HomeMy WebLinkAboutSite Certifications - 06/29/2009ADDRESS: PHONE:970.221.4158
NORTHERN 200S.CollegeAve. Suite100 WEDSRE:
ENGINEERING Fort Collins, CO 80524 FAX; 970.221.4159 www.northernengineering.com
June 21, 2007
Jay Barber
Fort Collins Stormwater Utility
700 Wood St.
Ft.Collins, CO 80522
PE: Lemay Avenue Estates
Drainage Certification
Project Number: 110-004
Dear Jay:
We have completed our review of the as -constructed major drainage improvements for
the above referenced project as it relates to the approved final construction plan design.
This certification is intended to verify compliance of the constructed major drainage
improvements for the approved construction plans.
Field surveys of the site were conducted by King Surveyors, Inc. in December of 2006
and June of 2007 and have been used to verify general conformance to the Plans. The
project engineer conducted site visits also in December of 2006 and June of 2007 to
verify grading and major drainage improvements\ Based on the survey data provided by
Northern Engineering and personal site inspection, we believe that all major drainage
improvements have been constructed in general compliance with the design.
The volumes for Detention Pond 1 and Water Quality/Detention Ponds 2 and 3 were
calculated from the topography provided by King Surveyors. The design volume for
Pond 1 was 6.40 acre-feet achieved at a water surface elevation of 4933.50. The as -built
pond achieves the required 6.40 acre-feet of storage at water surface elevation 4933.78.
Thus, we conclude that Detention Pond I will perform adequately with the design intent.
The design volume for Pond 2 was 4.32 acre-feet (3.80 acre-feet of detention achieved at
WSEL 4922.66 and 0.52 acre-feet of water quality capture volume). The as -built pond
achieves the required detention volume of 3.80 acre-feet at water surface elevation
4922.60. The 0.52 acre-feet of water quality capture volume is not fully provided. The
volume between the 100-year water surface of 4922.60 and the spillway crest elevation of
4922.80 is 0.20 acre —feet (thus short by 0.32 acre-feet). We feel this will not pose any
problems, as the assumption that the water quality volume is full prior to a 100-year
storm event leaves for an extra safety factor in the pond design volume.
The design volume for Pond 3 was 0.09 acre-feet achieved at a water surface elevation of
4929.07.
07 C�5' f -,-(
The as -built pond achieves the required 0.09 acre-feet of storage at water surface elevation 4929.49.
Thus, we conclude that Detention Pond 3 will perform adequately with. the design intent. It is noted
that the emergency spillway for Pond 3 was constructed with its crest roughly 6" higher than design.
We have provided calculations showing that the 100-year emergency spill from the pond of 3.8 cfs will
still be adequately handled by the weir in its as -built condition.
Please see the attached as -built information for Ponds 1 - 3, and the attached grading and detail sheets
showing as -built information pertinent to Ponds 1— 3.
There are minor inconsistencies throughout the site; however, the performance of the drainage design,
in my opinion, will not be hindered. To the best of my knowledge the major drainage improvements
for Lemay Avenue Estates, are constructed in substantial compliance with the design intent of the
approved construction drawings. If you require additional information or analysis regarding this
project please contact me at 221-4158 ext.106.
Sincerely,
NO RN INEERING SERVICES, INC.
Aaron Cvar, P.E.
Senior Engineer
cc: Stan Everitt, Everitt Companies
FEB-12-2004 THU 08:37 AN FT COLLINS UTILITIES FAX NO, 9702216593
DRAINAGE CERTIFICATION FORM
Please fill out all applicable items in this certification form
for single family, multi` -family and commercial properties.
Write "OK" for items checked or actual number checked in field.
Use "N/A" for items that are not applicable to the property that
is being certified.
A. Drainage facilities certification
1. Pond Certification
-volume verification
a. topographic records and volume
b. cross -sections and spot elevations
-positive fall to pan
-side slopes
-invert elevation
-spillway elevation
-placement and size of riprap
-side slopes
-grading
-orifice plate installation and size
-compaction of berm
-structural integrity of pond
2. Swales
O
S
-location (are they within easement) 0k-
-dimensions and cross-section verification Olr-
-longitudinal slopes and side slopes
-spot elevations ok�_
P, 03
hEH-12-'LUU4 1HU U8:31 AM HT UULLINS UTILITIES
FAX N0, 9702216593
P. 04
-permanent erosion control measures
(drop structures, riprap, etc....)
.-tie-in to pipes, pans, curbs, etc....
-weir size (elevations, size, opening, etc...)
-available freeboard
-landscaping infringement on swales
3. Pipes
-size and type
-slopes (as -built and comparison to minimum
0.4% slope)
-pipe capacity calculations if slopes are
significantly altered
-invert elevations
-installation and backfill material
-cover
-encasement and clearance from other utility
lines close by
-joints
4. Concrete Pan Chance is
-size
-slope
-super elevation
-cross-section
-thickness
-elevations
41--
ok
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hL-6-12-2UA 'IHU U8:3l AN FT UULLINS UTILITIES
FAX NO, 9702216593
P. 05
s. inlets
size and type OA'
-size of opening (or name of standard used)
-grate elevation
-invert elevation
-box size •-��
6. Cross pa
-size
_ type
-grade
-elevation J= L<<
-cross-sectional depth _JJ�
-tie-in to curb and gutter Off'
7. Culverts
R=
-size
-type
-invert elevation
-headwalls
8. Underdrains
-size
-type
-cover
-backfill
-geotextiles
3
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FAX NO, 9702216593
P. 06
-cleanouts
9. Curb cuts
-size
-tie in to Swale, pipe, etc....
�Pt
H. Certification of Grade Elevations Adjacent to
Drainage Facilities:
-minimum opening elevations _=IA-
-top of foundation elevations.
-comparison to 100 year WSEL's _
(Freeboard requirements and floodplain issues)
c. certification of Erosion control Measures:
1. Permanent Measures:
-Permanent vegetation (6" bare spots and weeds
under control)
-riprap
-riprap bedding --0�1�-��
-drop sections '=
-sediment basins/water quality ponds
-netting mats/blankets
-mulching Al—
A
htd-l'-2UU4 'IHU U8:37 AM FT UULLINS UTILITIES
FAX N0, 9702216593
P, 07
2. Temporary Measures:
-mulching
-inlet filter installation
-check bale dams
-seeding and temporary vegetation
-silt fence
D. site cleanup After Construction
-construction clean up
-smoothing of ruts
-reseeding
Ts. Statement of Compliance
This certification is signed And stamped and by signing this
form the engineer(s) attests that to the best of his knowledge
the as -built conditions of the drainage facilities are as.
described in the above form and in the redlined plans enclosed.
Failure to properly disclose all known, information could
result in the rejection of this certification and prevent the
release of any stormwater utility holds on Building Permits
and/or Certificates of Occupancy.
F. Signature and Stamp by a Colorado Registered Profe'saional
8ngineer.
POND
#. Elev
Acea
FICummUVAv-90
CummlLCon_L"c
4934
1.6944
6.8275
6.7606
4933
1.5739
5.1934
5,1269
4932
1.4865
3.6632
3.5969
4931
1.4
2.2199
2.1538
4930
1.041
0.9994
0.9377
4929
0.0311
0
0
'#.Elev'x'CummlTAvCumConic
4923
0.9687
4.2085
4.1641
4922
0.8748
3.2868
3.2427
4921
0.7889
2.4549
2.4112
4920
0.7058
1.7075
1.6643
4919
0.6252
1.042
0.9992
4918
0.5284
0.4652
0.423
4917
0.2005
0.1007
0.0715
4916
0.0009
0
0
POND3
L# Elev
Affi-a= ,_
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L
ft
acft
4930
0.0841
0.128
0.1274
4929
0.0644
0.0537
0.0534
4928
0.0431
0
0
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Trapezoidal Weir Performance Curve: POND 303
Project: 110-004
Date: 6/28/05
By: ATC
Governing Equation:
The trapezoidal weir is a broad -crested weir governed by the following equation:
" where Q = discharge (cfs) (-0
• where C = weir coefficient 0 = Cw L + 0.8H tail H
whereL = crest length (ft) J
" where H = head on weir (ft)
where b = 1,5
For 4:1 side slopes, 0 = 151,9276' so that tan (02) = 4
Input Parameters:
Top of Weir Elevation (ft) 4931.04
Crest Elevation (ft): 4930.56
Length of Crest (ft): 9
Weir Coefficient: 2.60
Death vs. Flow:
Depth Above Crest (ft)
Elevation (ft)
Emergency Overflow Weir Discharge (cfs)
0.00
4930.56
0
0,10
493066
1
0.20
4930.76
2 _
0,30
4930.86
4
0.40
4930.96
7
0.50
4931.06
10 WSS�
0,60
4931,16
13 h6
0.70
4931.26
17 �t�SJL !tst
0.80
4931,36
22
0.90
4931,46
26
1.00
4931.56
32
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