HomeMy WebLinkAboutNEENAN OFFICE BUILDING - RC SITE PLAN REVIEW & MINOR SUBDIVISION - 5-96 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTV. CONCLUSIONS
The drainage concepts for this project are consistent with current policies and practices for storm
drainage management. The building elevation was set to 1.5' above the 100 year flood elevation
and the parking lot primarily kept to no more 1.0' below the 100 year flood elevation. Due to the
location of this site in the floodplain no storm water detention is planned other than that shown in
Tract B.
IV. DRAINAGE FACILITY DESIGN
The developed conditions are shown on the "Grading Plan" located in the ma p g p pocket at the
I end of this report. Basin A includes the portion of Lot 1 that will drain to the east side of the
parking lot and empty into Tract A through a 2 foot curb opening. Basin B includes the
remaining portion of Lot 1 and the portion of Lot 2 that directly west of Lot 1 that will be
improved. Drainage from Basin B Will empty into tract A by the service area at the north side of
Lots 1 and 2 through a 2 foot curb opening. Basin C includes Tract B, the portion of Lot 2 that
will be improved and drain east, and offsite areas including the north side of Prospect Road from
the bridge over the Poudre River to Sharp Point Drive and the east side of the proposed private
drive. Drainage will enter Tract B though a 2 foot curb opening. Tract B will remain as a natural
depression, where storm water will now pond to a an elevation of 4896.5 and will overflow
I through a drainage swale to be constructed along with the future parking lot on the south side of
the site. The natural pond capacity will be about 44,200 cubic feet. No other storm water
detention is planed for the site due to the proximity and location in the floodplain. Basin D will
' includes the undeveloped portion of Lot 2 and that portion of Tract A that will drain into the Old
Spring Creek. Basin E will remain undeveloped and consists of the area of Tract A that drains
directly to the Poudre River. Developed flow rates for the site are as follows: Q2D= 6.00 cfs;
[ QSD = 10.07 cfs; Q10D =12.59 cfs; Q100D = 20.03 cfs.
III. DRAINAGE DESIGN CRITERIA
The city of Fort Collins "Storm Drainage Criteria Manual" was used as a standard. This report
I was developed using the above referenced manual. The Hydraulic criteria used for this report was
based on the "Intensity - Duration - Frequency" curves for the City of Fort Collins. Using the
rational formula method for runoff calculations, flow rates for each basin were determined for the
2, 5, 10, and 100 year storms. Calculations are shown in Appendix A.
C
H. HISTORIC DRAINAGE
BASIN DESCRIPTION
Offsite drainage enters the site through the drainage channel on the west side of the property.
Approximately 90% of the site drains into the drainage channel that enters the Cache La Poudre
River. The remaining 10% of the runoff drains directly into the Cache La Poudre River. Ponding
of about 3 feet occurs in an area of about 0.25 Acres in the southwestern portion of the site.
Detailed calculations for historic runoff can be found in the Appendix. The historic flows are as
Mows: Q2 = 3.44 cfs; Q5 = 5.79 cfs; Qio = 7.52 cfs; Q100 = 11.58 cfs.
I. GENERAL LOCATION AND DESCRIPTION
LOCATION
The proposed Neenan Company Office Building I1 will occupy 3.47 acres (Lot 1) of an 11.31
Subdivision currently being proposed North of Prospect Road and West of the Cache La Poudre
River, in the City of Fort Collins, Colorado. The proposed subdivision is situated in the Southeast
1/4 of Section 17, Township 7N, Range 68W of the 6th P.M. Larimer County, Colorado. The
site's general location is shown on the enclosed map located at the end of this report in the map
pocket.
TOPOGRAPHY
Existing improvements on the site include A 10' concrete path along the eastern side of the
property and the west bank of the Cache La Poudre River. The Old Spring Creek drainage
channel enters the site on the west side and passes through two 12" PVC pipes, below the
concrete path, before emptying into the Cache La Poudre River. The Cache La Poudre River
flows south along the eastern side of the property. The site is located with the floodplain. Trees
and tall grasses are scattered throughout the site. Slopes range from 0.50% to Steep banks along
the drainage channel.
"I hereby certify that this report (plan) for the drainage design of The Neenan
Company Office Building H was prepared by me (or under my direct supervision) in
accordance with the provisions of The City of Fort Collins Storm Drainage Design
Criteria and Construction Standards for the owners thereof'
Registered Professional Engineer
State of Colorado No. 16726
(Seal)
TABLE OF CONTENTS
Certification
I. General Location and Description
H. Historic Drainage
III. Drainage Design Criteria
IV. Drainage Facility Design
V. Conclusion
Appendix A - Drainage Calculations
Map Pocket
FINAL DRAINAGE REPORT AND EROSION CONTROL PLAN
THE NEENAN COMPANY OFFICE BUILDING II
FORT COLLINS, COLORADO 80522
Prepared for:
THE NEENAN COMPANY
2290 EAST PROSPECT ROAD
FORT COLLINS, COLORADO 80522
(397)493-8747
Prepared by:
PARK ENGINEERING CONSULTANTS
1240 MAIN STREET
LONGMONT, COLORADO 80501
(303) 651-6626
FEBRUARY 20, 1995
PEC Job #10736002.DOC
FM
PARK ENGINEERING
CONSULTANTS
FINAL DRAINAGE REPORT AND EROSION CONTROL PLAN
THE NEENAN COMPANY OFFICE BUILDING H
FORT COLLINS, COLORADO 80522
1240 Main Street Longmont, CO 80501 (303) 651-6626 FAX (303) 651-0331