7th Avenue and Bethany Home Road Water Quality Assurance Revolving Fund Site February 19, 2013

Monitor well network sampled January Ground water samples indicated a significant increase of tetrachloroethene (PCE) concentrations in the source area wells at both properties. Increasing water table elevations are suspected of mobilizing additional contaminants from the soils to the groundwater. Data received from Salt River Project indicated their well, located approximately one-half mile north of the source area, has been impacted at the Aquifer Water Quality Standard of 5 parts per billion. This well is cased from land surface to a depth of 600 feet and the interval open to the aquifer for water production is from 240 to 600 feet Groundwater Monitoring Results

7 th Avenue and Bethany Home Road Site Map

North-South Geologic Cross section

2012 Groundwater Monitoring Results

SRP Well 10.1N-13.5E Historical PCE Results

Final Remedial Investigation Report completed in April 2011 included the Remedial Objectives (ROs) for the site. Based upon review of public comment, the ROs are based on the following: Protect against possible exposure to hazardous substances in surface and subsurface soils that could occur during development of property based upon applicable zoning regulations. Protect against possible leaching of hazardous substances from the upper portion of the aquifer into deeper portions of the aquifer where groundwater use is occurring. Remedial Objectives Review

Based on public comment, ROs for current and future agricultural groundwater use in the 7th Avenue and Bethany Home Road WQARF site are: “To protect the supply of groundwater for irrigation use and for the associated recharge capacity that is threatened by contamination emanating from the 7th Avenue and Bethany Home Road WQARF site...” Remedial Objectives Review

Feasibility Study (FS) completed November Due to increases of PCE concentrations at the site, the FS evaluated three methods to reduce concentrations in the groundwater at the source area. 1. Enhanced reductive dechlorination (ERD) 2.In situ chemical oxidation (ISCO) 3. Groundwater Extraction and Treatment (GWET) Feasibility Study

Feasibility Study Cost Comparison

Based on the cost and other factors, ERD was selected for the pilot test at the site. ERD is preferred over the similarly priced GWET because it has the ability to destroy the volatile organic compounds in place and the potential to be completed in a quicker time frame. Feasibility Study

Dechlorination Occurring at MW-12

Feasibility Study/Pilot Test

Questions? Questions

Contact Information Scott Goodwin, Project Manager Remedial Projects Section (602) , ext Wendy Flood, Community Involvement Coordinator Remedial Projects Section (602) , ext Contact info