Remediation and Restoration (Pilot Treatability Testing): Pt. Mugu, CA

Remedial Action Design/Implementation/Operation, IR Site 24, NBVC, Pt. Mugu, CA
Remedial Action Design/Implementation/Operation, IR Site 24, NBVC, Pt. Mugu, CAOTIE prepared a design for an expanded EISB pilot test at IR Site 24. We optimized the design (prepared by others) for the in situ bioremediation by soil testing and revising the design for EISB.
The Navy expected that complete dechlorination would require 2 stages: (1) enhancing anaerobic dechlorination using lactate, and (2) enhancing cometabolism using oxygen and methane. Based on our experience at California sites, along with results of our biological genetic, geochemical, and groundwater modeling, we proved that dechlorinating microbes (dehalococcoides ethegenes) were indigenous and that the aerobic/ cometabolic phase was not necessary. Our one-stage approach resulted in an initial cost savings of over $150K for reduced pilot testing and was estimated to ultimately save over $500K for long-term implementation.
Groundwater at Site 24 has high natural sulfate concentrations (to 1,600 mg/L). Because sulfate-reducing microbes compete with chlorinated ethane-reducing microbes, sulfate created a large “demand” for electron donors that had to be satisfied first to achieve the overall goal of enhanced microbial dechlorination of VOCs. OTIE designed a custom injection mix using two electron donors: lactic acid (soluble), used to “kick start” the reducing process, combined with emulsified soybean oil (a less soluble “slow release” electron donor) that persists in groundwater and provides a continuous source of hydrogen for dechlorinating microbes. Using our plan, a single injection event provided continuous dechlorination for over a year and resulted in savings of over $125K due to reduced substrate costs and fewer mobilizations required for substrate injections.
Project tasks included the following:

    • Prepared pilot test design plans and specifications for expanded EISB at Site 24
    • Sampled groundwater for microbial population and performed genetic testing to identify indigenous bacteria (dehalococcoides ethegenes) which would make single-stage anaerobic EISB feasible
    • Injected 15,500 gallons of mixed organic substrate (lactic acid and emulsified soybean oil) in four areas at 62 points in Phase 1 and 8 points in Phase 2
    • Extracted/injected 1,727,667 gallons of groundwater to recirculate electron donors over 5 months
    • Installed a new 37-ft deep 4-inch monitoring well
    • Monitored groundwater at 25 wells in 11 sampling events for Phase 1 and 10 sampling events in Phase 2 for field parameters and offsite analysis for VOCs, anions, cations, TSS, TOC, dissolved gasses, and volatile fatty acids.
    • Selected and used laboratories certified by the CA Dept. of Public Health Environmental Laboratory Accreditation Pilot Test

 

Client Name: NAVFAC Southwest


Location: Pt. Mugu, CA


Contract Value: $7.9M


Project Features:

  • Received outstanding performance evaluation
  • Saved over $125K due to reduced substrate costs and fewer mobilizations for substrate injections