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HomeMy WebLinkAboutDrainage Reports - 01/29/19991 1 1 1 1 Final A oved Report Dad jhy 99 DRAINAGE AND EROSION CONTROL REPORT FOR 401 WEST MOUNTAIN AVENUE LOCATED IN THE OLD TOWN DRAINAGE BASIN PREPARED FOR VAUGHT-FRYE ARCHITECTS PREPARED FEBRUARY 4, 1999 PREPARED BY STEWART & ASSOCIATES 103 SOUTH MELDRUM STREET FORT COLLINS, COLORADO 80522 TEL: 970-482-9331 FAX: 970-482-9382 0 i I h 1 1 t 1 STEWART&ASSOCIATES Consulting Engineers and Surveyors February 4, 1999 Mr. Basil Hamdan Storm Water Utility City of Fort Collins P.O. Box 580 Fort Collins, CO 80522-0580 Dear Basil, We have prepared the following drainage and erosion control report for the proposed construction on a site in the Old Town Drainage Basin located at 401 West Mountain Avenue. This site consists of 9750 square feet and was originally a Sinclair gas station, but for the past 20 or more years it has been used as an auto repair shop. The site has historically been 100 percent hard surface, therefore, we do not propose any detention on the site. The proposed construction on the site will not increase the runoff or change the existing drainage patterns so there will be no adverse affect on downstream properties. ' The site is within the Old Town Basin, but it is not within a designated 100 year flood plain. ' The proposed site will be 94 percent hard surface, and there will be some additional landscaping in the streetscape over that which now exists. ' This report complies with the City of Fort Collins Storm Drainage and Erosion Control criteria. There have been no water quality measures proposed, because the runoff from the proposed site will have less pollutants than that from the existing site which has historically had a large amount of auto traffic as a gas station and as an auto repair site. We hereby request a variance from the requirement for Water Quality Measures, as required by the Land Use Code. Sincerely, 4502 Phillip I. kobinson, P.E. & L.S. 'Jot g�F ' meh + IV W"go�aA' laumaf`� 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 1 1 1 t L TABLE OF CONTENTS 1 Vicinity Map 2-3 Text of Report 4 Map of Storm Drains in the Area 5 Map of Old Town Basin 6 Calculation of Site Runoff Pocket Drainage Plan r I I I k p VICINITY MAP SCALE — 1"=1000' Chevy Street P 0 jQ 4��o l s Map Stree r v g `a La P e Avon je O�Z1 SITE Mouni 7in Aven ee r o Oak Street H O H h Olive Street c O U c o 3 e t Magno 6 Street c U M /berry 5 treet � r � �pp E P H of of N to Myrtle Street a' c E 3 a `3 Laura Street MEN I z 1 EXISTING SITE CONDITIONS The 401 West Mountain site is located at the southwest comer of West Mountain Avenue and 1 South Meldrum Street. The site is the North 1/2 of Lot 7 and all of Lot 8 in Block 81, EXCEPT the West 60.00 feet thereof The site is 130.00 feet east and west along Mountain Ave. and 75.00 feet 1 north and south along Meldrum Street, and has a net area of 9750 square feet or 0.2238 acres. The existing site is 100 percent impervious, consisting of a service station building and asphalt and concrete pavement. 1 There is an existing storm drain running to the north in Meldrum Street, and there are two existing catch basins at the southwest corker of Mountain Avenue and Meldrum Street. The existing drainage patterns on the site are to the north and east, to Mountain Avenue and ' Meldrum Street. 1 OFFSITE DRAINAGE At the present time, there are no offsite flows onto the site. There is an existing block 1 retaining wall along the south and west sides of the site which has historically blocked all runoff from the south or west. This block wall is in poor condition and would have to be rebuilt, so it has been decided that to provide a more pleasing landscape, portions of the wall will be removed and a sloped 1 landscape area will be installed between the existing grades at the southwesterly sides of the site and the new parking lot curb on the 401 site. The property to the south has roof downspouts on the west side of the building and the 1 parking lot to the west of the building drains west to the alley. This parking lot pavement is fairly flat and has some low spots, but the overall drainage pattern is to the south and west, and away from the 401 site. Some amount of runoff from the existing roof downspout located at the northwest comer of the building to the south apparently does drain towards the 401 site. At the present, this runoff 1 is stopped by the existing block retaining wall. The new retaining wall, which will be constructed approximately 3 feet north of the existing block wall, will have a lip extended above the ground to 1 stop any offsite flows. A perforated pipe will be placed along behind the new retaining wall to intercept and carry away any water which percolates down behind the wall. The outfall for this pipe will be onto the parking lot and then to Mountain Avenue. 1 417 West Mountain Avenue, which is the property located to the west of the site has a roof downspout on the east side of the building. The runoff from this downspout drains into a rock 1 mulched landscape area between the 417 building and the block wall This rocked area is about 10 inches below the wall so the water build up would drain south before overtopping the wall, but probably the water is just retained west ofthe block wall. By removing the wall barrier, we will allow 1 whatever portion of the runoff which percolates through the rock mulch to drain down the slope onto the 401 site and out to Mountain Avenue through the parking lot. 1 PROPOSED DEVELOPED CONDITIONS The development at 401 West Mountain Avenue will include a building on the east 6000 1 square feet of the site and a paved parking lot with a landscaped strip on the west 3750 square feet ofthe site. The nmofffrom the east 3000 square feet of the building will be carried through interior roof drains and a pipe in Meldrum Street to the existing storm drain system in Meldrum Street. This 1 I 3 ' roof drain will be tied into the back of the existing catch basin on Meldrum Street. Runoff from the west 3000 square feet of the building will also be carried through interior roof drains to a pipe in ' Mountain Avenue which will be tied into the back of the existing catch basin on Mountain Avenue. The parking lot located on the west 3750 square feet of the site will drain on the surface, through the driveway, to Mountain Avenue. This is approximately the same drainage pattern, with the same flow ' quantities, that has happened historically. The flow quantities from the east and west portions of the site are shown on the calculation sheets included in this report. ' The two existing catch basins at the southwest comer of the Mountain and Meldrum intersection will be maintained in their existing locations, except that the grate on the Mountain ' Avenue catch basin shall be repaired. EROSION CONTROL ' This site is small with restricted room for construction, so the use of silt fences or straw bales is not practical. Demolition of the existing building and of pavement on the east portion of the site will be required prior to construction of the new building foundation and basement. The existing ' pavement on the west portion of the lot and the existing sidewalks and curbs on Mountain Avenue and Meldrum Street should be maintained in place until the foundation and exterior building work is completed, so that there is not bare soil in the streets. Also the existing walks should provide a good platform for equipment and scaffolding during the building construction. Gravel filters should be placed around the two existing catch basins on Mountain and Meldrum. All excavated material should be hauled away immediately and not stockpiled on the site. Wind erosion is not a factor on this site due to its small size and the surrounding structures. The erosion control collateral for this project will be the minimum $1,000.00. t 1 [_1 1 1 LAPORTE AVENUE 7H-w-1lo TH-M•111 7H-M-1 - 7 7H-I-140 H-I-148 1h 7H-I-143 '� n va4lN I 423 419 1451 405 [ n a.a. w w sasiL_-- Ii wla Ci � lv 4• 408 g n.rol CD ReaO u..ar = r OOFO10 a.aPl O 1 N u lvv � a.a CD Ol.al G OIO i Y v OX c N.m rw »a• .wl s4.ar G •412 1408' 402 430 424 420 10 14 la I. e ST n 0 "J G C.D.( iu)n.oa m CC $I e 1 l 4/ '• n ] i 1 1___iI41 — 1 C Q if.i I]' _- 32B I J16 ' •v S.� a.w [� e201 _ v 1e a ON 1 � w a.cn n a 3 JI aav s' 6 !1 a YY N J! a m i Jl oLGV Lwu A -' aNa n 2 6 22 2 6 1 [ IIO k116 I-122 Ir18 y M-107 WEST MOUNTAIN AVENUE M-10e _ V. - I . 1-117 - I -le Y•I — r 1 401 4311 142314i1149 [417 a 9 W 9{m i ::::' W N B/ o C 1 i I SVGS. (D 1 1242B1424 BLOG GI voI 1420 1416 ]CONDO O •1 f. _ I w W 2 + /O/ ' `LAR/MER. i :.� COUNTY ' COURTHOUSE mo 114 it-103 WEST OAK OAK 1-IzeE M-loe .. ' STREET... ,.•" . I-121 I-Ize'. i •'1-36 !09 Q i wl n (I)SAVINGS p p BLO B 9/ O " p CONOD p ® O12 O 1 • i431'4271423 4193 411 1 .yp. a O 31! 1-129 ,ai 1 1191_____11 a © % I-I31 N 1-13 � Gf i S m-- O C ar ' m _a_c.--y_ r . O.. Q2 O Ix " e O 1 92 ^ W -------- -- U) O N N (aw ON N N ��U M1ti ` �p ^ _ rva.m N M N.PI • N. N Aga �, r N irli --- N M N ] 42B ! 424 R 41B 412 G 404 r I N I ^ 320 316 1 N 011 I M I :. 203 `;j 1 11 i p I � 2 Jzz; 1 aI I p .1 r.as i ra4 cs� _ i o I /02 O 200 I-221 I.33 WEST M-2u OLIVE Iw=zl3 STREET as T.• 1, `. n Y i., \♦ 4 ,��' n [ O i O 41 N.oa y, � II.00 Op i 2G eG o F IQ�� O 11 211 ii u.aJ I II ll•p4� 1f.00I _ O No Text I 1 1 1 1 1 i 1 1 I STEWART$,ASSOCIATES Consulting Engineers and Surveyors 103 S. MELDRUM, FORT COLLINS, CO 80521 PH. 482-9331 FAX 482-9382 By: �EJ 1Z Date: -6 I2� I Ye Client: llav-r� rYP Sheet No. G of Project: 4—o ! l ✓. �AA O vn �a 101 Subject: S fa r" w, oLi-e- J- r::�u n o 7 T Arec�(=�I4Zs.O�StF�=LO._2-23 c G_!n_ 2P e(oP ed. 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It most Per /I coed iffi P -�rny y3mvj IMpvrlo ;,Af ersandrut lfb hro I)1H0 rated, ae 9 al 1 eW°+W fl9e ,ik a -�e 9a a f e oto WA lue City O/ Fort Collins, Colorado U77LRY PLAN APPROVAL APPROVED. z-l-r� Pn.fi dEq ,, 1-7 Dole CHECKED BY,. NA CHECKED BY: m,za IG ,l s olm.olN u6xh mI. CHECKED By, rom s B«I.miM LNI. CHECKED BY,. LbN CHECKED BY. aa). 0 2 •� U Y 2 p � Q d J z o C 2 � oa J O w 999 4 O d V31 3 Q Z Q 'UI z ac WUBER CATE IT6199 SHEET NUMBER 6 a` 7 a