HomeMy WebLinkAboutDrainage Reports - 05/04/19971
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Final
STORM
DELLENBACH CHE
A PART OF LOT _ ,
LOCATED IN THE FOOTHHJ S DRAINAGE BASIN
MARCH 3191997
PREPARED BY
STEWART & ASSOCIATES, INC.
103 SOUTH MELDRUM STREET
FORT COLLINS, COLORADO 80521
970/482-9331
I
' INDEX
'
1-2
Cover Letter and Text of Report
'
3
Vicinity Map
4
Aerial photo of site
'
5-8
Original Calculations for a Part of Lot 3 (including this site)
9
Foothills Basin Plan
'
10
Stonmwater Runoff Quantities
11
Detention Calculations
12
Detention Pond Outfall Sizing
13-15
Erosion Control Calculations
16
Erosion Control Collateral
'
Pocket
Utility, Grading & Drainage Plan
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STEWAU&ASSOCATES
Consulting Engineers and Surveyors
March 31, 1997
Mr. Basil HAmdan
'
Storm Water Utility
City ofFoit Collins
P.O. Box 580
'
Fort Collins, CO 80522
' Dear Basil,
' re: Storm drainage for Dellenbach Chevrolet Auto Storage Lot at the southeast comer of
Swallow Road and McClelland Drive.
This site is part of Lot 3 of the Swallow Subdivision, which was platted in 1984. The site is
located in the Foothills Drainage Basin.
The east part of Lot 3 was developed several years ago. There are four office buildings and a
paved parking lot located immediately east of the Dellenbach site. There was a detention pond
constructed along with the four buildings and parking lot. This pond was designed to provide
' detention for the four office buildings and their associated parking lot, and also for the Dellenbach
site.
1
An "As Built" survey of the pond and adjacent office buildings shows that the top of the
berm around the pond is about 0.4 below the original proposed high water he elevation of
5029.1 and that the lowest floor of the adjacent building is at elevation 4929.5. If the top of the
berm were to be raised to provide the additional volume required by the Dellenbach site, the
freeboard between the high water line of 5029.1 and the lowest floor of 5029.5 would be only 0.4
foot. This is not acceptable per the city criteria.
Instead of trying to use the existing detention pond, we have decided to provide an additional
detention pond on the new site. This new on site pond will provide detention for the site as well
as for the east half of the adjacent McClelland Drive. Release from this new pond will be to the
south across the existing Dellenbach auto storage parking lot. There will be a paved hump
between the existing lotto the south and the proposed new lot, and the release from the new lot
will be piped through this hump. The paved hump provides the dike for the new detention pond,
and it will be constructed with a gentle enough grade so that it can be driven over to provide
vehicle access between the parking lots. Any overflow from the new pond will be to the south
over this hump.
James H. Stewart
and Associates, Inc.
103 S. Meldrum Street
P.O. Box 429
1 Ft. Collins, CO 80522
970/482-9331
Fax 970/482-9382 .
2
The overflow as well as the piped release of 0.25 cfs will drain south across the existing
Dellenbach parking lot. This surface drainage will be to the south through an existing swale in the
paved parking lot. At the south edge of the existing parking lot the drainage turns to the east
along the thalweg of the Foothills Basin. The flow along this thalweg drains east to the frontage
road along College Avenue and then enters a catch basin and a 48 inch diameter pipe to drain
under College Avenue. A copy of an aerial photo of this area is included in this report. The
drainage patterns are marked on this photo.
The runoff from the east half of McClelland Drive will be intercepted by a sidewalk culvert
and diverted into the new detention pond area.
The original detention calculations for the east part of Lot 3 of the Swallow Subdivision are
included in this report although they no longer apply'because of the proposed new detention pond
on the Dellenbach site. Calculations of the required detention volume, the release rate and the
detention volume provided on -site are included in this report.
t This site is located in a moderate wind and rainfall erodibility zone. The existing site has a
good vegetation cover, but most of the site will be disturbed when construction begins. The
parking lot will be graded and the curbs and base material will be installed as soon as possible.
' The asphalt will be laid when the plants open up in March or April 1997. A silt fence shall be
placed along the east property lime before grading begins and a gravel sediment trap shall be
placed over the pond outlet after the curb and outlet opening are installed.
Wind erosion control will be provided by the existing streets and structures around the site
since the site is only about 100 feet wide.
1 All calculations and procedures for drainage and erosion control on this Dellenbach site are in
compliance with City of Fort Collins Criteria.
' Sincerely, "„�e�.._
C
Phillip I. Robinson, P.E. & L. S. s S 4502
A
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STEWART&kSSOCIATES
Consulting Engineers and Surveyors
103 S. MELDRUM, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
By: p/m Date: 0!t ! Client: fle/1e,6,-A C/ie1171/ef Sheet No. LL of
Project:
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PH. 482-9 31 FAX 482-9380LLINS, CO 80521
Consulting Engineers and Surveyors
1 By: P/R Date: / 8 Client: Sheet No. � of
Project: Hy�rj Sfor- Lol a 4- S E con Sw it ow ¢ MSC/e/l��
1 Subject: Deien4ion -Tor 5,;4e- and ✓ojy,& oL on—.ri�e zond.
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STEWAIU&kSSOCIATES
Consulting Engineers and Surveyors
103 S. MELDRUM, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
By:
Date: /6—) q -7
Client:
6 o c
Sheet No. � of
Project: Ufa
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RAINFALL PERFORMANCE STANDARD EVALUATION
PROJECT: 4,)e11cn6ach
Aviv .54oro5e
Lot
STANDARD FORM A
COMPLETED BY:
DATE:
OEVELOPED�ERODIBILITY�
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)I/SF-A:1989
1.4-.
EFFECTIVENESS CALCULATIONS
PROJECT: S Oroje STANDARD FORM B
COMPLETED BY: DATE: Ole
Erosion Control C-Factor P-Factor
Method Value Value Comment
5r4re- Sail /. 0 a
GI-a✓el C3ase o. U S !. 0
Srlf Fence 1.0 0.5
MAJOR
PS
SUB
AREA
BASIN
($)
BASIN
(Ac)
CALCULATIONS
7&7AL
76.1 %,
0.556
Gra✓e( base 0-5/46
S17C
t3afC soil U. U5-6 RG
Cu.os) 4-(0, o C r )
0.5r6
tence
EFF= �1 — O.lSxo.S� -,,,too
MARCH 1991
DESIGN CRITERIA
SEQUENCE
10JECT: _DelleAbacA Car•-0-at-o% Lao STANDARD FORM C
�■■EQUENCE FOR 19 `I % ONLY COMPLETED BY: DATE: -�---
1Tldicate by use of 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
1proval by the City Engineer.
YEAR q!
MONTH
OVERLOT GRADING I
JND EROSION CONTROL
Soil Roughening
Perimeter Barrier
Additional Barriers
Vegetative Methods
Soil Sealant
' Other G�-a✓el
i NFALL EROSION CONTROL
STRUCTURAL:
Sediment Trap/Basin
Inlet Filters
Straw Barriers
Silt Fence Barriers
Sand Sage
'Bare Soil Preparation
Contour Furrows
Terracing
'Asphalt/Concrete Paving
Other Gra✓et
' VEGETATIVE:
Permanent Seed Planting
'Mulching/Sealant
Temporary Seed Planting
Sod installation
Nettings/Mate/Blankets
' Other
SIUCTURES: INSTALLED BY MAINTAINED BY
DIETATION/MULCHING CONTRACTOR
E SUBMITTED APPROVED BY CITY OF FORT COLLINS ON
1
MARCH 1991 8-16 DESIGN CRITERIA
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STEWARr& SSOC[ATES
Consulting Engineers and Surveyors
103 S. MELDRUM, FORT COLLINS, CO 80521
PH. 482-9331 FAX 482-9382
By: PIK Date: it i ?0 Client: De/IPnboc6 C6e✓ro/e4 Sheet No. Hof_
Project:_Ayfo _5-'oror&_ Lot of SF_ cor Swallow it/`Cle(lP��l
Subject: Err2.Sioh e-on�roCo(lafera/
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