HomeMy WebLinkAboutLot Certifications - 08/16/1996 STORMWATER
RECEIVED
0MAUG 14 1996 August 13, 1996
�
Mr. Basil Hamden � �
Stormwater Utility
City of Fort Collins Old
235 Mathews
P.O. Box 580
Fort Collins, Colorado 80522-0580
Re: Drainage Certificate for 1906 Canopy Court for issuance of C.O.
Ian low SP(Ar'%3
Dear Basil:
We have recently surveyed the existing condition of the storm drainage facilities in and adjacent to
1906 Canopy Court (lot 59, Willow Springs Phase One) for certification to allow the issuance of
the Certificate of Occupancy. We found the 10' curb inlet to be per plan and in working order.
This inlet drains into storm sewer line ST-2B which was designed as a 15" line at 4.58%. We as-
built this 15" line at 4.75%. We found manhole 2E at the terminus of this line to be in working
order with a grated cover to catch surface flow.
The swale between lot 59 and lot 60 was designed as 0.7' deep with a"V" shape and top width of
8.5'. The slope was designed as 7.5% using front of lot and rear of lot elevations. This lot
however, was intended to be, and is, a walk out lot. We therefore have a gradual grade front and
back with 6' of drop along side the house. We have asbuilt this swale and shot relevant
elevations on the house. We used a relative bench mark of 100.00 at top back of sidewalk. I
have attached hereto a drawing depicting our findings. I have also included a Xerox of the
grading plan and an analysis of normal depth in the channel.
As you can see, the channel has very little grade for the first 50' (1.42%). This area requires 1.62
feet of depth at 0+25 and 1.94 feet at 0+50. We currently have 1.48' and 1.93' respectively. The
grade from the top of bank continues up from the top of channel to the structure and therefore the
0.01' to 0.14' of depth above the channel is still confined between the houses. You may also
notice that the channel is only 3' wide from flow line on lot 60. This lot is currently under
construction and final lot grading is not complete. I would expect this slope to be laid back at
final grading thus increasing the capacity and lowering normal depth of flow. The channel in the
back yard is approximately 0.3' deep and our calculations show a normal depth of 0.47', The
grade of the yard, away from the house and toward the open space, will assure sheet flow into the
open space and towards the detention pond.
TST INC. 748 Whalers Way—Building D 102 Inverness Terrace East
Fort Collins,CO 80525 Suite 105
Consulting Engineers (970)226-0557 Englewood,Co 80112
Metro Denver(303)595-9103 (303)792-0557
Fax(970)226-0204 Fax(303)792-9489
TST, INC.
Though this existing situation does not conform to the original design, I believe that the storm
drainage facilities are in fact adequate to assure proper drainage.
Please feel free to contact me if you should have any questions or concerns.
Respectfully,
TST. INC. CONSULTING ENGINEERS
Steve F. Humann, P.E.
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Path: C:\UTILS
File: WS_L59 1 , 823 .a. . 8-13-96 11 : 40 : 56 am Page 1
WILLOW SPRINGS --- LOT 59 OVERFLOW SWALE
INPUT DATA: V oZ>
DISCHARGE = 10 . 000000 CFS
BOTTOM WIDTH = 0 . 000000E+00 FT
BED SLOPE = 1 . 600000E-03 FT/FT
SIDE SLOPE = 4 . 500000
MANNINGS N = 6 . 000000E-02
RESULTS: 1
NORMAL DEPTH = 1 . 619770 FT �Auo✓. = U• rf• t CNo)
FLOW VELOCITY = 8 . 470984E-01 FPS
HYDR. DEPTH = 8 . 097861E-01 FT
TOP WIDTH = 14 . 577930 FT
FROUDE NUMBER = 1 . 658902E-01
SPECIFIC ENERGY= 1 . 630913 FT
INPUT DATA: 0 + J V
DISCHARGE = 10. 000000 CFS
BOTTOM WIDTH = 0 . 000000E+00 FT
BED SLOPE = 1 . 200000E-03 FT/FT
SIDE SLOPE = 3 . 250000
MANNINGS N = 6 . 000000E-02
RESULTS:
NORMAL DEPTH = 1 . 941643 FT A lto�. j• ¢¢{�Cti�
FLOW VELOCITY = 8 . 162306E-01 FPS
HYDR. DEPTH = 9 . 707432E-01 FT
TOP WIDTH = 12.620680 FT
FROUDE NUMBER = 1 . 459932E-01
SPECIFIC ENERGY= 1 .951988 FT
INPUT DATA:
DISCHARGE = 10.000000 CFS
BOTTOM WIDTH = 0 . 000000E+00 FT
BED SLOPE = 8.000000E-02 FT/FT
SIDE SLOPE = 16 . 750000
MANNINGS N = 6 . 000000E-02
Path: C:\UTILS
File: WS_L59 1 , 823 .a. . 8-13-96 11 : 40 : 56 am Page 2
RESULTS:
NORMAL DEPTH = 4 .725019E-01 FT AICow, d. 3 o Ft ��✓)
FLOW VELOCITY = 2 . 673518 FPS
HYDR. DEPTH = 2 . 363026E-01 FT
TOP WIDTH = 15.828810 FT
FROUDE NUMBER = 9 .692168E-01
SPECIFIC ENERGY= 5. 834910E-01 FT