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Home My WebLink About2 Development Permit 555 Holditch Office Complex- DRAINAGE REPORT for TEMPORARY DETENTION HOLDITCH OFFICE COMPLEX PHASE II College Station, Texas December 1990 Prepared by : Garrett Engineering 4444 Carter Creek Pkwy. Suite 108 Bryan, Texas 77802 NOTE: Garrett Engineering is not responsible for the design of any building or parking elevations and grades. Garrett Engineering is al.so not responsible for the design of any stonn sewer for this project. - PRE-DEVELOPMENT The Project site is a 1.189 acre tract located adjacent to Phase 1 of the Ho/ditch Office Complex on Southwest Parkway. The site is presently covered with grass and weeds, characteristic of most undeveloped lots. 1he natural ground slopes toward the east. POST-DEVELOPMENT The planned construction consists of a 14,992 s.f office building and related parking. Runoff from the site is divided, with part flowing to Southwest Prkwy. and part flowing to the southeast into Phase ill. Detention will be provided on Phase Ill. Discharge will be released through a 4" P. V. C. pipe with the detention pond holding the increase in runoff due to development for a 10-year storm event. METHOD OF ANALYSIS 1he peak runoff from the site was computed using the "Rational Method" for pre-development and post-development conditions. The runoff was converted to a triangular hydro graph by plotting the peak rate of runoff vs . the time- of-concentration . The rescinding leg of the hydrograph was set at a length equal to 1. 76 times the time- of-concentration. The post-development hydro graph was routed through the proposed detention pond by the "Storage- Indication" routing method. PRE-DEVELOPMENT Avg. Slope = 1.53% Hydraulic Length = 180 ft. Runoff Velocity = 0.9 fps tc = 18010.9 = 3.33 min (use 5 min.) Sub-area Lot 1-B 0.30 Freq . Ian/hr) 5 9.85 JO 10.98 25 12.51 50 14.10 POST-DEVELOPMENT Avg. slope = 1.0% Hydraulic Length = 332 ft. Runoff Velocity = 2 . 0 fps .Area (ac) 1.185 QfJ;M 3.50 3.90 4.45 5.01 tc = 33212.0 = 2. 77 min. (use 5 min .) Sub-Area {;_ Pavement 0. 87 (toward S. W. Prkwy.) Landscaping 0 .30 (toward S. W. Prkwy.) Bldg. 0.87 Paving 0.87 (toward the S .E .) Landscaping 0 .30 (toward th e S .E .) Weighted "C" = 0. 73 0.3398 0.2956 0 .1359 0 .0408 0 .3471 0 .3020 0 .1855 0 .1614 0.2415 0.0725 Freq /(in/hr.) Q 5 9.85 8.52 10 10.98 9.50 25 12.51 10.82 50 14.10 12.20 Qiltcr<as< JQ-yrstoma '"'"' = 9.50 -3.90 = 5.60 cfs. Amount of Runoff contributing to detention Sub-Area Bldg. Paving La.ndscaping 0.87 0 .87 0 .30 Weighted "C" = 0. 69 0.3471 0.1855 0 .2415 QJQ-yr. stoma •v•fll = (0.69)(10.98)(0. 7741) = 5.86 cfs. 0.3020 0.1614 0.0725 * * * * * * * * * * * * * * * * DETENTION DESIGN * * HOLDITCH OFFICE COMPLEX * * PHASE II * * COLLEGE STATION, TEXAS * * * * * * * * * * * * * * * * * * * * DISK FILES : A:hold.HYD A:holdrev.RSV INITIAL CONDITIONS Elevation = 284 ft Storage = 0 cu.ft Discharge = O cf s GIVEN RESERVOIR DATA COMPUTATIONS ELEV. I STORAGE IDISCHARGEI (ft) I (cu. ft) I (cf s) 1---------1---------1---------1 I 284.0 I 0.0 I 0.00 285.0 I 5609.0 I 0.26 I 286.0 I 7891.0 I 0.26 I 2S/t (cfs) 1--------- 1 0.0 187.0 263.0 2S/t + 01 (cfs) ---------1 0.0 I 187.2 I 263.3 I -.. DISK FILES: A:hold.HYD A:holdrev.RSV GIVEN INFLOW HYDROGRAPH ROUTING COMP UTATIONS DATE 1000 1000 1000 1000 ,1000 11000 11000 11000 11000 11000 11000 11000 11000 11000 11000 HOUR 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 INFLOW I (cf s) I --------1 0.01 1.21 2.31 3.51 4.71 5.91 5 .11 4.5 3.8 3.2 2.5 1.9 1.2 0.5 0.01 Il +I2 (cfs) 0.0 1. 2 3.5 5.8 8.1 I 10.5 10.9 9.6 8.4 7.1 5.7 4.3 3.1 1. 7 0.5 2S/t -0 (cfs) 0.0 1. 2 4.6 10.4 18.5 29.0 39.8 49.2 57.4 64.2 69.7 73.9 76.7 78.2 78.5 PEAK OUTF LOW=.1. (cfs) 2S/t + 0 (cfs) 0 .0 1. 2 4.7 10.5 18.6 29.0 39.9 I 49.3 57.5 64.4 69.9 74.1 76.9 78.4 78.7 PEAK ELEVA T ION = 284.42(FT) STORAGE AT PEA K = 2359 (cu.ft) OUTFLO W! ELE V . (cfs) I (ft) --------1--------- 0.0 I o.o 0.0 0.0 0.0 0.0 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 28 4 .0 0 284.01 284.02 284.06 284.10 284.16 284.21 284.26 284.31 284.34 284.37 284.40 284.41 284.42 284.42 284.4 288.9 293.4 297.9 302.4 WATER ELEV. (ft) 0.1 1.3 2.4 3.6 4.8 6.0 I 1----------1-----------1-----------1-----------1-----------I I 0 -x PEAK ELEV. = 284.42 ft. I STORAGE = 2359 (cu.ft) Q MAX =.1. cfs 1 -xi/ * I 2 -x * 3 -x * 4 -x * 5 -x 6 x 7 x 8 x 9 -I x 10 -I x 11 x * \ I HOUR * * x * * * * Inf low Hydrograph Data Reservoir Outflow Hydrograph ROUTED FILES: hold.HYD; holdrev.RSV FLOW (cfs) ·-------5' -----·-~ 1-.· I . I PO'&-t -Development l-Jy dro9raph Con+ributtn3 w De t entio n Q peak = C?, BG, ct5' T;me. ------1 ! 0 I z '3 4- ~ (, 7 s 0 to II IZ ,., 14 Q 0 1.17 ~.-ot ::i. s +.&9 17. e& ~o~ 4.~ ~JJ9 3:z o 'l...00 /.<0 0 . J, 1.0 o,0Z 0 DRAINAGE REPORT for TEMPORARY DETENTION HOLDITCH OFFICE COMPLEX PHASE II College Station, Texas December 1990 Prepared by: Garrett Engineering 4444 Carter Creek Pkwy . Suite 108 Bryan, Texas 77802 NOTE: Garrett Engineering is not responsible for the design of any building or parking elevations and grades. Garrett Engineering is also not responsible for the design of any stonn sewer for this project. PRE-DEVELOPMENT The Project site is a 1.189 acre tract located adjacent to Phase l of th e Ho/ditch Office Complex on Southwest Parkway . The site is presently covered with grass and weeds, characteristic of most undeveloped lots. The natural ground slopes toward the east. POST-DEVELOPMENT The planned construction consists of a 14,992 s.f office building and related parking. Runoff from the site is divided, with part flowing to Southwest Prkwy. and part flowing to the southeast into Phase Ill. Detention will be provided on Phase Ill. Discharge will be released through a 4" P. V. C. pipe with the detention pond holding the increase in runoff due to development for a 10-year storm event. METHOD OF ANALYSIS The peak runoff from the site was computed using the "Rational Method" for pre-development and post-development conditions. The runoff was converted to a triangular hydrograph by plotting the p eak rate of runoff vs. the time- of-concentration. The rescinding leg of the hydro graph was set at a length equal to 1. 76 tim es the time- of-concentration . The post-development hydro graph was routed through the proposed d etention pond by the "Storage- lndication" routing method. PRE-DEVELOPMENT Avg. Slope = 1.53% Hydraulic Length = 180 ft. Runoff Velocity = 0.9 fps tc = 18010.9 = 3.33 min (use 5 min.) Sub-area Lot 1-B 0.30 Freq. !(in/hr) 5 9 .85 10 10.98 25 12.51 50 14.10 POST-DEVELOPMENT Avg. slope = 1.0% Hydraulic Length = 332 ft. RunojJVelocity = 2.0.fps Area (ac) 1.185 QJef1J. 3.50 3.90 4.45 5.01 tc = 33212.0 = 2. 77 min. (use 5 min.) Sub-Area ~ Pavement 0. 87 (toward S . W. Prkwy .) Landscaping 0.30 (toward S . W. Prkwy.) Bldg. 0.87 Paving 0.87 (toward the S.E.) Landscaping 0.30 (toward the S .E .) Weighted "C" = 0. 73 0.3398 0.2956 0.1359 0.0408 0.3471 0.3020 0.1855 0.1614 0.2415 0.0725 Freq !(in/hr.) Q 5 9.85 8.52 10 10.98 9.50 25 12.51 10.82 50 14.10 12.20 Qincreare Jf>.yrstonn even/ = 9 .50 -3 .90 = 5 .60 cfs. Amount of Runoff contributing to detention Sub-Area Bldg. Paving La.ndscaping 0.87 0 .87 0.30 Weighted "C" = 0.69 0 .3471 0 .1855 0.2415 Qlf>.yr. stonn even1 = (0.69)(10.98)(0. 7741} = 5 .86 cjs. 0.3020 0 .1614 0.0725 * * * * * * * * * * * * * * * * DETENTION DESIGN * * HOLDITCH OFFICE COMPLEX * * PHASE II * * COLLEGE STATION, TEXAS * * * * * * * * * * * * * * * * * * * * DISK FILES : A:hold.HYD A:holdrev.RSV INITIAL CONDITIONS Elevation = 284 ft Storage = O cu.ft Discharge = 0 cf s GIVEN RESERVOIR DATA ELEV. I STORAGE IDISCHARGEI I (ft) I (cu. ft) I (cf s) I 1---------1---------1---------1 I 284.0 I 0.0 I 0.00 I 285.0 I 5609.0 I 0.26 I 286.0 I 7891.0 I 0.26 I COMPUTATIONS 2S/t 12S/t + 0 (cfs) (cfs) 1---------1--------- 1 0.0 I 0.0 187.0 I 187.2 263.0 I 263.3 SK FILES: A:hold.HYD A:holdrev.RSV GIVEN INFLOW HYDROGRAPH RO UTIN G COMPUTATIONS ------------------------------------------------------------------------- DATE HOUR I INFLOW I Il+I2 2S/t -0 I 2S/t + 01 OUTFLOW I ELEV. I I (cfs) (cfs) (cfs) (cfs) I (cfs) I (ft) I ·--------1----------------1 ------------------1--------1--------1--------- 1000 0 0.01 0.0 0.0 0.0 0.0 I 284.00 I 1000 1 1.21 1. 2 1. 2 I 1. 2 0.0 284.01 11000 2 2.31 3.5 4.6 4.7 0.0 284.02 1000 3 3.51 5.8 10.4 10.5 0.0 284.06 1000 4 4.71 8.1 18.5 18.6 0.0 284.10 11000 5 5.91 10.5 29.0 29.0 0.0 284.16 1000 6 5.11 10.9 39.8 39.9 0.1 284.21 1000 7 4.51 9.6 49.2 49.3 0.1 284.26 1000 8 3.8 8.4 57.4 57.5 0.1 284.31 11000 9 3.2 7.1 64.2 64.4 0.1 284.34 1000 10 2.5 5.7 69.7 69.9 0.1 284.37 1000 11 1.9 4.3 73.9 74.1 0.1 284.40 11000 12 1.2 3.1 76.7 76.9 0.1 284.41 1000 13 0.5 1.7 78.2 78.4 0.1 284.42 1000 14 0.0 0.5 78.5 78.7 0.1 284.42 ------------------------------------------------------------------------- PEAK OUTFLOW=.1. (cfs) PEAK ELEVATION = 284.42(FT ) STORAGE AT PEAK = 2359 (cu.ft) 284.4 288.9 293.4 0.1 1.3 2.4 297.9 302.4 3.6 4.8 WATER ELEV. (ft) 6.0 I l----------1-----------1-----------1-----------1-----------I FLOW (cfs) I 0 -x PEAK ELEV. = 284.42 ft. STORAGE = 2359 (cu.ft) Q MAX =.1. cfs 1 -xi/ * I 2 -x * 3 -x * 4 -x * 5 -Ix 6 x 7 x 8 x 9 x 10 x 11 x * \ I HOUR * * x * * * * Inf low Hydrograph Data Reservoir Outflow Hydrograph ROUTED FILES : h o ld.HYD ; holdrev.RSV " . 5' 1-.· P~-t--Development Wydro9raph Contribuhn9 w Deten tion Q peak = 9, BG, cts- Tim& 0 J ·---------z ? 4- 5 & 7 I ---1 i 0 --l-----+--IO 11 ll ,., I 14 -: -------I : I I I ---i--+----i-------i-- I I l -----.--r -----------1---1 --- I I Q 0 1.17 ~.oz ~.s 4;'79 9. ec., ~OIS' 4.9 ~.SC? 3.i o 'l..t:;O /.0 0 · /,10 0.02 0 4 7 0 0 /0 II IZ '~ 14 11;7 j(, 17 '~ 19 'LL! January 2, 1991 Holster & Associates 7607 Eastmark Drive, Ste. 200 College Station, TX 77840 Re: Holditch Office Bldg. Phase II Dear Constantine: f ILE COPY I am in receipt of the drainage report prepared in part by Garrett Engineering. It appears the engineer has not designed the grades, storm sewer pipe, nor is his stamp on the plan showing details. Our ordinance requires these items be designed by a registered professional engineer. Therefore, we are unable to release a development permit for this project. Enclosed please find an application for a development permit. Please fill out the application and resubmit the report with the engineer's seal if you would like for staff to continue the review process. Sincerely, Deborah Leslie Keating, P.E. Project Engineer cc: David Pullen, City Engineer Veronica Morgan, Assistant to the City Engineer DK/ejm ' . / DRAINAGE REPORT for TEMPORARY DETENTION HOLDITCH OFFICE COMPLEX PHASE II College Station, Texas December 1990 Prepared by: Garrett Engineering 4444 Carler Creek Pkwy. Suite 108 Bryan, Texas 77802 DRAINAGE REPORT for TEMPORARY DETENTION HOLDITCH OFFICE COMPLEX PHASE II College Station, Texas December 1990 Prepared by: Garrett Engineering 4444 Carter Creek Pkwy. Suite 108 Bryan, Texas 77802 ( "----· . Figure XII-1 Applicat i on Form Development Perm i t For Areas Outside Flood Hazard Areas City of College Station, Texas ( re : 0 rd i n a n c e No . ) Site Legal Description: Lot 1 , Block 7 Southwest Crossing PH III Site Address: 902 Southwest Parkway Located in: Wolf Pen r;r eek -1 ,189 AC Wat e rshed Owner: Architect/ Engineer: SA Holditch& Associates ~---~--~------ Address: 900 Southwest Parkway E Telephone No.: -+-7 ~64:i:.......l~lu2~2~---- Address: 7607 Ea~tmark , Suite 200 Holster & Associates , Inc Telephone No.: 693 31 79 ~-------- Contractor: .James Holster Address: 7607 Eastmark, Suite 200 Tel e phone No. : __;..69._J.._-...... J=l ...... 79.__ ___ _ Date Application Filed: 1/7/91 -----------Approved: Application is hereby made for the following development: Holditch Office Complex , Phase II Attached as part of this application: Application Fee Drainage Plan with supporting documentation: two copies of each Other: ACKNOWLEDGEMENTS: I, ""$.A. y\dJ~ tc..l.. 1 l ..... c... , as owner, hereby acknowledge or affirm that: The above Drainage Plan and supporting documents complies with the requ i rements of Ordinance No. '~ l ,l '"fi t Da te ' 98