HomeMy WebLinkAboutDrainage Reports - 06/10/1992-��Py-�--
Oar cw Final A oved Report
PORT COMMA arrt Date 6 1a .�-
FINAL DRAINAGE & EROSION CONTROL REPORT
FOR
LOT 9, BLEVINS COURT, P.U.D.
FORT COLLINS, COLORADO
MAy 11, 1992
PREPARED FOR:
KENT GLOVER
PREPARED BY:
PARSONS & ASSOCIATES
CONSULTING ENGINEERS
432 LINK LANE PLAZA
FORT COLLINS, COLORADO 80524
(303) 221-2400
PROJECT NUMBER: 91.15 GLV
FINAL DRAINAGE & EROSION CONTROL REPORT
FOR
LOT 9, BLEVINS COURT, P.U.D.
INTRODUCTION
This drainage investigation has been prepared along with final plans for the
development of a duplex on Lot 9 of the Blevins Subdivision. This study was prepared in
accordance with the City of Fort Collins "Storm Drainage Design Criteria and Construction
Standards."
SITE DESCRIPTION
This project is to be constructed on Lot 9 of the Blevins Subdivision which is located
at the southwest corner of Blevins Court in the Southeast Quarter of the Southwest Quarter
of Section 14, Township 7 North, Range 69 West of the 6th Principal Meridian, Larimer
County, Colorado (see figure 1). Lot 9 includes 11,846 square feet (0.27 Acres) and was
platted as part of the Blevins Subdivision in 1958. Lot 9 remains the only vacant lot in this
area. Adjacent structures appear to be single family residences converted to rental usage due
to their proximity to the Colorado State University Campus. These units are typically raised
one foot above curb level with individual yards draining.into street curbs.
-1-
- — . 0114 st'<
w
!�N ' INi
'4
WWd u
d°
a
k
=r
_
EMDu
W 51
i
M F. $/
Z
z U
W",a.SI
<
N
v
E
N1
S A•N
i t,
@
HbcD S(
;
N
¢
Q
L
old
N l
�4Yh 'M -' •lain D/
iYSt N. hW
P.
J�3 O
COLORADOy r 1
a
0 ��
uM,..,h A.
?,f?sii,?�:t.
'bra 'Sou16W-�,:pt41(
• .
l:.k.�.'OPd D,
s STATE :fdr ,.
_.w
Pllkln St 4
,gym Jimd[C[
y"
``wm+' ,IW GbS
H.mvtt Rd
81,4n,cr
UNIVERSITY
Summr 51 W Pn, .m
PQ
gw111d.
N T.m,.,B 4
BMum L Dr
26
C4
.B.
Mobblt S1 JYPIPM L. B. Dr P kw S(
Ct
� wrty PI
VICINITY MAP
i
N
C PROJECT SITE
FIGURE 1
This site slopes from west to east at about a 2.0% rate and is covered by natural
grasses. It appears that no drainage facilities were constructed as part of the Blevins
Subdivision and runoff is conveyed via streets in this area towards Spring Creek. All other
utilities (including sewer and water) were located along back property lines and extend from
South Whitcomb Road.
CRITERIA
The Rational Formula has been used to develop runoff flows from this site. The
Rational Formula is an excellent predictor of flows from drainage basins with areas less than
200 acres.
HISTORIC DRAINAGE
Runoff in this area drains from northwest to southeast towards South Whitcomb Street
and Prospect Road at about a 2% slope. The area is primarily single family residences with
grassed yards. Little or no site grading was completed when homes were constructed and
runoff sheet flows through this area. No sideyard swales exist and the sheet flows typically
run against the house foundations and then are either detained in natural back yard low areas
or flow around the house foundation to the street. No improved storm sewers, detention
-2-
areas, inlets, swales or other drainage conveyances except for the curb and gutter on Blevins
Court are apparent.
PROPOSED DRAINAGE
OFF -SITE FLOWS
Runoff patterns, except for a 0.82 acre area immediately west of the proposed site,
will remain the same (see figure 2). This 0.82 acre area, designated as Basin A, is intercepted
by berms and the proposed parking lot and this drainage will be diverted into Blevins Court.
Flows to the north of this site continue to run through lot 8 and into Blevins Court. Flows to
the south and east continue to flow away from this site towards Prospect Road as shown by
the contour mapping and spot elevations. These site improvements will cause the 0.82 acres
represented as Basin A, which would regularly flow uninterrupted through this area towards
homes to the southeast, to be diverted to Blevins Court. This substantially reduces the
amount of water which flows towards Prospect Road
ON -SITE FLOWS
The runoff from the site including roof drainage and a small area of offsite flows is
collected by grass -lined swales along the north and south side of the proposed structure.
These flows are diverted (shown as Basin B,) to the parking lot which also is designed to act
-3-
LOT .9 BL V1 1 CT.' ,
.OFFSGE ITE DR x5a1 -�*• ± ,
, r�. �,' *"" �.; , kI, ems. 'v��%.� • � .
JW
5 X 5012.9
JI
KV
� .yv-�fl.H:C y •'� �� `t X � ti (' T� � .r �� v''
-sue.'. � ..t ! �. ' "`' � � ..�� r'I��•a/ s ��4' y,
-�^ r - - `� .w \`_ r••,iM1y��.�r�`.��.. rv`� C.,'�'•+^j.%r!-NM,ior•e.t: - t
' 50J•":.�._ ..�{ b�.x..:l�''z+,vr'.v V.X 50.51{<M✓a• -- ..
61 a � $• sue` f i� :.+ 9 • a �F• �• _ - f ^4A .1.. w.
77i-l
ca/
X 5012.4 Y (71
��py e
�'f}+p te�a► v,. FFee y �
� ����'�p'' ) C .fit• 9 i •.� v -'^�.� . fib."1�. t i,�r 'K•
• _ - - Ji:''-v ;mid FTFyv i;. ,i. y y , y� . \
v. .s?
��r.f-f.�rr+^Y .. •--�—, a+.. r, '�''.-. •r.....!!!!k'�!'IS'_`T'i ....,...p„4'I�q�$k� '- •"...T..•. y ..-�
L �, �.. Y �If r. •. .� .tS!, �'f � .ram
,
FIGURE 2
as a detention and sedimentation pond. An outlet pipe at the northeast corner of the parking
lot will restrict outlet flows to the historic two year rate. This pipe will outlet into Blevins
Court where flows will be conveyed in the existing curb and gutter easterly to South
Whitcomb Street (see figure 3). The calculations for the detention pond are attached. Due
to the proposed volume required for the detention pond, a slight berm will need to be built
around the parking lot. This will result in a small 0.03 acre area (shown as Basin B2)
discharging directly onto adjacent properties. This is primarily a five (5) foot strip of grassed
area along the south and east edge of the property. Sheet flows from this basin are minimal
and will be more than adequately replaced by runoff from Basin A.
Calculations for the runoff are also attached. They are summarized as follows:
On -Site (0.24 Acres)
Basin B,
Historic
Qz =
Qtoo =
Developed
Off -Site (0.82 Acres)
Basins A
Historic
.10 cfs QZ = .28 cfs
.36 cfs Q,00 = 1.01 cfs
QZ = ..20 cfs
Qioo = .78 cfs
-4-
EROSION CONTROL
The parking lot and building area will be stripped during construction. The back one-
third of the lot will remain in natural grasses. Due to the small size of this project all of the
improvements will be built at one time. Water erosion control will be accomplished by silt
fences and the placement of a sediment trap at the location of the proposed detention pond.
Wind erosion control will be accomplished by existing.trees and grasses at the west edge of
the site. The construction will be completed during the summer of 1992 at a time of low
wind potential. More detailed erosion control calculations and schedule are attached.
CONCLUSION
The construction of a duplex and parking lot on Lot 9 will improve the drainage
conditions in this area. The berms, swales and parking improvements/detention pond will
divert flows from the west onto Blevins Court and reduce the quantity of the water which
previously ran through this area. The parking lot provides 1 1-50 cubic feet of detention and
will release a historic two year runoff of .10 cfs through a 1 7/8" X 1 7/8" square orifice
plate. A 4" PVC outfall pipe and sidewalk culvert convey this water to Blevins Court. It is
-5-
anticipated that the -.10 cfs historic flow will have minimal impact on Blevins Court street
flows. An overflow elevation of 13.14 is established at the entrance driveway for the
detention pond and any overflow including the routing of offsite Basin A through the detention
pond will discharge through the driveway. All drainage improvements are to be maintained
1
by the property owner.
VARIANCE
A variance to discharge runoff onto adjacent property from Basin B2 is requested for
this project. Runoff from Basin B2 would be sheet flow from 0.03 acres of grassed area. This
area is primarily a five (5) foot strip of landscaped area along the east and south edges of this
project. These flows would travel in a southeasterly direction towards Prospect Road. It
should be noted that almost one acre (Basin B2 and Basin A) historically contributed runoff
through this area. These flows are now diverted through the proposed parking lot to Blevins
Court which will drastically reduce runoff towards Prospect Road.
Q fC- >/'arrahce �nx��
0
GRAPHIC SCALE
T (dnrr)
1 l h - EO K
�I 7 I 6 5
\ I
\ EXIST HOLLYWOOD CURB. GUTTER k WALK
/ � I
\� T
3927' BLE"S COURT
I
II I I 2' TAPER CURJ(TO I _ _ �XIISTINC 8! WA1pR LINE k FIREVAYDRANT _ _ _ _ _ _ _ _ —I
1 BACK OF WAUK I I (BY qTY OF FORT COLLINS) / — — — — -t —
(BOTH SIDES) I PROPOSED METER PIT SERVICE B
TDP OF a RY (SEE DETAIL) ,.� EXIST CURB STOP
BASIN A I I I ELEV. u.� / I PROPOSED jSttiEWALK CULVERT_
PROPOSED I+
0,82 AC. I I WATER SERVICE�`
TK!
6'II PROPOSED 2' CURB OPENING �,( ,) • 1 1 \
TRANS1110N FROM YEfiT.TO �.p0' PROPOSED 6 X 5' UEASEME)i1T 111
TFALL CURB AND GUTTER
� 1 I I I II
\ DRAIN PIPE SEE DETAL 1
OU A�L CURB k GUTTER 14 / 1 I /
RDOF FENCE �d141x
/ BASE/AENT FLOOR + GRAVEL FILTER / x ELEV. 07.00 PFlt CITY ST DA D
I ,
A 1 A 10 J� 1 1
9 III�m
OF EERY /
0
FIGURE
BASIN BI
FINISH FLOOR
ELEV.
,t
ELEV. 13.5
.24 AC.
❑.DO
NINE
-
BASIN B2
PROPOSED 2' CU
oRAlx
„ ,
q�\
�'
I 1 SILT o...
c'
Ir
EXIST 6' WOOD i
NCE
I
uFENCE
_----------:
--- O
�—
i 4SANITARY SEWER SERVICE MH -0 — — — — — — =--�'-�O= — —,
RIM 601250 Sinus m
w w I IN V OUT 5004:67 TOP OF BERM EXIST. 8" SAt. SEWER
PROP INV IN 5005.00 ELEV, 13.5
L J ` S0N.5
n p
1 I I I III �
I 11 I I I I—
o
L-- I IIII
12 i _ 1 14
f LJ 13 I
� I IR I II
- -----------�
•,�"„M'^'�`*�:�-
w.'...'.
SILT FENCE
,
wee.'-.r.'...-....
...r..` a.
urr orrdrt cou.ls
-mow
�rw�.N. -�
i1mMwArtA uru
isF
•': a-q
•_
" i
E¢`
i
Iai
s 1j
I
,i
n,p 1
_
W7
iis'-�lrf
6 ir3 t:t�[
!
IiI�lcA_
`rp _iisF
TYPICAL SERVICE DETAIL
==o wi
EXIST -� y
MH
N
I:
Y•1m MR (i[ RTM)
3-
rt.niT
f
�„bJ,IDI
I
r y.aw . •nla
-
DRAIN DETAIL
NI1
n lu.
Z.
STANDARD EXTERIOR SETTING
FOR 3/4•'i 1' WATER METERS
mcowx,. cb.O.IAi
A.
PLANW� i N4
f
SECTION A -A
CONCRETE DRAIN PAN
Ln./Ib
v�41 ea rv.�
0
IMZ
N
.dr
6¢NrlAA
rrn1O°`I
I ° \
NI /,CVI NNi
ORIFICE .
PLATE DETAIL
�rtr-
�lr•-x:
1! I H I 1 1 I A I S 1 O IN I u
...__.. _.....n-
+m Irsln (wlu
ba w.im+`� •
I
ul x mab mare
SIK u4.
. hriq. ��i
1-I/.I.wJi
II„11a
LN 1...
Yr, LII Ir.Nr.11w,
.wa.r"?«.al. rrly
a
�
,rYRM,1: I,f14,b .. MI.,I.IYO.r�
xYtllln/x,mn[ (b,M(Ib
mt LMuno uIWY(aa an b IMtb wA
wuv.alm
IOU I5.0
Y
1 A
SECTION A -A
.DRIVEWAY CURB TAPER
EXISTING PROPOSES
DESCRIP770N
o
DECIDDu09 TREL
6,HiCREW ]REE
w
PoIIH! Poll'
4
DDT RRE
t
ucRr PDu
T
=N
l CIF AS Sow
mRl nw! HItAD
° •
fODND RSRAR / SEl RAHAR
0 •
MANTIOLET
pA N
V"m
(70RTO :4 Al O ATlONS
TIT )K
l R)SRANT
,_•-1 �=ti
WATER I
Tom- ,�
SANITAJIY 9EIIA'R
91VRA/ 9EIA'R
,— • —� '—�„
FndPROM' Lm A RISER BOA'
pmR10 ! 1 VAULT
1
r I
L__—J
AN
0I111104`WN IRG
PARSONS
TC&c �h r eW oyl /(�p(�/ JOK/B� NO. 11-IS G ZV
ASSOC/A TES PROJECT 7/� 11 BIOII S9 C^' ' ty a' CALCULATIONS FOR
CONSULTING ENGINEERS MADE BY- I_/� `� CHECKED BY DATE SHEETOF
FL Collins, C 1orado 80521
C
C
C.
C
C
c
PARSONS & C k{n� �I odr� JOB NO. (r I • 1 "
I ASSOCIATES PROJECT Lei �' �s (k CALCULATIONS FOR h' O
CONSULTING ENGINEERS
Ft. Collins, Colorado 8057A MADE BY W ` DATE CHECKED BV DATE SHEET 2 OF
/I a
170 a
--
-�
�,_�.�Te'z � _�- l; �'�Ci.�)� �c•o)(.z)) lao l� � �� _ �> 8Z (U•1)- it-0��1t9)��� J`�=_i_l�•811 t .l_9Y = �8 rf��
_flyI
J41'(64) i•zs)(9) ��� ��IS}9ayt�L.9.7_; _17-9.11ih
I I I
1j
�1 � 3 1 5 I I
_
I
L
I
C
C
C
PARSONS & °' / Pill clover JOB NO. / 916 61V
FASSOCIATES PROJECT rd� iev145 -d It HVA CALCULATIONS FOR
CONSULTING ENGINEERS JW HY- !(. 3 5
Ft Comma, Colorado 80524 MADE BV DATE CHECKED BV DATE SHEET OF
. , T
�.� �0 P��,��� I!nl_un, e � � red . Br )�. -r�� �q�� � I �a� �� l►rov�a�l�Sr_�)�;--� -- - —+ . - —
_y
_.rl13�U1 C_/�rQleA.l(_ t�JaJM I:. I CI3 ' ,..._.. ._
1A;_. ri,zlr
j r 11 tl _
I
' V
17)
1 ,
I....-.i�.,-,---i.. jai i I _�... i" I i 3 �• , - ,
a
✓,
,
-- - -- - - -
io_727.;4�'�_�_.�
o.K9✓' J176� T,211 936`�i i i
- -i— r -
1 f
to
_
r !-102 0 loff..—
,
1
-, I t
,
I /_�. I ,�.__... ' ...._i..__!__. ...._;__... 5..
1
,
1 ,
1-4-
I i I I i
1
1 L i i
I
FPARSONS & r k', T 6 /w/, JOB NO. 7/,/S &LV
ASSOCIATES PROJECT lei I 0104,S G(Irlill CALCULATIONS FOR delt,711�11
CONSULTING ENGINEERS i
Ft. CoMrks6 Cotora& 80624 MADE BY Twc DATE 1-5-12 CHECKED BY- DATE SHEET
am am
L-4-
It
ILS
xL,
t
.Seri['
_Cf C
T
wl
AV
3l PARSONS & 6fawl -JOB NO. 71./5 6t V
rASS 0 CLA TES PROJECT 10t CWtIN CALCULATIONS FOR QU tl't t
CONSULTING ENGINEERS Twc 15'-1
MADE BY- a r OF
Ft. CoMn,6 ColoradoNS24 DATE L CHECKED BY -DATE SHEET
i-d
A.
a ow fs
7
A ....
RAINFALL PERFORMANCE STANDARD EVALUATION
1---------------------------------------------------------------------
PROJECT: LOT 9 BIed14S C004 V. STANDARD FORM A
(COMPLETED BY. Jeff COUGA DATE: 3-?-12
1----------------=-------=--------------------------------------------
IDEVELOPEDIEROOIBILITYI Asb I Lsb I Ssb 'I Lb I Sb I PS
ISUBBASIN I ZONE I (ac) I (ft) I (%) .1(feet) I (') I (A)
Lof 9 no, JefaIe o.Z7 170 2,0 i V-0'�
I I I IX l I I
take � I
i
I �
--------=------------------------------------------------------------I
HDI/SF-A:1989
EFFECTIVENESS CALCULATIONS
-------------------------------- / =--------------------------------i
PROJECT : Le q L oils Cou/� �.Q.Q• STANDARD FORM S I
(COMPLETED BY: Jeff, DATE: 3-el I
Erosion Control
C-Factor P-Factor
Method
Value
Value
Comment
-------------------
8q�e Sell
-----------=---------------------------
1.0 11•0
Pair i of
mat I/1I<W Cass
0.17
I•d
UpkfG/def dock �13 of ID�
Stcilm /Al%Ap
I.0
0.0
In PakHy A�t�
Burldr�g fjica
p, �
1. op
I
i
--------SiIf_ fee Rs---------1.0---------°=SD-----�I���
F1jf,E1,, cf O(Ifid��i
MAJOR[ PS I SUS
I AREA
I
I
SASINI (�) 15P.SiNI
(Ac)
I
CALCULATIONS
-----I------I-----i------i--------,---------------------------
Lot 9 79.0 I
0. Z7
I
I ESp�I rs�rd (jars
(o,b9 ntrrs) d��k 1 of ----
rl-
I
I sac 6roand
05l R(fes) I
Qu'dolil &ta
(0.03 4C/rs)
I I
I
I �,
G
_ alfoj
0,17 AciP3 T®14
I I
I
I gal(
8.;tjllj
G Ors
(o.l x .03) . (a.os x. Oil)
.27
Werybfr�_'��` jy_cfor
,0-
EFf = [I ft sy x o,.uj x laa = gS.3
----------------------------------------------------------------------
DI/SF-S:I929
CONSTRUCTION SEQUENCE
PROJI , 864S cilud ,_f.V.D• STANDARD FORM C
r
5LOU"I3VCE. FOR 19 .9Z ONLY COMPLETED BY: Jeff COU(V DATE:
Indicate ,by. use o-f a bar line or symbols when erosion control measures will be installed.
Major modifications to an approved schedule may require submitting a new schedule for
approval by the City Engineer.
YEAR
)MONTH I � I
IJ IF !Mid I1'11TITIfi IS10IN Ip I
--------------------
---------- 1---------------------------------- =------------------------
OV.ERLOT GRADING !
WIND EROSION CONTROL
Soil Roughing 1 I
Perimeter Barrier l I
Addltlonal:Barriers
Vegetative Methods
Soil Sealant
Other I I
RAINF'.LL EROSION CONTROL
STRUCTURAL:
Sediment-Trap/Ba•sin
Inlet Filters
.Straw Barriers
Silt Fence Barriers
Sand Bags
Bare Soil Preparation
Contour Furrows
Terracing
Asphalt/Concrete Paving
Other
I
.VEGETATIVE: 1
Permanent Seed Planting)
Mulching/Sealant !
Temporary Seed Plantinal.
Sod. Installation
Nettings/Mats/Blankets !
Other
STRUCTURES: INSTALLED BY
VEGETATION/MULCHING CONTRACTOR
DATE SUBMITTED
HDI/SF-C:1989
P(Al-nJ Lot
aunau
Ca.S{�4C len I
S
Lae SCa/l�
- I
i
----------------------------------------
MAINTAINED BY
APPROVED BY CITY OF FORT COLLINS ON
�J
No Text