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HomeMy WebLinkAboutDrainage Reports - 05/27/19901 Engineering Consultants 2900 South College Avenue Fort Collins, Colorado 80525 303/226-4955 May 7, 1990 ' Ms. Susan Hayes ' Stormwater Utility Dept. City of Fort Collins P.O. Box 580 Fort Collins, Co 80522 RE: .CITY SERVICE CENTER FINAL DRAINAGE REPORT ' Dear Susan: RBD Inc. is pleased to submit this letter as the Final Drainage Report for the City of Fort Collins Service Center. ' PROPOSED IMPROVEMENTS This City of Fort Collins project consists of a Building Addition to the current onsite facilities and the addition of more parking ' facilities. The Addition will be located between the two main buildings currently occupying the site, namely the Streets Department facility (Bldg. B) and the Water & Sewer Department and ' Light & Power Department facility (Bldg. A). Other proposed site improvements include additional parking facilities south of the present site, realignment of the main entrance to the facility and realignment and repavement of approximately 280 feet of Wood Street along the site's frontage. Wood Street improvements will also include the installation of curb and gutter along the east side of the improved street section. Although the entire 18.8 acre site is being platted for the P.U.D. process, site improvements will be limited to the western third of the site. EXISTING DRAINAGE CONDITIONS This site is located along the east side of north Wood Street at ' its intersection with West Vine St. The site is bounded by the Colorado & Southern Railroad right of way on the south, Wood Street on the west,. the Nauta property on the north and an unused street 1 Other Offices: Vail, Colorado 303/476-6340 • Colorado Springs, Colorado (719) 598-4107 I I 7 right of way and City owned property on the east. The City owned property on the east extends to the Poudre River. The vast majority of the site is paved parking and storage areas. Most of the site sheet flows to the east and north with a small area (Basin H5) draining to the northwest. Area inlets gather limited flows on site in various locations (See Overall Drainage and Utility Plan). These inlets are tied to various storm drain pipe systems which cross the site along six different alignments. Three of these systems outfall along the north property line into the Nauta property. The westernmost outlet flows directly into the Nauta pr_perty►�—slows from the two remaining outlets are intercepted in ,,eC 2e inch cla pipe and carried eastward to outfall into the City �owne operty just north of the northeast corner of this site. 'Ye The remaining storm drain pipe systems outfall to the east into the unused street right of way and City owned property to the north. All the site flows, with the exception of the first outlet 21 �� mentioned, eventually outfall into the City property north and east of this site. On this property they drain through a rather- UAAi ill-defined channe erect y to the Poudre River. EK 4/- P��/m•d� *117Offsite flows drain toward the site from the Vest and south. Flows 2 'from the west are intercepted by Wood Street. These flows drain to y the north and south from the high point of Wood Street which !- corresponds to its intersection with West Vine Street. Flows from the south are limited by the railroad embankme t and a 30 inch X 12 inch wooden culvert. PROPOSED DRAINAGE APPROACH,,gO�" No previous drainage analysis has been done in this area. On site drainage facilities appear to have been designed as interim solu- tions for drainage problems that may have been occurring at the time of their construction. Offsite issues particularly relating to the discharge of storm water flows onto adjacent properties have never been adequately addressed. Offsite areas draining toward the site are existing neighborhoods, therefore, the options for handling undetained flows in the area are extremely limited. Based on these observations the design approach taken for this site is based on the following assumptions: 1. The existing conditions on site and in the area surrounding the site are treated as the historic conditions. 2. Because o�_the site's proximity to the Poudre River no onsite detention will be required. ' 3. Analysis is limited A determining the effect of proposed improvements to existing drainage flows and the facilities tdownstream. 4. Offsite upstream drainage problems such as the impact of undetained flows ponding against the existing railroad ' embankment will not be addressed in this approach. _She proposed improvements will not -effect this area -expect to ' reduce some flows which may have been contributing to this area from historic basin H1. It is anticipated that this potential problem will be investigated in depth when the ' City or another developer chooses to develop the property to the south of the railroad. During investigation of the site, it was determined that the did ' Nauta's hf?ld water rights on drainage lines that lie within the City Service Center Property and that the City of Fort Collins was utilizing these lines as a part of their storm sewer system. This ' phase of the Service Center Improvements has focused on eliminating these tie-ins and further, to reduce off -site flows onto the Nauta Property. As such, any existing known tie-ins to the Nauta Drain /Z have been eliminated and transferred to storm drain lines A and C h [�' Storm drain line A is planned to service the p condition at e th sumu�.fitat new turnaround drive and a portion of the revised parking lot (Basin D2). A sump which drains under the building addition, three t safety features have been designed into the system. Concrete Q� encasement is required under the building, it has been designed to lei carry twice the 100 yr. event and 2 inlets have been incorporated as a backup. If for some reason though this system fails, an UW' outfall swale has been designed to carry the 100 year event n� ,offsite. Storm r da n_1ing B,1has not been modified in terms of �-� capacity. However to assure reduction of flows onto the Nau 7 ' Property the line will be relaid and connected into an existin 18" clay tile line, within the Nauta Property, which will tran r these flows to the Poudre River. The Cit-)z %f Fo t Collins has obtained permission from the Nauta's to use this line for ' storm -A er conveyances S orm rain ine C, which connects into storm drain line A, has been installed_to pickup those flows which previously were connected dint other'Nauta drain line. At the �- ' intersection of storm drain Fine A & C, a catch basin has been ' installed. It is intended for this catch basin a nuisance flows, after re ina is comple e as a part of the second phase of these improvements. 0�7 InlIvQweZ 7GCc�4j ft 1,7xcJ, 0/-/, Gl naP _ These assumptions clarify the overall drainage approach. A detailed explanation of the actual drainage design follows. \ WAS_14Q As stated earlier, the proposed improvements only affect the o western third of the site. The only exception to this statement is ' a increase in the flows which are directed toward the outlet of the railroad culvert at Design Point A. Within the western third of the site flow patterns will change �n ' slightly due to the additional parking which is proposed along the south edge of the site. This additional parking is developed through the acquisition of a portion of the railroad right of way ' and a small triangular property south of the existing railroad. These areas which historically drained offsite (Basins Hla and Hlb) will now be directed eastward as part of a larger basin (Basin D1 and Design Point C). Drainage from this proposed basin will drain ' to a low point in the new parking area and then will flow in a drainage swale to Design Point A. Inflow curb & gutter has been t 1 1 1 designed in this area to minimize nuisance flows. The Building Addition will block off drainage patterns which cur- rently flow between Buildings A and B (Basin H3). A pipe system is proposed to carry flows from the south side of the Addition through the Addition's foundation to an existing pipe system north of the new Addition. Since extending a storm drain through a building foundation is rarely done several safeguards are proposed: 1. The area draining into this pipe system has been minimized to reduce the extent of any possible drainage problem. 2. The inlets it -_this area and pipe extended under the building will be encase and oversized to handle over 100 y undetained ows.��cef,f� 3. In the event of the pipe system failure this area is designed to overflow into the adjacent basin at Design Point B. The pavement elevation at Design Point B is 0.3 feet lower than the finish floor elevation of the Addition and Building A. These safeguards should address the concerns raised by routing the storm drain under the addition. Throughout the remainder of the site historical drainage patterns are closely approximated. Offsite discharge rates do increase slightly by the proposed changes. By proceeding with this approach the drainage will flow through this site in a controlled manner. When the final design is implemented, this approach will satisfy the hydrologic and hydraulic concerns and current City of Fort Collins standards for storm water management. Sincerely, '�®v Qt 9• WOE Cort D. ickel, P.E.c©a?c,� CC: Jack Gianola, City of Fort Collins 9oslit p-5074 George Brelig, RB&B L.,�`••. 344-001 ,y��'Sy�N9i 022-1006.344 h��«�ae�aewin 11 i Im air k - - •� 0 �__ � ■ r? ''mil •'• � r't I SERVICE \\ \ CENTER o . V' -- -- SITE _VINE 50�- • 1 �� , '': `III � ` `'� I ■ // 990 C3 CHERRYia I'll L sc s LaI Portel Ave` Sch i i II \ I ' Ir M0UIV'7"All cI FORT COLLINS SERVICE CENTER OFF -SITE DRAINAGE AREA Engineering Cansullants 0 CALCULATIONS I �J r. 0 1 I 11 7 1 1 EDINC Engineering Consultants CLIENT R >j%4- B JOB NO, 244_6� 1 PROJECT C I TV S�V. 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S 1.1 L,1 �I UT le� col U _ d el I (�3 .6H �= z �= N,4L C.�.s� : � C'ti 9 • � .M.p;a SJ�c�.l' � Q,��,� � -y�f Q � '' I 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 CLIENT C-� `c' ' �� ( '\1 all — Engineering JOB NO..4 � ' Li ` � 1 NC PROJECT JE vJ .0 �Fn- t_ CALCULATIONS FOR lyJJ o N Consultants MADEBY ��'� DATE y 1 CHECKED BY DATE SHEET OF ' zl` (js)z z\ 0C3 (y Af- ---- - - - -- - - d n trAe c.•l ,Qc>, l vQ c 4y;,a.v, Se K / C Z� VA n (} O J I s I i �y �pNt p z L; � "- t Cc� w �:,(-;...."�l'MP...�e CAL I tini � �.�) 2. �l 4�y .P!J:.M_FD� Y f L, :1' I��-�J �U„ P..✓ !'v.�.iL�. . i c,� 1 YIrM . 5 1 ©Qy 2706 DMINAGF TABLE Ow•5.5cb '\\ \ BASIN (ACRES) 8 (ACRES) C O10 0100 \\ \ ELL 1.04 0.30 0.80 1.8 10 GOF \\ \ \ R1 1.44 0.81 1.6 6.9 flop OG •'"•� \\\\ \ RJ 2.24 0.92 9.1 16.1 Z PENILE I \ \\ RB 1.75 0.14 5.7 11.7 \ \\ \ B5 0.93 0.84 2.9 5.3 'N \ bin-5.1c4s DI 1.91 0.88 7.1 11.8 / '\ CAm'ILOc Dl 1.51 0.95 6.9 0.9 D] 1.51 0.85 6.6 15.5 --•• - y \\\\\\ D6 0.73 0.76 9.6 15.5 Ds o.n o.R• 2.9 5.3 i 9 U 0 Y iM 1!p GRAPHIC SCALE 1--50' ,.u' VCP ell °o 44, IX o I PROPOSED ADDITION SLOB. A Ir II I I I \ \ \� \\ \ \ • \ J \ BLDG. B \ i I / '> � o'R a \ \\ \ \ \`l 1 � \ 1\ \ A \\ �' -\ T9'w+•le'R� H" cPP.- _ _ ZIA T VINE Wil zr m 'S \ \I \ \ \l r •\ \�\ `\ imr f I ©/ BLDG. C01 r•' I I \! / 1 \ `` \ �\ N ZP•OCP 1 D�1I� dI+Q ` I I \\ S \ \\� .r• -��I _ .r // Ss 1.1 Its 3 �F �\� iJ /n•o.v°f6 \ � �__ I \�\ ` °m•r5.e�65 �... \ \ � I / � -� �� 40 =• � \ * � .w �/ / � gr op bio 6M LW.VERT \ / FF 00 \_, --- ----� ELM STREET RCP e- ASTORK BASINS e- DEVELOPED BASINS - HISTORIC BASIN BOUNDARIES DEVELOPED BASIN BOUNDARIES on• HISTORIC FLOWS Pm DEVELOPED FLOWS Gm• Q - EASTING INLET LOCATIONS ❑' - PROPOSED INLET LOCATIONS O _DESIGN MINT _ PROPOSED STORM DRAIN PIPE -'�---^- - EASTING EDGE OF ASPHALT PRELIMINARY DO NOT M Ice CoOgrucIlon L° MAY 01 IS OCH DRAWN DESIGNED CHECKED I:m EnphsesrYq COIMSNNIfII{ I CITY OF FORT COLLINS APRIL 490 iW-00I M CUwilAs C �A �ue� �Iwh�bSh BwLS WI W o FWla>MRa_ VAST s°n. sm SERVICE CENTER SITE OVERALL DRAINAGE AND ON -SITE UTILITY PLANFlp5 APPROVED DATE PROJECT N0, ppyii6 )I.A5p8flpg ,pyf186vp