Project Highlights

  • Effective bioremediation remedy implemented in a low permeability unit
  • TCE MCLs reached in half the expected time-frame
  • Remedy-In-Place designation by Wyoming DEQ and EPA within 2 years
  • Project won Assoc. of Consulting and Engineering Companies, Engineering Excellence Award for Colorado with submission “Empowering Nature, Delivering Results”

Summary

  • Client: URS Corporation, Denver, Colorado
  • Site Location: Spill Site 7 (SS7) FE Warren AFB Cheyenne, Wyoming
  • Project Duration: Full-scale bioaugmentation 2007/ongoing monitoring
  • Services Provided:
    • Biotreatability Testing
    • KB-1® Bioaugmentation
    • Gene-Trac® Dehalococcoidestesting
urs-web

Before full-scale bioremediation TCE plume exceeded 1,000 µg/L (top left-red) over large areas of SS7; 13 months after biostimulation (3 months after KB-1® bioaugmentation) large areas of SS7 (bottom left-white) were below MCLs (5 µg/L) for TCE. Gene-Trac® testing indicated Dhc concentrations increased up to 108 Dhc per liter and Dhc spread over much of the site (lower right–green) indicating the establishment of a robust dechlorinating microbial population after addition of KB-1®. Note baseline Dhc (top right) was result of KB-1® pilot test performed prior to full scale implementation. Courtesy of URS Corp.

Problem Definition

Widespread trichloroethene (TCE) contamination at Spill Site 7 (SS7) was present from releases at a liquid oxygen facility that operated from 1960-66. Site geologic units are low permeability including interbedded clays. Gene-Trac® testing indicated that dechlorinating Dehalococcoides (Dhc) microorganisms were not widely distributed.

Solution

Results from a bench-scale biotreatability study demonstrated that biostimulation and KB-1® bioaugmentation (to add Dhc) were required to promote complete conversion of TCE to ethene. A pilot test indicated hydraulic fracturing could be used to deliver electron donor into the low permeability geologic materials, followed by pneumatic injections to disperse KB-1® into fractured zones. Following successful completion of the pilot test, injection of 310 liters of KB-1® was conducted into 39 injection locations accessing 165 fractures.

Notable Results

Accelerated degradation of TCE to ethene was observed after KB-1® bioaugmentation. cDCE and vinyl chloride concentrations increased initially and subsequently decreased followed by corresponding increases in ethene. Dhc were detected at locations as far as 70 feet from injection locations indicating effective Dhc growth and spread in a low permeability unit. Site closure schedule has been expedited by 10 years based on the rapid biodegradation rates achieved.

 Download pdf