|
E11C�yt® ENSR International
<br /> 10411 Old Placerville Road
<br /> Suite 210
<br /> October 29, 2004 Sacramento, CA 95827-2508
<br /> 1 (916)362-7100
<br /> FAX (916)362-8100
<br /> www ensr com
<br />' Mr James L Barton n(�i��'��YED
<br /> California Regional Water Quality Control Board W
<br /> Central Valley Region
<br /> 11020 Sun Center Drive, Suite 200 NOV 0 2 2004
<br /> Rancho Cordova, CA 95670-6114 ENVIRUNMENI HEALTH
<br /> �s �, V�ICES
<br />'
<br /> RE, Updated Site Conceptual Model, Quarterly Monitoring and Remediation e I
<br /> Installation, and Well Destruction Report,Third Quarter 2004
<br /> Former Unocal Facility No 5098
<br />' 5400 and 5606 Pacific Avenue, Stockton, California
<br /> Dear Mr Barton
<br />' ENSR Corporation (ENSR) has been authorized by Union Oil Company of California (Unocal) to
<br /> prepare an updated Site Conceptual Model (SCM) and Third Quarter 2004 Monitoring and
<br /> Remediation Status Report for the subject site Additionally, well installation and well
<br /> destruction activities for wells MW-9R and MW-9, respectively, are detailed in this report The
<br /> former site facilities were located at the former Montgomery Ward, LLC (Wards) site located at
<br /> 5400 Pacific Avenue and the former Unocal site located at 5606 Pacific Avenue, Stockton,
<br /> California (Figure 1) Groundwater monitoring was conducted pursuant to requirements of
<br /> Cleanup and Abatement Order (CAO) No 5-00-707, issued to Wards, Unocal, Surry California
<br /> Limited Partnership, and Stone Brothers and Associated General Partnership (Stone Bros ) on
<br />' September 8, 2000, by the California Regional Water Quality Control Board, Central Valley
<br /> Region (RWQCB) (Section 1 1 5) Well Installation and destruction activities were conducted in
<br /> accordance with ENSRs Monrtonng Well Installation and Well Destruction Work Plan dated
<br /> IJuly 30, 2004 The work plan to replace MW-9 with MW-9R was approved by the RWQCB, with
<br /> conditions, as specified in RWQCB letter dated August 4, 2004 The work was performed in
<br /> accordance with the field methods and procedures included in Attachment A The locations of
<br /> former and current site features are illustrated on Figure 2
<br /> Groundwater Level Measurements
<br /> IDepth to groundwater measurements were recorded for onsite and offsite monitoring wells on
<br /> July 12, 2004 Four water bearing zones identified beneath the subject site and vicinity Unit A,
<br /> Unit B, Unit C and Unit D This nomenclature was developed by Environmental Resolutions, Inc
<br /> irr��. J 4.......rJ ren o.#. r-nn ��fir nC nrPQPntPCI in ERI's Work Plan for Supplemental
<br /> k"ERI) and is based v1 e u� — ,. ...
<br /> Environmental Investigation report dated November 12, 1998 Unit A wells include MW-10A, MW-
<br /> 14A, MW-18, MW-19S, MW-21 S, MW-22S, and MW-25S which are screened from approximately
<br /> 30 to 50 feet below grade surface (bgs) Unit B wells include MW-1 through MW-7, MW-9 through
<br /> MW-17, MWA 8D, MWA 9D, MW-21 D, MW-22D, MW-25D, AS-26, and MW-27 through MW-30
<br /> which are screened from approximately 50 to 70 feet bgs Unit C wells Include MW-23S and MW-
<br /> 24S which are screened from approximately 85 to 90 feet bgs Unit D wells Include MW-8D, MW-
<br /> 23D, and MW-24D which are screened from approximately 97 to 103 feet bgs
<br /> 1\Dcsacramento\prDjects\Projects\0694015098-2931FinahReports\Quarterly Monrtonng ReportA5098 3rd Otr 04-QMR doe
<br /> 35 Years of Excellence in Enwonmenral Services
<br />
|