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CA
<br />Revised Work Plan for Additional Site Investigation
<br />Raymond Investment Corporation
<br />Former Helena Chemical Facility
<br />February 27,2018
<br />Page 3
<br />Condor conducted additional soil and groundwater investigations at the Site in 2016, including the
<br />installation, development, and sampling of three groundwater monitoring wells, to determine the nature and
<br />extent of impacts to the Site from past uses and whether further cleanup activities are necessary or cost
<br />effective. The Central Valley Water Board required that additional constituents of concern, including
<br />triazines and the chlorinated fumigant 1,2,3-TCP, also be evaluated as part of the investigation. Based upon
<br />analytical results of soil and groundwater samples collected during the investigation, Condor concluded
<br />that soil and groundwater beneath the Site has been impacted by nitrates and potentially by the chlorinated
<br />fumigant 1,2,3-TCP.
<br />Periodic groundwater monitoring and sampling conducted at the Site have confirmed the presence of
<br />elevated concentrations of Nitrate-N and 1,2,3-TCP in shallow groundwater beneath the Site. Based upon
<br />groundwater elevation measurements collected at the Site, shallow groundwater has flowed toward the
<br />northwest (May 2016 and June 2017), south (September 2017), and southeast (December 2017).
<br />Appendix A of this report contains figures showing the Site vicinity (Figure 1), historical site features and
<br />locations of initial soil and groundwater samples (Figure 2), and locations of monitoring wells and soil and
<br />groundwater samples collected in 2013 and 2016 (Figure 3), among others. Appendix B includes data tables
<br />that summarize historical soil and groundwater data.
<br />4.0 SENSITIVE RECEPTOR SURVEY
<br />At the request of the property owner, and as directed by Central Valley Water Board, Condor conducted a
<br />sensitive receptor survey within a 1,000-foot radius of the Site. The intent of the sensitive receptor survey
<br />is to identify potential surface water bodies, wells, parks, schools, child and health care centers, and other
<br />potential sensitive receptors that are present within 1,000 feet of the site. A vicinity map is shown on Figure
<br />1 (Appendix A) and a well investigation map showing the area of study is shown on Figure 4 (Appendix
<br />A).
<br />The survey included contacting the California Department of Water Resources (DWR), California Water
<br />Service, the City of Stockton, and property owners; and reviewing available well records, current and
<br />historic maps, and other publicly available information.
<br />Based on our review of available well records provided by DWR, street and topographic maps, GIS parcel
<br />layers through California Online ParcelQuest, current and historic cleanup sites through GeoTracker and
<br />EnviroStor, communications with property owners, and inquiries to the City of Stockton and California
<br />Water Service, there does not appear to be a risk from the site's groundwater plume to sensitive receptors
<br />within the 1,000 feet of the site. Additional information is provided in the following Sections 4.1 through
<br />4.4.
<br />4.1 WELLS WITHIN 1,000 FEET OF THE SITE
<br />4.1.1 Department of Water Resources
<br />DWR provided Condor with 220 records for wells located near the site based on township, range, and
<br />section, and 22 records for wells potentially located within the 1,000-foot study area. Each of the 22 well
<br />records potentially located within 1,000 feet of the site was evaluated in conjunction with Assessor's Parcel
<br />Maps, street maps, and historical aerial maps for location relative to the site.
<br />Seven of the 22 DWR records were associated with wells within the study area. Five of these seven DWR
<br />records were for the destruction of groundwater monitoring wells associated with a former leaking
<br />underground storage tank (LUST) site located at 2150 West Charter Way, south of the site. One of the
<br />CONDOR
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