HomeMy WebLinkAboutDrainage Reports - 09/20/2012NORTHERN ADDRESS:
PHONE: 970.221.4158 WEBSITE:
200 S. College Ave. Suite 10
ENGINEERING Fort Collins, CO 80524
_
www.northernen meerin com
FAX: 970.221.4159 g g
%olly or . ins v Plans
Approved By,.,
Drainage Letter Report
Date. _ qaa-ice
Date:
August 22, 2012 .
Project:
Fairview Shopping Center. Filing Four
Project No. 688-001
Replat of Lot 1, Fairview Shopping Center
Fort Collins, Colorado
Attn:
Mr. Wes Lamarque
City of Fort Collins Stormwater Utility
700 Wood Street
i
Fort Collins, Colorado 80521
Dear Wes:
This letter serves to address the stormwater impacts of the above referenced multi -family redevelopment.
The existing building is situated towards the western portion of the site. The site currently consists of
rooftop, concrete walks and patio, asphalt parking areas, some turf, trees, and other vegetation. It
presently functions similar to a 'B' lot, with historic drainage being split towards Elizabeth Street to the
north and towards an area inlet to the south. The landscaped area adjacent to the western property line
has a low point such that it too drains primarily to the south. Flows then reach an area inlet located on
the C.B. & Pott's Restaurant and Brewery Property. Historic drainage patterns will generally be preserved.
The total impervious area of the existing site is. approximately 22,611 square -feet.
The proposed redevelopment will completely remove all existing above -grade structures and adjacent
hardscape. The new project will consist of a larger apartment building, as well as a modified parking area
and bioretention rain garden. Concrete pedestrian connections will be made from the units north to the
Elizabeth Street sidewalk. The total impervious area of the proposed redevelopment is roughly 22,688
square -feet.
The existing curb cut and concrete apron to Elizabeth Street will be slightly reconfigured to meet current
code requirements. The area of pavement draining north across the Elizabeth sidewalk will be
approximately,450 square -feet, which is less than the maximum 750 square -feet allowed by LCUASS.
• Q
The site is located in the Old Town master drainage basin, -and therefore, on -site detention is not required
so long as the increase in impervious area is less than 5,000 square -feet. The total increase in impervious
area proposed with this development is approximately 77 square -feet (22,688 - 22,611). A detailed
breakdown of the existing and proposed impervious areas is attached to this letter.
Page 1 of 3
DdPrcic &,688-001\Drainaee4Remrts\Drainaee Rem t1688-001 Drainaee-Letter 2012-08-22.dxz
NORTHERN
ENGINEERING
Although stormwater quantity detention is not required, stormwater quality mitigation will be addressed by
both temporary and permanent Best Management Practices (BMPs). During construction, the Contractor
l will follow the appropriate and applicable City of Fort Collins standards for erosion and sediment control.
A comprehensive Stormwater Management Plan has been prepared for this project, and a copy has been
supplied to the Environmental Regulatory Specialist with Fort Collins Utilities. Post construction water
quality and erosion control will be achieved by a fully established and stabilized site. All areas disturbed
during construction will receive permanent hardscape, landscape, or building structure.
i
This portion of the Old Town basin does not receive regional water quality treatment; therefore, on -site
water quality mitigation is required. Much of the existing landscaped buffers on the west side and north
side of the building will be preserved as permeable areas to promote infiltration and treat surface runoff
prior to entering the adjacent gutters and inlets. However, the primary water quality treatment method to
be employed is the construction of an on -site bioretention rain garden. Water quality computations have
been performed for this facility utilizing the UDFCD's UD-BMP Version 101 "Rain Garden (RG)" Design
Procedure Form. A copy of the RG worksheet is attached.to this letter.
The project site is'also located in the Canal Importation Basin floodplain. This is a City of Fort Collins
regulatory floodplain. A City floodplain waiver has been requested to utilize a Base Flood Elevation (BFE)
of 5035.0-ft (NGVD 29 — unadjusted) per the best available information contained in the Hydraulic
Evaluation and Floodplain Mapping Update for Canal Importation Basin prepared by Anderson Consulting
Engineers (ACE), dated June 10, 2005. All cross-sections,'BFE's, and floodplain boundaries shown on the
Floodplain Exhibit for Fairview Shopping Center Filing Four are from said ACE report. Not only does this
allow the project to make use of more current and accurate information, but it also affords a lower building
elevation.
Utilizing the 2005 ACE data, the proposed apartment building at 1409 W. Elizabeth Street lies within the
100-yr flood fringe for the Canal Importation Basin (CIB). Therefore, construction of this structure must
comply will all applicable regulations contained within Chapter 10 of the City of Fort Collins Municipal
Code. Specifically, the building's lowest floor elevation shall be at or above the Regulatory Flood
Protection Elevation (RFPE). For the City regulated CIB floodplain, the RFPE is 18-inches above the BFE.
The governing BFE for this structure (utilizing the ACE 2005 information) is 5035.0-ft (NGVD 29 —
unadjusted), which results in a RFPE of 5036.5-ft (NGVD 29 — unadjusted). The proposed Finished Floor
Elevation (FFE) for the multi -family residential structure at 1409 W. Elizabeth Street is 5036.57-ft (NGVD
29 — unadjusted). This building will be constructed with a slab -on -grade foundation without any basement
or crawlspace. Therefore the FFE is equivalent to the lowest floor elevation, which is slightly above the
RFPE. It should also be noted that all HVAC equipment will be located on the rooftop of the new
apartment building.
BUILDING SUMMARY
NGVD 29
EL. DESIGNATION
.(UNADJUSTED)
A
5035.00 FT
B
5036.50 FT
C
5036.57 FT
REGULATORY FLOOD
PROTECTION
5036.50 FT
ELEVATION (RFPE)
LOWEST FLOOR
ELEVATION = C
18"
MIN.
BASE FLOOD ELEVATION +_
= A
DETAIL
RFPE
T
ELEVATION = B
18"
1
BASE FLOOD ELEVATION
F = A
' Page 2 of 3
D3Proiects\688-001\DrainaeeUReoorts\Drainaee Reoort\688-001 Diainaee-Letter 2012-08-22.docx
i Since a good portion of the development (including the structure itself) falls within a City of Fort Collins
regulatory floodplain, a Floodplain Use Permit (FUP) shall be obtained prior to commencing with any
construction within the floodplain. This includes both sitework as well as vertical building construction.
As such, this project seeks to obtain a FUP with the initial Development Construction Permit (DCP), which
would then cover all work to take place within the floodplain. While the vast majority of the improvements
reside within the 100-yr flood fringe, it is important to note that the floodway currently follows the back of
sidewalk along the project's Elizabeth Street frontage. This means that some of the driveway and sidewalk
modifications will occur within the floodway. A No -Rise Certification is required for all work within the
floodway. Further details and supporting documentation for the No -Rise Certification shall accompany the
FUP application. A Flood Elevation Certificate.shall also be completed and approved before a Certificate of
Occupancy can be issued.
The proposed grading concept closely matches existing elevations and drainage patterns, and only varies in
an effort to improve the existing condition from a floodplain protection and water quality standpoint. On -
site detention is proven to be unnecessary. Stormwater quality has been provided to bring the historic site
into compliance in the redeveloped condition. The project is designed in accordance to the governing
floodplain regulations contained within Chapter 10 of the City Code, and the Floodplain Use Permit and
necessary certifications shall ensure that construction remains compliant with Chapter 10. Therefore, it is
my professional opinion that the new apartment building proposed with Fairview Shopping Center Filing
Four at 1409 W. Elizabeth Street satisfies all applicable stormwater criteria.
Please do not hesitate to contact me if you have questions or require additional information.
Sincerely
"mom' ILEED
Nicholas W. Haws, PE AP
enc.
i •
Page 3 of 3
D.\Proiecrsi588-001\Drainaee\Reoorts\Draina2e Reoort%688.001 Drainaee-Letter 2012-08-22docx
0
co
CL
O. E
C
E —
n
U
N
c \
U o
00
c 0
a N
N N
a
O W1.
N N II
N.N
h
d Z CY
�' o c 1)
6
0)
0)
m
cn
m
T
0 E w
O
C
•� o
"' U u
O
�
ii Q li o
g`
''"
N 0
V
V
a o
i. 0 `•'
o w
00
co
m o
f �'
<i
co
Q
V
U
C�
U LY
c
Lai>
CL "
000
000
N o IX W
O
O
y
U U
W
o
0
o
� s
O
C i
o
o m a
Ln
Ln
O
i
J N
J
2
N
N
O
On
O
0�0
QZQ
WUy
r CL
a E
00)0)N
EMn
QvO A
Ap0
C;
d
N
a
m
H
Ln
n
o
Ln
o
-
Up.)
Ln
E
`o w
...,
`N
C V
m
0)
In
0)
'
ti
N
m O C1
ti
.r
C
o00oo
00
Q `�
00
v9ci
c
u
ce.
c
o
CJ
O)
O N
W
a
e7 V v
N
00
N
�
c
Q
V
O
O
`m
U
Q
:
m
W
�
M
m
00
I►m
o. A
M
00
M
c
r
Q
o`
N
o
�
N
C)
8
c
o�
a
m
LL
U;
o
c
co
Qj
`
U
Q
W N
L
d
00
x
U O
E
Q •••�
N
O ,y co
s
N
N
2
co
0toa
A
C C
W
m
c
L) 4 L U N
d
F
j m T
`O
C
N
=
O
0 0 `°
O) U o 0: a-
Q C to U
m
= L 3p
IM
O
W
CL
E
o
�E
m
LO
00
-
N
OU
o U
00
a C N
a
o
r
N II
y «
Ln
W
nc
m0000ma
O
M
0
00
0
a� w m
Z a
o E
o
U U
Li Q Li o
g
Tr
N y
V
C
d
m
y O O V
In
LO
Lfl
LO
01
0
0
>. G a
NMW
00r-00
J
v o
o E� w
o00000
u II
m
W0
V>
o
m N "'
m a c u
LOLOLOLOrno
N
rn
tO
00
1-
00
\
U
nTj E � y
000000
< 7 L)
W
O
o
U
O
a
C C_
d
II
o
m
m N u
u
mom
00000.••�
OLn
cS
c
3
O
O
o
0
0
0
a
i
A
J m
J
2
N
H
Z
0
?
hm0 7
w
C
ym
Z
(D
n
E
d
000000
aL
00i
N
o
o
m> V
000000
2
V
Q
(:500000
Q
a E
"
-
m
N
a
N
LLJ
C
�
2
In
LO
O
LO
O
LO
LO
a
N
o u
N
7
0)0)Ln��
'.N
m
m
oOCV
000N
O
O
O
O
O
O
O
Q go
O
O
O
O
O
O
0
0
on
cc
LLJ
o_
Q
U
a
m u u
0
0
0
0
0�
iO
m
0
Q V
000000
O
Lai
,
=
\
m
m
0
O
O
0
O
0
O
0
N
N
N
d c m
000000
�
Q Q
o
m
o
Q
a
mo-0Lnn
ON.
-�ONtO
L
cg
m
W
o
y='
o00000
a
Vl
LL
p
m
m
�
U
W
LJ N
w
N
O»M
V
W
o° e
Q
c N
mmh°N°mo
000.
r
06
4
C6
CM
N
e '
-
O
N
Q d C m 0> m c m
'in
Q
00
U
0
W
O
Vj N O O m
N
cg
m
W Q U (.0 OC d C U
Q 4)
o
m
F
3
c
V VJS
¢
NORTHERN
ENGINEERING
Fairview Shopping Center Filing Four
Design Procedure Form: Rain Garden (RG) -71
Sheet 1 of 2
Designer: Andy Reese
Company:
Northern Engineering
Date:
February 28, 2012
Project:
Fairview Shopping Center Filing Four
Location:
Fort Collins, Colorado
1. Basin Storage Volume
A) Effective Imperviousness of Tributary Area, I,
I, =
75.8
(100 % if all paved and roofed areas upstream of rain garden)
B) Tributary Area's Imperviousness Ratio (i = I,/100)
=
0.758
C) Water Quality Capture Volume (WQCV) for a 12-hour Drain Time
WQCV =
0.24 watershed inches
(WQCV= 0.8' (0.91' i3- 1.19' i2• 0.78' i)
D) Contributing Watershed Area (including rain garden area)
Area =
29,309 sq It
E) Water Quality Capture Volume (WQCV) Design Volume
Vwocv =
cu ft
Vol = (WQCV 112)' Area
F) For Watersheds Outside of the Denver Region, Depth of
dR =
0.30 in
Average Runoff Producing Storm
G) For Watersheds Outside of the Denver Region,
VwaCv orRER =
419A cu ft
Water Quality Capture Volume (WQCV) Design Volume
H) User Input of Water Quality Capture Volume (WQCV) Design Volume
Vwacv USER =
cu ft
(Only if a different WQCV Design Volume is desired)
2. Basin Geometry
A) WQCV Depth (12-inch maximum)
Dwocv =
in
B) Rain Garden Side Slopes (Z = 4 min., hertz. dist per unit vertical)
Z =
ft / ft
(Use "0' If ram garden has vertical walls)
C) Mimimum Flat Surface Area
AM„ =
sq It
0) Actual Flat Surface Area
A,,., =
sq 1t
E) Area at Design Depth (Top Surface Area)
A,,, =
sq It
F) Rain Garden Total Volume
VT =
cu It
(Vr= ((AT.' Ann.) / 2)' Depth)
3. Growing Media
Choose One
10 O 18" Rain Garden Growing Media
Other (Explain);
City of Fort Collins Standard Planting media
4. Underdrain System
A) Are underdrains provided?
Choose One
* YES
ONO
e) Underdrain system orifice diameter for 12 hour dram time
i) Distance From Lowest Elevation of the Storage
y =
OS ft
Volume to the Center of the Orifice
ii) Volume to Drain in 12 Hours
Vol,, =
419 Cu ft
III) Orifice Diameter, 3/8" Minimum
Do =
0.63 in
Drainage Letter Report
688-001_UD-BMP_v3_01.x1s, RG 2/28/2012, 3:34 PM
■_ r� NORTHERN
ENGINEERING
Fairview Shopping Center Filing Four
Design Procedure Form: Rain Garden (RG)
Sheet 2 of 2
Designer: Andy Reese
Company: Northern Engineering
Date: February 28, 2012
Project: Fairview Shopping Center Filing Four
Location: Fort Collins, Colorado
5. Impermeable Geomembrane Liner and Geotextile Separator Fabric
Choose One
O YES
A) Is an impermeable liner provided due to proximity
ONO
of structures or groundwater contamination?
6. Inlet / Outlet Control
hoose One
Sheet Flow- No Energy Dissipation Required
rg
A) Inlet Control
Concentrated Flow- Energy Dissipation Provided
Choose One
7. Vegetation
O Seed (Plan for frequent weed control)
Plantings
10
Sand Grown or Other High Infiltration Sod
8. Irrigation
Choose One
OO YES NO SPRINKLER HEADS ON THE FLAT SURFACE
A) Will the rain garden be irrigated?
O NO
Notes:
Drainage Letter Report
688-001 LID-EiMP v3 01.xis, RG 2/28/2012, 3:34 PM
0
I
WEST ELIZABETH STREET AV
IV RIGHT OP WAD
ININIff. r. rr]wE.1aE(ticlw[�c n Jwf NMI mi.
] r r r1 �r wl rl I
c
—
{ an em I ] -
I} I
I
I y 1 �,
! I
�I g
WLOT1
RESTAURANT WO
&BREWERY A ' I
nm .� PROPOSED
APARTMENT
BUILDING p
LOT Y
I
LLD WGAFw
ASRINT PARNRND AEA'I � ' L• � �\ � \� I
O
1
�IP I
1
12'ORAINAGEk
UTILITY EASEMENT _ W
�I I ASR TPARAtNNN R
` 1
1 I
, TRASX J l i � � � 1
E�q
OSD� {
ry - �� 1
ID• UTILITY
EAYMEXi
i
01 M.InCC 011LARAAOV
oa�mmmm®®m
®
PO D
NORTH
20 AD 60 F.A1
o
m
( IN
FEET )
I FM1
= zo n
LEGEND:
PROPOSED STORM SEWER
PROPOSED INLET
MgPOSED CONIWR
.93
E% NG CONTWR
---_-A95]--- -
PROPOSED SWALE
.. ..
-
PROPOSED CURB It CUTTER
EC
PROPERTY BCMDARY
- - —
DESGN PENT
Q
FLOW ARROW
DRAINAQ BA" LABEL
mNDAAUwD e
E
DAMNAQ BA9N BOUNDARY
_�
PROPOSED SWALL SEC"ON
u
PROPOSED RARN GARDEN
O
-
Z �
of
W Cr-
NOTES:
Z -±
Ckf— 1
I. REEK TO THE'DRAINAGE LETTER REPENT FOR FAWMEW SNOP NK O C7 I
CONTENT FUND FOUR' By NORTHERN ENONEERVNG, DATED AUGUST 92, -L -
M11 FOR ADDIDMAL INFORMATION. Z
w
2 REFEA LO THE ROM LAIN EMIBIT FOR NOTEsLU$ LOTION
BAY R000 ELEVATION$ AND FLOOOPLAM NOIFi
FOR DRAINAGE REVIEW ONLY m
NOT FOR CONSTRUCTION ag �aa
BIO-RETENTION RAIN GARDEN SUMMARY
WATER
REQUIRED
PERCENT
DUALITY
WATERSHED
WATER
VOLUME
IMPERVIOUS
CAPTURE
VOLUME
AREA
(50. FT.)
QUALITY
VOLUME
I
PROVIDED
(CU. FT.)
M.
CU. FT.
81.80
0.29
Imu
N5
469
J
LL m
w
X
z W
w
L) w
CLLL VTArtV NDTNiG1gNGENTEROF
aMw
r
V
Z
d Z
a
O
ANrW OaATB YDURIp.
�
City of Fort Collins, Colorado
W
UTILITY PLAN APPROVAL
"PRD9®: CA,eer ---DT—
Q
LL
eseDT¢D Bx: .�A_�mEe�.L�r-ocD� �eG—
CIIPL'ID:D BY:
OmTDrmWn Wr Icy__
---
er Beau9n DeTe
Sheet
—D�
C5.0
`"D`� --Date
6RWrRRmeRW Plemer
Of 10 Sheets
® NORTH
20 D 20 10 60 FRaI
FEET
I NF)1 20 It
LEGEND:
FASTING STORY SEWER sl—
PROPOSED STORY SERER -a
PROPOSED STORM WLET [3
- -, PROPOSE) CON)WR 8.1
- ROUSTING DONTOUR
WEST ELIZABETH STREET i) PINPORD WALE
IVE%6TM]RpNTORW\Y)
PROPOSED aJRe a SUTTER
_ - _ -_ MOPERTY BOUNDARY
_ ! I•
/ PEDESTRIAN ACCESS RAMPS �I
W� �� W� WaWI W� W� Rs JAL W� IFI PI—
Ie♦.(a!� s
)�' *' .5 r/ � wr Itw w m m m m
mm PA CONCRETE
E)DSTNG 100-M TEMA ROOOPLAW
E15TN0 Ott MING RYA RDOUWAY
' \ T110-M 1
(ME rare 9) 1
SPROPOMD RAIN GARDEN
�ZYR FLWOWAY
ZZZgg moss-mcnm (m) 20554
'— Y
EIEVATdI NGq 29 (1JHMAISTED� 5'(AQ
I 'I --4 WLOT I BASE ROGO ELEVATHRI (BR)
I L0T1
C.B. B POTTS 1
RESTAURANT
B BREWERY
PROPOSED FIELD SURVEY BY:
I - APARTMENT - I ! i 6 WiNMIn Lma S on9. In..
BUILDING I Pm}N NR 2DIo-aOle
_ I (.�. ' e DnIF Ne..me. 14 2DID L0T2 I
�M1FRLL1 SIMVEY(5):
p... O
- B ENCHMARKS:
10
I BCNCIYMN /1
IIIIIIWWWtltly�/// 2 Y LIY PI Fwr CaXina Bmehmark 2IF97
1 EIe tl.- SMB 9) (NM 29 - UneR91Ltl)
COXC LGAWMG AREI '
m
— � f ._ � L#WMR
-,.m- SDu
56 BmwOun2
299
A9RkT PARI AREA-19u-n9e)a4awl ry t;� m'BfTS, z
o� 4"
NOTES: yg
yy(( m
1. REFER TO NE PLAT FOR LOT AREAS. TRACT SIZES. EASEMENTS. LOT 3 f
OWONSICN M1TY EASEMNN TIER EAMME R A W <•
\
Ti
1' SOEWAIN
CHASE
12' ORAWAGE e
uMJTY EASEMENT
`100-YR OlY
�—
ASPHALT PARNIHO PR4
BWNDMY�LAN
- -
1
(SEE NOre 9)
4lw
-'
EMCLOSV4E
.�..
g3
n_
D UTUTY
EASEMENT
BUILDING SUMMARY
EL DE9WAMMN
NOW 29
(UNAD.ANSTED)
A
W35M R
8
5OM.50 FT
C
WM57 FT
RCWLATORY FLDm
PROTECTION
MM.5O FT
ELEVATION (WPE)
BASE PL
1vq - w -
DETAIL
5, U TS• O N15• AIL OTK SUIT
NFdiYATM. n�m 'B•� gl
2 ALL ELEVATIONS DEPICTED W PLAN NEW AND SENOWAMS LISTED
HEREON ME PER THE OTY O FORT C NS VERTICAL CONTRO OATH
(KVO 29 - UNADASTED).
]. TINE LOWEST FLOOR (WRVAND MY BASLIFNT OR MAW WP ) ML
ALL NVAC EYAPLEi11 AND THE FYN91 RDOt AMO LOWEST Rl%YI
ELEVATION FM MY BIRLDWG W ME R.00pRAW SHPLL BE ELEVATED
ABOW ME RFPRARMiv RWD PROTECTON A£VATION.
A A FLOOOPLAW UM PERMIT SHALL BE REOMED FOR EACH STRuCN O
ANO EACH SITE CAISTRUCB0r1 ELEMENT (DETENTION PQ SINE PANS• LL
PANNING LOT. JOLTE% ETC.) IN THE RCLOPLUN.
5. M ELEVAMRI C mcATE sNA L BE COMPLETED MD MPROYID BEFORE
THE CERTIFICATE OF OCOJPMCY 5 IS91E0 FOR MY SMUCTJRE W 1NE Z
FLDwrtAx. J
6. NO STORAFE OF NATIONALS OR Eg ENT 9HWL BE NLOYEO W ME co
ROw'RAY. WETKR TEMPORARY (AMINO CMSTRUCMW) M U. _
PERYMEMT. LANDSCMWC SHALL ALSO MEET NE REWYEMEMTS FOR .y
NO RISE IN THE FLOODWAY. LL X
). REFER TO THE'ORAINAGE REPORT I£TTER FOR FARWIE SNOPPWG W
CENTER FILING FOM' BY NORTHERN ENGWEERWG. DAIS➢ AUWST 22. I— w
2A2 Fw ADOITRMAL M OEIATryH. Z B.A NO RISE ORTWaL11ON 15 REONRED FOR MY WORN WITHIN THE LU Z
ROOOWAY U
9, A OTY RDDORAN WALER "AS BEEN RCOESTED TO UTU2E A WE O UI WQISD-FT (N VO 20 - UNAOX59 PER E BEST AVMABLE 5
INFORMATION COITANIEO IN ME HY) TH
AVLIC EVALVATgN AND FLOOOPLAIN Z
YAPPING UPDATE FOR CANAL NPOITATIOV BASIN PREPARED BY
MIILA
OERSW CONSULTING EMONRRS (ACE). WC DATED .FJNE 10.W 25. y. Q
ALL w S-SECTIONS WV, AND ROmxux B ARES sNDwN a
HEREON ME FROM SAID ACE REPOT.
ID ALL HVAC EOWYENT IS TO BE LOCATED ON THE ROOFTOP OF THE O O
STRUCNRE At 14M W EUTABETH SNNXT. : O
J LL
f
T ERcvAnoN . FOR STORMWATER REVIEW ONLY meet
j BASES_ nooD EEVAna NOT FOR CONSTRUCTION G`CJ 1
or�o sneess
f
T ERcvAnoN . FOR STORMWATER REVIEW ONLY meet
j BASES_ nooD EEVAna NOT FOR CONSTRUCTION G`CJ 1
or�o sneess