Zill LLC Property

Since at least 1967, this site has been a gasoline station that sold gasoline and diesel fuel. In September 2006, the old steel tanks were removed and replaced with new fiberglass tanks. Petroleum contamination was found during the tank removal. Although 805 tons of petroleum-impacted soil was removed from the site and properly disposed, Zill LLC was unable to remove all the contamination. Levels of petroleum contamination above the department’s default target levels were left at the bottom of the tank pit and in the area of the product lines and dispensers. As a result, the department required Zill LLC to conduct an investigation, or site characterization, at the site to determine the extent of contamination remaining in soils and groundwater and to address the contamination according to the 2013 Missouri Risk-Based Corrective Action (MRBCA) Process for Petroleum Storage Tanks guidance. A work plan for conducting the site characterization activities was submitted by APEX and approved by the department on Oct. 9, 2013. 

The department also required Zill LLC to conduct investigation and mitigation activities needed to address complaints of petroleum vapors in nearby residences and businesses. These included, but were not limited to, installing interceptor trenches and repairing sewer lines, sewer laterals and indoor plumbing. Affected residents were also temporarily relocated during the vapor mitigation period.

Timeline of Events

• December 2013: APEX conducted a subsurface investigation at the site to define the extent of remaining contamination including the installation of nine soil borings and five groundwater monitoring wells. According to the 2014 MRBCA Site Characterization Report, the soil and groundwater samples collected showed significant contamination to the south and west of the underground storage tank system. Petroleum was also found in two of the newly installed monitoring wells. The sampling activities, however, did not determine the full extent of the petroleum plume or the soil and groundwater contamination. A work plan for conducting the additional site characterization activities was submitted by APEX and approved by the department on Oct. 2, 2014.
• November 2014: APEX conducted additional sampling at the site to further define the extent of the petroleum plume as well as the contamination in soil and groundwater. This included installing seven soil borings and three groundwater monitoring wells. Based on the data collected and presented in the 2015 MRBCA Site Characterization Report, the extent of the petroleum plume and soil and groundwater contamination is still not defined. Additional borings and wells are needed to define the extent contamination. 
• June 2015: APEX conducted additional sampling at the site to help define the extent of contamination. This included installing nine soil borings and monitoring wells. Based on the results of this investigation, presented in the 2015 Site Characterization Report, the extent of contamination is still not known and further borings and wells are needed. 
• June 11, 2015: The department collected free product samples from three groundwater monitoring wells at this site for laboratory analysis. The Laboratory Analytical Report, July 20, 2015, indicated the product present in each of these wells originated from the same source.
• July 22, 2015: The department surveyed and gauged the groundwater monitoring wells at the site and created a Groundwater Elevation Map, July 22, 2015, which illustrates the groundwater flow direction for the site.
• Aug. 4, 2015: During a site visit, the department observed APEX conducting a groundwater gauging event to check for the presence of free product in the groundwater monitoring wells. Based on the results of the gauging event, noted in the August 2015 site visit record, free product continues to be present in the tank pit observation wells and monitoring wells 7, 9, 10 and B.
• Sept. 18, 2015: The department issued a Notice of Violation to Zill LLC for failing to investigate a suspected release and for failing to install and maintain corrosion protection for the underground storage tank system.
• Nov. 5, 2015: The department excavated a portion of the sewer main at 3023 Cleveland Ave. and made repairs to an area of sewer that was allowing petroleum-impacted groundwater to enter the utility. 
• Nov. 11-12, 2015: Zill conducted two high vacuum extraction events to recover free-phase product from a number of on-site and off-site monitoring wells. During these two events, petroleum contamination, equivalent to about 280 gallons of gasoline, was removed from the subsurface. The 2015 Enhanced Fluid Recovery Results were submitted to the department.
• Nov. 23, 2015, to Dec. 5, 2015: Zill conducted a tightness test to determine if the underground storage tank system at this site was leaking. The test, conducted by Leak Detection Technologies, determined one of the underground tanks was leaking at a rate of 0.05 gallons per hour. As a result, the tank was emptied and taken out of service.   
• Dec. 28, 2015: The department oversaw a video inspection of the sewer main that runs between 3023 Cleveland Ave. and 3001 Cleveland Ave., to evaluate the integrity of the sewer connections along this stretch of main. This work was conducted as a part of continuing efforts to stop petroleum-impacted groundwater from infiltrating the sewer and the resulting vapor problems in nearby homes and businesses. 
• Aug. 1-5, 2016: Zill conducted groundwater investigation activities at the site, including gauging to check for the presence of free product and sampling the groundwater monitoring wells at the site. The department was on-site to observe some of this work. The results of the investigation were reported to the department in the 2016 Groundwater Investigation Summary Report
• Aug. 3-4, 2016: Zill collected free product samples from the groundwater monitoring wells and a product sample from a dispenser at the site for chemical analysis. 
• Aug. 22, 2016: The department attended a public meeting regarding the site. 
• Oct. 6, 2016: The department attended a public meeting regarding the site. Additionally, Zill collected additional product samples from a dispenser and a groundwater monitoring well at the site. The results of this sampling event and the August sampling event were reported to the department in the 2017 NAPL Forensic Analysis Investigation Summary Report.
• Oct. 27, 2016: The department attended a public meeting to provide updates to interested citizens regarding the status of the site.
• March 20, 2017: The department attended a public meeting regarding the site.
• April 1, 2017: The department attended a public meeting regarding the site.

The department will continue to direct the investigation and oversee cleanup activities conducted by Zill LLC's consultant. Anticipated milestones and reporting deadlines are summarized below:

• Within 90 days of the department’s concurrence that the extent of contamination has been defined, Zill LLC must submit a risk assessment evaluating the danger the contamination poses to human health and the environment under current and future conditions, according to the 2013 Missouri Risk-Based Corrective Action (MRBCA) Process for Petroleum Storage Tanks guidance. 
• Within 90 days of the department’s acceptance of the risk assessment report, Zill LLC must submit a corrective action plan to address any remaining petroleum and other contamination that poses an unacceptable level of risk to current or future receptors.
• Zill LLC must remediate, or cleanup, the site according to the approved corrective action plan. Zill LLC must also continue removing the petroleum until as much as practicable has been removed according to the Missouri Petroleum Storage Tank Law and regulations. Reports documenting the site remediation and petroleum recovery activities must be submitted every three months. 

Site information and sampling data collected during the tank closure activities and subsequent investigations into the extent of contamination are provided in the documents posted below. This list will be updated as new information and reports are received.

• Dec. 8, 2006 - Underground Storage Tank Closure Report prepared by MHS Environmental Inc.
• Jan. 8, 2014 - Site Characterization Report prepared by APEX Envirotech Inc.
• March 3, 2015 - Site Characterization Report prepared by APEX Envirotech Inc.
• July 15, 2015 - UST Compliance Inspection Report Checklist
• July 20, 2015 - Laboratory Analytical Report prepared by Pace Analytical laboratory
• July 22, 2015 - Groundwater Elevation Map
• Aug. 4, 2015 - Site Visit Record
• Aug. 24, 2015 - Site Characterization Report prepared by APEX Envirotech Inc.
• Sept. 15, 2015 - Notice of Violation #1730 TE issued by the department
• Oct. 16, 2015 - Investigation of Potential Contaminant Source Areas Report prepared by the department's Missouri Geological Survey
• Nov. 24, 2015 - High Vacuum Extraction Report by EcoVac Services
• Jan. 20, 2016 - High Vacuum Extraction Report by EcoVac Services
• Oct. 11, 2016 - Groundwater Investigation Summary Report prepared by GEI Consultants Inc.
• Feb. 28, 2017 - NAPL Forensic Analysis Summary Report prepared by GEI Consultants Inc.