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HomeMy WebLinkAboutDrainage Reports - 03/06/2015I I I I 7 I BA This Drainage Report is consciously provided as a PDF. Please consider the environment before printing this document in Its entirety. When a hard copy is absolutely necessary, we recommend double -sided printing. February 27, 2015 9 City of ft. t ._ Colli wrov PI ns Approved 'By Date— ;�lk f ii FINAL DRAINAGE LETTER FOR MUSIC DISTRICT Fort Collins, Colorado Prepared for: City of Fort Collins Prepared by: ■� I NORTHERN ENGINEERING 301 N. Howes Street, Suite 100 Fort Collins, Colorado 80521 Phone: 970.221.4158 Fax: 970.221.4159 www. northremengneerin8.conn Project Number: 1052-002 NorthernEnaineerina.com 11 970.221.4158 I ' I NORTHERN ENGINEERING ' February 27, 2015 Wes Lamarque City of Fort Collins Stormwater Utility 700 Wood Street Fort Collins, Colorado 80524 RE: The Music District, Drainage Analysis Fort Collins, Colorado Dear Wes: ' The site improvements for The Music District consist of renovating three existing buildings (633/639 S. College Ave., 633 1/z S. College Ave., and 621 S. College Ave.), removal of a fourth building (627 S. College Ave.), and improvements to the surrounding parking lots and landscaped areas. Due to the location of the buildings, the site was divided into three drainage basins: 1. Basin 1: The front yard of 621 S. College Ave. ' 2. Basin 2: The parking lots and landscaping between 621 S. College Ave. and 633/639 S. College Ave. This basin also includes the parking lot behind 633/639 S. College Ave. 3. Basin 3: The front yard and south side of 633/639 S. College Ave. ' Basin 1: .1 I The existing and proposed drainage patterns for Basin 1 remain unchanged and sheet flow east towards the curb and gutter along College Avenue. The proposed minor sidewalk and landscaping improvements to Basin 1 maintain the existing drainage patterns. However, the proposed improvements in adjacent drainage Basin 2 results in a decrease in area and flowrate for Basin 1 (see Table 1). The proposed 100-Year Storm Event for Basin 1 is 0.27 cfs (see Table 1). Basin 2: Table 1: Basin 1 Draina a Characteristics Existing Proposed Basin Area (sq. ft.) 3,680 2,288 Impervious Area (sq. ft.) 1,853 776 Percent Impervious 50.3% 33.9% 10-Year Flowrate (cfs) 0.16 0.09 100-Year Flowrate (cfs) 0.42 0.27 The existing drainage pattern for Basin 2 sheet flows across the rear parking lot towards the east; along the existing driveway between 627 S. College Ave. and 633/639 S. College Ave.; and into the curb and gutter along College Avenue. The proposed drainage patterns will remain unchanged and sheet flow across the rear ' parking lot, along the existing driveway, and into a proposed rain garden (water quality pond). A proposed 0.5-ft deep rain garden (water quality pond) at Design Point 2 will intercept the proposed drainage to provide water quality treatment/extended detention prior to exiting the site. ' 301 N. Howes Street, Suite 100, Fort Collins, CO 80521 I 970.221.4158 I www.northernengineering.com r] 1 1 1 1 1 1 NORTHERN ENGINEERING Within Basin 2, the developer proposes to replace the existing parking lot surfaces and landscaping, remove 627 S. College Ave., and renovate 633/639 S: College Ave. The proposed improvements will result in a minor increase in the basin's flowrate (see Table 2). The proposed 100-Year Storm Event for Basin 2 is 5.03 cfs (see Table 2). The aforementioned rain garden (water quality pond) provides water quality treatment/extended detention which is an improvement from existing conditions. Table 2: Basin 2 Drainage Characteristics Existing I Proposed Basin Area (sq. ft.) 24,440 33,128 Impervious Area (sq. ft.) 23,375 29,021 Percent Impervious 95.6% 87.6% 10-Year Flowrate (cfs) 2.03 2.24 100-Year Flowrate (cfs) 4.39 5.03 Basin 3: The existing drainage pattern for the north three-quarters (east side of existing building) of Basin 3 sheet flows east towards the curb and gutter along College Avenue. The proposed drainage pattern for the north three- quarters (east side of existing building) of Basin 3 will remain unchanged and sheet flow across proposed landscaping and into the curb and gutter along College Avenue. The existing drainage pattern for the south one -quarter (south side of existing building) of Basin 3 flows towards an existing drainage swale along the south side of the existing building. The existing drainage swale discharges across the sidewalk and into the curb and gutter along College Avenue. The proposed drainage pattern for the south one -quarter (south side of existing building) of Basin 3 will remain unchanged. A 1 proposed 0.5-ft deep rain garden (water quality pond) at Design Point 3 will intercept proposed drainage to provide water quality treatment/extended detention prior to exiting the site. 1 Proposed improvements in adjacent drainage Basin 2 results in a decrease in area and flowrate for Basin 3. The drainage area for the south one -quarter (south of existing building) Basin 3 will decrease by 8,098 W. The proposed 100-Year Storm Event for the entire Basin 3 is 1.32 cfs (see Table 3). The aforementioned rain garden (water quality pond) provides water quality treatment/extended detention which is an improvement from existing conditions. Table 3: Basin 3 Drainage Characteristics Existing Proposed Basin Area (sq. ft.) 19,107 11,016 Impervious Area (sq. ft.) 14,440 6,342 Percent Impervious 75.6% 57.6% 10-Year Flowrate (cfs) 0.99 0.51 100-Year Flowrate (cfs) 2.31 1.32 1 1 301 N. Howes Street, Suite 100, Fort Collins, CO 80521 1 970.221.4158 1 www.northernengineering.com I NORTHERN ENGINEERING ITotal Impervious Area: Table 4: Total Impervious Area Existing Proposed Basin 1 (sq. ft.) 1,853 776 Basin 2 (sq. ft.) 23,375 29,021 Basin 3 (sq. ft.) 14,440 6,342 Total Impv. Area (sq. ft.) 39,667 36,139 For the entire project, there is a net decrease 3,528 SF of impermeable area (see Table 4). City of Fort' Collins Stormwater Requirements does not apply since the change in impermeable area is less than the allowable increase of 350 SF. Minor storm water quality treatment/extended detention will be provided within a total of 595 SF of proposed rain gardens/water quality ponds. Impacts to Adjacent Streets and. Properties: The stormwater impact on the adjacent streets and properties from this project is negligible. The increase in the area for Basin 2 is a result from decreasing the areas in Basins 1 and 3. The existing and proposed drainage outfall locations for Basins 1, 2, and 3 continue to drain east towards College Avenue. The reduction of impervious area throughout the project reduces the overall flow rate on College Avenue by 0.5 cfs (see Table 5), and the proposed rain gardens/water quality ponds will provide water quality treatment within Basins 2 and 3. Table 5: Total 100-Year Flow Rate Existing Proposed Basin 1 (cfs) 0.42 0.27 Basin 2 (cfs) 4.39 5.03 Basin 3 (cfs) 2.31 1.32 Total 100-Year Flow Rate on College Avenue 7.12 6.62 If you should have any questions or comments, please feel free to contact me at your convenience. Sincerely, NORTHERN ENGINEERING SERVICES, INC. ' Frederick S. 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S } �. .• - • - . • / \\ / PROPOSED PAVERS (RE LANDSCAPE ARCMIELn P N . .. • w Y . •• ° i I ' — PROPOSED CprtWRS I • I• • \ " • � � �" � Ir , METRO TREE O • l '�' • • • / . ""No DONNSPWn _ • • V 633 1/2 SOUTH / ' "ON POINT Q Efi I, •,�' „ /' .• i COLLEGE AVENUE // FLOW ARBOR � 4110111111 aA Ik y/ EK FFa AeB]BB _A ;' ••' • � • I IRO ■ DR4NAQ BASIN LABEL vl / •i ' DRAINAGE BASIN BWNDARY ee■ ee- NEW ee- eer g 5• 'S ., I'' - ✓, , /a „ I ,' Ili ,• ,- r • • / - I �/y�•� PERMANENT 8MP'S W4 , .. W� •' .. • I W4 • • — _ ' { CONCRETE FORMAT FB Z Z - - i` .i . .II R - • .. , I - . _ _ - - - ' PROPOSED POROUS RG w Er R AN • , I * I♦ E • • L ,{ , :' , ■ LDSCAPE OERIYIIdI T W i0 yW '• T/ I .• ' � i •'/• A � -• . ■ I ' TEMPORARY BMPS � Z ■ ' 1 PnaFneDNmncAL \ `;/1! ■ ,^_ c CONTROL PAD DeVEHICLE nACNw OF VTC O ya f W VYYER - - A ° ■ n SILT FENCE O RS ° RueEDcwma FANcew. ■ ° ° eW:LANoeGIW ARtlf1ECT ♦ C1 ■ ■� 11 ■ ■ ■ ■ ■ min ■ ■ ■ ■ ■ ■ ■ to ■ wATitF LLNIB INLET PWOIECTpI W3 i - i IN 0 • p� Im WATTLE (CLMBSIO[ O#CN OAYJ O €� l-.I� � RD i' • ' I • - • . . ° ' . o ��_ _—ice Y� / , ,(, : II. . •# • •• 1\ ' CONCRETE WASHWT AREA CWA 5f 633/639 SOUTH O 1 I\, I. '. �. •' ;■ ROCK SOCK •\ COLLEGE AVENUE -_-� - „ Y • ' - ; - , I RS Ex FF-500001 \. •EJ O• /r. i ■ ' 1 n f , sfoeWNr TRAP n • / �• \ '1 • 1 I_ , NOTE: m • / N /• , • ' • O ■ SOUTH ALL BMP'8 N AR SNONM ON THIS PLAN! GRAPHIC REPRESENTATIONS ONLY. FINAL DETERMINATION OF SIZE S 621 W�W'g eeT�bb g i ELsnNG PRLPERTr uNE •` ■ AND LOCATION SHALL BE DETERMINED BY THE CONTRACTOR O^' A• �• Ng, \"• ••; _ COLLEGE AVENUE E. Ex FF=ABBRR2 FIELD SURVEY BY: _ NNLNOFED caNGETE pNEyYIYE RT.VLI - r \ •/ t-.-- -- •• -� • Nr�l E \ ! . \ • ti .I •;, 1 • • \ ■ NORTHERN ENGINEEPoNG SER•A(SS, INC. PRO.IECT NUMBER: 10E2-001 YYO A •l q ..• i � OATf.: sEPTEYBER tOtA \ i •e %= _ • •\ : • FB f ■ , NOTES: FB , - -. I W3 ': PKV. 09[OOWCIWIE i " + ,, ■ .+D. L. �E MUSIC DI TRIG DAM 0 DECEµY I:. �=4 BYOP • / •POMJEAV IEEE DETAIN i •i I / ■ ■ NORTHERNOMOLDERING SERNCES. INC FOR MgRONAL ` I / I , 1- '\ • • ) • 'I // // ♦ I •' L e !. 2 =NTRACTIT:IIS WTH UTHEW \ - - L e , y' I' • . \, f •� : 7 j, ■ ■ ■ * INPIO.TNC ADJAACEENNTT'NATE PRCPERTES PNOP TY COMERS PRIOR TO BEGINNING ANY • , I 1 CONSLRUCTW 11[MB I INSNRBED AREAS SHALL SE REVEGETAIFD PDt 3 T • 1 ♦ / / ME APPROVED LANDSCAPE PLANS SEE /' • ' ! 1 I \ SHEET COOI - GENERAL 8 CONSTIUCT011 NOTES - FOR CONTROL \ I , AWITONAL EROSION NOTES, mNolEn'OIMeE WIm AETAL •, � I ' / RG O,OFJ RG __ —/ �' /,, ' ' ,• OC. GLLIf11Ll [N of TY NOTIFICATION ' ST ' Y •�_ .------�__�_ _� _„—J e o o0 0o Z .•• '• , vIERNO RIOInoF+wr 'N C811 De1m you DW. WIFFEnN •■ •/`-----� Co ns, Colorado ■ ■ ■ i ■ ■ ■ ■ ■ ■ ■ ■ • ■ ■ ■ RS UTILITY APPROVAL \ ! M ! s eF eF— ■ i ■ SF y/ ._--- _ --------------- --� ■ S- O TA (!C1tLEGE AIENL A N ° SF APPROVED' CHECKED BY: Water A, Wastaxeter UUtty Di c— CHECKED BY: Sheel CHECKED BY: rmxe er y --Due Of B Sheets