WORK PLANS - Laserfiche WebLink

Home Browse Search

constituent concentrations. Therefore, a follow-up sampling for indoor air will be tentatively scheduled for approximately six months after the initial indoor sampling is implemented. However, the frequency and timing of follow-up sampling may also be guided by the initial concentrations of VOCs detected in accordance with January 2016 DTSC Human Health and Ecological Risk Office, Human Health Risk Assessment Note Number 3 and August 23, 2014 DTSC Human Health and Ecological Risk Office, Human Health Risk Assessment Note Number 5 (discussed in Section 1.3). The air samples will be transported under a sample chain of custody to Eurofins/Air Toxics, in Folsom, California, a laboratory certified by the State of California for analysis of air samples. To protect sample integrity, soil gas samples to be analyzed will not be chilled. The samples will be analyzed by Modified Method TO-15 Selective Ion Mode (TO-15 SIM). 5.2.2 Proposed Sub-Slab Soil Gas Probe Installation Methods The proposed sub-slab soil gas assessment will be conducted in general accordance with the July 2015 DTSC document titled Advisory-Active Soil Gas Sampling (Advisory). The three proposed sub-slab soil gas sample locations within the interior of the Quality Cleaners as shown on Figure 6. One sample will be proximate to the floor drain in the boiler room and the location of the December 2014 sub-slab soil gas sample SG1, a second sample will be proximate to the dry cleaning machine and December 2014 sub-slab soil gas sample SG2, and a third sample will be within the southwestern portion of the dry cleaners suite and proximate to the inferred location of the sewer lateral. The soil gas probes will be completed with a four-inch diameter well vault. The permanent soil gas probes will allow for resampling as necessary. Eight-inch diameter cores will be removed from the concrete slab at the sample probe locations. The well vaults will be installed flush with the floor and secured with a redi-mix concrete. Eight inch diameter holes will allow for observation of the sub-slab material. Sub-slab soil gas probes consisting of sample tubing and a porous tip will be inserted to approximately four to six inches below the concrete floor. Flexible sampling tubing will be 1/4 -inch in diameter made of Teflon that will not react or interact with VOCs. Clean, dry, dedicated tubing will be used for sampling. No moisture, water, or any unknown material will be present in the probes prior to insertion. During installation of the probes, clean sand will be used to support the sample tip and a transition seal of dry granular bentonite will be placed between the sand pack and neat cement grout. To allow for the subsurface to equilibrate o representative conditions, each probe was not purged or sampled for at least two hours following probe installation. The sample probe will covered with a shroud (plastic tote or overturned 5-gallon plastic bucket) during the sampling process. The permanent soil gas probes will be secured and completed to prevent infiltration of water or ambient air into the subsurface and to prevent accidental damage or vandalism. The tubing will be marked at the surface to identify the probe location and depth. A gas-tight valve or fitting for capping will be affixed to the sampling tube. The sub-slab soil gas samples will be collected and analyzed by on-site mobile laboratory using gas-tight glass syringes which will allow the analytical results to be available within approximately 30 minutes after Sampling and Analysis Plan Tracy Corners Shopping Center 3225 North Tracy Boulevard Tracy,California 95376 Partner Project Number SM14-129814 Docket Number HAS-VCA 14/15-108 August 15,2016 Page 14