Challenge

During routine sampling performed by the New Mexico Environment Department (NMED) in 1993, perchloroethylene (PCE), a chlorinated solvent commonly used as a degreaser and as a dry cleaning agent, was detected in City of Las Cruces municipal drinking water supply wells. In 2001, the groundwater plume underlying the intersection of Griggs and Walnut was listed as a Superfund Site. In 2004, the United States Environmental Protection Agency (EPA) funded a remedial investigation of the area to assess the steps necessary to return the water to a beneficial use for the Doña Ana County community.

Solutions

DBS&A was contracted in 2004 by the joint clients as a consultant to assist on the EPA funded feasibility study. We initially assisted in evaluating remedial alternatives that incorporated existing City infrastructure. After the EPA completed the remedial investigation and feasibility study, the City awarded DBS&A with the remedial design and remedial action (RA) contract through a qualifications-based selection that was heavily influenced by our evaluation work. DBS&A had primary responsibility for design deliverables and supporting reports, and our team relied on our recommendation from our evaluation to modify existing water supply wells for use as extraction wells at the Superfund site.

Our team completed all aspects of the RA, including design of the modified production wells and conveyance, a treatment compound and building, conveyance piping for both treated and untreated water, contract management, and project management. Our team designed a modular system that is capable of being expanded to address increased flows or the treatment of heavy metals through the use of low-profile tray air strippers. This design removes PCE from the water to below detectable concentrations, and the treated water is then conveyed via new and existing pipelines to an existing City storage tank.

DBS&A was also heavily involved in completing the regulatory aspect of the RA, writing many of the plans required by the EPA, all of which were completed and submitted in a timely manner through our close cooperation with both the EPA and NMED. We drafted the Construction Quality Assurance Plan and provided bidding assistance for construction of our RA designs, including preparation of bidding documents, bid review, and construction oversight.

Since construction of the system, DBS&A has continued to provide a variety of services for the City, including ongoing support for groundwater modeling, groundwater monitoring, quality assurance, reporting, and ongoing negotiations with the EPA.

Results

Our assistance during the RA phase has been absolutely instrumental to the continued success of the Superfund site. Our modular system design has minimized both construction and future operations and maintenance costs. Through supervisory control and data acquisition (SCADA), City engineers are able to monitor the plant remotely, resulting in additional cost savings. Immediate capital savings, in addition to savings in future operation and maintenance costs, totals more than $5 million over 20 years. We also cooperated closely with the City, the EPA, and NMED during this period to expedite review of all internally-produced documents so that all required plans were completed in a timely manner, keeping the overall project on or ahead of schedule at all times. This helped in providing the City with significant cost savings.

Our design system has also proven highly effective, providing County residents with safe drinking water since installation. This is the only Superfund Site in New Mexico (and one of very few nationally) that is able to return the disinfected water directly into the drinking water distribution system.

GLA demonstrates and explains both the Federal and State regulations surrounding the project and effectively defends the compliance to the matrix of environmental regulations and compliance limits.

Former Client Project Manager