Groundwater Remediation at a Superfund Site
Since 1983, M&A has played a critical role in characterizing and remediating groundwater contamination at Arizona’s largest Superfund site.
Clients: North Indian Bend Wash Participating Companies; Motorola, Inc.- Time frame: 1983–present
- Location: Scottsdale, Arizona
Located in the Salt River and Paradise Valley groundwater basins, NIBW was added to the EPA's Superfund list in the early 1980s after VOCs were detected at several municipal supply wells. Soil and groundwater characterization efforts uncovered a regional plume caused by multiple historical industrial facilities.
Working initially on behalf of Motorola and later representing the entire group of participating companies, M&A has been integrally involved in the strategic management of the project since its inception.
Services
- Conducted depth-specific groundwater sampling and geophysical, hydrophysical, and spinner flowmeter logging to evaluate aquifer properties, VOC distributions, and the potential for vertical contaminant migration at individual source areas and within the regional plume
- Used data from the drilling of soil vapor monitoring and extraction wells to characterize the hydrogeology of vadose zone sediments and evaluate the concentration, distribution, and movement of VOCs
- Analyzed historical data to evaluate the relationship between VOC source areas in vadose zone sediments and VOC concentrations in the uppermost aquifer
- Analyzed monitoring data to assess the distribution, concentration, and movement of VOCs
- Designed and conducted pilot tests and developed a vadose zone remediation program using SVE technology
- Used the results of soil vapor monitoring and vadose zone modeling to assess performance of the SVE system and develop criteria for program termination
- Sited, designed, and supervised the installation of numerous soil borings and monitoring wells
- Designed and oversaw the construction and testing of three large-diameter extraction wells completed to depths exceeding 1,200 feet as part of the pump-and-treat remedy
- Selected favorable drilling sites for these wells by evaluating hydrogeologic, water quality, and land ownership data
- Negotiated property access for the extraction wells
- Managed purge water and noise abatement in a populated metropolitan area during drilling
- Developed or participated in a development team for several models (groundwater flow, particle tracking, solute transport, and vadose zone) to achieve various remedial design objectives
- Used the models to evaluate groundwater and contaminant movement within and between aquifers, to assess plume capture and containment under a range of extraction regimes, and to compare the effectiveness of remedial alternatives for the final selection process
- Updated and recalibrated the flow-and-transport model in 2010 to assess remedy performance as part of a 5-Year Review process; used this site-wide model to project the hydraulic capture of the operating groundwater remedy and to meet other requirements of the review process
- Used vadose zone models at the various source areas to identify the need for SVE and assess the potential threat to groundwater from VOCs
| Target Zone | Model Type | Objective |
|---|---|---|
| Groundwater | Flow | Evaluate groundwater movement within and between aquifers |
| Flow / particle tracking | Assess plume capture and containment under a range of extraction regimes | |
| Flow / solute transport | Compare the effectiveness of remedial alternatives for remedy selection | |
| Vadose zone | Assess the potential threat to groundwater from VOCs in the vadose zone and identify areas requiring soil vapor extraction |
- Designed, constructed, and tested an extensive monitoring network
- Designed and implemented long-term programs for monitoring water levels and water quality, for tracking VOC migration, and for periodically verifying our containment projections
- Prepared technical summaries, reports, interpretative work products, and presentation materials for regulatory agencies, water providers, and a community involvement group
- Interfaced with state and federal regulatory agencies to negotiate technical aspects of the vadose zone model, SVE system design, and SVE system operation
- Prepared numerous deliverables for regulatory agencies, including reports on our evaluation of groundwater threats, an analysis of SVE system requirements, and the SVE system design
- Analyzed hydrogeologic and water quality data to investigate responsibility for groundwater contamination
- Represented Motorola in an alternate dispute resolution process to allocate costs for operating a pump-and-treat-system
- Developed cost-sharing approaches for ongoing pump-and-treat activities
- Provided expert testimony during a court proceeding related to alleged loss of value for property overlying the zone of VOC contamination
- Projected long-term capital and operation and maintenance costs for remediation based on assumptions about the statistical probability of a range of potential outcomes in support of settlement negotiations between PRPs
- Developed a site-wide relational database for water level, water quality, well construction, and lithologic data from all monitoring and extraction wells
- Developed a project-specific dashboard with menu-driven queries to output data tables, graphs, and reports
- Incorporated an archive library into the dashboard system for easy access to site reports, maps, regulatory documents, and correspondence
- Hosted the site-wide dashboard interface on a secure, web-based system with password-protected access for project personnel
- Used the environmental database in a GIS platform to develop model inputs and prepare maps for data analysis and reporting
Outcome
We have played a key role in developing, gaining regulatory approval for, and implementing all aspects of the remedial actions.
Acronyms & Abbreviations
