Site Closure Support Services for Groundwater Wells
City of Los Angeles, Harbor Department (Port of Los Angeles) • Los Angeles, CA
Solution Overview
Client:
City of Los Angeles, Harbor Department (Port of Los Angeles)
Business Challenge:
- Post-remediation concentrations in site groundwater wells indicated low but persistent concentrations of dissolved-phase petroleum hydrocarbons
Solution:
- Assessed site conditions, developed a conceptual site model, and evaluated treatment technologies
- Evaluated soil confirmation data and concentration trends in groundwater
Results:
- Demonstrated that residual contaminants were harmless to future receptors and remaining plumes were stable with decreasing concentrations
- Regulator placed both Sites on an annual groundwater monitoring program with minimal sampling requirements which will produce significant savings for the City
Challenge
Following the City’s Harbor Department’s efforts involving remedial actions at Canner Steam and 1500 East Anaheim—including source removal, high‑volume contaminated groundwater extraction, and in situ biotreatment at two sites located at the Port of Los Angeles—post-remediation concentrations in site groundwater wells indicated low but persistent concentrations of dissolved-phase petroleum hydrocarbons. Despite the evidence that the groundwater has been de-designated as a drinking water source and that the residual concentrations of hydrocarbons do not represent either a human health or ecological risk, Los Angeles Regional Water Quality Control Board (LARWQCB) resisted requests for No Further Action (NFA) status.
Solution
Apex assessed site conditions, developed a conceptual site model, and evaluated treatment technologies to determine best approach for each Site. After a remedial approach was selected, Apex provided technical oversight on behalf of the City of Los Angeles during implementation of remedial measures for both soil and groundwater. Following the completion of active remediation, Apex evaluated soil confirmation data and concentration trends in groundwater. The interpretation of these data sets were used to prepare expert technical arguments, interpretative maps and graphs, and develop regulatory framework descriptions for inclusion in closure request presentations to the agency.
Results
Through multiple meetings with LARWQCB, Apex worked with Harbor Department staff to establish the structure and approach that will be used to present the final required technical data and arguments to the LARWQCB by which site closure will be requested. Although both Sites were largely petroleum hydrocarbon releases, the presence of other chemicals of concern, including chlorinated volatile organic compounds, precluded the use of the State’s low threat closure policy. Therefore, Apex prepared risk-based arguments and developed multiple lines of evidence to demonstrate that exposure routes were incomplete, thus rendering residual contaminants harmless to future receptors, and that the remaining dissolved-phase plumes were stable with concentrations decreasing due to natural biodegradation processes. Although the State has not yet granted full closure, both sites were placed on an annual groundwater monitoring and sampling program with requirements that only a subset of wells be sampled, saving the City of Los Angeles tens‑of‑thousands of dollars in long-term monitoring costs.