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Home My WebLink AboutMiscellaneousPLM15 EXAMWATION - Permit Number. Page of Dater ~~ Dtwg. .Code Num. Questions ~or Comments Num. Ref. From: Shirley Volk To: CWarren Subject: Desert Hills Carl: Did you get revised site plans on this showing the fire lanes? Have you issued a moving permit. yet? i 1 `~ ,~~ UJf~CE Wolton & flssociotes Consulting Engineers, lnc. 17Q4 Broodmoor, Suite 106 Bran, Texas 7780Q Phone 409-776-1000 Fax 409-776-1004 February lb, 1996 Mr. Robert L. Payne, Jr., AIA Holster & Associates.. 7607 EastMark, Suite :200 College Station, Tx 77840 Re: Revisions to the Drainage Study for Sandstone Psychiatric Center (Now Desert Hills Medical Center) Dear Mr. Payne, As per your request I have reviewed the drainage report and drainage plan issued in April 1987 .for the Sandstone Psychiatric Center in College Station, which was done by Walton & Associates and bears my engineering seal and signature. You requested that I provide this letter supplement to that report to consider the effects on the drainage system from adding 2700 square feet of roof area, in the form of a portable type building, to the site. The proposed construction would change 2700 square feet of what was previously considered landscaped area, having a runoff coefficient of .35, to hard surface, having a runoff coefficient of .90 These changes .would be made in what was. analyzed as drainage area 11 in the report. The attached "Revised Drainage Calculations" indicate that this change would result in an increase in runofffor the 5, 25, and 100 year return interval storms of .22 CFS, .10 CFS, and .36 CFS respectively for the. addition you propose. Tables 6 and 7 from the original report would indicate that the increases calculated would .cause no problem -for the detention basin, as far as requiring. additional storage volume. The additional runoff was not routed through the outlet control structure, however, no problems would be expected from the minimal additional flows for that analysis point. It must be noted however, that the original routing for the `5 year storm indicated a slghf increase (1.7 CFS) over the pre-development condition.. Now,. as then, this represents' only a slight increase and would not cause problems downstream, in all engineering probability. The 25 year and .100 year return intervals show routed'peaks below the pre-development condition.. It in unknown whether or not water depth at Junction Box 2 has been objectionable for the people using the parking and driveway areas, .based on an analysis that. shows 6" water depths. These depths can be expected to increase slightly due to the proposed construction, however, the changes should not be significant, and may not be noticeable. Supplemental Drainage Report Sandstone/Desert Hills February 16,1996 Page 2 In general changes such. as the one proposed do not affect the outfalls of tracts of this size, but can affect localized drainage patterns. Care must be takem when. grading the site around the proposed construction to provide adequate site specific drainage needs. If you need additional information on this matter please let me know. Sinc rely, ~. ~~a~h, ' d~ ~ 0 ~' o /} e ~ I I~~~ /li _-~ ~~..~...o.~~ ~A Jef~i-ey T. Milburn, P.E. ~b.q6 SANDSTONE /DESERT HILLS REVISED DRAINAGE CALCULATIONS (2-16-96) AREAS CONTRIBUTING TO ANALYSIS POINT 2 (JUNCTION BOX 2) AREA AREA PRE DEV NET PRE POST DEV NET POST DESCRIPTION NAME ACRES COEFF ACRES COEFF ACRES A7 0.385 0.30 0.116 0.85 0.327 PVMT W/ISLANDS A8 1.000. 0.30 0.300 0.35 0.354 LANDSCAPE A11 0.497 0.30 0.149 0.35 0.174 LANDSCAPE A12 0.463 0.30 0.139 0.85 0.394 .PVMT W/ISLANDS A14 0.095 0.30 0.029 0.90 0.086 PAVEMENT A16 0.468 0.30 0.140 0.35 0.164 LANDSCAPE A17 0.332 0.30 0.100 0.85 0.282 PVMT W/ISLANDS SUBTOTAL 2 3.241 0.30 0.972 0.55 1.776 AREA AREA PRE DEV NET PRE POST.DEV . NET POST DESCRIPTION NAME ACRES COEFF ACRES COEFF ACRES A7 0.385 0.30 0.116 0.85 0.327.. PVMT W/ISLANDS A8 1.000 0.30 0.300 0.35 0.350 LANDSCAPE A11 (MOD) 0.435 0.30 0.131 0.35 0.152 LANDSCAPE A11A 0.063 0.30 0.019. 0.90 OA57 BUILDING A12 0:463 0.30 0.139 0.85 0.394 PVMT W/ISLANDS A14 0:095 0:30 0.029 0.90 0.086 PAVEMENT A16 0.468 0.30 0.140 0.35 .0.164: LANDSCAPE Al T 0.332 0.30 0.100 0.85 0.282 PVMT W/ISLANDS SUBTOTAL 2 3.241. 0.34 0.972 0.559 1.8.11 PEAK FLOWRATES AT THE ANALYSIS POINT (iN CFS) ANALYSIS POINT 2 WUNCTION $OX 2) REVISED ORIGINAL DIFFERENCE Q ( 5 YR) = 0.559 X 7..69 IN/HR X 3.244 AC = 13.93 13.71 0.22 Q ( 25 YR) _ 0.559 X 9.86 iN/HR X 3.241 AC = 17.86 17.76 0.10 Q (100 YR) = 0.559 X 12.5 fN/HR X 3.241. AC = 22.64 22.28. 0.36 F ~s i6 ~~ 2~: d~Hr~ r~a~5 ~ ~ ~ HS~~H i t5 F.z ~ P.02 .. a TABLE 6 SUrIl~lARY OF RESIILTS RETIIRN PRE DEV POST DEV ROQTED Q PEAK MAX WS FREQUENCY PEAK Q PEAK Q IN PEAK OIIT STORAGE ELEVATION (CFS) (CFS) (CFS) (CF) 5 YEAR 20.97 `' 38.87 22.7 14077'.. 285.4 25 YEAR 26.89 51.09 25.2 20348:.. 285.8 100 YEAR 34.09 64.82 28.5 28997 286.3 TABLE 7 CAPACITY AND FLOWRATE SIIrIl~IARY __ 5 YEAR 25 YEAR 100 YEAR ANALYSIS CAPACITY FLOWRATE FLOWRATE FLOWRATE POINT (CFS) (CFS) (CFS), (CFS) 1 37.78 21.25 27.16 34.44 2 17.59 13.71 17.76 22.28 ~,} ~~_~ CITY OF COLLEGE STATIOI`I ~ P~r~~ '-~'~~~e ~~~: ~96f~ l ;ot Texas Avenue ~ ~oiiege Station, Texas ??II42-9960 (409) 76~-35t1m February 26, 1996 Jef~-ey T. Milburn, P.E. Walton & Associates Consulting Engineers, Inc. 1722 Broadmoor, Suite 106 Bryan, Texas 77802 RE: Addition of Classrooms Desert Hills Medical Center Drainage System Analysis Dear Mr. Milburn: We have reviewed your drainage report on the above referenced site and have found that it is in compliance with the City of College Station Drainage Ordinance. Therefore, the '~ report is approved. However, we will need an application prior to issuing a permit. Should you have any questions, please call me at 764-3570. . Sincerely, ~;~ Samantha Smith Engineering Assistant cc: Shirley Volk, Development Coordinator ,~J ~~ `tid - , D~ ~ ~ ;~ t"id"3Ys&F°, o~ ~ax2;:~c~ Rig- ~£n~=,r~~Sa~y~ G'~ \I Holster & Associates Transmittal Letter To /r`~~°~ G/JIJ~I~i~IA~. Date ~~ U~~ i~t`1 tP ~-t"~ ~~ ~'~t/~'~~ ~~C-~ Protect No. Attention /~ ~-t i2t~~~ ~~~~ 11 enclosures dre not as noted. please noafy our ott~ce Project ~f~-2,'~~t~ ~~.~,1- i~t1)f..fJl~-~ It checked below, please ~~~T ~ 1 ~~ 1 )Acknowledge receipt of enclosures. l ).Return enclosures to us. We Transmit: (~erewith ( )under separate cover via ( ) in accordance with your 'request For Your: ( )approval (.distribution to parties ( )information l )review 8 comment ( )record ( )use ( ) The Following: (~Tdrawings ( )specifications ( )change order l )shop drawings ( )product literature ( )samples ( ) correspondence t ) copies date no. description ~ l ~t.t..- ~ ~ ~~ ~ ~~~ - ~ ~ ~ ivy r-m~ ~~. ~ ~ ~ ~, =a r~'~ 1l"® C~ )3t~-,a1~t~ 1~~.,'k~B ~ ~ ~t~e~ 1F'iCAt`ta~ra3~ ~/~ I~ ~'1.1~ ~a V~In.IA ~TUD°°r' Cai~(~l~a~ f3~j' Remarks: O 0 0 Architecture, Planning and Interior Design 7607 EasiMark Drive. Suite 200 College Station, Texas 77840 409/693-3179