ARCHIVED REPORTS_XR0002252 - Laserfiche WebLink

Home Browse Search

initials of the person collecting the sample. The samples will be placed ' into an ice chest containing wet ice for delivery under chain of custody to a CAL-EPA certified analytical laboratory. Soil from the remaining tubes not sealed for analysis will be removed for hydrogeologic description and will be screened for volatile compounds with an OVM. The soil will be screened by emptying soil from one of the tubes into a plastic bag. The bag will be sealed and placed in the sun for approximately 10 minutes. After the hydrocarbons have been allowed to volatilize, the OVM will measure the vapor through a small hole punched in the bag. These OVM readings will be used as a screening tool only since these procedures are not as rigorous as those used in an analytical laboratory. All sampling equipment will be cleaned in buckets with brushes and TSP or Alconox solution, then rinsed twice with tap water. Rinsates will be contained on-site in 55-gallon steel drums until off-site disposal can be arranged. All of these shallow wells will be constructed within the hollow stem augers using 2-inch diameter flush-threaded, schedule 40, 0.020-inch slotted PVC well screen and blank casing. Each of these monitoring wells will be screened to monitor the top of the first water-bearing zone encountered. Based on the boring logs and depth to groundwater (6.5- feet bgs) during the previous soil and groundwater assessment at this site, ASE estimates that these wells will be screened between approximately 4 and 19-feet bgs. The well casing will be lowered through the augers and #2112 filter pack sand will be placed in the annular space between t h e well casing and the borehole from the bottom of the boring to approximately 1-foot above the screened interval. Approximately 1 -foot of bentonite pellets will be placed on top of the sand pack prior to placing the cement sanitary seal. Since the bentonite seal will be placed in the unsaturated zone, the bentonite will be hydrated with potable water prior to placing the cement sanitary seal. Cement mixed with 3 to 5 percent bentonite powder by volume will be used to fill the annular space between the bentonite layer and the surface to prevent surface water from infiltrating into the well. The seal will be placed by simply pouring the seal into the boring. The well heads will be protected with a locking well plug beneath an at-grade, traffic-rated well box (See Figure 4 - Typical Monitoring Well). 574 West Grand Line Road, Tracy, CA Workplan — June 2000 -6-