SW1200502_Arboretum Stormwater Narrative & Calculations - sealed_5/14/2020

The North Carolina Arboretum
Parking Reconfiguration & Expansion
Stormwater Management Narrative & Calculations
The North Carolina Arboretum has an existing facility located at 100 Frederick law Olmstead Way,
Asheville, North Carolina. The facility proposes to make revisions to the existing parking area by
removing tree islands and milling/re-paving the entire lot. An additional overflow parking area is
proposed across the main entrance drive from the existing lot. The two areas (existing parking lot and
proposed overflow lotj are discontinuous and will utilize separate stormwater management measures.
The existing parking a i a consists of four (4) aisles of parking with earthen berms) between the aisles.
The entire lot will be milled and re -paved. Approximately 45 existing tree islands Will be removed and
replaced with parking spaces. The existing lot pre -dates NPDES stormwater requilements in Buncombe
County. The existing lot is served by a catch basin and pipe stormwater collectionisystem that discharges
through a former sediment basin associated with the original construction of the lot and/or adjacent
building. This basin was recently rehabilitated into an educational wetland stormwater management
area. A more extensive discussion of that treatment system follows.
The proposed overflow parking lot will initially have a gravel surface. The lot is expected to be paved
when funds become available to do so. For purposes of stormwater management the lot is assumed to
be paved. The stormwater from the lot will sheet flow to a narrow linear bioretention cell surrounding
the lot on three sides. The cell underdrain will discharge via an outlet structure onto existing grade at
the north end of the new parking lot. The call has been designed utilizing the StorlmwaterEZ spreadshee
to achieve volume matching. The spreadsheet calculations follow this narrative.

ASheville,NC BUNCOMBE County
Dan J. Bolden, P.E., Bell Engineering
The orth Carolina Arboretum Parking Reconfiguration & Expans ZMA
16 Asheville, NC BUNCOMBE County NODE/NR
Dan J. Bolden, P.E., Bell Engineering
Type of apt Ilcatlon:i New permit I
complete act 311callon packages will be accepted and reviewed. A complete package Includes all of the Items in the
list below. A Jd any comments, and Indicate the page or plan sheet number where the following Information can be
please Indic to that you have provided the following required information by Initialing In the space provided next to
each item.
Notes l Comments Initial.
and one copy of this application form (all worksheets) antl the permit
cation fee. For applications submitted to the DEMUR regular permitting
mm. the fee is$505 payable to NCDENR. For Express Review, dick onnk
below for information antl fee schedule. Contest the appropriatenal
office Express Review Coordinator to Schedule Me requiretl Are-
-finn rn inn
Jnal
here for Exress Permitii info
GS map identifying the site location. If the receiving stream is reportedass
SA or the receiving abeam drains to and is within 12 mile of SA
may}rs,
Men includethe 12mulereduson Iremep,
Tpy
of the most current property
dead,copies
of additional calculations
(as needed). Sealed, signed antl dated.
6 T
a sets of sealed signed&dated Poll -sized plans of the entire site at
atlable scale, including:
. Project name, engineer and film, revisbn number and dates.
b. Location map with street names and SR numbers, legend, north arrow,
cale.
. Dimensionetl property/project boundary with beatings&distances.
FilAle
N
. The boundaries of all surface waters, regulatory flood zones, and
muscled riparian buffers or a note on We plans Met none ed5t.
i
. The boundaries of all vegetated or protected riparian buffers.
. Site layout showing all built -upon areas, drainage features, ni m u ater
Ilectiun systems (Inlets, outlets, wattles, pipe elevations, slopes and
iamete s), and SCMs at ultimate build -out.
. Editing contours, proposed contours, spot elevations, and finished floor
evalittl
. Existing drainage (including off -site), drainage easements, pipe sizes,
noff calculations.
. Drainage area boundaries (included in the main set of plans, not as a
Separate document).
. Existng and proposed maintenance access routes, utility easements,
relnage easements, public rights -of -way etc.
A construction sequence that shows how Me SCMs will be protected kom
Sediment until the entire drainage area is stabilized.
6 T
a sets of sealed, Signed. & dated full-sized plan details of each SCM (or
ty
lal H appropriate) in both plan view and cross-section W a scale of I-- 30'
larger, including:
. Dimensions, side slopes, IengM to width adios and elevations with a
nchmarit for deannut H appropriate.
. All applicable conveyance rbvkes.including: bypass structure.
rebeatment area, flow distribution device, underdrali outlet device, outlet
issipaber and level Spreader.
. A table of elevations, Incremental volumes and accumulated volumes (if
pplirable).
. Specifications for applicable materials, such as plumbing media,
ggregabe.!sod, underdrains, outlet devices, eh:.
IE
STORM-EZ
Version 1.4
Application
5W020
Page 1 of 14

Asheville, NC BUNCOMBE County
Dan J. Bolden, D.E., Bell Engineering
Directions
Receiving
Status
If an application
Tha North Carolina Arboretum Parking Reconfiguration & Expansion
100 Fretledtk Law Olmsted Way
Asheville I Zip:28806
Project is IOt2ed adjacent to Frederick law Ohmslead way south of
Intereectio with Blue Ridge Parkway
This:
Address:
City:
State:
Zip:
Phone:
F.
Email:
Address
City
etc, whkh Owns the project.)
George Briggs, Executive Director
Owner
100 Fiederl k Law Ohmstead Way
Asheville
NO
28806
828-66S2492
brincerbaretum.o
of applicant: Owner
Coastal wetiaM area (aCy 0 I
Total Dmled area (ecfi.52
Volume Matching (LID) NO Drains to
Low Density NO Within Si
High Density YES Within 5
needed: �YES Sedimentation& erosion control NO 40 Ise.111401
NO CAMA Major Permit NO Isolated Wetlaw
NO Threatened B Endangered Species I NO NPOES Indushi;
Provide the permit e, numher and issue date for any permhs that have already been obtained for this project
S iment aM Erosion Conbd Permit BUNCO-2020-009 issuM WM020
Ifdelming vested ri ghts, then Identify (and attach) the supporting documents and approval dales:
Approval of a site-sped8c develepmerd plan or PUD Approval date:
Valid building permit Issue date:
Other Date: I
Not Started
Point of Contact Phone numbecC
id Application I Pa,M3 o14

he No Carolina arboretum Parking Reconfiguration &
(Asheville, NC BUNCOMBE County
French Broad River Basin
DATA
Project County: BUNCOMBE
Project City: Asheville
Rainfall Source 1 Aahevllle
Loa
disainfall:
Asheville
Oea
n5tormd
P59 I
Oalcul
tion Method
Olatrete 5C5 MOMMI,
Pie - Post
Samn=FSO for man -SA, 1-yn 24-hr Ior SA)
Please use the Sjoni calculation sheets to document the slonnwater design
and eate the O&M Agreement.
INFORMATION
Tonal
roperty Area
652
acres
Total Coss
el Wenerds Area
000
acres
Total Su
es WwherlArea
I 000
Is..
Complete the breakdonT of impervious area for the project
Enfirli
Receiving Searle
name I
I Wesley Creek
Sbeen Cle
-I
a
Stream Index
Number
1 6-67-10
Total Drainage
Area
93.668
On -Site Drainage
Are. (Sfl
93,668
Ofrsile Drain
eArashili
0
Proposed Moline
... 4,ea (sp
55,321
%Imperviit
Area(tote
59%
threpervithoustS
rface Avast
I Entire, she
Oni Build
gWWt.
0
01
is (A
0
OnSih Parki
s
53.521
On -Site Stan
diflas
1,800
Other On -Sit
Future a
Ott -se,
E s5ng BUA
s
I Totes
W,,321
Storm Event I
Ames and land
ern
NCDENR
1.4 P.jw Ones I Pape S5M14

The North Carolina Arboretum Parking Reconflguration & Expansion
Nn.AIx.NC BUNCOMBE County
FmncB awE Nl—solo
emmmw
hNNN 6Ye
"n
a mem
rmw
eM
Yo�
MWNx
x5
M111
lei
Icea•I
VO
lam�l
Nx
ml
IM
flemxMln IanL Yea:
9
-I c..m.u.
ON
INOrNn V.I-- xIs nsnve- 1o.M. d
Fwnal?*Axa nLpr,m—,x
n100
Fer�]NM

I
E ox.o w.mpuntlOn B Expansion
The N0dN Carolina ArOeirotum s ParNlnp Recon....
e,n
NCDENR
pNprpYPFlnad Iw Nuxunvwaecpxread
I
EM.r only mnortwwne bi
m that Will eannllmm ordn down Duesx to sdays. Additional mlum. pnMaee In aaN.e..nould nW G
enlenl In this worbneet
'
onwdinwntm. m4ulmm.nt.pPll.. m.II awm.v.nla.
rm
son
ase
w~� w w.A .r
eaa �yvy�
•�M rM
M IM M
Insy
o"i
pass wmnrmdinmair
pamall V.mm.- a o..� - ip.ew n
PunmPmua cammmmounsbn
wn..m.dw
.w amascxadm». tp,ew
M
n
'
mmmuBumpname -
Iry ..sonimsaan-
AS
--VOLUME MATCHING
ACNIEV%p '
rw w�o�w+evrvos..wr..minar
.v�Ne�...ra..vMauan
rpee .

The North Carolina Arboretum Parking Reconfiguration & Expansion
Asheville, NC BUNCOMBE County �i+fgn
French Broad River Basin it NCDENR
Drainage AeaA 1 Of i
q. Imi
O (i
Length In)
Slope (nln)
xalue
ow a
(WI
Wan04 setlmedr
(fl)
(h.)
Pre -development T.=
5.00
min
Iwn...nrs,r. el
Leri (n)
I slope(1ah)
aurfaos Cover
Longer (a) I slope(m) I n-value I (fl°) I Weneopetlmeter Im I Thhml I
Analysts Area = 2.15 Across (0.000 sq. miles)
ow r
am
0,18
1 1
1 0]1
1 1,611
1 2.11
5
991
a.00
.
111.aBas
as
.00
0..23
1.10
2.23
fi.1
Ofi
-fO0es..
00%000%45%
-f0.00
150.0%
102.8%
..
113%
f08%
5%
%0
STOli I 5N3020
Version 14 Peak Floss Calm Per', I of 14

t operation and aintenahce procedures:
Immediately afto ir the bioretention cell is established, the plants will be watered twice weekly if needed until the plants
become establi had (commonly six weeks).
Snow, mulch or any other material will NEVER be piled on the surface of the bioretention cell.
Wheeled or trac ked equipment will NEVER be driven over the bioretention planting surface.
Special care wil be taken to prevent sediment from entering the bioretention cell.
If standing wate is present 2 days after rainfall, conduct an infiltration test of the sail media.
After lh'e bioretention cell is established, inspect it quarterly. Inspection activities shall be performed as follows and maintenance
act, Mel shall commence immediately to remediate any problems observed per the table below.
BMP element:
Potentialproblem:
How to remediate the problem,
The entire
BMP
Trash/debris is present.
Remove the trash/debris.
The part
meter of the BN
P
Areas of bare soil and/or
Regrade the soil to remove the gully, and plant a ground cover and
erosive gullies have. formed.
water until it is established. Provide lime and a one-time fertilizer
application.
Vegetation is too shod or too
Maintain vegetation at a height of approximately six inches.
long.
i
The inlet
device
The pipe is clogged.
Unclog the pipe. Dispose of the sediment
off -site.
The pipe is cracked or
Replace the pipe.
otherwise damaged,
Erosion is occurring in the
Regrade the swale to smooth it over Pnc
provide erosion control
swale
devices such as reinforced turf matting
r dprap to avoid future
problems.
Stone verge is clogged or
Remove sediment and replace with cleai
i stone.
covered in sediment (if
applicable).
The pretreatment
area
Flow is bypassing I
Regmde if necessary to route all flow to
he pretreatment area.
pretreatment area and/or
Restabilize the area after grading.
gullies have formed.
Sediment has accumulated to
Search for the source of the sediment ar
d remedy the problem if
a depth greater than three
possible. Remove the sediment and res
abilize the pretreatment area.
inches.
Erosion has occurred.
Provide additional erosion protection suc
i as reinforced turf matting or
dprap if needed to prevent future emsior
problems.
Weeds are present.
Remove the weeds, preferably by hand.
The bioretention
vegetation
cell:
Best professional practices
show that pruning is needed
Prune according to best professional pre
ices.
to maintain optimal plant
health.
I
Plants are dead, diseased or
dying.
Determine the source of the problem: soils, hydrology, disease, etc.
Remedy the problem and replace plants.) Provide a one-time fertilizer
application to establish the ground cover if a soil test indicates it is
necessary.
Tree stakes/wires are present
six months after planting.
Remove tree stake/wires (which can kill the tree if not removed).
STORM-EZ
Version 1.4
O&M Manual
Sl0/2020
Page 13of 14

STORMWATER MANAGEMENT PERMIT APPLICATION FORM
401 CERTIFICATION APPLICATION FORM
BIORETENTION CELL SUPPLEMENT
This /unn must be filled out printed and submitted.
ad Hems Checklist (Pad Ilp most be pointed, filled out and submitted along with all of I
Yroleci name
Contact name
Phone number
Date
Oramage area number
NoM Gamllna AMMWM Failing Lot Expansion
Drake Fowler, Chief Fimmchial Ctfaer
82M65-2492
Apn130, 2020
1
Ill. DESIGN INFORMATIO
I I_
Site Characteristics
Percen I Impervious
Design rainfall depth
Peak F low Calculations
Is preJj ord control of the 1-yl
1-yr, 2 -hr mnaff depth
1-yr, 2 hr intensity
Pre-0e vilopment l-yr, 24-hr
Post-th velopment 1-yr, 24-1,
Proft it 1-yr, 24-hr peak oo
Storage Volume: Noni
Minimumm volume required
Volum( provided
Storage`I Volume: $A Were
1.5, mpoff valume
Pre -de Ilyelopment 1-yr, 24-hr
Post-dovvehpment l-yr, 24-h
Minima m volume required
Velum provided
Cell DI trensions
Pondin 1 depth of water
Pond depth of water
Suit area of the top of thi
Media and Solis Summary
Drawdawn time, ponded vole
Drawdglwn time, to 24 inche
Drowdown fine, total:
Soil p�areability
Ialdl nmdia soil.
Soil p�Meability
Soil Wmposit
% Sand by volume)
%Fines(by Winne)
% rgank(byvolun
msphpres Index(P-Im
media
g3,66e If
54,784 fl'
58.5% %
74 inch
N (Y or N)
in
in/nr
h'/sec
tl'/sec
h'Isec
OK
P
Insufficient surface are
OK
Insufficient length
OK
OK
OK
OK
OK
OK
OK
of n.w
102