ARCHIVED REPORTS_2006 - Laserfiche WebLink

Home Browse Search

® 5.2 QA/QC RESULTS The QA/QC program completed for the fourth quarter 2006 water quality monitoring event included analyses of one duplicate sample, one field(ambient)blank, one trip blank, and one laboratory method blank. The trip, field, equipment, and laboratory method blanks were analyzed for volatile organic compounds (VOCs)by EPA Method 8260. Trace and/or quantifiable concentrations of VOCs including bromoform, chloroform, chloromethane, and dibromochloroethane were detected in the QA/QC ambient blank sample during the fourth quarter 2006 monitoring period. Bromoform, chloroform, chloromethane, and dibromochloromethane were detected in several of the primary samples collected, and were flagged suspected laboratory contaminants. BC Laboratories(BC)was notified of the suspected laboratory contaminants. A duplicate groundwater sample was collected from well MW-2 and was labeled MW-Dup. Duplicate groundwater test results are presented along with the primary data in Table 3. With the exception of bicarbonate, comparison of the primary sample with the duplicate sample indicates good agreement(within 10%) for the water quality constituents. 5.3 GROUNDWATER ELEVATIONS AND CONTOURS Prior to purging and sampling, each well was sounded for water depth using a weighted electronic sounder, and the static water level was recorded on a Well Data Sheet ® (Appendix Q. The groundwater elevations were calculated for each well by subtracting the depth-to-water measurement from the top-of-casing reference elevation. The current groundwater elevation data for the French Camp Landfill are summarized in Table 5. The groundwater elevation data obtained during this quarterly monitoring period were used to generate the groundwater elevation contour map shown on Figure 1, which indicates that groundwater flows to the east-northeast with an average hydraulic gradient of approximately 0.005 ft/ft. To calculate the approximate linear groundwater flow velocity for the site, conservative assumptions were used, including a hydraulic conductivity of 300 gallons per day per square foot(0.014 cm/sec), and an estimated effective porosity of 35 percent(CH2M Hill 2000). An estimated range in groundwater flow velocity was calculated using Darcy's Law: V = Ki - [(0.014 cm )* 0.005 ) 2835 sec— ft 0.567 ft/day ne sec 0.35 an —day where: V=Groundwater flow velocity. K=Hydraulic conductivity of the water-bearing unit(0.014 cm/sec). i=Hydraulic gradient: i m 0.005 for the site during the current(fourth quarter 2006) monitoring period. ne=Effective porosity(n,=0.35);an estimated value. ® The groundwater flow rate is calculated to be 0.567 feet/day(207 feet/year). n:\2003_021\1Fc_1Kdoc Geologic Associates