HomeMy WebLinkAboutSite Certifications - 07/11/2007Starrtec Consulting Inc
209 South Meldrum Street
Fort Collins CO 80521-2603
Tel: (970) 482-5922 Fax: (970) 482-6368
stantec.com
stantec
June 25, 2007
Mr. Basil Hamdan
Fort Collins Stormwater Utility
700 Wood Street
Fort Collins, Colorado 80522
Re: Drainage Certification for Pond Re -grading in Lind Filing 1, Phase 2
Dear Mr. Hamdan:
The purpose of this report is to certify the pond re -grading and provided volume for Lind Filing 1,
Phase 2.
Stantec Surveying visited the Lind Filing 1 site on June 20, 2007, to topo the pond.
Because the pond was re -graded and two trickle pans added to provide 2% cross -slopes in the
bottom of the pond, the pond must be re -certified. The required detention volume for Lind Filing
1 (see attached excerpt from the Final Drainage Report for Lind Filing 1, May 9, 2003) is 11.30
ac-ft. The provided volume, based on the topographic survey from June 20, 2007, is 21.03 ac-ft.
The reason for the provided volume exceeding the required volume is due to the pond being
constructed to detain both Lind Filing 1 and Filing 2, in their developed state. Lind Filing 2
construction has not begun, but the plans have been approved.
It is important to note that upon construction of Lind Filing 2, there will be minimal grading on
the east and north sides of the pond to provide not only the required detention for Filings 1 and 2
(21.93 ac-ft), but also to accommodate the proposed storm drainage improvements for Lind Filing
2.
The two trickle pans installed with the pond re -grading improvements provide conveyance of the
nuisance flows to the proposed outlet structure, located in the southeast corner of the pond. The
attached exhibit shows the pans and the associated slopes of the pans. There are a couple areas
where the slopes are 0.32% and 0.33%, but these areas do provide positive drainage and are
therefore do not pose any problems.
V:\52870f\activeVOBS\614003\docs\Lind I PondRegrade Drainage Cert 6-25-07.doc
1I�0ID-1
Stantec
In summary, the pond re -grading meets the intent of the grading plan and the pond exceeds the
required volume specified in the Lind Filing 1 Drainage Report, dated May 9, 2003.
This certification is signed and stamped. By signing this letter, I attest that to the best of my
knowledge, the conditions of the site are as shown on the attached redlined photocopy. Failure to
properly disclose all known information could result in the rejection of this certification and
prevent the release of any storm water utility holds on the Building Permit or Certificates of
Occupancy.
Thank you for your time and consideration of this submittal.
cc: Linda Purdy, Centex Homes
Ken Mills, Centex Homes
File
V:\52870Nctive\JOBS\614003\docs\Lind! PondRegrade Drainage Cert 6-25-07.doc
PondAsbuilts6-25-07.txt
Lind Filing 1: Pond regrade Drawing of Record Rating curve
].Gooch 6-25-07
#Units=Elevation,ft,Area,ft2,volume,acft,volume,acft
# Elev
Area
Cumml Avg
Cumml Conic
# ft
ft2
acft
acft pA
5020.8400
164205.1782
21.1414
21.0322 -- IQO-YR frovl%k4
5020.0000
159932.7252
18.0161
17.9070
5019.0000
155017.5644
14.4009
14.2920
5018.0000
149707.6397
10.9032
10.7944
5017.0000
142332.5186
7.5510
7.4426
5016.0000
126546.4697
4.4647
4.3581
5015.0000
92171.4975
1.9542
1.8579
5014.0000
35889.8156
0.4842
0.4378
5013.0000
6295.1503
0.0000
0.0000
Frcw C:»I Fl,w� 1 I lams 1 'J0UOI. t2�✓t : M 9i zoo
Qep.W1 lOa-YA Vel"e = �I, 3o Ac- Ff
ZI.03 ar. �� ✓
Pro�l:dts f�✓ �� F(.�y 2 a�so , N►,,„r nyr.�c,�
►+tea{ Ltid 2 daoft"gc QtAOI(f Ore tK,reIMAf5,
Page 1
6ce✓pP 4-vit, ` z,,,i r Itxy I
po
pa
P4
PW
Pil
pf
Pil
PEI
PW
po
Pil
Pil
P0
PW
Pil
FAA METHOD
Wcl Property - Fding I
Oetenopo Pound vduma
Released at VoWme Agreed Aeon by Ditch Cpmpany
Detention WOCV I Total
BASIN AREA 41.53 Acres Required RBgUlrad
RUNOFF 60EFFICIENT-1.25 0 7875 10.33 1 0 96718I 11.30
RUNOFF COEFFICIENT
0.63
RETURN PERIOD
too Year
ALLOW RELEASE RATE 2.54 CFS
Basins = 140, 4245, 49
' Release rate was deleemined by
the ditch company as 0.057c1s1acre
RAIN DURATION
RAINFALL ITRENSITY'- 1 OW OUTFLOW
RE09
Lyjr
L YOL STORAGE
min
InclYbr -
47 ACf
0.00
0.00 0 as
0.00
5
9.95
2.42 0.02
2.41
10
7.72
3.76 0.D4
3.72
is
6.66
4.87 0.05
4.81
20
5.80
5.45 0.07
5.38
25
5.06
6.16 0.09
&07
30
4.52
&60 all
6.50
35
4.13
7.04 0.12
6.92
40
3.74
7.29 0.14
7.15
45
3,49
7.64 0,16
7.48
50
3.23
7.87 0.18
7,69
55
3.05
9,16 0.19
7.96
60
2.86
8.36 0.21
8.15
65
2,74
8,67 0.23
8.44
70
262
8.93 0.25
8,69
75
2.50
9.13 0.26
8.87
60
2.38
9.27 0,28
8.99
85
2,30
9,52 0.30
9.22
90
2.22
9.73 0.32
9.41
95
2.14
9.90 0.34
9.57
100
2.06
10.03 0.35
9.68
110
1.95
10.45 0.39
10,06
115
1.90
loAl 0.41
10.21
120
IM
10.75 0.42
10.33
125
1.73
10.54 0.44
10,10
130
1.62
10.28 046
9.82
135
1.52
9.95 0.48
9A9
140
1.41
9.59 0.49
9.10
145
1.30
9.17 0.51
8.66
150
1.19
8.59 0.53
8.16
155
1,17
8,81 055
8.26
160
1.14
8.91 0.56
8.35
165
1.12
9.00 0,58
8.42
170
1.10
9.08 0.60
8.48
175
107
9.15 a 62
8.53
INTENSITY (IN7HRj,
DURATION
INTENSITY
5 9.95
10 772
20 5.6
30 4.52
40 3.74
50 3.23
60 2,86
80 2,38
too 2,06
120 144
150 1.19
180 1 05
LINK FIWAK i Pm& ndemc of R 96
la-vR JI[L - S'eze. B/
Im-YR vN..n (PWm) . L.e3 .vA
Ia-Yt YUY (P m • IL;e ... x
ib.. uNe 1 LAN W
RebRr CRY �3 )
V \52871f\active\ D7110016\SURVEY\DRAWING\10016V-P❑ND620.dwg
SURFACE; POND62007 JA
6/21/2
1
�07
8:45:20 AM MDT