot water column, the predicted time to fully
infiltrate is 24-48 hours. Larger storm events are designed to discharge as diffuse flow over a 50-
foot long stone protected weir. It is predicted that the detention pond will be capable of handling
Ward Consulting Engmem, P C
Robertson's Miff Pond Park
Storm«ater Impact Analysis
January 7, 2015

Ir
the 100 -yr storm without encroaching on the bottom chord of the pedestrian boardwalk with a
maximum surface elevation of 294.06 For maintenance purposes the slopes of the detention
pond embankment are designed at 4:1.
During construction, the detention basin will serve as a sediment basin. The bottom of the
sediment basin is proposed to be 291 in order to allow for sediment collection. A skimmer device
will dewater the sediment basin during construction The spillway for the sediment basin is set at
295 Once construction is complete, the basin will be restored to proposed conditions, the
skimmer will be removed, and the spillway will be set at 294.
The detention basin was routed with Dr Malcom's Chain Saw routing program due to the small
size of the drainage basin and proposed detention pond Based on the proposed contours Ks and
b relationships were established for the proposed detention basin shape and size. This
information was then entered into the chain saw routing spreadsheet and the basin sized through
an iterative analysis Drainage Area DA -2 BMP calculations in the Hybrid Stormwater Tool are
included in Appendix C. The proposed detention pond routing analysis for the 1 year, 10 year,
and 100 year storm events are included in Appendix D. Table 2.0 shows a summary of the
detention pond modeling analysis results
Table 2.0 Detention Ra-in Peal QrauP anA n..rn, . c.....
Storm Return Period
Peak Stage ft
Peak Outflow cfs
1 ye ar
293.82
0.0
10 year
29403
062
100 ye ar
294.06
2.09
2.3 Water Ouality Impact Analysis
Based on the DA site summary stormwater pre -post calculations in the hybrid stormwater tool,
the pre- project total nitrogen loading rate was calculated to be 1.1316 /ac /year and the post -
project (before BMP) total nitrogen loading rate was calculated as 1.55 lb/ac/year These rates
are lower than the allowable 3 61b /ac/year for the Neuse River watershed The Hybrid
Stormwater Design Tool DA Site Summary Stormwater Pre -post Calculations are included in
Appendix C.
3.0 Driveway Culvert Sizing
The existing driveway has a 15 -inch RCP culvert that receives flow from approximately 1.71
acres. The culvert is within the right of way for Robertson Pond Road and lies in the roadside
ditch. The peak discharge that the pipe needs to convey is 3 4 cfs for the 10 -year storm event An
18 -inch RCP has been designed installed with the proposed driveway improvements. The
driveway culvert calculations are included in Appendix E.
Ward Consulting Engineers, P C
Robertson's Mill Pond Park
Stormwater Impact Anelhsis
January 7, 2015

r
4.0 Buffer Impacts
The riparian buffers for Robertson's Pond are located on the west side of the project There are
both permanent and temporary buffer impacts in both Zones 1 and 2. Temporary Impacts involve
grading and re- vegetation Permanent impacts Include the matting for the boat launch and
concrete walkway. The concrete walkway Is minimized to access points for the existing picnic
shelter and the proposed floating dock Table 2 0 quantifies the temporary and permanent
impacts for both buffer zones. A Pre- construction Notification will be sent to the Corps of
Engineers and North Carolina Division of Water Resources for 404 and 401 permits respectively.
The buffer impacts are anticipated to be allowable.
5.0 Open Water Impacts
The impacts to Robertson's Pond will be limited to the proposed floating dock. No fill or loss of
open water will result from the proposed project and therefore the dock is anticipated to be
allowable.
6.0 Wetland Impacts
Wetlands have been delineated on the site along the water's edge. Impacts to the wetlands are
limited to the boat launch area and the floating dock, approximately, 006 acre. It is anticipated
that the wetland Impacts will be allowable.
7.0 FEMA Impacts
The floating dock will be coded into the HEC -RAS model and submitted to Wake County for a
no -rise approval It is anticipated that the dock will not cause a rise in the 100 year floodplam
The proposed dock is located outside of the FEMA floodway for Buffalo Creek.
8.0 Conclusion
Through the Hybrid Stormwater Tool analysis it was determined that detention was required for
the project site and a detention basm was designed to control the 1 year 24 how peak flow for
drainage area DA -2 The nitrogen loading for the project property is below the target rate of 3 6
ib /ac /yr and therefore a water quality BMP Is not required for the site. A PCN will be submitted
for 401 and 404 Permits for the project. A flood study will be submitted to Wake County to
quantify the no-rise impacts of the floating dock for the project.
Ward Consulting Engineers, P C
Robertson's Mill Pond Park
Stormwater Impact Anah sis
Januan 7.2015

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PROJECT LOCATION MAP
WAKE COUNTY, NORTH CAROLINA
DATE JAN 12, 2015
<< WARD CONSULTING ENGINEERS, PC
4805 Green Road, Suite 100 919 870 -0528
Raleigh, NC 27616 FAX 919; 870859

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WAKE
COUNTY
SITE DATA
Project Information
Project Name,
Robertson's Pond Park
Applicant.
Wake County Department of Parks and Recreation
Appllurd Conact Name:
Enc Staehle
Applicant Contact Number-
919-856 -6369
Contact Email
enc staehlenwakedov com
Site Data:
River Basin:
Neuse
Regulatory Watershed:
NIA
PhystagraphkdGeofagle Region:
Piedmont
Type of Development (Select from Dropdown menu):
Non - Residentlal
Zoning:
R40
Total Srte Area (Ac)
81.71
Existing Lake/Pond Area [Ac)
6551
Proposed Disturbed Area (Ac):
159
Proposed Impervlous Surface Area (acre):
053
Percent Built Upon Area (BUAj:
1%
Is the proposed Project a site expansion?
No
Number of Drainage Areas on Sha:
3
Annual Rainfall On)-
4541
One -year, 24-hour rainfall On):
300
Two -year, 24 -hour rainfall (In):
360
Residential Stormwater Details (U applicable).
She Square Footage:
3,559,288
Total Acreage In Lots:
Lot Square Footage:
Number of Lot.:
Average Lot Slze (SFI:
Total Impervious Surface Area Devoted to Lots (SF).
Total Impervious Surface Area Devoted to Roads (SF).
Other Impervious Surface Area (SFj:
SUE DATA Page 1

LStormwater Narrative (limit to 1,200 characters - attach additional pages with submittal if necessary)-
he Robertson Pond Perk m a recreational project to be owned and managed by Wake County Parlor and Recreation The site parcel n 13171 acres The proud area is in
�e eoudroast mirror of the parcel Clime dranage bypasses the project arm and flows through the existing open channel that name alongside Robertson Pond Read
dNag conditions in the project area stckrde managed open space with pass, a small block stnxture, a well house, eM a covered oriels pad The arm is currently used
t e recreational area with fishing, carweing and boating, and as a natural conservatory The proposed improvements would enhance the amenities by providing designated
irking spaces and greater accessibility for people with drsabildies These enhancements Include a gravel driveway and perking lot designed to allow trucks with boats and
rilers to access the site, a concrete sidewalk mathellcaMy designed to conform to the eoshng topography vdxle providing handicapped accessibility, a mulched walking tri 1,
sandy beech arm to launch boats and canoes, and a Mating dock The improvements will Increase the Impetuous arm and change the graded landscape
V emsLtg prgxi arm is in two drainage arms Drainage Arm 1 (DAt) flown in a south esterly dsectlon and discharges into the open channel along Robensen Pond
cad Drainage Arm 2 (DA2) discharges as sheet flow into the pond as shoves by the contours
is proposed pmjed area changes the grading so that DA7 is reduced in sore The portion of the gravel cl v y that is In DA1 Increases the fbwrate more than 10% of the
wpmject conditions To mitigate this addition fkwaate, additional vegetation is proposed to naturally reduce the post - project flowrate to pre- project conditions DA2
creases in sm. but the added Impetuous area creates the need to use additional control measures to reduce the pmt - project flowrate A starmaler BMP is proposed to
San the change In the i-yr 244r storm flomate in DA2 This BMP vall be located north and doansUeam of the parking lot The parking lot sell be graded to sheet Bow into
Is BMP The outlet structure for the BMP me weir that wll diffuse flaws over the 1 -yr 24-hr storm The mmalrang arm m DA2 mM be graded to maintain Wwmt flow
.Mums
SITE DATA
Pape 2

Project Name RObert en's Pond Park
WAKE - DRAINAGE AREA
COUNTY STORMWATER PRE -POST CALCULATIONS
LAND USE &SITE DATA
PRE - DEVELOPMENT
POST- DEVELOPMENT
Drainage Area (Aces).
130
050
Site Acreage vmhln Dralnsge=
130
060
One-year. 24hour nudall On)=
3 00
Land Use (acres)
A
B
C
D
A
B
C
D
Commercial
PerkIng lot
Slle OOsue
site 1 Of
Site Oflss
Site OSalte
Sue ; Of."
-
SBe 011ute
Ste OBalte
Sne OOslte
Roof
I
1
I
I
OpenhanEscapad
1
I
1
1
I
Industrial
Padung lot
fine OSSAe
fills ORSIfe
fine ORada
SOS OlTahe
bile Olfsife
fine IXhue
bile ORaXe
I
fine pllsde
Rod
Open/ anderapW
Transportation
High Dsuty (Iraerstale, mein)
Site 011
Sne I OXsne
Su offs,.
Sao prsrye
She I ptfsue
Sue Offers,
I
She I owe
Sib I Oflule
Hph Donuty, (Grassed Right-of- ys)
I
Lox Danaher (secondary, feeder)
Lax Denady ( Gaswd Rlghtot -ways)
Rural
Rural (Grewed Right- of-xays)
1
S iexelk
I
I
I
I
I
I
Mlsc PeNlow
Managed pervious (Open Space)
Site I OlhXe
9s, ORSite
093
SR. j OBute
Site OBslb
See OnaM
fine 011ade
018
Sib 011ene
6s, 011slte
I
Unmanaged (pasture)
Woods (red on lots)
032
021
Residential
Roedvay
Site 1 011ane
fide off."
I
Ste OXnta
Slte Chun.
1
Sit. OSUIe
fine Clean.
1
Sea ODshe
I
Sale OOabe
I
Grassed Righbfivays
1
I
1
1
Dma any
008
I
I
Porialp M
Rod
S Ievalk
002
003
002 ;
002
Loin
I
I
I
Managed pervious (Open Space)
I
I
I
1
I
Wond4 (an Idle)
I
Land Taken up by BMP
JURISDICTIONAL LANDS
Natural vaalland
Site ; Olhne
_
Site : OXute
She Offal.
Sle OXebe
Sile OSSIIe
Slle ORahe
All
6s, ORslb
Ripeden buffer
1
I
Open va er
I
I
1
I
SITE FLOW
PRE - DEVELOPMENT Ts
POST -0EVELOPMENT TO
Sheet Flaw,
longb (10=
10000
10000
Slope (MO=
0118
0080
Surface Cover
Greek
Grow
n- value=
024
0 240
T�(h.).
014
014
Shallow Flaw
Length (gN
17000
17000
Slope(OA)=
_
003
003
Surface Cover
Unpaved
_
Unpaved
Average Vebclly Mftea).
275
279
T� (h.).
002
002
Channel Flow 1
Length PV'
22000
22000
Slope (NO).
003
—- -
003
C. Sucher.] Fl Ame �°
6 W
800
-
Welled Pedmeler (ft)=
-
- 12 fS_ -
12 86
OAI
Pap

nA,
Poga 2

Project Name
Robertson's POntl Park
WAM DRAINAGE AREA 2
COUNTY STORMWATER PRE -POST CALCULATIONS
LAND USE A, SITE DATA
PRE-DEVELOPMENT
POST- DEVELOPMENT
Dminage Area (Atlas)=
093
1 74
Site Acreage within Dminage+
093
174
One-year, 24hlur annfall (In)-
3 00
Land Un (iclaa)
A
B
C
D
Comrkingt
Parking lot
Site Chat.
Sao CANb
See ; Deane
SNe OIFaNa
A
Sib 011s1te
B
Site OOWIe
C
Site Oflub
p
Site ; 011uls
Root
'
I
I
I
I
I
OPMandarapod
I
Indiumiriall
Perking lot
fide Oflane
fide Clete
I
Sn! D6GIt0
fills Oltede
Sde OINIIe
sne OANO
sne Olhna
silo OSUb
Roof
oPenn onaelapee
Transportation
Ste Onsite
Slte I Came
Site Onaib
SdO Olfslte
site I Chile
I
I
Ibph Dens ity (mlerslato main)
I
Slb O6sne
Site Onub
Site OSUb
High Danury (Glassed Rightofiwys)
I
I
1
I
Lew Denvlly (samndary, leader)
Low Density (Grossed Right- olwap)
Rual
Rural (Glassed Riga as _,ep)
Sltwolk
I
1
I
Masc Iftm .a
AWaped puwoua (Open Specs)
Ste OSUte
Site j Othlle
Site j OIkNe
Slle j Ofltlb
Sit. Olrede
Sde Olfnb
Sne OOSIb
SNu 011alle
Unmanaged (paebrs)
078
106
WOods (net lots)
On
014
Rnldenual
Roadway
sne onane
I
sna , on.ne
She , olfene
sne olr:ne
sna o0ade
024
sna , on.Ne
sne olrade
sna onene
Classed RWhtNwrge
I
Ddaway
I
)
I
I
I
I
Perking M
037
Reef
Sldowvl4
Oat
001
lawn
006.
Managed Pervious (Open Space)
I
wow. (On Iota)
I
Land Taken up by BMP
JURISDICTIONAL LANDS
Sit° Opeite
Site 011alto Site Otfub
Sao ONute
Site Olfshe
Sne OlM1:l1.
Natural wetland
sit. Ciliate
Sne : Olfane
Rlpenon huller
I
OPea water
SITE FLOW
PRE - DEVELOPMENT T.
I I
POST - DEVELOPMENT Te
Meet Flay
Length (ft)-
230 W
200 00
si.pe (Sm)=
005
00
05
Surl or<COpr
Gran
Gan
n -value
0 24
0 240
T. (hn)-
0 30
SNllaw FIaW
027
Length g0=
30D 00
Slope (Mg•
0
132
Sudece Cover
Average Voloca, (NSec)•
Pored
T. (h.)-
0 00
000
287
Clean N Flay 1
0 03
Length (the
Slope mqw
Grua Seclwnal Flaw Are. (f1�•
Waned Pervasion (0)°
DA2
Page 1

Channel Uning
n- r+lue=
Hydraulic Radius (10•
000
000
Averegs Velocity Mkw)=
000
0 0)
Ti (li
000
000
Tc Ihnp
030
030
RESULTS
PRE - DEVELOPMENT
POST- DEVELOPMENT
1 -year, 24hour storm (Peak Flow)
Volumed runoff (tl) •
1.223
5,979
Volume (ej •
cherpe
1.756
Runoff (inches) • p+
0 392
0917
Peek Decherge (ds)• 0•
0 220
15M
Compomle Curve Number (DA)-
W
ID
Composite Cu" Number (Site only),
60
]0
DISCONNECTED IMPERVIOUS - Credit given only to residential development whin drainage area with less than 30% Impervious
Percent Drcconowani Impamous Credit (Residential Only) •
Disconnected impervious erne (AC)
000
Dionne Arse CN - e
70
She Only CN.
70
Post-devalOOmwne was nOW e d
xcee c pre-develop mem peak flow for this DAI
DA2
Page 2

Proles[ Hams• Robertson's Pon Part
��
WAKE DRAINAGE AREA J
COUNTY STORMWATER PRE -PORT CALCULATIONS
AM
Pape 7

Channal Lining
yyeoft
Weeds
n- luw
0 W
oow
kydmulm Rvdlua mY
589
589
Average Velocity Dlraae)'
768
7 Sa
T, (h.).
013
013
Tc (hrap
013
027
RESULTS
PRE -DEVELOPMENT
POST- DEVELOPMENT
t -year, 24-hour storm (Peak Flow)
Volume of mnoll(M),
1,042,614
1,043,560
Volume cherpe m9 -
765
Runod (Inches) a 01
3611
3 616
Peek Discharge (ufi)- 0•
172 061
CunlMite Curve Number MA)w
S
6
Comgoene Curve Number (Sde c iih.
g
6
DISCONNECTED IMPERVIOUS - CyeAN given only to residential development whin drainage leu
area with 11un 30% Impewlous
Percent Dlscormwed ImPervlous Cmdn (ReaMenbal Only) a
Dutconnscted Imperious erne (Ac) a
coo
Drainage Aree CN;�
SNe Onty CHq�
DA3
Pop 2

WAKE
COUNTY
NI)P111 l 111111X/.
DA SITE SUMMARY
STORMWATER PRE -POST CALCULATIONS
Project Name:1 Robertson's Pond Park
SITE SUMMARY
DRAINAGE AREA SUMMARIES
DRAINAGE AREA
DAt
DA2
DA3
DA4
DA5
DAB
Pre-Development (1 -year, 24-hour storm)
Runoff (in) =0'=
0411
0362
3614
Peak Flow (cfs)=Q.=l
0 467
1 0 220
11720611
Post -Development (1 -year, 24 -hour storm)
Proposed Impervious Surface (acre) =
011
044
Runoff (in) =0• =
0 837
0 947
3 818
Peak Flow (cfs) =0.=
0 465
1 509
TARGET CURVE NUMBER (TCN) - Residential Only
SITE \SOIL COMPOSITION
HYDROLOGIC SOIL GROUP
Site Area
%
Target CN
A
7108
87%
N/A
B
573
7%
NIA
C
190
2%
WA
D
300
4%
WA
Total Site Area (acres) =
8171
Zoning =
R -40
Target Curve Number (TCN) =
N/A
%Impervious =
1%
Past Development CNbI„. =
2
Required Volume to be Managed (TCN) = fts =
N/A
SITE NITROGEN AND PHOSPHORUS LOADING
Nitrogen and Phosphorus Targets (Based on Regulatory Watershed)
Target Nitrogen Load (Ib/ac/yr)=
3,6
Target Phosphorus Load (Falls and Jordan Lakes Only) (Iblaclyr)=
N/A
% N Loading Reduction Option for Expansions (Falls and Jordan Lakes Only) =
NIA
% Loading Reduction Nitrogen Target (Falls and Jordan Lakes Only) (Ib/ac/yr)=
N/A
% P Loading Reduction Option for Expansions (Falls and Jordan Lakes Only) =
NIA
% Loading Reduction Phosphorus Target (Falls and Jordan Lakes Onlv) (Ib /sctyr)=
N/A
Pre Development Nitrogen and Phosphorus Load
Total Nitrogen (lb /aWyr)=
1,13
Total Phosphorus (Ib /aclyr)=
NIA
Post Development Nitrogen and Phosphorus Load
Total Nitrogen (Iblactyr)=
1.55
Total Phosphorus (lb/ac/yr)=l
NIA
SITE SUMMARY Page 1

Project Name Robertson's Pond Par
-� DRAINAGE ARC
WAKE BMP CALCULATIONS
COUNTY
lll.I "
DA2 BMPs
Pape 1

DA2_BMPs
Page 2
1,753
Outflow Total Nitrogen (Ib/anlyr)=
481
Outflow Total Phosphorus (Ib/ac/yr)=
105
Sub- DA2(b) BMP(s)
If Sub-0A2(b) re connected m upstream a1 :1 012 n(a), select all contributing sub- basm(e
from dro "menus)
Device Name (As Show on Plan)
Device Type
Water
Quality
Inflow N
Total
Inflow P
Total
Outflow
Total
Outflow
Oul
Total
Provided
yP
Volume
EMC
Inflow N
EMC
Inflow P
N EMC
P EMC
Outflow
Volume
(c f)
(mi
ObMcfYO
(mg/L)
Ob/al
(ma)
(mg /L)
(IhleUYr)
(Ibrarlyr)
of (c f)
Outflow Total Nitrogen Ob/acryr)=
Outflow Total Ph osphorus (Ib /aUYr)=
Sub -DA2 (c) BMP(a)
If Sub- DA2(c) is connected to upstream su4basn(s), select all contributing sub-basn(s)
Watt r InflowN
Device Name (As Shown on Plan) Devlce Typo y
Total InnowP
Total Outflow Total Outflow Total
OOw
Provided
Volume EMC
Inflow N EMC
Inflow P N EMC P EMC Outflow
Volume
(c I) (m VL)
(Ibh r m
UY) ( l
Ob/al (mg/L) N P
(mg/L)
ONaUyr) (Ibfadyr)
d (c f je
Outflow Total Nitrogen (Iblac/yr)=
Outflow Total Phosphorus (INaUyr)=
Bub -pq2 (tl) BMP(a)
1 Sub- DA2(d) is connected to upstream subbesn(s), select all coranbubng sub -basm(s)
Water InflowN
Device Name (Ae Shown on Plan) Device Type h•
Total IrtflewP
Total Outflow Total Outlow Total Provided
Volume EMC Inflow N EMC Inflow P N EMC OutfIovv Outflow Volume
P EMC
(ml�) (Wit r N P
(c f) Y) (mgrL) OWacM) (mil-) (ni Manage
Oblao/yr (INadyr)
d (c f )
Outflow Total Nitrogen (Ilvac/yr)=
Orrtflow Topl Ptros Wrorus Obraci
ub-DA2 (e) BMP(a)
Sub- DA2(e) is connected to upstream subbasul select all cordnbuting sub- basln(s)
Water Inflow N Total Inflow P Total Outflow Total Total Provided
Device Nama (As Shown co plan Quaht Outflow
Device Type Y
Volume EMC InflowN
Oumow
EMC InflowP NEMC PEMC Oumaw Voume
(c Y) (mWL) (Ih4Ur'r) (me/U (Ib/aUYr) (mw
d rrnage
(b1(mgli
a (blacly
Outflow Total Nitrogen (INadyr)=
OuMow Total Phosphorus (Ib/ec/yr)=
DA2 BMP SUMMARY
Total Volume Treated (c 1)=
15 572
DA2 Outflow Total Nltrogen (Iblac/yr)=
481
DA2_BMPs
Page 2

DA2 Outflow Total Phosphorus phlaciyr) =I
24-hour storm
Pre Development Peak Discharge (cfs)=
022
Post BMP Peak Discharge (cfs)= Ord
019
DA2_BMPs
Page 3

IWWW Project Name: Robertson's Pond Park
WAKE DA SITE SUMMARY
COUNTY BMP CALCULATIONS
NORTIICA RD[INA
BMP SUMMARY
LINKS /COMMENTS
DRAINAGE AREA SUMMARIES
BMPs are required in each DA where post - development
peak flow is higher than pre- development peak Flow
Only under special circumstances will a BMP not be
required In these cases, the engineer must show the
" DRAINAGE AREA
DA1
DA2
DA3
DA4
DA5
OAS
Post - Development (1 -year, 24 -hour storm)
following
1. Total runoff volume for the DA must be less than 10%
of the entire site runoff for the 10-yr, 24-hr storm event.
2 TN and TP must be handled for the site elsewhere.
3. Runoff must not leave the DA at an erosive velocity.
Otherwise. BMPs must be utilized to mimic pre -
Peak Flow (cfs)= O,y,a,=
0 47
1.51
Post-0evelopment wan BMPs (1 -year, 24 -hour storm)
% Impervious=
1 %
Post BMP Peak Discharge (cfs)= O,.,.= 0 19
Have Target Curve Number Requirements been met?
development peak flow in each drainage area
WA
• Post -BMP Nitrogen Loading
Outflow Total Nitrogen (lb /ac/yr)=
0.10
" Outflow Total Phosphorus (lb /ac"=
002
-
Has site met requirements for offsetting?
YES
-
BMP SUMMARY
Paae 1

Appendix D - Detention Basin Design

KS&B 11- 7- 2014.xis
Pond Analysis Ks & B relationshi s
Project:
ROBERTSON POND
By:
CDR
Date
11/1412014
Scale 1" ___> 10
Diagram "A" - BMP 11 -14 -2014
ft.
S
Z
Zest
Contour
Contour
Incremental
Accumulated
Estimated
Contour
Area
Isginl
L641808
Area
IsQftI
1643
3033
4457
6758
Volume
[tuft]
0
2338
3745
-56075
Volume
[cuftl
0
2338
6083
11690.5
Stage
Ift
0
1
2
3
Stage Based on Z= 2 & 3
Ift l
0 Calculated Ks =>
1.00 2338
2 00
3 21 Calculated b =>
1 38
Page 1

MSTRRES 11- 7- 2014>d5
PROJECT: ROBERTSOMS POND
Resemolr Routlng - Microsott Excel
By. CDR Date: 711142oi4
Steen Data lected Retiim Periods Raleigh/Durham
Description Item ID This-Run 1 10 100
Return Period R 20 356 555
6 hr PreG P 108 194 302
Notes 8 Refercnxa:
Reference Elements of Urban Sturm
by H Rooney Malcom, P E
Water Design
Ste function h d re method eabom, to rate
the inflow h d h
Stage -S e
9
h
18 25
e- Diachar a Item ID
er /Barrel
mber N
er Demeter Dr
er weir cueff CM
er orfioa waft Cdr
er crest Zcr
rel Diameter Db
rel onfice co I Cdb
VElamel invert elev Bsw
vert No. t _ Inlet control
mhei N
iCuNen Demeter I D
Darnargo coeR_ Cd
iPipe Inv Elev Iriv
Culvert No. 2 Inlet control
35
Units
-
d ORct 25Tp than 0= 0P2(1- cos(Pi�TP))
dt125 TIP than O= 434Ope^(- 13dTp)
S star ICs
In ster ft b
Initial stage, R I Zo
Initial water level, ft I_Zn
Na
E uatios used for Met control culvert discha
miles
-
e
Ei c =Zc= D/12 + Ei than 0 - 0 372 Cd• D' Z- Ei ^32
Ne
Z D112 + Ei than D = 00437 Cd • D ^2 • Z -D124 - E M2
_
Na
R
Equations used for chamsaw routing through the reservoir
H re Date
Time Inc mm
I dT
inches
Stege Z=(S / Ks )M/ b
Peak Discha , ds
0
Na
S
ft
Time te Peak, mm
T
Nit
E ueeons for dwhar a over shit
crested weirs
rested d bread
Waessted Data
Item ID
Unite
inches
O =Cw L H "32
Sharp crested weir Cw
3 33
_
Na
Broad crested weir Cw=3 0
Area
A
H
IAc
127
Basin Elev
Ft
6
R
Weir with a free overfall Cw=3 0
Hyd Length
I L d
Cc l Na
CN Na
250
Number N rVe
lCutvert Diameter 1 D inches
IDischarge coeR I Cd Na
Pipe Im Elev Inv R
Weir No. 1 broad crested
(Length L R
Crag elevator • Zcr R
(Weir Coeff Cw Ne
Wetr No 2 broad crested
Length �! L ft
,Crest elevation Zcr R
Mew Coen Cw Na
ROUTING TABLE
R ac. fL
293 82 H tl h Val 121 1
000
Outflav Riser eu Raer Banal
cis cfs (Orfice ),ch cfs
Riser actin as a war Riser rim acts as a war with length
Rational comp'
0 223
SCS Curve No
80
ual to its circumference and a dwng head equal b the
water surface elevabon- the elevation of the nser
1000/CN -10
P-0 2S ^21 P+0 8S
(031H)^ 3851128
S
Ro, 0•
Na
in
250
1 15
50
crest
Riser acting as an orfice Orfice s fumed tj the top enoe ce
of the riser, the area bete me crosssectional area of the riser
Te
min
2 3
h +Tc
0 -Cc°b -
T =Ro•A/1 39 O
I
0
T
Mhr
M I
min
47
133
479
294
The drmn head measured from the water surface to the
3
horizontal lame d the riser crest
0= Cd
=eccelerahon duo b 32 2 Nsec2
Volume
ARo
a R
53171
Computed Results: Gil a ac.
Normal surface area Cl 00 0 W
Max aurlace area 4049401 009
Tune t Inflow Storage
Units Min c!s d
1
Peak
Peak outliow i
Ste
FL
Wau no 1
cfs
War no 2
cis
Culvert M1
cfs
Bartel behaves
Culvert n12
cfs
as a mlvert
under inlet
control arnd'itions
0
1
2
0
0
0
0
0
0
0
0OD
000
009
043
120
258
488
773
292°0
29200
29200
28200
29200
29201
29201
29202
000
000
000
-000
000
000
ODD
0m
000
000
000
- -- 000
000
D00
000
000
00D
O00
000
000
000
000
000
0W
000
000
D00
000
000
000
000
000
000
O00
000
0°0
000
000
000
000
000
000
000
000
0001
000 1
0001
oat
000
°W
0001
000
0001
0 001
000
000
0W
000
OOD
000
000
oat
_
3
4
5
B
. 7
0
6
9
10
0
°
0
11 es
nz1
2395
z9zoz
2szo3
29204
DDD
Doo
.1
oaD
000
0W
DDO
0°0
u uuI
o0o
000
0001
Dao
- o00
0001
o.00
000
000j
aoo
000
000
000
ooD
000
Pape 1

MSTRRES 11 -7 -2014 AS
11
12
13
14
15
16
17
0 3221
0 4214
0 53.85
0 67.47
0 8311
0 100.88
0 12088
0 14318
0 167 B6
0 194.99
22462
256.80
291 56
29204
29205
29207
29208
29209
29210
29212
29213
29215
29217
29218
29220
292 22
000
000
0 00
000
000
000
0 00
0 OD
0 W
non
0 DO
000
O oO
000
000
0 00
000
000
000
000
000
000
000
0 DO
000
000
000
000
0 00
OOD
000
0 00
0 DO
000
O DO
000
0 00
0 o0
000
000
000
000
0 D
000
000
000
000
000
000
000
000
0 00
000
OOD
000
0 D
000
000
0 00
000
000
000
000
000
0 00
000
000
000
000
000
000
0 o0
-ODD
000
-coo
000
000
000
000
00o
0 00
000
000
000
000
000
000
000
000
000
000
OOD
000
0 co
- 000
000
0 00
000
000
000
000
0 Op
000
0 00
18
19
' 20
21 1
23 1
23 1
24 1
25 1
328.92
368.89
411 -47
458.68
2922
292 28
29228
292 31
000
000
0 00
0 OD
000
0001
0 DOI
000
000
0001
000
000
0 00
Iml
000
000
000
000
000
000
000
000
000
000
000
000
0 00
000
000
000
000
000
26 1
27 i
26 1
504.42
554 73
29233
292 35
292 3B
292 40
29243
29245
29248
29250
27253
29256
292 58
29261
29264
000
0 00
000
000
000
000
000
000
000
000
000
O DO
000
000
0 00
000
0 00
0 00
000
0 DO
000
000
000
000
O DO
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
0 00
000
000
000
000
0 00
000
000
000
000
000
000
000
000
00o
000
000
000
000
000
000
000
000
0 00
000
0 00
000
000
000
000
000
000
000
000
000
000
000
000
000
0 DO
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
29 1
30 1
607 54
31 1
32 1
33 1
34 1
35 1
68278
720 42
780.35
84250
9os.n
97306
1041 25
1111-21
118284
125597
36 1
37 1
38 1
39 1
40 1
41 1
1330.48
292 66
000
000
000
coo
O DO
000
000
000
42 1
1406.22
292
000
0 DO
000
000
000
000
000
000
000
43 1
1483 02
292 72
282 75
292 n
29280
29283
29285
29288
29290
28293
29296
29298
29300
29303
293051
3971
29310
29312
O OD
000
000
000
000
000
0 00
0 DO
0 00
000
000
000
000
000
0 00
0 00
0 W
O DO
000
000
000
000
0 DO
0 00
0 DO
000
000
000
000
000
000
000
000
000
000
000
coo
000
000
000
000
000
000
000
000
000
000
ODD
000
000
000
0 DO
000
000
000
000
000
000
000
000
0 00
000
0 00
000
000
0 W
000
000
O,Op
000
0 00
000
000
0 00
000
000
000
000
0 OO
000
000
000
000
0 OD
000
000
000
000
000
000
000
000
000
000
000
0 00
000
000
000
0 OD
000
000
000
000
000
000
000
000
000
000
0 00
000
000
000
000
0 OD
000
000
0,00
000
000
000
000
0 DO
O DO
000
0 00
0 OO
0 W
Goo
000
000
000
0 00
0 OD
000
000
000
000
44 1
45 1
46 1
-47 1
48 1
49 1
50 1
51 1
52 1
53 1
54 1
55 1
5B 1
-57 1
58 1
1560 74
1639 21
171826
1797.73
187746
195724
2036.93
2116.36
219536
2273.74
2351 36
242805
25U&551
2578 01
265097
272240
s9 1
- 61 1
279217
29314
29318
29318
29320
000
000
000
0 00
000
0 o0
0 00
000
000
0 DO
0001
000
0001
0 DOI
0 DDI
000
000
W1
0001
000
000
uW1
000
000
0 00
0 00
0 W1
000
000
000
0 00
0 a0
0 Oo
0 00
61 1
62 1
63 1
286022
2928.48
2990.92
Pape 2

MSTRRES 11 -7 -2014 )ds
64 1
3053.65
293 21
000
000
0001
0001
0001
000
000
000
65 1
311471
29323
000
000
0001
0001
0001
coo
000
000
66 1
317414
29325
000
000
000
000
000
000
0 OD
000
67 1
3231.97
293 26
000
D W
0 DO
000
0 00
0 00
000
000
68 1
328fl28
29326
000
000
000
000
000
000
000
000
69 1
3343 04
293 30
000
000
000
0 QD
0 oo
000
000
20 DD
70 1
3398.38
293 31
000
0 DD
000
0 W
000
000
000
00
71 1
3448.25
293 33
000
000
cool
0001
0 o0
0 DO
000
000
72 1
3490.75
29334
000
000
000
000
000
000
000
000
73 1
354790
29335
0 00
000
0001
000
000
0 00
000
0 OD
74 1
359573
293 37
000
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Page 3

MSTRRES 11- 7- 20141de
117
118
119
120
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293 69
293 69
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293 70
293 70
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293 71
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293 72
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293 73
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283 74
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293 75
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293 75
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Page 4

MSTRRES 11 -7 -2014 ds
170
171
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Page 5

MSTRRES 11-7-2014 )ft
223
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Pepe 6

MSTRRES 11- 7- 20141ds
PROJECT: ROBERTSON'S POND
Reservoir Routing - Microw" Excel
CDR Date:
Storm Date
Dears n hem ID TMs Run
11/142014
Selected Realm Periods Ralai h/Durham
1 10 100
Notes 8 Rehrenees.
Reference Elements of Urban Stenm
by H Rooney Malcom, P E
Water Design
Return Period
8 hr Prey
R
P
h125
10
356
267 356 555
106 194 302
18 25 35
St Daich a Item ID Unite
RIW /Barrel
;Number N Na
IRlsar Diameter Or inches
Riser weir coeR Cwr Na
(Riser orifice coati Cdr Na
,Riser crest Zcr R
Banal Diameter I Ob inches
IBerrel onfice co Cdb Na
Barrel invert elev_7 BM R
Culvert No 11_ Inlet control
Number N rife
;Culvert Diameter I D inches
iDiwherpe ccaR Cd Na
Pipe Im Elev _' Im ft
Culvert N0 2 Inlet control
(Number J—i N Na
!Culvert Diameter D inches
(Discharge cuaR ; Cd Na
Pipe Irn• Elev_i Im ft
Welr No 1 bicatl created
!Langer L fL
(Cant elevmai Zcr fL
(Wee Coen _ _ I Cw Ne
Welr No. 2 broad created
Gngrh i L fL
(Crest alevabon i Za fL
LWes Coen_ , Cw Na
ROUTING TABLE
In I ac. R.
294 031 Hydmgmph Vol 018
062
Outflow Riser War Riser Barrel
cfa c1s Ortce ,ds ct
000 000 000 L-0-00T-0-051
000 000 000 0,00
000 000 000 000
000 - 000 000 000
000 000 000 000
000 000 000 000
000 000 000 000
000 000 000 000
000 000 000 000
000 000 000 000
0001 0001 0001 UO0j
Ste functon d re metlrotl ratraiste
the lnfiow h dr re h
d0<t<125Tpthan 0= Op2(lcos(pi'trrp))
d L 725 Tp than O=4 39Ope"f•1 3tfip)
E uatons used for inlet control culvert discha a
erax -ass
-
Ste - Storage
$ 56N re1M0ar Ks
S etor remoter ! b 213,98
Instal st e, ft ' Zo 282
Instal water lewl,R Zn 282
Ei < =Z<= D/17 + Ei then O = 0 372
Z > D/12 +
Ei than 0 = 0 0437 Ctl' D"2 • Z -D24 - E "12
Equations used for chamsew routng through the reserrou
Stage = S/ ^
( �) 1/ b
H dm reph Data
Time Inc mm 1 dT 1
Peek Di a cis O 183
Time t Peak, mm T 51
S =SI+ 1! -Oi dTi
E uatorrs for discha a over c
crested wars
8 broad
Watershed Data Item ID I Units
- -
O =Cw L H ^32
Bread created weir Cw=30
Sharp nested vvw L\v� 33
Am A Ac
Basin Elev I H !Ft
H d Length L Ft
Rational ral cote 'C' i Ce ' Na
SCS Curve No CN i Na
1 27
War with a flee overfall Cw=3 0
6
Riser echo as a war Riser nm act war with length
ea a w
250
0 223
50
- 284
3
Ue to it argrmfarerice and a dim head equal to the
water surface alaraton- the elevabon of ere near crest.
Riser actn as en orfce Orfce is loaned b the m entrance
d the tear, the arm ban the cross- secyrorW ales of the rear
The tlrmn head maeaunad from ea voter svface te ea
horizontal lane of the nser crest
O = Cd A 2 h "0 5
= acmkrabon due to 32 2 Neec2
80
1000/CN -10
P-0 2S 38 112 BS
L ^3M " 3&5/126
S
Ro, O'
Tic
Na
m
250
168
min
2 3
h Ccl
=CcIA
I
0
irvhr
6 5
1 83
T
T fume, 139 0
Vdume
T
ARo
min
min
cu R
50 8
7763 9
Computed Result: $ ft ac. I
Normal surface arm 0 Do 0 00
.Mm surface arm 1 4219 27 I 0 10
Time t Inflow S e
Urine Mm cfa d
0 0 000
1 0 000
2 0 010
- - -- 3 0 052
4 0 147
I
Peak staine 1
Pmk cutilow I
St a
Ft
292 DO
29200
292 00
29200
29200
292.01
29201
28202
29203
29203
292041
War no 1
cis
000
000
000
000
000
000
000
000
000
0001
War rro 2
cfs
000
ODD
000
OOD
000
000
000
000
000
000
0001
-
Culvert N7
rtt
0W
000
000
000
000
000
'000
000
0(p
000
00011
Barrel behaves
Culvert
Culvert N2
ppp
000
- 000
p00
000
OOD
000
000
ppp
000
000
as a culvert
under inlet
control condniam
5
0
314
6
0
0
574
947
7
S
0
1454
9 01 2112
10 ul 29 4Uj
Page 1

MSTRRES 11 -7 -2014 )ds
11 0
38.56
292 D5
0.00
000
0 DO
0 DO
000
000
000
000
72 0
5178
29206
000
000
000
000
000
000
000
000
13 0
6621
29208
000
000
000
000
000
000
000
000
14 0
8301
29209
000
0 D
000
000
000
0 D
000
000
15 0
10233
29210
000
000
000
000
000
000
000
000
16 0
12429
29212
000
000
000
000
000
000
000
0 00
17 0
149 04
29214
000
000
000
000
000
000
000
000
18 1
17668
29215
0 DO
coo
0 DO
000
0 DO
000
000
000
19 1
207 31
29217
000
000
000
000
000
000
0 OD
0 DO
20 1
241 04
29219
000
000
000
0 00
000
000
000
000
21 1
277 93
292 21
0 Ool
000
000
000
o0ol
000
000
000
-
22 1
318 07
29224
000
000
000
000
000
000
000
000
23 1
361501
29228
000
000
000
0 DO
000
000
000
000
24 1
40827
29228
000
000
000
coo
000
000
000
000
25 1
458 411
29231
000
000
000
000
0.00
000
000
000
26 1
511951
29233
000
0 00
000
000
O 00
0 OO
0 DO
000
27 1
568 88
282 36
000
000
000
000
000
000
000
0 o0
2B 1
62919
29239
000
000
000
000
000
000
000
0 DO
29 1
89287
29241
O DO
000
000
000
0 00
0.o0
000
000
30 1
75989
29244
000
000
000
000
000
000
0 00
000
31 1
83019
292.47
000
000
000
000
000
000
000
000
32 1
90373
29250
000
000
000
000
000
0001
000
000
33 1
98042
29253
000
000
000
000
0 00
000
000
000
34 1
106018
29256
0 OD
000
000
000
000
000
000
000
35 1
114293
29260
0 DO
0 00
0 00
000
0 DO
0.00
0 DO
000
36 1
122855
29263
0001
000
000
0 00
0 00
0 00
000
000
37 2
131693
29266
000
000
000
000
000
000
000
000
38 2
140793
29269
000
000
000
000
000
000
000
000
39 2
150143
29273
0 DO
000
000
000
000
000
000
0 00
40 2
159727
29276
000
000
OD
000
000
000
000
000
41 2
189530
29279
000
000
—0
OWL_
000
000
0 00
O DO
000
42 21
179535
29283
0 o0
000
0 00
0 00
0 00
000
000
000
43 21
189726
29286
000
000
000
000
coo
000
000
000
44 2
2000 83
29289
000
000
0 OO
000
0 00
0 00
0 Do
000
45 2
z105 90
29293
000
000
000
000
000
000
000
0 00
46 21
2212-251
292 96
000
coo
o 00
0 00
0 00
000
000
o DO
47 21
2319711
29299
000
000
000
000
000
000
000
000
48 21
2428061
29303
ODD
000
000
000
000
000
000
0001
49 ?
263711
293 06
000
o ao
000
o a0
—ODD
000
000
000
50 2
2646 64
29309
000
000
000
000
000
000
000
000
51 2
2758 46
29313
000
0 DO
000
000
000
0 DO
000
000
52 2
2868 341
29318
000
000
000
0 OO
000
000
000
coo
53 2
2976 08
29319
0 00
000
0001
000
000
000
000
000
54 2
308547 1
293221
000
000
0001
000
000
000
000
0 DO
55 21
3194311
293251
000
000
0001
000
000
0 DO
000
0.00
56 2
3302381
293281
000
000
0001
000
000
000
000
000
57 2
340948
29331
000
000
—000-000
0001
0 DO
000
000
000
000
5B 2
3515 421
29334
000
000
000
000
000
000
'
59 2
3820 001
29337
000
000
000
000
000
000
000
000
60 2
3723031
29340
000
000
000
0 DO
000
000
000
0.00
61 2
3824 33
29343
000
0 00
000
000
000
000
000
000
62 2
3923 71
293 46
000
ODD
000
000
000
000
000
000
63 2
4021 02
293 48
000
0001
000
0 DO
000
0001
000
000
Page 2

MSTRRES 11 -7 -2014 #a
64
2 4116081
29351
0 00
000
000
000
000
000
0001
000
65 2
4206 88
29363
000
o o0
000
0 00
000
000
0 ODI
000
66 1
429934
29355
000
000
000
000
000
000
000
, 000
67 1
4367.52
29358
000
000
000
000
000
coo
000
000
68 1
— 447347
29360
000
O DO
000
000
000
000
000
000
69 1
456725
29362
0 00
000
000
000
000
000
000
0 DO
70 1
4638 92
29364
000
000
000
000
000
000
000
000
71 1
471852
29366
000
000
D00
000
000
000
0 D
000
'
72 1
479611
29368
000
000
000
000
0 DO
000
000
000
73 1
487174
29370
000
0 00
coo
000
000
000
000
000
74 1
4945 47
293 72
0001
0001
000
coo
000
000
0 DO
000
75 1
501733
000
000
000
000
000
O DO
000
000
78 1
5087 38
000
000
000
000
000
000
000
000
77 1
515566
000
00 0
000
000
000
000
000
000
78 1
522221
0 00
000
000
000
000
000
000
000
79 1
5287 OB
000
CSSO
000
000
000
000
000
000
000
BO 1
535032
000
000
000
000
000
000
000
000
81 1
541196
000
000
000
000
000
000
000
000
B2 1
547204
000
000
000
000
000
000
000
0 DO
63 1
5530 61
0 00
000
000
000
000
000
000
000
84 1
5587 69
0 00
000
000
000
000
000
000
000
-
85 1
564334
293 89
000
000
000
000
000
000
000
000
86 1
589758
3 91
000
000
000
000
000
0 00
000
0 DO
87 - 1
5750 45
3 92
000
000
—000-00o
000
000
000
000
000
000
"
88 1
5801 98
3 93
000
000
000
000
000
000
89 1
585222
394
129
000
000
000
000
000
000
OOD
000
90 1
5901 18
3 98
000
000
0 DO
0 DO
000
000
000
000
91 1
594891
3 97
000
0 DO
000
000
000
000
000
0 00
92 1
5995 43
3 9B
000
0,00
000
000
000
000
000
000
83
293 99
000
000
000
000
000
000
000
000
94
29400
000
000
0 DO
000
000
000
000
000
95
29401
016
000
0DO
000
016
000
000
000
96
P16:112008
294 02
036
0 DO
0 00
000
038
000
000
000
97
29402
0 51
000
000
000
0 51
000
000
000
98
299 02
0 59
000
000
000
059
000
000
000
89
29403
062
000
000
000
062
000
0 DO
000
100 1
819404
29403
062
000
000
000
062
0 00
0 00
0 00
101 1
8193 51
294 0q
062
coo-0001
000
062
000
000
000
102 - 1
619232
29403
061
000
0001
000
061
000
000
000
103 1
819083
29403
060
000
000
0o0
060
000
000
000
104 1
618921
29402
058
000
000
0 00
058
000
000
000
105 1
618754
29402
057
000
000
000
057
000
000
0 ao
106 1
618587
29402
058
000
000
000
058
000
000
6o0
107 1
618421
29402
0 54
000
0001
0001
054
0001
0 DO
000
108 1
618257
29902
053
000
0 o0
000
0 53
000
000
000
109 0
618095
29402
0 52
000
0 o0
000
0 52
000
000
000
-" -- - -'110 - - - -0
617935
29402
050
000
000
000
050
000
ODO
000
111 0
8177 78
294 02
0 48
000
000
000
049
000
000
000
112 0
617624
29402
048
000
000
000
048
000
000
0 00
-
113 0
617473
29902
047
000
000
000
047
000
Ooo
000
114 0
617323
29402
046
OODI
0001
0001
0461
000
115 0
6171 77
29402
044
OOOL
0001
0001
0441
0 00
000
000
118 0
617033
29402
043
000
o 00
O DO
0 43
000
0001
000
Page 3

MSTRRES 11- 7- 2D14,)do
Page 4
117
118
0 816891
0 616752
29402
29402
042
041
000
OOD
000
042
000
000
000
119 0
120 0
121 0
1
123 23 0
0
616815
616480
616347
616217
6160,A9
6159 83
615839
6157 18
6155 98
6154 80
615365
2940?
284 02
29402
294 02
29402
294 02
28902
294 0z
294 02
289 02
29402
294 02
294 02
29402
29402
040
0 39
038
0 37
036
0 35
035
034
033
032
031
030
0 30
029
028
028
027
028
028
025
0 24
000
000
000
000
000
000
0 o0
OoD
000
000
000
000
0 DD
000
000
000
0 00
0—
000
0 oo
000
0 00
000
000
000
000
0 O
000
000
000
000
0 W
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
0 D
000
000
0 OD
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
041
040
0 39
038
0 37
038
035
035
034
0 33
032
031
ui0
030
028
028
028
027
028
028
025
0 24
0 21
023
023
000
000
0 00
000
000
0 00
000
000
000
0 00
000
000
j 0001
000
000
000
000
000
000
000
OOD
000
0 0
000
000
000
000
000
000
000
000
000
000
000
000
'000
000
000
000
000
000
O OD
000
000
000
000
000
000
000
000
0DD
000
000
000
000
000
000
.000
000
000
O p0
000
0
000
OOD
000
000
000
000
0
000
000
p
000
000
124 0
125 0
126 0
127 0
128 0
129 0
130 0
8152 51
131 0
132 0
6151 39
15028
133 0
6
614821
134 0
14615
294 02
135 0
6
614710
29101
138 0
if 0
138 0
6146 (008
614507
614407
294 01
294 01
284 01
139 0
614310
284 01
140 0
614214
294 01
0 24
141 p
142 0
6141 +B
814026
294 01
2&101
023
023
022
143 0
613935
29401
144 0
613845
79101
021
000
000
000
000
000
000
022
021
000
000
OOD
000
000
D QD
145 0
8137 57
28/ 01
0 21
146 0
8136 70
794 01
020
000
000
000
uwl
000
000
00011
000
000
000
000
021
020
020
018
019
OOD
000
000
000
000
000
000
000
000
000
000
O a0
147 0
148 0
813585
813501
294 01
29901
037
019
000
O00
149 0
613418
794 01
019
000
150 0
151 0
152 0
153 0
154 0
155 0
+58
133 37
6132 58
6131 79
6131 02
613028
812952
294 01
29401
299 01
294 01
79901
289 01
018
018
018
017
017
0 18
000
000
000
0 OD
000
000
000
000
000
016 000
000
000
000
000
000
000
078 000
000
000
000
000
000
000
000
000
000
000
0 18 0 OD
017 000
017 000
016 000
000
000
000
000
000
000
000
0 00
-- -
0
157
6128 76
294 01
018
000
000
000
016 000
000
0 01)
0
158
8126 O6
294 01
0 18
000
000
000
000
000
000
000
000
000
000
000
000
000
000
000
016 000
000
000
0
169 0
180 0
161 0
+82 0
-- - -1� --
- - - -- — 0
164 0
6127 36
6128 fib
612597
612530
612464
612399
612335
612272
612210
612149
612089
612030
294 01
294 01
2&101
29401
28101
2910+
29401
79401
29401
29401
29401
29401
015
015
0 14
01'
014
- ^ 013
013
013
012
012
012
012
000
000
000
000
000
— " - - OOD
- 000
000
Op0
000
000
000
000
015 000
000
000
000
000
000
000
000
000
000
000
000
000
000
015
014
014
014
013
013
013
012
012
012
012
0 W
000
000
000
000
000
000
000
000
000
000
0 �
000
000
- 00D_
000
000
000
000
OOD
000
000
000
Op0
D 00
_ 000
000
000
000
000
000
000
000
-- - --
- - -
- - --
--- -- - -
+� 0
+� 0
167 0
188 0
189 0
Page 4

MSTRRES 1;-7-2014 ,ft
Pape 5

MSTRRES 11 -7 -2014 ffi
Pepe 6
mommommm
Pepe 6

MSTRRES 11-7-2014)k
276- - -
277
- 276
279 _
260 -
261
262
0 6091 25
0 8097 15
0 6091 OB
o I 6090-86
0 6090 67'
0 609076
O _6090 89
0'' 6090 60
0 6090 511
0 _ 6090 -43
01 609034
0 6080-26
0 6090.16
0 6090.10
_ 284 00
25400
294 00
_ 29900
_299 00
_ 29900
284 00
294 00
29q pp
_ 299 00
29400
_ 294 DO
294 a0
_ 294 00
294 00
_ zsC 00
29400
284 00
29400
294W
001
001
001
0 p1
0 01
0 01
0 01
0 01
001
001
001
0 01
0 01
0 01
0 01
001
001
0 01
0 01
001
o O1
001
000
000
0 00
o ao
000
000
0 00
000
000
0 00
0 DO
000
000
000
000
000
000
000
0 OD
000
000
000
O o0
000
0 00
_ o ao
-0 00
000'
000
000
_ 000
000
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Appendix E — Driveway Culvert Calculations,

WEIGHTED RATIONAL RUNOFF COEFFICIENT CALCULATIONS
Project ROBERTSON POND
LocationWAKE COUNTY, NC
Existing or Proposed PROPOSED
Date 10/23/2014
Prepared C Y C DR
Storm Event Return Period (Year) 10 -YEAR
— Llunai Loerriaents Elements of Urban Stormwater Design, H. Rooney Malcom, P E
Data changed specific to protect
Ward Consulting Engineers, P C
1of1

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STORM DRAINAGE DESIGN DISCHARGE CALCULATIONS
Protect
Ward Consulting Engineers, P C
1 of 1
Rational Equation
Q= CIA
A= Drainage Area (Acres)
C= Composite Rational Runoff Coefficient
Tc= Time of Concentration (Min)

PIPE SYSTEM CAPACITY - MANNING'S EQUATION
Project
ROBERTSON POND
Location
WAKE COUNTY NC
Erishng or Proposed
DRIVEWAY CULVERT
Date
10232014
Prepared by
CDR
Ward Consulting Engineers, P C
1 of 1

PIPE SYSTEM ENTRANCE CAPACITY - ORIFICE EQUATION
Project ROBERTSON POND
Location WAKE COUNTY, NC
Ebsting or Proposed DRIVEWAY CULVERT
Date. 10232014
By. CDR
Onfice Equation h
Q= Cd'A'(2gh) "(12)
Cd= Discharge Coefficient
A =Area of Opening
h= Center of Pipe to Point of Interest Invert
g =32 2 ft/s"2
Pipe segment I I Area of
Opening
Interest Pipe Elevation
evallon !ar Invert Out (ft)
i Consutting Engineers, P.C. 1 of 1
Entrance Flow
k)I
Point of Interest Elevation
Center of Outlet Pipe
esign
Deslgn Flow
fs)
Velocity (fps)
j
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May 30, 2014
Wake County Facilities Design and Construction
P.O. Box 550
Raleigh, North Carolina 27602
Attn• Mr. Eric 0. Staehle, RLA
Email: eric [e-mail]
Re: Report of Geotechnical Services
New Parking Lot and Access Drives
Robertson's Mill Pond Park
Robertson Pond Road
Wendell, Wake County, North Carolina
Terracon Project No. 70145073
Dear Mr. Staehle:
Irerracan
Terracon Consultants, Inc. ( Terracon) has completed the report of geotechnical services for the
above referenced project. The purpose of this study was to evaluate the existing subgrade
conditions and provide geotechnical engineering recommendations for earthwork and thickness
design of the gravel surfaced parking lot and access drives. Additionally, a Seasonal Hlgh Water
Table (SHWT) determination was performed by a licensed soil scientist to assist with
stormwater design. These services were performed in accordance with our Proposal ith
P70130547 -R dated May 14, 2014.
1.0 PROJECT INFORMATION
Our understanding of the project is based on correspondence with you and the provided site
plan
ITEM
Project Components
Grading
DESCRIPTION
The planned Improvements Include constructing stone base course
drive lanes and 21 associated parking spaces, a stormwater
management feature, and additional landscaping
Up to four feet of cut are planned for the northeast portion of the
Proposed parking area We expect balanced earthwork quantittes
for the protect.
F-11a y consist of passenger vehicles Some
Traffic loading maintenance vehicles and grading equipment will use the new
road.
Terracon Consultants, Inc 2401 Brentwood Road, Ste 107 Relelnh Nnrrn r,...i.__ --

Report of Geotechnical Services
Proposed Robertson's , 2014 ■ Terracon Project No. P7014507
Mill Pond North Carolina lrerraeon
May 14
Should any of the above information or assumptions be inconsistent with the planned
construction, we request the opportunity to revise our report. The following table outlines the
existing conditions and is based on our site visit and our discussions with project designers.
11 EM
Location
Existing improvements
Current groundcover
Existing topography.
DESCRIPTION
The new park is planned for an existing open area located near the
intersection of Robertson Pond Road and Old Mill Farm Drive near
Wendell, North Carolina For further details regarding project
location, refer to the attached Site Location Plan
The site is adjacent to the Robertson's pond dam and the
remaining portion of the historic former mill The site is gated and
contains an existing shelter and an overhead light. There is also a
single -story residence and a water supply well
The majority of groundcover within construction areas is grassed
Two rock outcrops exist at the surface near the entrance
The site slopes down gently to the south and west towards the
Robertson Pond Road and the existing pond.
2.0 FIELD EXPLORATION
Soil samples were obtained through depths of up to 10 feet below the existing surface at the six
requested locations. The exploration locations were established in the field by measuring from
existing site features and estimating right angles. Hand -held GPS technology was used record
geographic coordinates of the boring locations. Ground surface elevations were estimated using
the obtained geographic coordinates, mapping software, and topographic contours from available
Wake County GIS data.
A Geoprobe Model 6620DT was used to obtain sod samples from the subsurface profile. Soil
samples were obtained by alternating between advancing a split- barrel sampler and a direct push
sampler.
In the split - barrel sampling procedure, the number of blows required to advance a standard 2 -inch
O D. split- barrel sampler the last 12 inches of the typical total 18 -inch penetration by means of a
140 -pound safety hammer with a free fall of 30 inches, is the standard penetration resistance
value (SPT -N). This value is used to estimate the in -situ relative density of cohesionless soils and
consistency of cohesive soils. Soil samples were taken at approximately 2.5 -foot intervals.
An automatic SPT hammer was used to advance the split - barrel sampler in the borings
Performed on this site. A greater efficiency is typically achieved with the automatic hammer
compared to the conventional safety hammer operated with a cathead and rope. Published
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2

Report of Geotechnical Services
Proposed Robertson's Mill Pond Park ■ Wake County, North Carolina 11'erracon
May 14, 2014 ■ Terracon Project No. P70145073
correlations between the SPT values and soil properties are based on the lower efficiency
cathead and rope method. This higher efficiency affects the standard penetration resistance
blow count (N) value by increasing the penetration per hammer blow over what would be
obtained using the cathead and rope method. The effect of the automatic hammer's efficiency
has been considered in the interpretation and analysis of the subsurface information within this
report.
The samples collected in the field were tagged for identification, sealed to reduce moisture loss,
and taken to our laboratory for further examination, testing, and classification. A field log of each
boring was prepared by the drill crew. These logs included visual classifications of the materials
encountered during drilling as well as the driller's interpretation of the subsurface conditions
between samples. Final boring logs included with this report represent the enginee
of the field logs and include modifications based on laboratory observation of the r s interpretation
samples.
Information provided on the final boring logs attached to this report Includes soil descriptions,
consistency evaluations, boring depths, sampling intervals, and groundwater conditions in
accordance with the enclosed General Notes. Also shown are estimated Unified Soil
Classification System (USCS) symbols. A brief description of the USCS is attached to this
report. All classification was performed using visual manual procedures.
Additionally, we retained licensed soil scientist Fred Smith to perform a seasonal high water
table (SMNT) evaluation for the purpose of assisting with design of the stormwater BMP tl a ger is
t the
site Mr. Smith performed two hand auger borings at the requested locations The han au
an open cylinder with curved cutting blades. As the auger Is twisted, soil cuttings from the
blades are collected within the cylinder where they can be retrieved for visual examination when
the auger is pulled from the ground. The cuttings from the hand auger borings were observed
for characteristics including soil type, texture, structure and color to determine the presence and
depth to a seasonal high water table. Soil descriptions in Mr Smith's report are in accordance
with the United States Department of Agriculture (USDA) classification system.
3.0 RESULTS
Geologically, the project site is located In the Piedmont Physiographic Province, an area underlain
by ancient igneous and metamorphic rocks. The residual soils in this area are the product of In
place chemical weathering of rock. The typical residual soil profile consists of clayey sods near the
surface where soil weathering is more advanced, underlain by sandy silts / silty sands that
generally become harder / denser with depth to the top of parent bedrock. In residual materials the
transition from soil to rock occurs gradually over a vertical distance ranging from a few feet to
tens of feet, This transitional zone is tgrmed "partially weathered rock" which is defined for
engineering purposes as residual material that can be drilled with sod dulling methods and
exhibits standard penetration test values in excess of 100 blows per foot Standard penetration
test N- values of 50 or more blows with no penetration are indicative of crystalline bedrock.
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3

Report of Geotechnical Services
May 14. Mill County, North Carolina 1r
2014 ■ Terrac n Project No P70145073Lrr7con
According to the 1985 Geologic Map of North Carolina, the bedrock under the site is foliated to
massive granitic rock of the Permian period. The bedrock outcrop observed near the site entrance
consisted of light red and gray granitic rock.
At the subsurface sampling locations, two to five inches of grass and topsoil were encountered.
The subsurface materials generally consisted of slightly clayey, low to moderately plastic, residual
silty sand. These materials were generally loose to medium dense. Partially weathered rock and
apparent bedrock were encountered at depths of approximately 3 feet below the surface in Boring
Nos. B -1 and B-4, respectively. These locations are on the west and southwest portion of the site
near the pond and the depth to the top of rock corresponds to an approximate elevation of 289
feet. As previously noted, rock outcrops were also encountered at the surface in the vicinity of
Boring No. B-4.
The open boreholes were observed for the presence and level of groundwater following the
completion of sampling. Groundwater was encountered at a depth of 4 feet below the surface in
Boring No. B -1 which was performed near to the existing pond. The water encountered at this
location is likely perched or trapped over the underlying rock. Groundwater was not encountered
in the other borings performed at the site. Licensed soil scientist Fred Smith did not find evidence
of a seasonal high water table (SHWT) through maximum exploration hand auger explorat
attached report. ion
depths of 72 inches in the proposed BMP area. Mr. Smith's complete findings are detailed in the
4.0 GEOTECHNICAL RECOMMENDATIONS
The near surface soils are moisture sensitive and subject to degradation when exposed to
moisture. To the extent practical, construction should be performed during periods of dry weather
to avoid degrading and otherwise acceptable subgrade. Some remedial
subgrade may become necessary if earthwork is performed during periods of we measures for the
t weather.
4.1 Earthwork
Earthwork should begin by stripping the existing topsoil and rootmat. We expect stripping depths
of 2 to 5 inches, however, actual stripping depth may vary and should be evaluated at the time of
construction.
Prior to placing fill or upon reaching the subgrade elevation in cut areas, a representative of the
geotechnical engineer should evaluate the subgrade and observe proofrolling operations.
Proofrolling should be performed with a moderately loaded, tandem -axle dump truck or similar
rubber -tired construction equipment. The proofrolling operations should be performed after a
suitable period of dry weather to avoid degrading an otherwise acceptable subgrade. Areas
exhibiting excessive deflection or rutting, or areas where otherwise unsuitable material is
encountered should be remediated as directed by the geotechnical engineer. We do not expect
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4

Report of Geotechnical Services !�
Proposed Robertson's Mill Pond Park ■ Wake County, North Carolina lrerracon
May 14, 2014 ■ Terracon Project No P70145073
significant remediation for unsuitable areas if earthwork Is performed during periods of favorable
weather.
Engineered fill should meet the following material property requirements:
Fill Type'
Imported Low- to
Moderate - Plasticity
Soil with at least 20%
fines
Sand / Gravel with
less than 20% fines 2
(silt and clay)
On -site Sod
USCS Classification I Acceptable Location for Placement
CL, ML, SC 2 or SM 2 I All locations and elevations
GW /GP, SW /SP 2 I NCDOT CABC within gravel - surfaced drive lanes
and parking sections
SM I All locations and elevations
1 Controlled, compacted fill should consist of approved materials that are free of organic matter and
debris A sample of each material type should be submitted to the geotechmcal engineer for
evaluation.
2 Soil with less than 20% fines (silt and clay) should not be used as general fill to raise site grades to
Prevent perched water conditions where water infiltrating the surface zone becomes trapped over
the underlying less - permeable soil zone
compaction Requirements
hem
Fill Lift Thickness
Compaction Requirements'
Moisture Content
9 -inches or less in loose thickness (4" to 6" lifts when hand -
operated equipment is used)
Minimum of 95% of the materials standard Proctor maximum
Within the range of -3% to +3% of optimum moisture content
as determined by the standard Proctor test at the time of
Placement and compaction
1. Engineered fill should be tested for moisture content and compaction during placement If in -place
density tests indicate the specified moisture or compaction limits have not been met, the area
represented by the tests should be reworked and retested as required until the specified moisture
and compaction requirements are achieved
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5

Report of Geotechnical Services
Proposed Robertson's Mill Pond Park ■ Wake County, North Carolina 1 rerracon
May 14, 2014 ■ Terracon Project No P70145073
Excavations
Near surface partially weathered rock (PWR) and rock outcrops were encountered near the
western and southwestern portions of the site We understand that the grading plan will be
developed to avoid cuts in these areas. Therefore, we do not expect difficult excavation
conditions to be encountered. If requiring removal, rock or PWR will likely require the use of
pneumatic hammering or other means to excavate.
Vehicle Surfaces
An approved subgrade is expected to be suitable for support of the proposed crushed stone base
surfacing. Stone base course thickness design for vehicle traffic is dependent upon:
■ the anticipated traffic conditions;
■ subgrade and material characteristics;
■ climatic conditions of the region.
We anticipate relatively light traffic loading (less than 30,000 18 -kip ESALs) for the new drive
lanes and parking spaces. We recommend that the surface consist of layer of compacted crushed
aggregate base course (NCDOT CABC) at least 5 inches thick. Base course materials should
conform to the North Carolina Department of Transportation (NCDOT) "Standard Specifications for
Roads and Structures."
The performance of all pavements and unpaved roads can be enhanced by minimizing excess
moisture which can reach the subgrade soils. We recommend constructing the base course
surface with a minimum 1/4 inch per foot (2 %) slope to promote proper surface drainage and
site grading at a minimum 2 percent grade away from the pavements. Maintaining the proper
slope over the life of the drive lanes with motor grades or by other means will ensure the best
long term performance,
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6

Report of Geotechnical Services !�
Proposed Robertson's Mill Pond Park ■ Wake County, North Carolina 1�Arracon
May 14, 2014 ■ Terracon Project No. P70145073
CLOSURE
We trust that the information in this letter and attachments is sufficient for your present
Purposes. We appreciate the opportunity to be of service to you on this project. If you have any
questions concerning this report, or if we may be of further service, please feel freatole littaat iia
Sincerely,
Terracon Consultants In
Thomas R. Bartlett, El
Staff Geotechnical Engineer
R. L. "Levi "Denton,
Principal / Geotechnical
Registered, NC 034749
Attachments:
Site Location Plan
Bonng Location Plan
Boring Logs (B -1 through 13-6)
General Notes
Unified Soil Classification System (USCS)
Report of a Soil Evaluation for Stormwater Treatment (Fred D Smith Soil Consulting)
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Consulting Engineers & scientists
84—m Rmq a� 107 U-0 Nr Crorn�
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NG LOCATION
GEOTECHNICAL ENGINEERING REPORT
PROPOSED NEW PARKING LOT & ACCESS DRIVES
ROBERTSON'S MILL POND PARK
WENDELL, NORTH CAROLINA
EXHIBIT
A -2

2 -2 -2
N =4
3-4-6
d I I I 1 1 5-�
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'•I�III I 1A I N=6
dn n 4-3-6
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N
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BORING LOG NO. B-3
Nodes
a
Promdures
PROJECT: Robertson's Mill Park
Sea gppendu S Icr desarptlan of laboratory
Pa el of 1
Pr°cadures end additional data (f any)
CLIENT: Wake County Facilities Design & Construction
SITE: Robertson's Pond Road
Raleigh, North Carolina
O
abhrgo bana
Wendell, North Carolina
0
WATER LEVEL OBSERVATIONS
Elevallon esbmaled from Wake Ca GIS
z No free wafer obsert,9d
rc
Oo LOCATION
0
°
m
m
6rracon
Bodng Stanad 5/Z7 /207d Bonn C
i
2401 Brentwood Road, Sidle 107
w
a
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APPmtdmate Surface Elev leg (FL) +/_ wo
a>
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aJ
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EL nON t
30
W
w
Q
SILTY cusp fcaa
micaceous fine to medium grained, brown to tan, loose to medium dense,
2 -2 -2
N =4
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dn n 4-3-6
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See Ednbd A3 for desuiption of field
Nodes
a
Promdures
Sea gppendu S Icr desarptlan of laboratory
i Abandonment Method
Pr°cadures end additional data (f any)
L SadMiled upon comple0on
Sae Appandlx C for explanation of symbols and
O
abhrgo bana
0
WATER LEVEL OBSERVATIONS
Elevallon esbmaled from Wake Ca GIS
z No free wafer obsert,9d
rc
°
m
m
6rracon
Bodng Stanad 5/Z7 /207d Bonn C
2401 Brentwood Road, Sidle 107
Drill Rig GEOPROBE 6620DT Dnller WrD
Raleigh, Nod4 Carolina
Pmlect No.� MlAgma

GENERAL NOTES
DESCRIPTION OF SYMBOLS AND ABBREVIATIONS
DESCRI SOIL CLASSIFICATION
Soil classification is based on the Unified Soil Classification System Coarse Grained Soils have more than 50% of their dry
weight retained on a 4200 sieve, their principal descriptors are. boulders, cobbles, gravel or sand. Fine Grained Soils have
less than 50% of their dry weight retained on a #200 sieve; they are principally described as clays If they are plastic, and
slits if they are slightly plastic or non - plastic. Major constituents may be added as modifiers and minor constituents may be
added according to the relative proportions based on grain size. In addition to gradation, coarse - grained soils are defined
on the basis of their in -glace relative density and fine-grained sods on the basis of their consistency.
LOCATION AND ELEVATION NOTES
Unless otherwise noted, Latitude and Longitude are approximately determined using a hand -held GPS device. The accuracy
of such devices is variable. Surface elevation data annotated With +/_ Indicates that no actual topographical survey was
conducted to confirm the surface elevation. Instead, the surface elevation was approximately determined from topographic
maps of the area.
RELATIVE PROPORTIONS OF ce�D AND eV i GRAIN sLZE TERMINOLOGY
Deauiotiva Termlel
9-wher esnsti uema � Major of C_ . ole Particle Six
Trace Boulders With ; 51528 Over 12 in. (300 mm)
Modifier > 30 Cobbles 12 in. to 3 in. (300mm to 75mm)
Gravel 3 in. to #4 sieve (75mm to 4.75 mm)
Sand #4 to #200 sieve (4.75mm to 0.075mm
Silt or Clay Passing #200 sieve (0.075mm)
RE ATl PROPORTIONS OF FIh c
PLASTICITY D R1P'IION
Dosed wa T rmisl
W other constituents Drv� kIgbt �� Plasticity Index
Trays < 5 Nonelastic 0
WIth Modlfler > 122 M Low edium 111 - 30
High > 30
Irer�ac® Exhibit B-1
® � Water initially (HP) Hand Penetrometer
Encountered
Auger Split Spoon � Water Level After a
1
Specified Period of Time (11 Torvans
m J � Water Level After y
(= W a Specified Period of Tlrre � (�) Standard Penetration
Z
Shelby' Macro Coro N Test (blows per foot)
d J Water levels Indicated on the Boll boring � (PID) Photo- lonlratlon Detector
g � a � logs are the levels measured In the O
� F borehole at the limes indicated. W
Ring Sampler Rork core Q Groundwater level variations will occur LL (tea Organic vapor Analyzer
3 over time. In low permeability soils,
accurate determination of groundwater
levels is not possible with short term
water level ohserv
RELATIVE DENSITY OF IbARSE- GRAINED SOILS
CONSISTENCY OF FINE-GRAINED SOILS
(More than 50% retained on No. 200 sieve.)
Density determined 6y Standard Penetration Resistance
(50% or more passing the No 200 slave.)
Includes gravels, sands and silts
Consistency tletennined by laboratory shear strength tasting, field
casual- manual procedures or standard penetration resistance
�
Descriptive Term
Standard Penetration a
�
(Density)
N•Value
Ping
9 Sampler
Descriptive Tenn
Unconfined Compressive
Penetration or
�����
BlowalFt
WON'B�
(Consistency)
Strength, Oup�shre
N -Value
W
Blows/FL
H
Very Loose
0-3
0 - 6
Very Soft
less than 600
1
F
0
<g
2
Loose
4-9
7 - 18
Soft
500101.000
2 -4
3_q
FW
ahons.
10 -29
19 -56
Medium-Stiff
Grab Sample No Recovery
4
RELATIVE DENSITY OF IbARSE- GRAINED SOILS
CONSISTENCY OF FINE-GRAINED SOILS
(More than 50% retained on No. 200 sieve.)
Density determined 6y Standard Penetration Resistance
(50% or more passing the No 200 slave.)
Includes gravels, sands and silts
Consistency tletennined by laboratory shear strength tasting, field
casual- manual procedures or standard penetration resistance
�
Descriptive Term
Standard Penetration a
�
(Density)
N•Value
Ping
9 Sampler
Descriptive Tenn
Unconfined Compressive
Penetration or
�����
BlowalFt
WON'B�
(Consistency)
Strength, Oup�shre
N -Value
W
Blows/FL
H
Very Loose
0-3
0 - 6
Very Soft
less than 600
1
F
0
<g
2
Loose
4-9
7 - 18
Soft
500101.000
2 -4
3_q
FW
Medium Dense
10 -29
19 -56
Medium-Stiff
1,000[02,000
4
-B
5-9
h
Dense
30 -50
59 -98
SUIT
2,OOD to 4,000
9 -15
10 -fe
Very Dense
>50
>99
Very Stiff
4,000 to a,000
15 -30
19 -42
Hard
> 5,000
> gp
> 42

UNIFIED SOIL CLASSIFICATION SYSTEM
Criteria for Assigning Group Symbols and Group Names Using Laboratory Tests A
Group
Symbol
Group Name
Coarse Grained Soils
More than 50% retained
Gravels:
More than 50% of
coarse fraction retained
on No 4 sieve
Clean Gravels:
Less than 5% fines c
Cu 2:4 and 1!; Cc!; 3
GW
Well -graded gravel
Cu < 4 and /or 1 > Cc> 3
GP
Poorly graded gravel
Gravels with Fines,
More than 12% tines °
Fines classify as ML or MH
GM
Silty gravel
Fines classify as CL or CH
GC
Clayey gravel
on No 200 sieve
Sands:
50% or more of coarse
fraction passes No 4
sieve
Clean Sands:
Less than 5% fines °
Cu 2:6 and 1 5 Cc:; 3 a
SW
Well- graded sand
Cu < 6 and/or T> > Co> 3
SP
Poorly graded sand
Sands with Fines:
More than 12% fines °
Fines classify as ML or MH
SM
Silty sand
Fines classify as CL or CH
SC
Clayey sand
Fine-Grained Soils:
50% or more passes the
Silts and Clays:
Liquid limit less than 50
Inorganic:
PI > 7 and plots on or above 'K line'
CL
Lean clay
PI < 4 or plots below'A' line
ML
Sift
Organic:
Liquid limit - oven dried
<0 75
OIL
Organic clay
Liquid limit - not dried
Organic sift
No 200 sieve
Slits and Clays:
Liquid limit 50 or more
inorganic.
PI Blots on or above 'A' line
CH
Fat clay
PI plots below'A' line
MH
Elastic SjftKLM
Organic:
Liquid limit - oven dried
I <075
OH
Organic clay
Liquid limit -not dried
Organic sift
Highly organic soils.
Primarily organic matter, dark in color, and organic odor
PT
Peat
" Based on the material passing the 3 -mch (75 -mm) sieve
B If field sample contained cobbles or boulders, or both, add'wnh cobbles
or boulders, or bolh'to group name.
c Gravels with 5 to 12% fines require dual symbols GW -GM well -graded
gravel with sill, GW -GC well- graded gravel with clay, GP -GM poorly
graded gravel with sift, GP -GC poody graded gravel with clay
° Sands with 5 to 12% fines require dual symbols SW -SM well -graded
sand ewth silt, SW-SC well -graded sand with clay, SPSM poorly graded
sand veth silt, SP-SC poorly graded sand with clay
(D
Dio x DW
F If soil contains z 15% sand, add'wdh sand' to group name
° If fines classify as CL -ML, use dual symbol GC-GM. or SCSM
60
W,
4.
W
G
Z_
30
U
F
20
g
a
" If fines are organic, add'vnth organic fines" to group name
i If soil contains 215% gravel, add'vAth gravel' to group name
If Atterberg limits plot in shaded area, soil is a CL -ML, silty clay
If soil contains 15 to 29% plus No 200, add'vnth sand' or'wrth gravel,'
whichever is predominant
L If soil contains k 30% plus No 200 predominantly sand, add'sandy' to
group name
1° If soil contains 2 30% plus No 200, predominantly gravel, add
'gravelly to group name
" PI 2 4 and plots on or above'A' line
° PI < 4 or plots below'A' line
° PI plots on or above 'A' line
° PI plots below'A' line.
10 r
71
4�
0 I,
0
10 16 20 30 40 50 60 70 6o 90 100 110
LIQUID LIMIT (LL)
lrerracon
Exhibit B -2

r FRED D.
May 28, 2014
Mr. Thomas Bartlett
Terracon Engineering
2401 Brentwood Rd Suite 107
Raleigh, NC 27604
Subject: Report of a Soil Evaluation for Stormwater Treatment
Robertson's Mill Perk
Wendell, NC
Dear Mr. Bartlett,
This letter concerns the soil evaluation I performed at the above mentioned proposed sites chosen for
stormwater BMP's. You authorized me to perform a soil evaluation to determine the depth to the
'seasonal high water table' (SHWT) at two locations. You provided me with site drawings that show the
location of the two hand auger locations and other deep borings. The soils were classified into the USDA
Classification system and are presented in Table 1. I also reviewed the deep boring logs that correspond
to my stormwater evaluation.
Seasonal High Water Table (SHWT)
The SHWT has became more frequently used as an indicator of the highest level of water table
fluctuations due to agricultural considerations, regulations for septic system designs and, mole recently,
stormwater design. The SHWT is routinely estimated by Soil Scientists from soil morphology (soil
forming factors) and landscape position. Soil colors are evaluated because gray colors are associated with
saturated and chemically reducing soil environments - the presence or absence of iron. Red, reddish
yellow, brown, and brownish yellow colors are associated with aerobic and chemically oxidizing
conditions.
During weathering of soil minerals, over a period of time, soluble constituents are removed from the soil
profile and more stable compounds will precipitate. Iron is released from minerals and coats 'soli particles
with thin oxide coatings that give soils their red to yellow colors. The natural color of soil particles is
gray until they are coated with iron.
Soils also contain microorganisms that generate energy from the oxidatton of soil organic matter. When
the soil becomes saturated from flooding or slowly percolating water, oxygen is removed from the soil
layer and anaerobic conditions prevail. Under anaerobic conditions, other types of soil microbes can
derive energy the chemical reduction of oxidized iron and change its state from ferric to ferrous iron (loss
of an electron). The requirements for this chemical- micmbiological process are the absence of oxygen
for several weeks, a temperature of at least 41 degrees (I), and the presence of organic matter (roots, etc).
During periods of alternative wetting and drying cycles, or SHWT cycles, ferrous iron may move short
distances and precipitate during the drying (reoxidetion) process. These mottling patterns are'cailed
redoximorphic colors.
Soil Scientists use the Mousell Color System to evaluate the degree of color changes visible in the soil.
Low chroma colors are considered to be gray or black in the Muasell System (chroma less than 2). We
normally consider that once a soil layer has about 5% gray colors and redoximorphic patterns (red -
yellow colored mottles), then that soil is saturated at least 21 days and qualifies as a SHWT. :
OAVCa✓MObila (M) 90&42ee
Peat ON7ce Box 1575— Nashville, North Camilaa =58

Some SHWT's am actually 'parched'. A perched water table forms above an Impermeable layer of soil
or rock or saprolite that separates it from the actual groundwater table below. This happens in some
piedmont soils and some upper coastal plain soils in NC. Perched water tables are identified by a layer of
soil that does not contain redoximotphic conditions between the main water table and the layer in
question.
soils
The site is a grassed field beside the mill pond. Rock outcrops are present inside the gate and near the
lid
The soils are farmed from granite, gneiss and schist Slope at the site is about 3 to 4 percent. The
landscape position at the designated location of the stormwater borings Is ridge or shoulder.
The soils consist of sandy loam topsoils underlain by clayey 'B' horizons to about 30 inches below the
surface. Below 30 inches in depth is a transition horizon of sandy clay loam that grades into the sandy
loam saprolite. Saprolite was present to at least 72 inches beneath the surface.
Colors of the soil profile at S -1 did not show redoximorphic properties. However, gray colors were
present at S -2 throughout the profile below the topsoil.
No groundwater was found in any of the hand sugar borings or deep borings except B-I which is beside
the pond.
Conclusions
Boring B -5/S -1 did not show any evidence of seasonal or perched groundwater conditions.
B -6/S -2 is only about 30 feet away from B -5. This boring had gray colored mottling in the clayey 'B'
horizon and 'C' saprolite horizon. This coloring pattern is from relic colors of the parent rock at the site
end's not from perched or seasonal water tables. Some saprolite materiel is mixed into the 'B1 horizon.
I appreciate the opportunity to work with you on this project Please contact me if you have questions or
need additional information.
Sincerely,
k'red D. Smithth
NC Licensed Soil Scientist
OfAae/Mohlhr [phone]
Post Of/l" Box ff78— NaahV114 NorW CAMMM 278M

Table 1
Boring Descriptions in USDA Classification
Robertson's Mill Perk
Wendell, NC
S -1 and B -5
Landscape position — ridge, shoulder
Slope — 3%
Horizon/ Depth
inches
Tee
Color and description
A/ 0-8
Sandy loam
Dark brown l OYR 4/4
Bt/ 8-28
Clay
Strong brown (7.5YR 5/6); firm to very firm, sticky, plastic;
moderate, medium sub angular blocky structure.
B-C/ 28 -48
Sandy clay
loam
Strong brown (7SYR 5/6); very four, sticky, very plastic; coarse
bloc m massive.
C/48 -72+
San loam I
Brownish yenow loYR6/ firm massivo
S -2 and B -6
Landscape position — Ridge/shoulder
Slope — 3 to 4%
Horizon/ Depth
To=m
Color and description
inches
A/ 0-6
Sandy
Dazk brown (IOYR 414)
loam
B2t/ 6 -32
Clay
Strong brown (7.SYR 5/6) with gray (7.5YR 6/2) mottles; vary firm;
mottles appear to be relic from the grainy parent tucks. Massive,
compacted.
C/ 32 -72+ Sandy clay
_p2s3ib!y
Brownish yellow (lOYR 6/6) and gray (1 OYR 62); massive; rock -like
loam
OfikWA9oh//s [phone]
Post Ofikw Box ff75— Nsshr/ /hr, North CATOZIM 278x6