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LIGHT, AIR & SPACE CONSTRUCTION <br /> ENVIRONMENTAL SERVICES COMPANY <br /> ' State Contractors License Number 445403 <br /> State EPA R.E.A.Number 04072 <br /> Office 405-979-0661 <br /> ' contamination and tampering, and an at-grade well completion used with a traffic-rated well box <br /> noted as "monitoring well." <br /> ' 3.1 Monitories Well Development <br /> Each well was developed until the water is relatively free of fine grained sediments and sand <br /> pumping was minimal and/or until field measurements of pH, and electrical conductivity <br /> appeared to have stabilized. The actual number of volumes withdrawn for development is well <br /> dependent and based on the field judgment and are well-dependent. Duration of development <br /> ' was specific for each well and site aquifer conditions and continued until the water turbidity <br /> decreases and fine sand content decreases or is minimal. Well development notes were kept <br /> including quantity of water removed, and some general observations of turbidity, sand yield and <br /> ' well recharge. The well development field notes are attached. <br /> 3.2 Monitories Well Elevation Survey <br /> ' The new monitoring well casings were surveyed a known City of Manteca (monument in center <br /> of road lanes at comer of McKinley Avenue and Bronzan Road, 16.70 feet above NGVD) <br /> elevation datum for groundwater level measurements. <br /> 3.3 Monitories Well Sampling and On-site Drinking Water Well Sampling <br /> All sampling equipment was pre-cleaned prior to arriving on-site, decontaminated following <br /> each sampling event, prior to use the next monitoring well and prior to leaving the site. Depth to <br /> groundwater was measured to the nearest 0.01 foot, and the well checked for presence of <br /> separate phase product; no separate phase product was observed in any well. <br /> Each standing well volume was calculated, and well volumes were purged from the well prior to <br /> sampling depending on well performance and yield (LA&S used USEPA sampling guidance and <br /> the number of purge volumes are related to aquifer strata and specific to each well). <br /> Measurements of aquifer parameters (conductivity, temperature and the pH, turbidity, dissolved <br /> oxygen and salinity) of the water were taken with a Horiba U-1 meter calibrated on the day of <br /> ' use to the manufacturers specifications. Purge volumes were removed until parameters have <br /> stabilized to indicate that aquifer water is entering the well over at least two purge volumes. <br /> Aquifer water is assumed to be entering the well when these parameters are measured within a <br /> 10% range of the previous measurements. The sample was collected when the well recovers to <br /> within 80% of the original depth to water measurement (see attached Well Sampling Forms). <br /> The groundwater samples were collected using a Teflon© or PVC disposable bailer. <br /> ' One water sample was collected from the on-site drinking water well. The sample was collected <br /> from a nearby faucet. The faucet was opened and allowed to run for about 5 minutes, and then <br /> one sample was collected using the procedure described below. <br /> January 5 2009 Page 4 of 12 <br /> MAIN OFFICE • 1707 LITTLE ORCHARD STREET, SUITE A•SAN JOSE•CA•95125 <br /> MAILING ADDRESS•P.O.Box 36303•SAN JOSE•CA•95155-6303•408/979-0661 •408/979-0621 E.Ax•I.ASCONS I d AoL,(1\1 E-nuR <br /> GENERAL AND ENGINEERINGCONTRACTOR•I IALARDOUS SUBSTANCE REMOVAL CONTRACTOR'SITE EWIRONMENTAL ASSEssNIENTS <br /> WEI LAND AND RIPARIAN HABITAT—ASSESSMENT—DESIGN—RESTORATION—CONSTRUCTION—MITIGATION MONITORING <br />