Loading...
HomeMy WebLinkAbout82 Development Permit 539 College Mail Parking Garage0 8/30 /0~~ED 0~:02 FAX _713 630 7396 W P M A HO USTON ~001 WALTER~;;IVIOORE FAX ST FI UC TU RllL C I V IL TRAFF IC PAl'IK I NG eNGINEEAS HOUSTON DAI.LAS TAM PA ATLA NTA ORLANDO TRANSMITTAL Data: Tot Attention: Oe5tinatlon Fax Number; From: Project Reference: Project No, 0 Original to follow via mall Remarks: August 30 , 2000 City of College Station Development Services Spencer Thompson (979) 764-3496 Rich Llewellyn /t~ {. ' College Main Garage 23-97099-00 0 Original to follow via courier 0 Please call on receipt Attached is a sealed estimate of probable constmction costs for the proposed utilities in. public street rights-of-way for the garage project. Please call me at (713) 630-7369 if you have any questions. Cc: Cc: Flle(s) This transmission is 2 pages, Including cover page. If any part of this transmissi on is not legible or Is incomplete, please notify the sender at the telaplione number below. Thl& f~i::s i mlle transminlon Is lntend•d for the UH of the person or entity lo whom it is addrHnd :ind may co11t;iin Information th:it Is prlvll•ged, confidential, and exempt from disclosure under applk:able taw. If th• reader of thi5 message Is not the Intended recipient or an employee or agent responiilble fot delivering this message to the Intended rec ipient. you <ire l'le~by notified tl'lat any dissemination, distri bution. or copying of l/115 communication Is strictly prohibited . If you have received this transrnl&&lon in error, plnn notify th• &ender lmmedlaltl)' by telephone and return the ortglnal transrnisslon to the address below. Th~nk you. 3131 Ea ~ts i de . S e c o n d Floo r Houston . Texa s 77096·1919 Te l 713 .630 ,7300 F a x 713 .6 30 .7396 • 0 8 /30 /00 WED 08 :02 FAX 713 630 7396 W P M A HO USTON College Main Garage College Station , Texas WPM Project No. 23-97099 -00 Estimate of Probable Construction Costs Utilities in Public Street Rights-of-way Item Unit College Main Street 12" x 6 " TS& V w/Box Ea 12" x 2" TS& v w/Box Ea 2" Auoer (w/oioe) LF 6" Auge r (w/pipe) LF Pavement Repair SY Second Street 18" Storm Sewer LF Storm Sewer Manhole Ea Pavement Repair SY ~ubtota l ;ontin9enc~ I 5%1 jTotal I I Quantity 1 1 35 35 30 360 1 240 PublicUtilEst.xls 8/30/00 Unit Price, $/Unit 1,600 300 30 50 35 35 2 ,000 35 I I ~002 Cost,$ 1,600 300 1 ,050 1,750 1,050 12,600 2,000 8,400 I 28,7501 1,438 I 30,188j 1 of 1 Development Permit Issuance Checklist 1 $100 Application Fee 2 Application Completed and Signed 3 Grading Plan (submitted and approved) 4 Erosion Control Plan (submitted and approved) 5 EPA N.0.1. Submitted for sites > 5 acres 6 Tree Barricade Plan (if applicable) 7 Drainage Report /Letter (submitted and approved) 8 $300 Infrastructure Inspection Fee (if applicable) 9 Easements Dedicated (separate instrument) 10 TXDOT Permits issued (if applicable) 11 Sealed Engineer's Estimates Received 12 Inside I Outside Floodplain (circle one) 13 Drainage Basin--------------- 14 Site Plan Approved. Date: ---------- 15 Development permit Issued. Date: ______ _ January 23,1998 Arkitex Studio 511 University Dr. East Suite 201 College Station, Tx. 77840 Attn: Chad Grauke, AlA ~s g,J 1/-z,>\ct'> Dear Chad: Below are my comments to the Memorandum from Walter P . Mooore and Associates, Inc. regarding the Design Issues -To Date on the College Main Parking Garage. 1. Throughout the document, Main Street is refered to . To avoid confusion, the correct name ofthis street (College Main) should be used. 2 . On page 2, the runoff coefficient used is 0 .6 . Is that correct? The 0.29 acres appears to have little impervious cover on it. Please check. 3 . On page 3, the area used in the calculations is 1.5 acres, which is the appears to be the area draining to Second Street. Is that correct? This area added to the .29 acres is a total of 1.8 acres . Is that the total site area? 4. On page 4 & 5 there is reference to the fact that the detention facility should be sized to contain the surface runoff volume difference between the sites existing conditions and proposed conditions for the one hundred year storm event. Please do not forget that all storm events must be checked, (i.e . 5, 10, 25, 50 and 100 year) for runoff control. 5. On page 5 there is a comment regarding the extent of offsite storm drainage improvements (i.e. Patricia Street). Mark Smith with the City of College Station should be contacted to determine the timing of these improvements. These are all the comments to the memo . It appears that the general understanding and methodology meet the intent of our drainage ordinance. Please contact me if you have any questions . Veronica J.B Morgan, P.E. Asst. City Engineer -:·:·:·:·:;:·:·:·:···· ~ff::;:.=} iji[!:::'::!:i.f:,:' :::::::111:1·1.:·1:. te;;,* ii§tl.itJ.:Ili:t.t.i::: 511 UnlverslyOt-. East Suite 201 Cdl"9• Stal!on, -:-JC 778';1 Voloo 409 ~ 2635 Fax -409 146 1224 www.arldt•.x.com Principals Charlie Burri&, ~ cbw-ri•@arkitex.com Dr . Elton Abbott, AJA cabbott@arlcitex .co m Chad Orauke, AIA cgraukc@arlcitex.oom MINUTES FROM Subject: Date: Attendees : • General Pre-Development Meeting College Main Parking Garage City of College Station, Texas 20 October 1997 (2:30 p .m.) Jane Key, City Planner Shirley Volk, Development Coordinator Sabine McCulley, Elanning & Zoning Veronica Morgan, Engineering Tony ichalsky, Electrical Mark Smith, Public Services Tom Brymer, Assistant City Manager /Project Manager Todd McDaniel, Economic Dev ./Northgate Coordinator Chad Grauke, The Arkitex Studio, Inc. Mark McClure, Walter P. Moore & Assoc . VM 1M MS TB 1Mc CG MM 1Mc gave a brief overview of the project, including site location, property owners, status of land aquisition, scope of project, anticipated parking capacity, height, etc. CG distributed a print of the land survey and a copy of one of the preliminary building layouts. Also, noted the boundaries of the original site and the subsequent inclusion of Lot 14, Block 7 at the northwest corner. It was noted that the Preliminary Review Committee (PRC) and the Northgate Revitalization Board (NRB) would be involved in the approval process. • Drainage CG noted that the vast majority of the site would be covered by the new development and that drainage would be hard piped and metered into existing storm drains. TB observed that the site generally drains to Church Street (south). MS commented that directing drainage to the north would be preferable. SM indicated that a drainage report would be required and VM noted that an analysis of the drainage basin would be required. VM further noted that the site was located near the dividing line of two drainage basins and that 100% impervious coverage would be assumed if drainage re-routed to new basin (as requested by TB) whereas only the increased impervious area would need to be addressed if drainage routed to south (historical drainage direction). VM commented that requirements were fully defined in the drainage ordinance. CG requested a copy of the drainage ordinance for MM at the conclusion of the meeting. Storm sewer improvements along Chw·ch Street, approximateiy one block to the southwest of the site were noted. MM commented that he would usually prefer to not cross drainage basins. It was mentioned that the northwest corner (Lot 14, Block 7) could be used as a detention area. MM requested copies of water and sewer plans, design reports and plans of recent improvements, and the topo map indicating drainage basins. (VM to provide). • Electrical Service CG questioned how the City would advise that we handle the service lines currently located in the middle of the site. 1M indicated that the City would remove the existing lines and provide service to the northwest comer of the site to a transformer for the new garage. Our new project would need to include extension of conduit for electrical service to properties located south of the site (Lots 14 & 15 of Block 7 and Lots 26 &27 of Block 6). 1M also mentioned that a 10 foot electrical easement would need to be aquired along the northwest property line of Lot 15, Block 7 (Benning property) from 2nd Street to the north corner. Minutes From Pre -Deve lopment Meeting College Main Parking Garage Page 2 • Water and Sewer Service VM provided maps of water and sewer service in the area. A 6" water line was noted along the south side of Church Street. The site survey indicates a 12" water line on the east side of College Main . The 6" sanitary sewer line that now runs through the middle of the s ite will need to be re-routed (under this project) to serve the existing buildings at the south end. MM requested that the surveyor provide locations of sanitary sewer tie-ins to the existing buildings . • Setback Requirements JK indicated that a 15' rear setback would be required with zero setbacks on other sides. It was noted that traffic planning consultant John DeShazo had developed concept layouts with no setbacks. JK stated that a variance can be gran~d by the Zoning Board of Adjustments, the process takes 21 days and requires that the Owner establish special conditions to show hardship. CG questioned which face would be interpreted as the "rear". TMc mentioned that the ingress/egress is to be located on College Main and therefore, the rear would face 2nd Street. During the discussion, JK and SM conferred and later indicated that IlQ setbacks would be required. • Landscaping SM mentioned that the requirements within the Northgate area are different than normal landscape requirements and that specific information could be found in the Zoning ordinance. It was noted that the R.0.W. could be utilized to satisfy requirements. SV mentioned that benches, planters and other items can be utilized as landscaping. No streetscaping is required nor screening to adjacent properties . It was noted that an artists rendering of the proposed design would be helpful in describing the project to the NRB. • Sidewalks The existing sidewalk along College Main will be demolished during the new construction and will be replaced. Brick pavers similar to other sidewalks along University and College Main are preferred. A sidewalk on 2nd Street to the pedestrian entry to the building will be necessary. TMc noted that 2nd Street is in poor condition. Street improvements are not to be included within the project. Specific sidewalk requirements will be set by the NRB and PRC. • Fire Protection A fire hydrant is indicated on City maps at College Main and Church Street CG noted that the new garage is to have a fire sprinkler system. Fire walls were discussed and CG was referred to Lance Simms for requirements. Concluded meeting around 4:30 p.m. and departed. cc:vfo"'m Brymer Todd McDaniel Walter P. Moore & Associates Burns DeLatte McCoy, Inc. DeShazo Tang & Associates STRUCTURAL, CIVIL, TR AFF I C AND P ARK! G ENGINEE RS 3131 EASTSIDE SECOND F LOOR H OUSTON, TEXAS 77098-1919 FAX 713/630-7396 TEL 713 I 630-730 0 WWW. WALTERPMOORE.COM H OUSTON DALLAS/FT. WORTH T AMPA ORLANDO ATLANTA . ~ ;.' .. Walt e r P. Moore an d A ssoc i a t es, In c. Memorandum December 15 , 1997 To: Chad Grauke, AIA/Arkitex Studios , Inc . Fromo M.,-k A . McClure, P E . 11 Re: Drainage Issues -To Date College Station, Main Parking Garage College station, Texas WPMA Project Number 97099 This memorandum presents the status of the drainage issues to date in reference to th e College Station Main Parking Garage project. This memorandum is not intended to be a completed drainage report, but to present a basis of understanding of the project drainage issues to date . This memorandum presents bri ef descriptions of the following : • Site Description • Available Documentation • Existing Site Conditions • Proposed Site Conditions 1 • Recommendation ~ · Site Description tM e Main Garage site is located in Brazos County, College Station, Texas , reference Figure The approximately 1.5 acre site comprises Lots 16 through 25, of Blocks 6-7 of the W .C . Boy Estate Partition in the Northgate area . For planning purposes Lot 14 has been potential addition to the project for detention pond purposes . For purposes of this memorand ; onl y plan north is assumed to the left on Figure 1. Therefore, the site is bounded on the east by ain Street (50 ' right-of-way), to the west by Second Street (40 ' ROW/variable), to th e north by Lots 14 and 18 , and to the south by Lots 15 and 26 . Presently , site access is from \Main Street and Second ~ ~ Available Documentation The following documentation has been received b y Walter P . Moore and Associates , Inc . (WPMA) and provides the basis of this memorandum 's understandings and assumptions : • Topographic Survey Lots 16 and 25, Block 6-7 W .C. Boyett Estate Partition , College Station , Texas , prepared b y Joe Orr, Inc ., dated October 7 , 1997 . Chad Grauke, AIA December 15 , 1997 Page 2 • Water and Sewer Specifications City of College Station, Texas . • "DRAFT" City of Bryan and City of College Station, TX, Texas Joint Design Manual -Streets and Alleys, Storm Drainage, Domestic Water, Sanitary Wastewater, Revised 9/15 /97 . • Drainage Report for Patricia Street, prepared by McClure Engineering , Inc ., dated 11/25 /97. • Drainage Report for College Main , prepared by McClure Engineering, Inc ., dated 1/30/95 . • City of College Station , Texas aerial photography taken February-March, 1994 by Williams- Stackhouse, Inc , sheets 549-210 and 212 Existing Site Conditions Site topography is flat and ground surface elevations range from approximately elevation 352 to elevation 348 (NGVD -1929 elevation datum) as depicted on the previously identified topographic survey and as shown on Figure 1. Existing drainage of the site occurs by overland sheet flow that is described generally from the northeasterly comer of the site to the southwesterly comer of the site . The site is presently occupied by existing one and two primarily wood-framed buildings. Areas of the site not characterized by dwellings are occupied by dirt and gravel driveways and parking areas , concrete sidewalks , miscellaneous fencing and trees , and residential type grass areas . ~Main Street ain Street to the east of the site, is an improved fifty-foot R .O.W. with a thirty-five foot back of curb (B/C) to B/C concrete street. Existing drainage improvements are presented in the College Main drainage report previously identified , reference Figure 2. According to the drainage report , the ~ Main Street project drains from University Avenue and discharges to the Burton Creek Tributary "A " located at the intersection of Spruce Street and College Main . The College Main Garage site is shown to surface drain t<\Main Street and gutter flow south to an inlet located at the intersection of ---Main Street and Church S~ ~ ~ Based on a review of th e College Main Garage site topography and pl~imetric mapping and the City's Stomwvater Management Plan the following existing drainage I~racteristics were determined : • Area (A) = 0 .29 acres . \~ , ·,I\ ? ,., v l\{\O ~ 1 C \ \S~J cX I ~ \!) ~)\) ~#. CoefficientofRunoff(C)~ ~ ~~A\"~/ ,yS Time of Concentration to ~ 10 minutes (minimum) ~ ~; ~ • • Chad Grauke, AIA December 15 , 1997 Page 3 • Ten Year Storm Intensity ((1 10) = 8.63 inches/hour (in/hr) • One Hundred Year Stonn Intensity (inches/hou r) 1100 = 11.64 in/hr • Ten Year Flow (Qi o) = 1.5 cubic feet per second (cfs) • One Hundred Year Flow Q100 = 2 .0 cfs Based on the City 's Stom1water Management Plan the Burton Creek Basin is recognized as a special drainage basin and has channel reach design standards . For purposes of meeting location requirements for drainage control the policy states Burton Creek Basin requires detention of the one hundred year ultimate event for proposed development. The Main Street Drainage Report depicts future storm drainage improvements designed to accommodate the ten-year design storm event , based on undeveloped conditions. Sec ond Street Second Street to the west of the site, is an unimproved variab le R.O .W. asphalt paved street with gravel and dirt shoulders . Proposed drainage improvements are included in the Patricia Street drainage report previously identified . According to the drainage report, the Patricia Street project drains to the west, eventually discharging to an existing outfall located at the intersection of Church Street and Wellborn Road . Based on the Patricia Street drainage report and the City 's Stormwater Management Plan, it would appear the proposed College Main Garage site occupies a portion of a drainage basin ridgeline between the Burton Creek Drainage Basin (previously discussed) and the White Creek Drainage Basin. For further purposes of this memorandum, it is assumed and appears that most, if not all of the project, contributes existing storm water runoff to the White Creek Drainage Basin . The proposed garage site 's existing site conditions are shown to surface~ Second Street and then flow via unimproved gutter or ditch flow to a proposed future inlet ~ collection system at the intersection of Second Street and Church Street. Based on a review of the proposed College Main Garage garage topography and planimetric mapping and the City 's Stonnwater Mana&ement Plan the following existing drainage characteristics weredetennmed _ ">~ \¥~ IP~# [s~<WP---V, ~~-.kJ • Area(A)Q y-P5 ll"y ~ i.St<CM-S tc,Lute._Jo ~- • Coefficie~noff © = 0 . 60 r. 1 ,,, ; ,, _ _, , L l1. llW\Q.O. iw µc,~~? • Time of Concentration (tc) = 5 minutes \'-"'-V"v-. ~ -~JN rv.o, • Ten Year Stom1 Intensity (1 10) = 8 .63 in/hr • One Hundred Year Storm Intensity (1 100) = 11.64 in/hr • Ten Year Flow (Qi o) = 7 .8 cfs • One Hundred Year Flow (Q1 00 ) = 13 .3 cfs Chad Grauke, AIA December 15, 1997 Page 4 Based on the City 's Stormwater Management Plan the White Creek Drainage Basin is a recognized basin with Tributary "D " as an identified channel reach . For identification and classification the College Main Garage project would contribute runoff to the Patricia Street project, which based on City definition, would be considered as a secondary drainage system . The City 's Stormwater Management Plan and policy states that the emphasis at the performance level is to mitigate the nuisance aspect of stonn drainage to reasonable occurrences . Prop osed Con dit ions The proposed College Main Garage concrete parking structure is shown on Figure l to occupy approximately 244 feet x 2 + 7 feet of property for a total of 60,268 square feet or nearly 1.4± acres of the 1.5 acre tract. The balance of the site area and the area between the property lines and adjacent lots and streets will either be occupied by a combination of sidewalk, driveways, entrances , and landscaping . The Patricia Stre-ainage Report depicts future stom1 drainage improvements designed to accommodate the ten-ea(d ign storm event, based on a coefficient of runoffs factor "C " = 0 .65 (developed). Storm drainage for the proposed structure is expected to be collected on the upper parking deck and conveyed by a system of building structure drains and gutters to a subsurface collection system. Based on a review of the size and impervious characteristics of the proposed structure and the City 's Stormwater Management Plan the following proposed drainage characteristics were determined: • Assumed site is developed completely with an impervious structure • Area (A)= 1.5 • Coefficient of Runoff (C) = 0 .90 • Time of Concentration (t.:) = 10 minutes (minimum) • Ten Year Stom1 Intensity (1 10) = 8.63 in/hr • One Hundred Year Stonn Intensity (I 100) = 11 . 64 in/hr • Ten Year Flow (Q 10 ) = 11.7 cfs • One Hundred Year Flow (Q 100) = 19 .9 cfs The proposed subsurface system would collect the parking garage building stormwater runoff and convey the runoff to a detention facility . The detention facility should _!>e sized to contain the surf e A ..L water runoff volume difference between the sites existin orlcl~d propo onditions for e d2J!.M~ one hundred year stonn event. The detention facility: ould be desigl)ed to release sto ter at t present site 's existing stormwater runoffflowrate( t ~g~ Chad Grauke, AIA December 15 , 1997 Page 5 If the Patricia Street drainage improvements are completed (e .g . proposed inlet at Church and Second Street), the detention facility could be connected to the proposed inlet and conveyed to the White Creek Drainage Basin. If the Patricia Street drainage improvements (e .g. extension of storm water system to the intersection of Church and Second street) are not completed, consideration should be given to completing this system or as a minimum the storm sewer piping to the inlet discussed . Reco mmendatio ns In summary, Walter P . Moore and Associates , Inc . reconunends providing the following storm drainage improvements to the proposed College Main Garage site as follows : V'• Collect developed stormwater runoff from the proposed parking garage via structure drains and p1pmg ; ~­ /. /. Route the developed stom1water runoff to a stormwater detention facility , presentl y identified as Lotl4, ~~ Release the stormwater runoff at existing flow ratf and ~ Route the released flow rates to the Patricia Street Storm Sewer System. To implement the above stated improvements the following will need to be determined : /. Conform City 's acceptance of assumptions presented, v . /. Determine the extent of offsite .storm drai~1a77 i,mpr9v~!:nt~l Ifg:pir~; (i .e .~ Patrici ~ Street improvements constructed) d~0 1 /U/J..A.,/<:_{)~ /..J'. Develop existing and proposed development stormwater hydrographs , ~ Based on the hydrographs developed , determine the storage requirements and resulting site constraints ; V • Detemune the stomw;ater detention system release rates (i .e ., Q 10 and/or Q100), and V • Prepare fatal plans and techrncal specifications implementing the design . 18 . Some type of decorative element is needed west of the garage entry on Second St. (e.g., plantings and period light standards). 19 . There are five lamp posts along College Main but none along Second St. Will any be needed? 20. What are the hatch marks on sheet C-2? Reviewed by: MOLLY HITCHCOCK Date: 07/10/00 ENGINEERING REVIEW 21 . A Drainage Report has not been submitted for this project. Staff has reviewed a preliminary drainage report , however, the report was not stamped and signed by a registered/ professional engineer, as is required , and some calculations were not performed as per City requirements. These calculations may affect the detention pond sizing and the outlet piping sizing . 22 . A 3" domestic water meter is specified for this project. The engineer needs to tee off this line and install two separate meters ; one for domestic use and one for irrigation , along with the required irrigation check valve . According to plan estimates , domestic water flow rates would require , at most , a 1" meter (PM5). Irrigation flow estimates are not provided. 23 . The fire line connection to the City's water main does not appear on the plans . A 6" tap should be made onto an 8" water main to supply fire flows to the building fire system . A 2" connection is shown going to the fire pipeline (PM2). This connection should not be installed . 24 . Sheet C2 shows a 6" PVC drain pipe . This pipe apparently drains the swale along the east side of the building . It is not clear whether this drain connects to the 24 " storm drain or drains to the street gutter If it dra ins to the gutter, a 6"pipe may be too large to penetrate the curb? Reviewed by: Spencer Thompson Date: 1 O-Jul-00 NOTE: Any changes made to the plans, that have not been requested by the City of College Station, must be explained in your next transmittal letter and "bubbled " on your plans . Any additional changes on these plans that have not been pointed out to the City , will constitute a completely new review. Staff Review Comments Page 2 of 1 I ·.·.·.·.·.·.·.·.·.·.·.·.:-:-:-.-:·:::-:-:-:-:-:-:-:-:-:-:··-·.;.· .. 511 University Or . East Suite 201 College Station, TX ne40 Voice 409 260 2635 Fax 400 846 8224 www .arJdtez.com Principals Charlie Burris, AJA cburris@arkitex.com Chad Gr auke, AlA cgrauke@arkitcx .com Dr . Elton Abbott , AJA eabbott@arkitex.com Mike Tibb~.tta, AJA metibb@swbcll.net Austin Office Voic e .512/2 44 -7 870 Fax ~12 /244 -0237 LETTER OF r~c 1dW. TRANSMITTAt - TO : ___ -'V'""'"'e=r=on=i=c=a...::.M==or:..-;g;i.=a=n ___ WITH: City of College Station FROM: __ C_h_a_d~G_r_au_k_e~, _AIA ___ DATE: __ ~1~4~J~a~nu~a~r_y~1~99~8~ PROJECT: College Main Garage PROJECT N0: __ "--97'--="3-=-6 __ The following items are hereby transmitted for your usage, review and/or action as noted. For your review and comment: • Memo concerning "Drainage Issues to Date " from Walter P: Moore Let me know if you have any questions or need of additional information. WALTE~OORE STRUCTURAL CI V IL TRAFFI C PARKING ENGINEERS HOUSTON DALLAS TAMPA ATLANTA ORLANDO KA NSAS CITY June 26 , 2000 ~ ~-z.7..oP Ted M ay o <::::::?~' ' Assistant City Engineer, Development Services 1101 Texas Avenue College Station , Texas 77842 Re: College Main Parking Garage Detention Pond Design Notes Walter P. Moore Project No. 97099 Dear Mr. Mayo: Attached, for your review and approval , are revised design notes for the proposed detention pond for the College Main Parking Garage project. The preliminary design notes had been reviewed previously by Spence Thompson ; dated April 14 , 2000. We have revised the design notes to incorporate the review comments, and to meet the College Station Drainage Policy and Design Standards. With the verbal approval of Mark Smith, City of College Station, we have also revised the detention pond design to provide compensating detention capacity for "The Tradition,'' the new dormitory project north of Church Street and between Second and Boyette Streets. The College Main Parking Garage project has been advertised for bids by the City of College Station, and the project will be submitted for a building permit in the near future. Therefore , we request that you expedite your review . If you have any questions regarding the proposed detention pond design , please call me at 713-630- 7369 . Very truly yours , WALTER P. MOORE AND ASSOCIATES , INC . ~d~. Richard G. Llewellyn, P.E. Senior Associate RGL/mr \IHO U-SE RVER\ClV-ROO T\23\Fi le-Civ\Projects\97099\Corres\Leners\T Mayo.doc 3131 Eastside, Second Floor Houston, Texas 77098-1919 Tel 713 .630 .7300 Fax 713 .630 .7396 www .walterpmoore .com • COLLEGE STATION P. 0 . Box 9960 April 14, 2000 Attn: Mr. Rich Malone Walter P. Moore and Associates, Inc . 3131 Eastside, 2nd Floor Houston, TX 77098-1919 RE: Stormwater College Main Parking Garage College Station, TX Dear Mr. Malone: 1101 Texas Avenue Tet. 409 764 3500 College Station, TX 77842 We have been reviewing your firm's plans for the College Main Parking Garage along with a letter written by Mark McClure addressed to Chad Grauke (w/ Arkitex Studios) dated 10/7/98. The letter states some design assumptions for the project's stormwater detention requirements . We would like to make a few comments concerning the assumptions stated in your firm's letter. Primarily, due to inadequacies of the downstream. conveyance system, no increase in run-off will be ~llowed from the site into either watershed unless it can be specifically shown that the increase will not have . an adverse impact. Based upon this criteria, it is assumed for the rest of this letter that on-site detention will be required for all storm frequencies as stated in the City's Drainage Manual and Design Standards (Tf = 2, 5, 10, 25, 50, and 100 year storms). Based upon previous conceptual designs, it is assumed that your design will include pumping of stormwater from the detention facility to a loca~ion which will allow gravity conveyance to the White Creek drainage basin. Such a location might be the gutter along Second Street toward the south end of the project property line. It must be noted that free flow from the detention site, Lot 14, will drain into the Burton Creek drainage basin. Please base your detention pond design on inflow and outflow according to the proposed outlet structure or device. As stated in our design standards, the design pond storage is based on the greatest difference in area of the hydrographs for the pre-development inflow and pond outflow versus time and not a pre- determined flow rate . The pond volume may significantly increased ifthe pumping capacity of the outlet is significantly less than the pre-developed flow. If you have any questions feel free to contact me at 979-764-3570. Sincerely, ~~· Spencer G. Thom on, ., EIT Graduate Civil En · Home of Texas A&M University o:\group\dev _serv\txdot\ParkingGarageDrainage.doc Design Calculations for Storm Water Detention Basin College Main Parking Garage Prepared for City of College Station Prepared by Walter P. Moore and Associates, Inc. 3131 Eastside, Second Floor Houston, Texas 77098-1919 Walter P. Moore Project No. 23-97099-00 June 2000 I. INTRODUCTION Summary Proposed Project Design Basis II . DRAINAGE Site Drainage Watersheds College Main Street Second Street TABLE OF CONTENTS III . DETENTION POND DESIGN Garage Project Dormitory Project Combined Pond Outfall and Overflow Design Basin Geometry Sheet Flow TABLES 1. Detention Calculations -College Main Parking Garage 2. Detention Calculations -Dormitory Project 3 . Combined Detention Basin Volume 4 . Allowable Runoff Rates 5. Design Elevations EXHIBITS 1. Vicinity Map 2. Project Layout 3 . College Main Street Drainage Area Map 4 . Patricia Street Drainage Map 5. Project Site Drainage Area Map 6 . Detention Pond Cross-sections I. INTRODUCTION 7< This report presents the design calculations and layout for a storm water detention basin to serve the College Main Parking Garage project, which will be owned by the City of College Station. With the approval of the City, the detention and will include capacity for a dormitory pro "ect, "The Tradition", located west of the Second Street. Summary Detention v olume requirements for the College Main Parking Garage project ("garage project") will be approximately 7,400 cubic feet. With the addition of the dormitory project, the required detention volume is approximately 17 ,000 cubic feet. In order to provide this volume on the designated s ite , a vertical-wall basin will be required. The vertical walls, up to 4 feet high , will be constructed of manufactured concrete blocks for landscaped retaining walls. Second Street does not have a storm system ; therefore, drainage outfall for the detention basin is not currently. To avoid including a storm water pump station in the College Main Parking - Garage project, the following storm sewer system improvements are required: Extend the existing storm sewer in Church Street from Boyett to Second Street. The project is currently under design by another engineermg consultant. .fr • Extend the storm system in Second Street from Church Street to the detention pond. This segment of storm sewer is included in the garage project. Proposed Project The proposed College Main Parking Garage site ("project site") is located in Brazos County, College Station, Texas , (see Exhibit 1). The site consists of Lots 16 through 25 , Lot 14 and a portion of Lot 18, of Blocks 6-7 of the W.C. Boyett Estate Partition. Lot 14 has been reserved for the detention pond. The project site is bounded on the east by College Main Street, on the west by Second Street, to the north by Lots 14 and 18, and to the south by Lots 15 and 26. Presently, site access is from College Main Street and Second Street. The City of College Station plans to construct a 4-story, 713 car concrete parking garage in the Northgate area (see Exhibit 2). The 1.69-acre project site is located 110 feet north of Church Street between College Main Street and Second Street. Storm water runoff from the parking garage will be collected in floor drains and the inte al A. drainage system will be r ~ed to a detention and located on the north side of the project site. r The detention pan outfall pipe w"ll e connected to a proposed storm sewe · nd Street (to be included in this ro · ect), which illfurn will be connecte to a future s · C S.m.t_(under design by others). The storm sewer system in Second and Church Street is necessary to avoid a storm water pump station to drain the detention pond. Design Basis The design of the detention pond is based on the following documents: • Storm water Management Plan for the City of College Station, Drainage Policy and Design Standards . -1- II. • Drainage Report for Patricia Street, prepared by McClure Engineering, Inc., dated February 1997 (Revised November 1997). • Drainage Report for College Main, prepared by McClure Engineering, Inc ., dated January 1995 . Based on correspondence and conversations with City representatives, detention is required for this site to maintain runoff levels from the proposed development at existing runoff levels . DRAINAGE Site Drainage Until recently, the project site had been developed as a single-family residential subdivision, as shown in Exhibit 1. After the City acquired the site , all buildings and site improvements were removed, except overhead and underground utilities. Ground surface elevations range from approximately elevation 352 to 348 (NGVD-1929 elevation datum). Existing site drainage occurs by overland sheet flow from the northeasterly comer of the site to the southwesterly comer of the site (from College Main Street to Second Street). A 50-feet deep portion of the project site drains to College Main Street. Watersheds Watershed boundaries for the project site area are defined in the drainage reports for College Main Street and Patricia Street drainage reports. The project site is partially within both the Burton Creek watershed and the White Creek watershed. See Exhibit 5. The existing Burton/White Creek watershed boundary is along the north side of Lots 14 and 18 , then 50 feet west of the College Main Street ROW. Approximately 0.51 acres of the project site currently drains to Burton Creek and 1.18 acres to White Creek. Exhibits 3 and 4 show the drainage area maps for the College Main Street and Patricia Street projects, respectively. A detailed drainage area map for the project site is on Exhibit 5. Construction of the proposed garage will result in a minor alteration of the drainage patterns and in the watershed divide. All runoff from the garage building and most of the site (1.58 acres total) will be routed to the detention pond. The detention pond outfall will go to the Second Street and Church Street storm sewer, which is in the White Creek watershed. Only a small area, 0.11 acres between the east side of the garage structure and the street ROW, will drain to the College Main Street storm sewer and remain in the Burton Creek watershed drainage area. The existing and revised drainage areas are summarized below: Drainage Areas 0.51 Proposed Conditions ----l 0.11 Existing Conditions Burton Creek White Creek 1.18 1.58 Total 1.69 1.69 College Main Street According to the drainage report for College Main Street, the storm sewer system drains north from University Avenue and discharges to the Burton Creek Tributary "A", located at the -2- intersection of Spruce Street and College Main. Based on that drainage report, the drainage area for the street includes a 50-foot depth on the project site. The existing composite Rational Formula "C" value for the drainage area on the project site is approximately 0.73. For the proposed condition, the "C" value will remain approximately the same. Since there is no change in the "C" value, and the drainage area to Burton Creek will be reduced , no detention is required for the portion of the project site within the Burton Creek Watershed . Second Street Drainage improvements for Second Street and Church Street are described in the drainage report for Patricia Street. The Patricia Street project drains to the west and discharges to an existing outfall located at the intersection of Church Street and Wellborn Road. The downstream segment of the storm sewer system has been constructed west from the intersection of Church Street and Boyett Street. The segment in Church Street from Boyett to Second Street is currently under design by others . The Patricia Street drainage report did not identify any storm sewer improvements in Second Street north of Church Street. ill. DETENTION POND DESIGN Garage Project The proposed detention pond design is based on the City of College Station Drainage Policy and Design Standards. The Rational Formula was used to calculate peak runoff flow rates. A "C" value of 0.65 was used for existing conditions, as used in the Drainage Report for Patricia Street. A "C" value of 0.90 was used for the fully developed site, based on Table III-1 of the Design Standards . The drainage area is small; therefore, a minimum time of concentration of 10 minutes was used in all calculations. Runoff volumes were determined by the triangular hydrograph approximation method. The design calculations for the garage site are summarized on Table 1, and include the following design frequencies: 5, 10 , 25, 50, and 100 years . Dormitory Project The develops of "The Tradition" a private dormitory project on the west side of Second Street has requested capacity in the College Main Parking Garage detention pond. Based on information provided by the project's engineer, Urban Design Concepts, the following are design parameters for detention: Drainage Area to White Creek • Existing 1.88 acres • Proposed 2.30 acres Rational Formula "C" values: • Existing 0.65 • Proposed 0.90 Detention volume calculations for the dormitory project are summarized on Table 2 . -3- Combined Pond The volume requirements for the combine detention pond are on Table 3. The allowable runoff rates for the two projects are summarized on Table 4. As can be seen, the design runoff from the College Main Garage detention pond is 0 cfs, meaning that the pond is to be designed to detain 100% of the runoff for all storm return frequencies, or approximate 17,000 cubic feet. Outfall and Overflow Design Natural ground in the area of the detention pond is approximately Elev. 351, and the nearest top-of- curb (projected for future potential street improvements) is Elev. 349.5 . The design water surface is Elev. 349 and the extreme event spillway set at Elev. 349.5. The draina es stem for the ond will consist of a 6" drain i e from the pond to an inlet, then an 18" line to the proposed 24" storm sewer m econ treet. The inlet wi 1 ave the 3-foot wide opening, with the weir set at Elev. 349, r-Ja.~ the design water surface elevation. Design water surface and hydraulic grade lines for the outfall system are on Table 5. Basin Design The size of the detention pond is restricted by the site, as shown on Exhibit 2. An earthen basin, with 3: 1 side slopes will provide sufficient volume for the garage project alone. Vertical 4-foot high retaining walls will be required to provide the additional capacity for the dormitory project. The design is based on using a landscaping concrete block gravity retaining wall. Exhibit 6 shows cross-sections of the pond required for the two design conditions. Sheet Flow Extreme event sheet flow runoff from the project site will be to the west into Second Street. The sheet flow route will then follow Second Street to the south to Church Street, then west in Church Street to the outfall channel at Wellborn Road. Second Street has an asphalt pavement section of variable width and condition, and is located in a nominal 40-foot wide ROW. Parts of the street have concrete curb and gutters; the remainder has dirt shoulders with shallow roadside ditches. Modifications are in the planning stage to convert Second Street in the area of the parking garage to a pedestrian mall. Provisions will be necessary to maintain the extreme event sheet flow route. -4- Table 1 Detention Calculations College Main Parking Garage White Creek Basin Existing Conditions C=0.65 Drainage Area = 1.18 Acres Return Frequency Qp , CFS 5 5.90 10 6.62 25 7 .56 50 8.54 100 9.59 White Creek Basin Proposed Conditions C=0 .90 Drainage Area =1.58 Acres Return Frequency Qp, CFS 5 10.94 10 12 .27 25 14.02 50 15.84 100 17.80 Required Detention Volume Return Frequency Vol., CF 5 4 ,554 10 5,085 25 5,814 50 6,570 100 7 ,389 Notes : Tc, Min I, In/Hr 10 7 .69 10 8 .63 10 9 .86 10 11 .14 10 12 .50 Tc, Min I, In/Hr 10 7 .69 10 8 .63 10 9.86 10 11 .14 10 12.50 1. Qp , peak flowrate, from Rational Formula 3 Tc Vol., CF 30 5 ,310 30 5 ,958 30 6 ,804 30 7 ,686 30 8,631 3 Tc Vol., CF 30 9 ,864 30 11 ,043 30 12 ,618 30 14 ,256 30 16 ,020 2. Volume calculations based on triangular hydrograph method College Ma in Parking Garage.xis 6126100 Table 2 Detention Calculations Dormitory Project White Creek Basin Existing Conditions C=0.65 Drainage Area = 1.88 Acres Return Frequency Qp, CFS 5 9.40 10 10.55 25 12.05 50 13.61 100 15.28 White Creek Basin Proposed Conditions C=0.90 Drainage Area= 2.30 Acres Return Frequency Qp, CFS 5 15.92 10 17.86 25 20.41 50 23.06 100 25.88 Required Detention Volume Return Frequency Vol., CF 5 5,868 10 6,579 25 7,524 50 8,505 100 9,540 Notes : Tc, Min I, In/Hr 10 7.69 10 8.63 10 9.86 10 11.14 10 12.50 Tc, Min I, In/Hr 10 7.69 10 8 .63 10 9.86 10 11.14 10 12 .50 1. Qp , peak flowrate, from Rational Formula 3 Tc Vol., CF 30 8,460 30 9,495 30 10,845 30 12,249 30 13,752 3 Tc Vol., CF 30 14,328 30 16,074 30 18,369 30 20,754 30 23,292 2. Volume calculations based on triangular hydrograph method The Tradition .xis 6126100 Return Frequency 5 10 25 50 100 Table 3 Detention Calculations Combined Volumes Detention Volume , CF Garage Project Tradition 4 ,554 5,868 5,085 6,579 5,814 7,524 6,570 8,505 7,389 9,540 CMPG and t he Tradition .xis 6126100 Combined Volume 10,422 11,664 13,338 15,075 16,929 Table 4 Detention Calculations Allowable Runoff Rates Return Existing Runoff Rate, CFS Proposed Runoff Rate, CFS Frequency Garage Dorm Total Dorm (A) Garage (B) 5 5.90 9.40 15.30 15.92 0 10 6.62 10.55 17 .17 17.86 0 25 7.56 12.05 19.61 20.41 0 50 8.54 13.61 22 .15 23.06 0 100 9.59 15.28 24.87 25.88 0 A. Proposed runoff rate from Dorm project, with no detention B. Net allowable runoff from detention pond; Total existing Rate -Proposed Dorm Rate= Proposed Garage Rate Allowable Runoff rate .xis 6126100 Return Frequency 5 10 25 50 100 Table 5 Detention Calculations Design Elevations HGL In Street Pond Description Elev. WSEL Top -of-Pipe 343.70 346.70 Gutter Line 349.0 347.40 Top-of-Curb 349.50 347.80 Top-of-Curb 349.50 348.20 Top-of-Curb 349.50 348.20 Design Elevations.xis 6126100 0 0 ........... (!) N ........... (!) 0 ~ z u > I (J) (J) 0 !'-.. / Q) ...... (/) / 0 <( u / (J) (J) 0 !'-.. (J) / 0... ~ Q) Q) L ~ (f) Cf) Cf) 0 L Tauber Street 1-----_ _Ju C~o~l~le~g~e:-7M7a~i-n--=-s~tr_e_e_t_J ~/,,---~~!=:::§~~~~~ c Q) > <( Q) Cf) ::::l 0 _J Second Street Project Location Boyett Street F.M. 2154 - w fib & South e orn Road ern Pacific WALTER;;MOORE STRUCTURAL CIVIL TRAFFIC PARKING ENGINEERS HOUSTON DALLAS 3131 Eastslde, Second Floor TAMP A Houston , Texas 77098-1919 ATLANTA Tel 713 .630 .7300 Fax 713.630 .7396 0 R LA N 0 0 I I 1 " 500' DD (!) > L 0 Q) >... ::::l -+-' c (/) Q) L (/) > (!) ::l <( > 0... ..c c E u ~ 0 L ::::l u ..c u 2 0 ~ <D <{ 2 (/) 0 LL x (!) I- VICINITY MAP WPMA P.N.: 97099 Engineer: RGL EXH IBIT No . Dote : 06/26/00 Drafter: cw 1.0