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Dana G. Parry - 2 - 15 March 2019 will be used to backfill the storm drainpipe excavation on Parcel A. Soil will not be removed from Parcel A for offsite use. The scope of work is to, attain clean closure for the portion of WU1 on Parcel A by removing the remaining waste and industrial debris as well as associated impacted soil to environmental screening levels for commercial/industrial uses to protect public health and safety, eliminate the need for post -closure maintenance, and to prepare the area for post closure land use. A post closure maintenance plan will not be necessary for a clean closure which eliminates some maintenance requirements that would otherwise be required as part of the post closure land use. Additional Work Plan objectives include fulfillment of the requirements of: ➢ CCR Title 27 Sections 21810, 21090(f), and 21770(a), and the guidance outlined in the Local Enforcement Agency (LEA) Advisory #16, published by Cal Recycle to obtain clean closure and establish and identify all regulatory requirements. ➢ Clean Water Act and the State of California Porter -Cologne Water Quality Control Act to evaluate potential impacts to underlying groundwater that may pose a risk to human health and the environment. Following the completion of clean closure activities, a Verification Report confirming that waste and residual contaminated soils have been removed and disposed in concurrence with all relevant and appropriate regulatory requirements. Regional Water Board staff will review the Verification Report, and if appropriate, issue written confirmation that potential groundwater impacts were evaluated and does not appear to be impacted based on available data. Regional Water Board Comments 1. Regional Water Board staff concur with comments on the Work Plan provided by SJEDH in its 22 January 2019 letter Work Plan Addendum - Excavation and Material Management Plan for Parcel A (APN 198-120-08) of SWIS 39 -CR -00-0022, Former Pilkington North America -Lathrop Facility, 500 E Louise Ave, Lathrop, CA, and included as an attachment to this letter. 2. While staff also anticipate the area of WU1 waste beneath Parcel A is of similar character and composition to the waste found to the south on Parcel B, groundwater impacts must be verified through sample collection and analysis for COCs beneath Parcel A if staining is observed in the soil beneath the waste cell upon excavation. 3. DI WET analytical method testing was used at Parcel B to evaluate potential impacts from the historically unauthorized landfilled manufacturing waste and debris from WU1 to the underlying groundwater and the potential threat to human health and the environment. The Work Plan indicates that DI WET testing is not necessary for Parcel A since the excavated materials are planned for offsite disposal. Staff request inclusion of DI WET testing in the verification sampling plan in order to evaluate potential waste impacts to groundwater through leaching pathways and verify that pollution that was contained from WU1 at Parcel Bis also not impacting groundwater in this section beneath WU1 located on Parcel A. 4. Section 5.0 of the Work Pian discusses facility features that are not captured in Appendix C nor represented in Figures 2 and 3. Figures 2 and 3 show dated site photo for the Site Plan and Excavation and Waste Removal Site Plan figures. These figures