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Proposed Plan for Cleanup of Groundwater

Fact Sheet for Proposed Plan for Cleanup of Groundwater
   - En Espaņol

Background Document - 2014

FAQs - 2014

Fact Sheet - Jan. 2014

The Administrative Record

NDEP Interim-Action Level

Sampling Equipment & Chemical Checklist

Home Mitigation
[SSD Systems]

Cleanup Technologies

Indoor Air Quality

Indoor Air Quality In the News
[External Links]

About Units of Measure

Maryland Square PCE Plume Map
(JPG - 3rd Quarter, 2012)

History of Monitoring Well Installation

Posters from Community Meeting
(October 26, 2011)

Vapor Intrusion Process

Slides from Community Meeting to Present the Proposed Plan for Cleanup of Groundwater
(November 19, 2014)

Technical Resource Links

Maryland Square PCE Site

This webpage provides information about the discovery, subsequent investigation and cleanup of a hazardous substance called tetrachloroethylene [PCE] that was released from the former Al Phillips Cleaners in the Maryland Square Shopping Center at 3661 S. Maryland Parkway.

The history of site discovery, investigation and cleanup is provided in the Background Document for the Maryland Square PCE site. Additional information is provided in the FAQs and the January, 2014 Fact Sheet.

Proposed Plan for Cleanup Available for Public Review and Comment

The NDEP is the lead agency that provides regulatory oversight for the investigation and cleanup of contaminated sites in Nevada. As part of the process for community involvement, the NDEP has prepared a Proposed Plan that describes the remedy proposed for cleanup of contaminated groundwater at the Maryland Square PCE Site.

The NDEP proposes to use “pump and treat” on the east side of the Boulevard Mall property as part of the remedy. This technology would reduce the amount of contaminated groundwater entering the residential neighborhood and start to reduce contaminant concentrations. Additional cleanup technologies are proposed for the western side of the Mall to destroy PCE and further reduce concentrations of PCE in groundwater near the site of the former dry cleaner.

Public Comment Invited

The NDEP has provided a Fact Sheet to request public comments on the Proposed Plan for cleanup of contaminated groundwater at the Maryland Square PCE Site. Members of the public are encouraged to attend the public meeting on November 19, 2014 and provide comments on the preferred remedy and other remedies evaluated for the cleanup of contaminated groundwater at the Site.

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Progress on Cleanup, 2011 - 2014

Removal of PCE-contaminated soil at the former Maryland Square Shopping Center —Excavation of source area soil began on August 23, 2011 and was completed on September 19, 2011. Soil samples were collected from the sidewalls and floor of the excavation to confirm the removal of PCE-contaminated soil. Based on these confirmation samples, additional excavation was required on the northern side of the excavation.

The floor of the excavation was treated with an oxidant prior to backfill. The oxidant (potassium permanganate, KMnO4) was applied to further degrade the PCE in groundwater and soil beneath the water table. The excavation was backfilled with clean soil that had been excavated onsite to attain a safe grade on the sidewalls of the pit, as well as clean soil imported from offsite. Backfilling and grading of the site were completed in late October, 2011.

Cleanup of Groundwater: What are the Challenges?

Not all technologies are appropriate for all sites, due to geochemical, hydrological, geological or engineering issues. In the Las Vegas Valley, cleanup of PCE-contaminated groundwater is technically difficult due to the types of geologic deposits and the geochemistry of the shallow groundwater. Data from pilot testing and information from successful remediation of other PCE sites in the Las Vegas Valley were evaluated, and a multi-component remedy was selected.

The NDEP has prepared a Proposed Plan (released on October 15, 2014) that summarizes the proposed remedy and requests public input. There is a 90-day period for public review and comment, running from October 15, 2014 through January 13, 2015. All comments and responses on the Proposed Plan will be compiled and provided as an appendix to the Record of Decision (ROD). The ROD is the document that describes the remedy selected to clean up the Site, after all public comments are considered.

A Multi-Component Remedy for Cleanup of Groundwater

Logistical and technical issues led to preference of a remedy that combines hydraulic containment in one area of the site and treatment in another area. To reduce the amount of PCE-contaminated groundwater entering beneath the residential neighborhood east of the Boulevard Mall, groundwater extraction and above-ground treatment (known as “pump and treat”) is proposed for use on the east side of the mall. Extraction of groundwater upgradient of the neighborhood would provide hydraulic containment of the PCE plume.

Extraction wells are used in other areas of the Las Vegas Valley to draw down groundwater or dewater sites where underground parking garages and other subsurface structures are built. Extraction wells installed in the eastern parking lot of Boulevard Mall, just upgradient of the neighborhood, would capture contaminated groundwater before it migrates beneath the neighborhood. The current plan is to treat the extracted groundwater to remove the PCE, then re-inject it downgradient of the extraction wells.

The other component of the proposed remedy would be located just downgradient of the former dry cleaner, near S. Maryland Pkwy, in the western parking lot of the mall. This area is proposed to host remedies that physically remove or destroy PCE. Such remedies include air sparging (AS), which is typically combined with vapor extraction (VE) to capture fugitive vapors, and chemical oxidation. These remedies have less control over contaminant migration than groundwater extraction and therefore were judged as “not ideal” to implement adjacent to the residential neighborhood.

Details of remedy design and function will be presented in the Remedial Design documents. Preparation of these documents follows selection of the remedy and documentation of the selected remedy in the ROD.

Cleanup of Groundwater: Timeline for Remedy Design and Implementation

The current schedule is that at least some components of the remedy will be in place by the end of 2015. All components of the remedy should be in place and operating by the end of 2016.

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