Case Studies

Type of Project:
Soil and groundwater contaminated with ethylene dibromide (EDB), 1,2-Dichloroethane and 1-2,Dichlorpropane.

Date work was completed:
On Going

Name of Regulatory Oversight Agency:
Santa Ana Regional Water Quality Control Board

Description of project:
A major international corporation operated a pesticide packaging facility. The former operations at the site contributed to the contamination of the soil and groundwater. The first groundwater is located approximately 13 feet beneath the surface. This aquifer is identified by shallow and intermediate zones. A deeper aquifer is present at approximately 50 feet beneath the surface. The first aquifer is contaminated on the site with concentrations of EDB of up to 200,000 ppb. This contamination extends off-site to more than a quarter of mile down gradient. The deep aquifer has also been impacted.

The remediation system at the site operates through 27 groundwater extraction wells, 47 multi-phase extraction wells, and 49 vapor extraction wells.

The 27 groundwater extraction wells are located down gradient of the subject site. The ½ H.P. pumps in each well deliver the groundwater to a 1,000-gallon equalization tank located inside the remediation compound. The groundwater is batch-treated by first going through an air-stripper and then through two 2,000-pound water carbon beds before discharge to the OCSD sewer. The vapor from the air stripper is pushed through two 5,000-pound vapor carbon beds before discharge to the atmosphere.

The 47 MPE wells are operated by three 7.5 H.P. vacuum blowers. Each blower operates roughly a third of the wells. The MPE system is designed to remove groundwater and vapor from the subsurface. The groundwater is removed from each air stream by a knockout tank and then is pumped into the equalization tank for treatment. The vapors are pushed through two 10,000-pound vapor carbon beds before discharge to the atmosphere.

The 49 vapor extraction wells are operated by two 25 H.P. vacuum pumps. The vapor extraction wells and the MPE wells are collocated. The vapor extraction wells remove mainly vapors from the subsurface. Any groundwater extracted in these wells is removed in the knockout tanks and then pumped to the equalization tank. The vapors are pushed through the same vapor beds as the MPE vapors.

Leymaster Environmental Consulting assumed the responsibility of operating and monitoring the remediation system in late November 2001.


Type of Project:
Soil and groundwater contaminated with tetrachloroethylene (PCE) from the past use of a dry cleaning facility located in a strip-mall.

Name of Regulatory Oversight Agency:
Los Angeles Regional Water Quality Control Board

Description of project:
The soil and groundwater had been contaminated with PCE and TCE from the subject site's use as a dry cleaning facility. Leaks and spills had resulted in soil concentrations as high as 100,000 parts per billion (ppb) and groundwater contamination as high as 30,000 ppb. Sand fill is present beneath the concrete slab floor to a depth of approximately 6 inches. A silty-clay then extends to a depth of approximately 12 feet below the ground surface. Silty-sand then extends to approximately 25 feet. The groundwater is present at approximately 12 feet below the surface. The silty-clay limited the contaminants from spreading laterally. The groundwater, while considered potable by the RWQCB, was of poor quality and had no beneficial use. The contamination was detected before down-gradient spreading was significant. We recommended that a dual-phase groundwater and vapor extraction system offered the best possibility of meeting the client's objectives based on the previous subsurface investigation data and the testing we completed. We designed the remediation system after the client and the RWQCB accepted the recommended remediation method. Quarterly monitoring of the vapor extraction system eventually led to the conclusion that the vapor extraction system had completed a significant portion of the soil remediation. The analytical data from the verification soil samples indicated that the soil remediation had been completed to the RWQCB's requirements. We asked for and received a closure letter from the RWQCB for the soil remediation. Quarterly groundwater monitoring results indicated that the PCE and TCE concentrations were approaching the Maximum Contaminant Levels (MCLs). We recommended that the groundwater remediation system be shut down after 18 months of operation. The groundwater was monitored for another 18 months, and then a closure letter was issued by the RWQCB for the site.


Type of Project:
A former aerospace manufacturing facility had releases of chlorinated solvents from solvent tanks into the soil and groundwater. The contaminant plume had progressed several thousand feet down gradient in both of the top two aquifers.

Date work was completed:
On going

Name of Regulatory Oversight Agency:
Santa Ana Regional Water Quality Control Board

Description of project:
The soil and two aquifers had been contaminated with chromium, PCE, TCE, and associated breakdown products resulting from the operations of the former manufacturing facility. Leaks and spills from a chromium plating line had resulted in groundwater contamination over 100,000 ppb that had migrated down gradient several thousand feet from the subject site. The PCE and TCE soil concentrations were over 100,000 ppb. The previous environmental consultant could not prove that the existing dual-phase remediation system was working properly. We installed vapor probes at various depths and locations near the extraction wells and measured the vacuum. With this information, we completed calculations that indicated that the effective radius of influence was extremely small and was not remediating the subsurface as presented. Calculations for the air-stripper and vapor carbon beds were completed for the existing system to determine their capacity. We designed and completed groundwater-pumping tests to determine the radius of influence, the effective pumping rates, and the potential gallon-per-minute capacity of the new remediation system. Based on this information, we designed a remediation workplan that included the groundwater extraction well design, location and number of extraction wells, air-sparging points and locations, vapor extraction wells, and the treatment system itself. The remediation plan consisted of dual-phase extraction wells in the source areas. The dual-phase wells were closely spaced to aid in lowering the water elevation in the source areas. Sparge points were also installed in the source areas near the bottom of the first aquifer. These points were located between the dual-phase extraction wells to assist in removing the DNAPL. No groundwater extraction wells were installed in the B aquifer in the source areas for fear of drawing additional contaminants into the B aquifer. However, many A and B groundwater extraction wells were installed down gradient to capture the contaminants beyond the source areas. After approximately one year of the new remediation operation, the groundwater contaminants have been reduced two to four orders of magnitude.


Type of Project:
Remediation of a Former Refinery

Date work was completed:
On going

Name of Regulatory Oversight Agency: Los Angeles Regional Water Quality Control Board

Description of project:
An old refinery has been demolished for future development. Past operations of the facility have resulted in soil and groundwater contamination with crude and refined hydrocarbon product. Up to ten feet of free product has been reported on the groundwater, which is approximately 70 feet beneath the surface. LEC is responsible for the remediation of the facility. LEC began work on this project in October of 2000. A sparging and vapor extraction pilot test was completed. A Remedial Action Workplan and a Corrective Action Plan Addendum were submitted and approved by the Los Angeles Regional Water Quality Control Board.

There are 23 dual vapor and sparge wells installed on the site. A 1,000 CFM thermal oxidizer vapor extraction system was installed and is operating. Vapor remediation started in March of 2004 and sparging started in June 2004. Approximately 1,300 pounds of gasoline are being removed from the subsurface on a daily basis.