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HomeMy WebLinkAboutResponse to CommentsKimley-Horn and Associates , Inc. Southwest Crossing -College Station, Texas Memorandum To: From: Erica Bridges Chris Harris Subject: Southwest Crossing, Lot 2-R William Brooke Hunter Estates Response to City Comments Date: August 18, 2009 This memorandum is to address the City of College Station staffs comments on the above mentioned project as received by Kimley-Horn and Associates, Inc. on August 12, 2009. The following information has been included in this submittal for your review. • Response to Comment Letter • Easement metes and bounds • Current property deed • One set of revised construction documents Please find the written responses to staffs comments on the following pages. The original city comment is listed followed by our response in bold print. ENGINEERING COMMENTS NO. 2 I. Easement -The Easement Dedication Application cannot be processed until we receive the following items: • One copy of the current deed or title insurance policy (within 90 days). • One metes and bounds description and diagram of the easements being dedicated. Please see the attached property deed and easement metes and bounds. J Sh. 3 -Please provide a note specifying that Open Cut construction methods are not permitted and the waterline installation across Southwest Parkway will be by Dry Mechanical Bore. Comment addressed, refer to Water Note #17. J Sh. 3 -Please provide a note specifying that these grades and vegetation must be maintained by the owner to insure the creek will function hydraulically as designed. Comment addressed, refer to Grading Note #11 Page 1of4 KHA Job No. 066076000 K:\CST_Civil\67543000\docs\Response to Review Engineering Comments 20090812.DDC Kimley-Horn and Associates, Inc. Southwest Crossing -College Station, Texas /Sh. 8 -Please verify that minimum TCEQ hmizontal separation distance is being me where the waterline is tying in on Southwest Parkway. Comment addressed. A deflection has been added to the water line to maintain a parallel separation from the sanitary sewer. I Sh. 8 -It appears that 6x6 tees are being proposed for the domestic waterlines to the buildings. Please verify what size the domestic service lines and meters need to be. j Comment addressed V Sh. 8 -The fire hydrant lead should only be a 6-inch waterline. Please revise. j Comment addressed V Sh. 8 -At Sta . 2+67 .16 a tee and gate va lve should also be specified in addition to the fire hydrant assembly. j Comment addressed ../ Sh. 9 -In addition to the flow lines provided, please label the flow line at I 00-ft intervals. Comment addressed /sh. 9 -The waterline material should be labeled as C909, DR14, Class 200. / Comment addressed ~Sh. 9 -Label the separation distance between the water and storm sewer pipe at their crossing. I Comment addressed . Sh. I 0 -There should be two additional tees shown on the public portion of the waterline. Comment addressed Liss 10 -Profile drawings are also required for the li nes serving the fire hydrants. Comment addressed, profiles added to sheet C-10 . Sh. 11 -Note #5 makes it appear that the rip rap at the curb cuts are temporary and should be removed at the end of the project. The rip rap needs to be shown and labeled on the site plan. It should be clear that these are permanent structures. KHA Job No. 066076000 Comment addressed. The call out has been revised to indicate that the rip-rap is permanent. Page 2 of 4 K:\CST_Civil\67543000\docs\Response to Review Engineering Comments 20090812.DOC Kimley-Horn and Associates , Inc. Southwest Crossing -College Station, Texas 14. Drainage Report -What is the velocity at the curb cuts? Verify that the rip rap is the appropriate velocity dissipation device ba sed on the di scharge velocity at those points. DA The velocities have been calculated and are shown below. All of the velocities are below 3 fps in the 100 year event. DEPTH OF FLOW AREA 0 100 LENGTH FLOW (FT2) VELOCITY DA-1 2.37 5 0.27 1.37 1.729 DA-2 1.92 5 0.24 1.19 1.612 DA-3 0.48 5 0.09 0.47 1.014 DA-4 6.16 5 0.52 2.59 2.376 DA-5 10.42 5 0.74 3.68 2.831 DA-6 10.57 5 0.74 3.72 2.845 DA-7 9.67 5 0.70 3.50 2.762 DEPTH OF FLOW = (0100/(C*L))213 VELOCITY = 0 100/(Height*Length) 15. Drainage Report -Why are the "Site" flows in the supplementary report recently submitted different from the flows for Basin "A l" given in the original report? The differences in flows are a result of using different methodologies in the modeling. In the original report, KHA utilized the NRCS curve number method where we adjusted curve numbers to account for differences in impervious cover between existing and proposed conditions. The model provided to l(jmley-Horn by the City for the downstream analysis utilizes exponential loss and the Snyder Unit Hydrograph method. In order to maintain consistency with the methodology of the modeling provided by the City when breaking out the proposed site, KHA kept the values from the original drainage basin and adjusted the impervious cover to match the proposed impervious cover on site. KHA also adjusted the lag time for the site to be consistent with the modeling of the detention timing study. 16. Drainage Report -Please clarify the difference between the 100-year flow on Sheet C07 of 38.75cfs and the 100-year flow on the Watershed Drainage Area Map of 31.Scfs. KHA Job No. 066076000 The flow values shown on Sheet C07 were calculated for the on-site drainage areas using the rational method with an assumed 10 minute time of concentration. The Page 3 of 4 K:\CST_Civil\67543000\docs\Response to Review Engineering Comments 20090812.DOC KHA Job No. 066076000 Kimley-Horn and Associates, Inc. Southwest Crossing -College Station, Texas flows shown on the Watershed Drainage Area Map provided with the detention timing analysis were generated using the NRCS method in HEC-HMS. Page 4 of 4 K:\CST_Civil\67543000\docs\Response to Review Engineering Comments 20090812.DDC