FULL SCALE PUMP & TREAT SYSTEM IMPLEMENTATION

FOR CONTAINMENT OF A LARGE PCE PLUME Authors: Omer Uppal, Matthew Wenrick, Imtiyaz Khan, Terrance Stanley, Stewart Abrams, Jeff Smith

Site Background The site is an active facility that manufactures MRO chemical products such as cleaners, degreasers, lubricants, and sealants, etc. The primary COCs are PCE and TCE. PCE is prominent in the shallow groundwater. The source of TCE in the intermediate zone is most likely the upgradient former Superfund site which has impacted a nearby municipal supply well.

Site Geology Bedrock underlying the site is comprised of alluvial arkosic sandstone, inter-bedded with red shale, siltstone, and fine-grained sandstone of the Triassic-age Stockton Formation.

• Based on existing site data, PCE-contaminated groundwater associated with the site primarily occurs in the shallow groundwater zone within shallow sandstone beds between shale interbeds.

• DNAPL have been observed at monitoring well MW-1 which is screened

in the shallow zone and located in the suspected source area near the locations of the AST area and the former USTs.

• The Township Municipal Authority operates a water supply well at an

average rate of 200 gpm and pumps water through an air stripper treatment system that was installed to remove CVOCs that originated from the federal agency property. Based on the groundwater flow and fate and transport modeling, area-wide groundwater flow and contaminant migration are significantly influenced by the pumping of well. Pumping influences groundwater flow and contaminant migration in both the shallow and intermediate water-bearing zones at the site.

Environmental Risk

Applicable remedial technologies were evaluated based on short-term and long term effectiveness, relative risk reduction, ease of implementation, cost and minimum disruption to the facility operation. Three technologies were fully evaluated: 1) Enhanced Bioremediation, 2) Chemical Oxidation, and 3) Pump and Treat. Enhanced Bio and Chemical Oxidation applications were not feasible for this site due to difficulty in injection, multiple injection requirements, and major disruption to the facility operation. Pump and Treat to achieve hydraulic containment and prevent further off-site migration was determined to be the optimal solution to reduce the short-term and long term risks to the municipal well. P&T provides the fastest, most certain and effective means of controlling the potential further migration shallow contamination that otherwise would migrate offsite and potentially further impact the municipal supply well.

Final Design The final full scale design of P&T included: 1) Six Recovery Wells – equipped with submersible pump, transducer and controller. 2) Equalization Tank – equipped with transfer pump. 3) Bag filters 4) Air Stripper – equipped with blower to capture stripped VOCs and transfer pump to drain effluent from the collection sump. 5) VGAC and LGAC Units – for captured VOCs treatment before discharge.

Why Pump & Treat Prior to finalizing the system design, aquifer pump tests were conducted to determine the yield of the extraction wells, the number of wells required to capture the flow from the source area, and the optimal well construction. The optimal pumping rate of 1.5 gpm was determined using aquifer characteristics and capture zone analysis. A sensitivity analysis of variable pumping scenarios was simulated through spreadsheet based analytical models.

Pre- Design Testing

Capture Zone Analysis Capture zones of the six recovery wells were developed based on 1.5 gpm flow rate using groundwater modeling software. Recovery well RW-3 yield was very low. Delineation of the capture zones of the recovery well show full capture of the shallow PCE plume within site boundary and thus preventing further migration.

System Performance Pump and treat system is in operation since September 10th, 2013. At an average flow rate of 7.5 gpm it removed 230 lbs of PCE mass from 2.16 million gallons of contaminated water in six month. The system up time is 95%.

Tetrachloroethylene (PCE)

IMPORTANT PHYSICAL PARAMETERS PCE TCE 1) Vapor pressure > 1.0 mm Hg 14 58

2) Henry’s Law constant > 0.001 atm-m3/mole 0.0153 0.0091

OPERATOR INTERFACE PANEL

RECOVERY WELLS CAPTURE ZONES

DESIGN OBJECTIVE • Containment - to prevent the contamination from spreading • Restoration - to remove the contaminant mass

DESIGN PARAMETERS • Design Pumping Rate of the Recovery Wells • Influent Concentration • Appropriate Treatment of the Captured VOCs

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