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�{ �l K,J E L D S E N Stephen K. Sinnock, RE <br />S S I N N O C K Christopher H. Neudeck, P.E. <br />Neal T. Colwell, P.E. <br />N NEUDECK Barry O'Regan, P.E. <br />inc. CIVIL ENGINEERS & LAND SURVEYORS <br />May 18, 2020 <br />Michael Callahan <br />Senior Civil Engineer <br />San Joaquin County <br />Department of Public Works <br />1810 East Hazelton Avenue <br />Stockton, CA 95205 <br />2414-0010 <br />08-300 <br />Re: Grindstone Joe's Wastewater Holding Tank — Floodway Determination & Impacts <br />Dear Mr. Callahan, <br />This letter is in response to your 4/27/2020 email regarding the floodway determination for the Grindstone Joe <br />Association site. This email requested additional information related to floodway definition No. 4 as stated in the <br />San Joaquin County Code Title 9 Section 9-110.4, which states: <br />Floodway. "Floodway" means: <br />(4) the river or other watercourse itself, between its levees or banks, to the elevation of the one -hundred <br />(100) year flood, if the Flood Insurance Maps do not indicate the floodway and the State Reclamation <br />Board has not established a designated floodway; or <br />There was a typo in the previously submitted letter, and based upon the evaluation, the project site does meet this <br />definition. However, it should be noted that his evaluation showed a reduction in cross-sectional area and fill <br />volume in the floodway. Although this reduction in volume would likely result in insignificant reduction in flood <br />stages or flood surcharges, a reduction in flow impedance can be expected in the 100 -year flood event. <br />The reduction in flow impedance is due to the fact that all proposed improvements to the site will be below grade. <br />Previously used above ground holding tanks have been removed, and the proposed wastewater holding tank is <br />entirely subgrade, and therefore not physically within the floodway. To ensure it is properly anchored and <br />compliant with County code, concrete deadman anchors are included in the design, and fill will be placed above <br />the tank (see previously provided Project plan set). All buoyancy calculations are based on a completely empty <br />tank, resulting in conservative calculations for the required ballasting. <br />We appreciate the SJC PWD's consideration of this information and we will be assisting the Association in <br />making application to the SJC EHD for construction of the new holding tank system. If you have any questions, <br />please contact me at ithomasa,ksninc.com or (916) 403- 5900. <br />Sincerely, <br />KJELDSEN, SINNOCK & NEUDECK, INC. <br />Joseph E. Thomas, RCE 90850 <br />CC (via e-mail): Jeffery Wong, Senior Registered Environmental Health Specialist, San Joaquin County <br />Elisabeth Beckensten, Kjeldsen, Sinnock & Neudeck, Inc. <br />Grindstone Joe's Association <br />Corporate Office: 711 N Pershing Avenue I Stockton, CA 95203 1 209-946-0268 1 www.ksninc.com <br />West Sacramento: 1550 Harbor Boulevard. Suite 212 1 West Sacramento. CA 95691 916-403-5900 <br />