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April 24, 2014 Mr. Michael Carroll, PE San Joaquin County Public Works Department (Solid Waste Division) PO Box 1810 Stockton, CA 95201 CB&I 180 Promenade Circle Sacramento, CA 95834 Tel: 916-565-4359 Fax: 916-565-4356 eric.schneider@CBI.com Subject: Response to final construction quality assurance report, Corral Hollow Sanitary Landfill, San Joaquin County Dear Mr. Carroll: On behalf of San Joaquin County, CB&I Environmental and Infrastructure, Inc. (formerly Shaw Environmental, Inc.) provides the following letter to address concerns of the California Regional Water Quality Control Board (RWQCB), Central Valley Region detailed in a letter from Mr. Vinoo Jain dated March 10, 2014 in regard to the potential impacts of over -compaction of the vegetative soil layer at Corral Hollow Sanitary Landfill, in San Joaquin County. CB&1 provides the following data and analysis regarding equipment used for the fine-grained vegetative cover soil placement, properties of the geomembrane installed, and the thickness of the vegetative cover used in the construction of the cap at Corral Hollow Landfill (Landfill). This analysis below verifies that the integrity of the geomembrane was not compromised during compaction of the vegetative cover. It is evident that equipment used to compact the cover soil did not damage the geomembrane at the Landfill when the vegetative cover was compacted to the densities reported in the Certification Report. Please note that the vegetative cover was specified to be placed at a maximum density of 88% to promote root growth, not to protect the geomembrane. The geomembrane cover was not subject to damaged when the vegetative cover was compacted to higher in-place density than intended. The analysis below details the basis for our conclusions. Review of Geomembrane Material Properties The 60 mil LLDPE Microspike geomembrane material product used for the Landfill Cover has a puncture resistance strength of 70 pounds (lbs.). Please see attached product data sheet. This is based on the ASTM D4833 test method which uses an 8 -mm (0.315- inch diameter rod, having test surface area of 0.078 square inches (sq. in.) subjected to 897 lbs. per sq. in. (psi). Review of Equipment Used The compactor used on site to compact the vegetative layer was a Caterpillar (CAT) compactor model CP563E. Please see the attached equipment specifications sheet. This compactor is a drum roller with pads. Each pad has an area of 13.9 sq. in. The drum has 10 pads in each row. The compactor's effective area of contact with the soil/geomembrane used in the landfill cap is a total of 139 sq. in. (i.e. 13.9 sq. in. x 10 pads). The maximum force this compactor can apply is 59,799 lbs. Therefore, the ground pressure