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Home My WebLink About218 WEST MAGNOLIA STREET (EDWARDS RESIDENCE) - PDP - 27-99 - SUBMITTAL DOCUMENTS - ROUND 1 - DRAINAGE REPORTV) �L.q j OF ZO OF THE. F. J; .5PENc:ep SVRVEY OF LOT SVBGIvIS10N OF LOTS /¢� fS�Np NI BLOCK /031 CITYOF FO)ZT COLLIN5, COLVFcRDO I PRiv/-A7E , (P,9RT f oLOT 17 Nj 4-7.50 - ru `e 9 DW � nr z� z Nd LOT (�� 1 19 1 ZO `' � _WSST. S-DO I C Q N W i W C1 N W wQ 47.50 I 47,SU 47•SU h� a 7.50� W Q V1t 0 0 a� M �f Qa O y �d V- W V> .5r-ALE : /"=20I MAGNOLIA" STr7EET (100' rlw) `,`�..�.�NO! , CER"Tii=iGATE O� sumVFY �,.�.��e.•�sTE'� •y so. KtU• 77-71s is i-o ce4i;�o, H7c+ on Tune P 1473, the b0vmJor�/ corners oF- Lc4 2v" o� }he F J, spencer .5v Ivis►on of Lofs 14-1 15 a••d IG, :t: 4502 6: t31oc,K 103I Gibe of Fort G'ollins) Colorado, were, svrveyed _ under n y sl/ er- islo.?. IT Pfr�lliP 1 • Rob �r,son j RE. STEWAKT 4-r4SS9CIA 7ES :q: Table of Contents 1 and 2 Letter and narrative report 3 Vicinity Map 4 Map of lot showing easements 5 Runoff coefficients 6 Historic & developed runoff, release and orifice sizing. 7 Required detention and volume of proposed pond 8,9 & 10 Basin calculations and concentration points 11, 12 & 13 Concrete drain pan along west side of lot 14 Drain chase at southwest corner of lot 15 Effect of new building on 100 year WSEL 16 Letter from Bill Wyatt, owner of property to west 17 1978 Photo of site 18, 19 & 20 Tables and map from Old Town Basin Master Plan Pocket Drainage and Erosion Control Plan Ialley was vacated by a previously proposed development of the 218 W. Magnolia site. There is offsite runoff onto the site from the existing building and parking lot located just west of the site. This offsite runoff will be routed south to Magnolia Street in a concrete pan which will be constructed along the west line of the 218 W. Magnolia site. The west portion of the 218 W. Magnolia site will also drain off the roofs into this concrete pan. The east portion of the site will drain into the detention pond in the driveway along the east side of the site. The release from the detention ponding area will be through the curb which will be installed along the west side of the driveway. This release flow will be carried from the curb opening by a 4 inch diameter pipe which will be extended southerly through the curb to the north flow line of W. Magnolia Street. A restriction plate with an orifice opening will be placed over the entrance to the 4 inch diameter ' outflow pipe. 1 1 1 1 1 I r I Any overflow from this detention ponding area will be over the high spot in the driveway and into W. Magnolia Street. The concrete pan to be constructed along the west property line will be set low enough so that it does not block any flows from the property to the west, and some minor grading may be required on the easterly 2 or 3 feet of the property to the west. The owner of the property to the west is Bill Wyatt, and he gave a license to do work along his east boundary for the previously proposed project. This license from Mr. Wyatt will be updated for the currently proposed project. There are no practical ways to provide water quality measures for this site. The existing site has been used as a parking lot for the First National Bank for several years, and by eliminating the parking lot and constructing a residence with some landscaping, there will probably be a reduction in the oils, salts and other harmful particulates which were deposited on the site and then washed into the street gutters. A variance from the requirement for water quality measures is hereby requested for the 218 W. Magnolia site. A silt fence shall be installed along the south and east property line during the grading process. The minimum erosion control collateral of $1000 will apply on this project. Drainage calculation sheets are included in this report. A copy of the 1978 aerial photo showing the original residence and garage is also included in this report, along with tables and a flood plain map from the Old Town Master Drainage Plan. A copy of the Drainage and Erosion Control plan is included in the pocket of this report. This report was made in compliance with City of Fort Collins Criteria. Sincerely, Phillip I. obinson, P.E. & L.S.4502 PIR/meh_ i. A _ ..y I STEWARF&ASSOCIATES Consulting Engineers and Surveyors September 7, .1999 Mr. Basil Hamdan Storm Water Utility . City of Fort Collins P.O. Box 580 Fort Collins, CO 80522 Dear Basil, We have prepared a drainage study of the lot located at 218 West Magnolia Street. This is Lot 20 of the F. J. Spencer Subdivision of Lots 14, 15 and 16 in Block 103 of the City of Fort Collins. The lot is 47.50 feet wide and 138.00 feet deep and is located on the north side of Magnolia Street and on the west side of a 20 foot wide alley. This site is located in the Old Town Basin, and is located within the 100 year floodplain. The proposed new residence to be constructed on the lot will take the place of a residence and detached garage which were taken down a few years ago. This residence and detached garage are shown as existing on the aerial photo which was used to determine the floodplain in the Old Town Basin. the new structure will cause no more rise in the floodplain than was caused by the previous buildings. We have calculated the=rise in water surface elevation to be 0.03 feet, which is less than the allowable rise of 0.04 feet. Since the new building is located in the 100 year floodplain, no basement will be constructed. The base flood elevation at this site is 4993.4 and the proposed lowest floor elevation is 4997.90 for the residence and 4994.90 for the proposed garage floor. The existing site is a graveled parking lot which is used by the First National Bank. There is a 1978 aerial photo which shows the site with the original residence and detached garage. A site runoff coefficient of 0.5 is calculated using this original house and garage as hard surface, and that is equal to the existing graveled site runoff coefficient of 0.5. The Old Town Master Plan indicates 70 percent imperviousness for this developed site and the proposed new site is about 85 percent impervious. It is proposed to provide detention on the site for the additional amount of runoff generated by the increase in imperviousness. The amount of detention is calculated to be 365 cubic feet, and the proposed detention ponding area will be in the new concrete driveway which will be located on the vacated alley along the east side of the site. This James H. Stewart and Associates, Inc. 103 S. Meldrum Street P.O. Box 429 Ft. Collins, CO 80522 970/482-9331 Fax 970/482-9382 STORM DRAINAGE REPORT FOR 218 WEST MAGNOLIA STREET LOCATED IN THE OLD TOWN BASIN PREPARED FOR DAVID EDWARDS C/O VAUGHT-FRYE ARCHITECTS SEPTEMBER 7, 1999 PREPARED BY STEWART & ASSOCIATES, INC. 103 SOUTH MELDRUM STREET FORT COLLINS, COLORADO 80521 970/482-9331