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IF 1117 Lone Palm Avenue, Suite 201
<br /> Modesto, California 95351
<br /> Wr kTc 209-579-2221
<br /> ENVIRONMENTAL • GEOTECHNICAL Fax: 209-579-2225
<br /> BUILDING SCIENCES • MATERIALS TESTING
<br /> Monitoring wells MW 16, MW 18, and MW 19 were developed on February 28, 2008. MW 17 was purged
<br /> dry after removing one gallon of water. The odor of grout in the purged groundwater coupled with high
<br /> pH measurements (9.5 - 11.6) indicated the potential presence .of grout inside the well. The total depth
<br /> of the well was measured to be approximately 50.6 feet. Monitoring wells MW16 through MW19 were
<br /> surveyed relative to NAD 83 and NGVD29 for position and elevation.
<br /> On March 6, 2008, groundwater samples were collected from MW1 through MW6, MW8, MW9,
<br /> MW 12, MW 16, MW 18, and MW 19. Petroleum hydrocarbons were detected in all the groundwater
<br /> samples, with the exception of the groundwater sample collected from MW 16. The results of the
<br /> subsurface investigation activities are presented in ATC's Subsurface Investigation Report, dated April
<br /> 23, 2008.
<br /> On March 31, 2008, an ATC geologist supervised the destruction of MW 17 and installation of its
<br /> replacement, also identified as MW17 to a depth of approximately 59.75 feet using 2-inch diameter
<br /> Schedule 40 PVC casing. Refer to ATC's Second Quarter 2008 Monitoring Report, dated July 31, 2008,
<br /> for additional information.
<br /> On August 25 and 26, 2008, an ATC geologist supervised the installation of vapor extraction wells
<br /> VE1, VE2, VE3, and VE4 to depths of approximately 40 feet bgs. One long term and four short term
<br /> vapor extraction tests were performed at the site in October of 2008 in an effort to evaluate the feasibility
<br /> of soil vapor extraction as a remedial option. Refer to ATC's Vapor Extraction Well Installation and
<br /> Pilot Test Report, dated April 30, 2009, for additional information.
<br /> On August 28, 2008, ATC staff collected soil and groundwater samples for bench scale testing to
<br /> evaluate the potential effectiveness of ozone sparging as a remedial option under laboratory conditions
<br /> prior to implementation in the field. The bench scale study results indicate ozone sparging at the site
<br /> would be effective in remediating the impacted groundwater. Refer to ATC's Ozone Bench-Scale
<br /> Treatability Study, dated February 26, 2009, for additional information.
<br /> On September 9, 10, and 11, 2009, an ATC geologist supervised the installation of two dual nested
<br /> ozone sparge wells identified as OS and OS2. Each sparge well consisted of a shallow well and a deep
<br /> well extending to depths of approximately 65 and 90 feet bgs, respectively. A four week long pilot test
<br /> was conducted at the site from November 11 to December 9, 2009, in an effort to evaluate the feasibility
<br /> of ozone sparging as a remedial option under field conditions. Refer to ATC's Ozone Sparge Well
<br /> Installation and Pilot Test Report, dated March 10, 2010, for additional information.
<br /> In late June of 2011, an ATC geologist supervised the installation of three dual nested ozone sparge
<br /> wells identified as OS3, OS4, and OS5. Each sparge well consisted of a shallow sparge point and a deep
<br /> sparge point extending to depths of approximately 65 and 90 feet bgs, respectively.
<br /> On January 14, 2013, electrical service was supplied to the remediation system compound. The concrete
<br /> slab for the remediation system compound was poured on February 14, 2013, and an electric catalytic
<br /> thermal oxidizer was placed in the remediation compound on March 5, 2013.
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