SU0004419 SSNL - Laserfiche WebLink

Home Browse Search

KLEINFEL DER Impacts, Hantzsche and Finnempre (1992)), which is presented below with an explanation for each factor and the values used in our study. Since the site will be developed for commercial use, only one residence was assumed in our analysis rather than two residences as required by SJCPHS for residential properties. The selection of other parameters was based on previous studies by our firm, as well as a report dated March 19, 1997 prepared by the Questa Engineering Corporation and authored by Mr. Hantzsche. We have chosen to use the same values considered appropriate by Mr. Hantzsche for his report, with the exception of an increased value for percent denitrification(D)that has been modified based on recent local testing. N,=AWNS(1-D)+(Nb)r AW+r Where: N. = Average calculated nitrate in groundwater resulting from domestic sources and precipitation —mg/l, as N A = Number of dwelling units per acres on septic tanks (unit/acre) = 0.11 (single occupied building on 9.53 acres) W = Annual wastewater loading per dwelling unit per acre (inches) = 0.21 inches (based on 150 gpd/residence) Nw = Nitrate concentration of nitrified leachfield effluent (mg/1) = 45 mg/1 typical (Hantzsche and Finnemore (1992)) D = Percent dentrification of leachfield effluent=0.35 percent R = Annual deep percolation of precipitation(inches)= 4.0 inches (used by Mr. Hantzsche in the Stockton area to reflect the sandy soil conditions anticipated at the percolation depths for the leach trenches.) Nb = Background nitrate concentration of the deep percolating precipitation—mg/1=2.2 mg/1 as N Our calculations are as follows: Single Office/Apartment Building N� _ .11 (0.21 (45) 0 — 0.35)+2.2 (4) = 0.68+ 8.8 = 2.36 mg/l as N .11(0.21)+4 0.02 +4 In summary, the Hantzsche equation indicates that effluent generated by the proposed office/apartment building will not raise the nitrate level in groundwater above state standards. One of the factors required b the SJCPHS is to determine the existing value of nitrate in the groundwater below the site. rjAccordingly, a sample of groundwater was obtained using clean procedures from a well located at a home site immediately to the ea 5f the sub' ct site The results of our evaluation showed a nitrate as NO3 concentration of 19.6 mg/1. Thif value correlates to a nitrate as N concentration of about 4.4 mg/L 04. 'JI I''� During our recent services, the sample of groundwater obtained f6r nitrate testing was also evaluated for DBCP in accordance with EPA method 504.1. The results of the tests indicated a non-detectable concentration of this constituent. Results of our tests are attached. 204654-01.601/2011R1357 November 6,2001 ®2001 Kleinfelder,Inc. Page 3 of 4