Laserfiche WebLink
LOGE 1844: Farris NLS Addendum Page 2 <br /> March 5, 2019 <br /> adsorption and adhesion in the soil would tend to substantially reduce the concentration <br /> of percolating effluent. <br /> The Hantzsche and Finnemore equation is a conservative approximation of ground- <br /> water nitrate-nitrogen concentration resulting from the combined effect of on-site <br /> sewage disposal systems and percolating recharge waters. The equation and method <br /> is for estimation of long-term effect ground-water quality, and is not intended for <br /> prediction of seasonal changes (Hantzsche and Finnemore, 1992). <br /> The method takes into account the development area, soil denitrification factor, rate of <br /> recharge from percolating waters, waste effluent quantity, and waste effluent nitrate <br /> concentration from on-site septic systems, and predicts the nitrate concentration of <br /> percolating effluent. <br /> On-Site Sources of Nitrate <br /> There are no current on-site sources of nitrate. No septic permits were identified for the <br /> Site from among the San Joaquin County Environmental Health Department permit <br /> files; the files are organized by address. <br /> The future on-site source of nitrate will be the new septic system for the proposed <br /> house. <br /> Percolating Recharge Waters <br /> Background <br /> One of the most determinant factors in the Hantzsche and Finnemore equation is the <br /> rate of recharge from percolating waters, which mix with the downward-percolating <br /> effluent generated by on-site septic systems. In the original Hantzsche and Finnemore <br /> paper, only "average recharge rate of rainfall" was considered. For the Chico area, <br /> Hantzsche and Finnemore present an average rainfall of 22.5 inches per year and an <br /> estimated recharge of 16.8 inches per year; the recharge value is 75 percent of the <br /> average rainfall. The source of the recharge value is not cited in the paper. <br /> Since the 1992 publication of the Hantzsche and Finnemore paper, numerous <br /> consultants have attempted to apply the method to calculate nitrate loading rates of <br /> projects and developments. Most notably, the City of Chico has continued to use the <br /> method to calculate desired urban density (County of Butte, 2000). In a 1996 technical <br /> memorandum published to support Chico's urban density requirements, the consulting <br /> firm Dames and Moore has discussed that "recharge ... is comprised of two major <br /> components: applied water ... and precipitation and streams." <br /> Dames and Moore discuss three methods of calculating the rate of recharge from <br /> percolating waters, two of which are computer models (SWQCB and HELP) that <br /> consider measured water levels, soil types, irrigation, stream flow, and other factors, <br />