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APPENDIX B Page 2 of 3 <br />Holly Commerce Center Michaels TI’s, Formerly E&E Trading <br />Tracy, CA <br /> <br />Stockton San Jose Sacramento Modesto <br />3428 Brookside Rd. 111 N. Market St., #300 900 Howe Ave., #200 100 Sycamore Ave, #100 <br />Stockton, CA 95219 San Jose, CA 95113 Sacramento, CA 95825 Modesto, CA 95354 <br />t: 209.943.2021 t: 408.754.2021 t: 916.520.2777 t: 209.762.3580 <br /> <br />F:\17projects\17017 Holly Sugar Industrial\Civil\Septic Sizing - Prelim\17017 Holly Commerce Center E&E Nitrate Loading Memo <br />Ver 4.docx <br />along with any additional testing. It is likely that if the building use were to change to include more office <br />and demand a larger septic system, a portion of the trailer parking would no longer be necessary, and a <br />portion of the loading docks would be converted to auto parking and leach field. If nitrate treatment is <br />required due to an additional expansion beyond the currently proposed one that system will be designed <br />at the time a building permit is requested for additional office improvements to the building. <br /> <br />IV. Updated Nitrate Loading Analysis <br />It is understood that due to large amounts of impervious area in the historical Hantzsche-Finnemore <br />equation nitrate loading should be analyzed in the form of Attachment 1. The site is designed with a <br />detention and water quality basin that serves a dual purpose. The basin is designed to attenuate large <br />storm events so that Sugar Cut is not impacted while also capturing and treating the 85 th percentile storm <br />event with a total annual capture of least 80%. The following analysis is intended to replace the nitrate <br />loading calculation found at the bottom of Page 8 of the Chesney Report Dated May 6, 2019, due to the <br />increased flows from the Michaels TI’s expansion. <br /> <br />Revised Equation per Attachment 1 <br /> <br />nr = Wnw(1-d)+Rnb / (W+R) (See Attachment 1 for definitions of terms) <br /> <br />For this project: <br /> <br />W = 3.32 ac-ft/yr <br /> <br />nw = 146 mg N/L (per original report) <br /> <br />d = 30% (per original report) <br /> <br />nb = Assumed 0.1 ppm, NO3-N (per original report) <br /> <br />R = R1 + R2 = Average annual rainfall in ac-ft/yr (see below for analysis) <br /> <br />Total Site Area including the basin area = 45.57 acres (42.00 acres for the site plus 3.57 acres for <br />proportional share of the basin (80.8% of 4.43 acres) <br /> <br />Annual Rainfall = 9.5in (per San Joaquin County Standard Drawing D-3) <br /> <br />Total Runoff = 9.5in/yr x 45.57 acres x (1/12) = 36.08 ac-ft/yr <br /> <br />R1 = Portion of annual rainfall that is absorbed into leach field areas, landscaping less evaporation from <br />paved surfaces. For the sake of this analysis it is assumed that the site is 7% pervious and that 1% <br />of the runoff is retained in the pavement area and evaporated. The paved areas are approximately <br />32.1% of the site. <br /> <br />R1 = (35.57 ac-ft/yr x 7%) - (35.57 ac-ft/yr x 1% x 32.1%) = 2.4899 – 0.11418 = 2.3757 ac-ft <br /> <br />R2 = Portion of the annual rainfall that is captured by the basin and infiltrated, including any <br />evapotranspiration. Although Attachment 1 suggests a month by month analysis this analysis has <br />simplified the approach due to the fact that the County mandated storm water quality requirements <br />dictate that the basin capture and treat the 85th percentile event and capture and treat at least 80% <br />annually. Our storm water modeling estimates that in large storm events approximately 20% of the <br />storm water will be pumped to Sugar Cut. Per the figure below from Appendix D of the California