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Civil <br /> En��Crnmental <br /> Ft ateReures <br /> -1� <br /> MEMORANDUM <br /> ENGINEERING CORP. <br /> TO: Linda Turkatte,REHS <br /> Director, San Joaquin Environmental Health Department <br /> FROM: Norman Hantzsche,PE, Questa Engineering Corporatio��� <br /> DATE: October 11,2019 <br /> SUBJECT:Final-OWTS Design Review for Holly Commerce Center,Buildings A&B <br /> In my Memorandum of August 15,2019 I provided review comments on the plans and <br /> supporting design and Nitrate Loading Study for an onsite wastewater treatment system(OWTS) <br /> to serve the subject project in the Holly Commerce Center,Buildings A&B,in San Joaquin <br /> County.My comments and recommendations pertained to two main items: (1)provisions.for <br /> wastewater treatment and disposal to accommodate potential future changes in the uses and <br /> occupancy of the buildings; and(2)alternate nitrate loading methodology for sites developed <br /> with large impervious area. <br /> Revised plans, design analysis and responses addressing the review comments were prepared by <br /> Siegfried Engineering in a Memorandum, dated October 1,2019, I've reviewed the Siegfried <br /> Memorandum and find it satisfactorily addresses the issues and recommendation raised in my <br /> initial review,with my concluding notes as follows: <br /> 1. Provisions for Future Wastewater Needs. Appropriate provisions are included for ongoing <br /> monitoring and reporting of wastewater flows under the County's program for OWTS <br /> monitoring. <br /> The Siegfried Memorandum includes calculations of projected wastewater flows and disposal <br /> needs for potential future occupancy of the facilities up to their architectural capacity as <br /> office space. A drawing is provided depicting locations for future leachfields in the areas that <br /> would no longer be needed/used for loading docks(current plan). This is a reasonable <br /> assessment of how a future hypothetical change in use could potentially be accommodated <br /> for wastewater disposal(leachfields). However,it does not address the significant increases <br /> in wastewater nitrate loading that can be expected to accompany future changes in <br /> use/wastewater flows. My preliminary calculations indicate this would most probably require <br /> the inclusion of a supplemental treatment system for nitrogen removal in order to meet <br /> discharge criteria. Given the limited percolation information for the site,it's also likely that <br /> supplemental treatment would be needed to overcome soil/percolation limitations in areas <br /> impacted by years of truck traffic.Recognition of the probable future need for supplemental <br /> treatment, and where it could be located,should be included in the plans and/or permit <br /> documents,as clear notice to all parties. <br /> 1 <br /> Box 70356, 1220 Brickyard Cove Rd.Suite 206 Pt.Richmond,CA 94807 T:5101236.6114 F:510/236.2423 E.Questa®QuestaEC.com <br />