ARCHIVED REPORTS XR0009904 - Laserfiche WebLink

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�l Corrective Action Plan Page 31 All water samples will be analyzed by a laboratory certified by the CEPA to perform the cited analyses Back-filling of Excavation When the remedial excavation has reached its maximum area and depth, the excavator will be used to carefully remove loose or soft material from the submerged floor of the pit Immediately that the bottom of the excavation has been prepared, clean crushed rock in the 3 in to 1 1/2 in sieve-size grading with no fines will be placed in the bottom of the pit in a umform lift until a hard standing is formed just above the water table The crushed rock will then be thoroughly compacted using a vibratory roller depth of the remedial excavation with clean open-graded, Back-filling of the submerged dep crushed rock will permit contaminated groundwater to be pumped from the pit while reducing the risk of instability in the walls of the pit or subsidence of surrounding ground W due to displacement of flowing sands by the action of the resultant groundwater flow As noted previously, when the crushed rock has been compacted in the bottom of the remedial excavation, a sump will be opened in the rock to permit pumping of groundwater When pumping from the remedial excavation is complete, the remaining open volume of the pit will be backfilled with imported Caltrans Class II aggregate-base material In the upper 2 ft , the aggregate base will be compacted to 95% relative density as determined by nuclear density gauge tests performed according to American Society for Testing and Materials (ASTM) Standard D2922 calibrated against a compaction test performed according to ASTM Procedure D1557 (Method A) The aggregate-base fill beneath the upper 2 ft thickness, down to the depth of the previously placed crushed rock in the bottom of the pit, will be compacted to 90% relative density (Note Subject to the approval of the engineer, clean soil suitable for the purpose may be substituted for the aggregate base material except in the upper 2 ft of fill ) Treatment of Excavated Soil As previously described, contaminated soil removed from the remedial excavation will be transported to a site on fallow agricultural land in a rural area off West Blewett Road southeast of Tracy This location is shown on Figure 9 and is more than 1000 ft from any structure and remote from any residence A permit to treat the soil by aeration will be obtained from the STVUAPCD under District Rule 4651, Volatile Organic Compounds Emissions from Decontamination of Soil Section IV B - Limited Aeration (Ref 5) The actual volume of contaminated soil that will be excavated and transported to the treatment site will depend upon the specific distribution of components of hydrocarbons found in the subsurface and any restrictions that the engineer in responsible charge of the