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HomeMy WebLinkAboutDrainage Reports - 05/27/1990 (2)I �'. . i / !? i 1 1 1 ■WINC 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 tRE: 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. tPROPOSED IMPROVEMENTS This City of Fort Collins project consists of a Building Addition to the current onsite facilities and the addition of more parking t 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 ' Other Offices: Vail, Colorado 303/476-6340 • Colorado Springs, Colorado (719) 598-4107 I 1 1 1 1 1 1 1 1 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 property.--F1 wws from the two remaining outlets are intercepted in 24_inch cla _pipe and carried eastward to outfall into the City ,fowned— 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 Zen mentioned, eventually outfall into the City property north and east of this site. On this property they drain throu h a rather wkWill-defined channe3 3irectly to the Poudre River. O� s;WIV. Mea Ltddlzfd w i ,�4Y4/ ffsite flows drain toward the 'west / +1170 site from the and south. Flows Au l 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 9 corresponds to its intersection with West Vine Street. Flows from the south are limited by the railroad embankment and a 30 inch X 12 inch wooden culvert. k 60o f� � P," PROPOSED DRAINAGE APPROACH 1p _ _.mod. Aa„-d.anreQ�c� t�.ne tip 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 3. t 1 The existing conditions on site and in the area surrounding the site are treated as the historic conditions. Because 0(i the site's proximity to the Poudre River no onsite detention will be required. Analysis is limited determining the effect of proposed improvements to existing drainage flows and the facilities downstream. Offsite upstream drainage problems such as the impact of undetained flows ponding against the existing railroad embankment will not be addressed in this approach. The proposed improvements will not effect this areaxpec to 1 I 1 J Jig 4,o z I 1 1 1 1 1 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. n During investigation of the site, it was determined that the Nautays hAld water rights on drainage lines that lie within the r City Service Center Property and that the City of Fort Collins was 1 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 have been eliminated and transferred to storm drain lines A and Storm drain line A is planned to service the sump condition at the new turnaround drive and a portion of the revised parking lot (Basin D2). A sump which drains under the building addition, three safety features have been designed into the system. Concrete�"� encasement is required under the building, it has been designed toaCylJ� carry twice the 100 yr. event and 2 inlets have been incorporated (mil as a backup. If for some reason though this system fails, an U outfall swale has been desigqned to carry the 100 year event P�offsite. Storm drain line B;has not been modified in terms of capacity. However to assure reduction of flows onto the Na 7 Property the line will be relaid and connected into an existin 18" clay tile line, within the Nauta Property, which will tran these flows to the Poudre River. The Ci+.. of F M Collins has obtained permission from the Nauta's to use this lira fnr Nzc✓ i taac V, Wl"i 11 VV1111CV 1.d 1i1GV storm drain 1 ne A, has been in a to pickup those flows which previously were connected t oth , Nauta drain line. At the intersection of storm drain Ina A & C, a catch basin has been installed. It is intended for this catch basin nuisanc flows, after rears ina is comp e e as a part of the second phase of t else improvements. /jtcU ap/ 17z11ydOU 74'-4WJ fD /7�cJ3 �ll�� d a2 e o oil l [ rainag rnjd�t�zj, \ These assumptions clarify the overall drainag� approach. A detailed explanation of the actual drainage design follows. As stated earlier, the proposed improvements only affect the 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 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 I L 1 1 1 1 1 1 t t 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 H35. 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 area and pipe extended under the building will be encase and oversized to handle over 10� undetained ows. net�Va 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, ON `O�tOQj i J/� Cort D. Nickel, P.E. CC: Jack Gianola, City of Fort Collins 9 : 435074 George Brelig, RB&B *�•�c�••••• 344-001 y''V* 'Yo w. 022-1006.344 �o \.'...'- �...... _ 40Ll f ; ■ r 41-0 \ \ I�' ?t^i•Y;' ^'�~ SERVICE II 0 CENTER 1 SITE ��. VINE R."?�■ ■ o ' 990 I j+ CHERRY S Fa lily La Port . Ave Sch�i {L_ I ^I �MOUNj7-Al jV� - QI -7 N FORT COLLINS SERVICE CENTER OFF -SITE DRAINAGE AREA Enginfe.in0 Con.ullanl• I i 1 1 i 1 1 1 CALCULATIONS 1 1 1 1 1 1 L 1 0 I i ■ DINC Engineering Consultants CLIENT rL PROJECT CI TV SMV. CALCULATIONS FOR k'UNOFF-oNSITE MADE BY SM& DATE 3-24. 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' PROJECT �GT'V 1Gf�. �C�/9+ Engineering Consultants � 1l' CALCULATIONS FOR MADE BY72DATE CHECKED BY DATE SHEET OF a -I i3o t /a7O f /S20 f SD = a 0 0 3Sao S/3 0.5 / / 0 /.as i00 yr �\ 5- Body — Y9X8 O. 91/ /' /tide m //vGL /4,0v/ 1/7. dLv f s 70 rnrn�fes �Avz V�I = O. 9 �kISec inoyr i� - /.off(/,,/- o,5.xiaSJlGi•8 C)J;2 ls"c,) ' GGeGk a4 a -�4f5ec. 3.7 d.x,Go 50' o✓rr�a✓�d - 8 m �'n✓�S ' 39 i��'nLc{-ets r I �N �111 1 11 i _i o m o ,IV MAY 1984 5-3 DESIGN CRITERIA I 1 1 1 ■MIW- Engineering Consultants CLIENT PROJECT ]LiV ACC. LCV��I` CALCULATIONS FOR MADE BY-11BL- DATE /7 tf CHECKED BY DATE NO, -EH - 0 01 A 3 OF C,O IG,AaAe. R.uNd4— it U�dq A G� CliPi GON'n�c4' Alec" = 170x I7-0 190 x-70 t- 90 xs0 t--a2&0xvs� 35-500 sl= L Z. In. 8 Ac- C= 0.95 9y=9.? =e2,�g _7s0 ' Q= o,9Sh 5.csxa,8 ,o ' r N 3 ctS �<apprct S tQroa - /, od -,'y c�s Vie, 9 ,'aA1 4— G, V 67cs 2G16- /S"of /,0 al-- 0, v �d/. 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Engineering Consultants MADE BY 7- DATE CHECKED By -SHEET Q - -Otb_ ll S 1�$1 CTS O d O. yz (. 000 z 1 JL- -ia-en:z+aa-- llo� sue. ff Q °tea ar J o c 1 1 1 1 1 1 1 1 1 1 1 *MIIJC Engineering Consultants tie I CLIENT t C' l.f \.A �`. L....� JOB NO. �i ll� PROJECTJ�l'^'�"`—t CALCULATIONSFOR � MADEBY-1_OATEy II CHECKEDBY_DATE SHEET 1 OF I ' 013 Lls i2_ .. REF Cry - A n-.�x2,_-'v V•� W'�cl ! ✓�P�1 � li =�c� � m T VINE DRI' / 4 •w, 0 DRAINAGE BASIN TABLE AR (ACRBB) C GIG 0100 N1 1.06 0.30 0.80 1.8 N3 1.66 0.83 3.6 6.9 H3 2.28 0.92 9.1 16.1 X6 1.75 0.76 5.7 11.7 H5 0.73 0.96 2.7 5.3 a -51cf D1 1.91 0.86 7.1 13.8 nvp•Hlc D2 0.79 0.86 2.9 5.6 D3 1.51 0.95 6.3 10.9 06 2.2] 0.]6.6 15.5 an•lb cfi �� OS 0.73 0.86 2 .] 5. \ lam\ \ \ e F I\ PROPOSED ADDITION / /• SLOG �W B. A Da .% i 1 ©/ BLDG. C I \� ver w,• I \ 1\ \\ \\\ \\ 4•-\ �\ t9'r'10N0NP ��/ IT �\\ �1j5 .I nn''Abds I�.. \ V Q.y b.9 cf� 1 \._ \ w CP I/ pRss / f C Qw T.1 1{ o.zo � 30'.IT' wwvIlo �' \\ \ \ '• / '•n��ew. cowBP. - \\�� \ AFI EW STREET \ t A• m 2�•t- ECP U/ e- HISTORC BASINS e- DEVELOPED BASINS - - HISTORIC BASIN BOUNDARIES DEVELOPED BASIN BOUNDARIES - HISTOW FLOWS - DEVELOPED FLOWS 0 - BASTING INLET LOCATIONS - PIIOMSED INLET LOCATIONS O _ DESIGN POINT v _ PROPOSED STORM DRAIN PIPE --�- -�-- - EASTING EDGE OF ASPHALT PRELIMINARY WIND ..ur corwhlGw MAY 0 7 IM