RCRA Facility Investigation/Corrective Measures Study for major chemical distribution
Rubicon conducted a RCRA Facility Investigation (RFI)/Corrective Measures Study (CMS) at a former chemical distribution facility in accordance with a consent agreement between our client and DTSC. The facility featured 50 underground storage tanks (USTs), numerous aboveground storage tanks (ASTs), dispensing facilities, clarifiers, a solvent recycle facility, a corrosive area facility, and wastewater treatment facilities. During the 50 or so years it was in operation, numerous chemicals were handled at the facility. The chemicals included aromatic VOCs, chlorinated and fluorinated VOCs, alcohols, ketones, and 1,4-dioxane. We have conducted four phases of RFI and several interim remedial measures at this facility. A summary of the work performed includes preparation of RFI work plans, SAP, QAPP, data management plan, HASP; drilling and soil sampling at 95 locations to a depth of 125 feet; installation of 40 ground water monitoring wells to a maximum depth of 260 feet; aquifer testing; several soil gas surveys; indoor air and ambient air sampling and analysis including modeling using Johnson & Ettinger modeling software; hydrogeologic characterization; comprehensive risk assessment; numerical ground water/chemical transport modeling; quarterly ground water monitoring; preparation of quarterly reports; preparation of Public Participation plans; development of Community Profiles and fact sheets; off-site well inventory; off-site source inventory; waste management; interim remedial measures; preparation of a work plan for removing 50 USTs under the jurisdiction of the County of Los Angeles Department of Public Works (LADPW); permitting and compliance with South Coast Air Quality Management District (SCAQMD), removal of 50 USTs; installation of a soil vapor extraction (SVE) network under the former USTs prior to backfilling and site restoration; trouble-shooting and operation & maintenance (O & M) of a SVE system featuring a granular activated carbon (GAC) unit and a catalytic oxidation unit; installation of 8 dual phase extraction (DPE) wells for soil and ground water remediation; preparation of the draft Corrective Measures Study (CMS) work plan; treatability studies conducted to assess the most appropriate treatment technology; and recovery of approximately 42,000 pounds of VOCs. Both catalytic oxidation and granular activated carbon (GAC) are used to treat the vapor-phase VOC streams. This project is ongoing with DTSC (Sacramento) oversight.
Indoor air sampling and analysis at residential and commercial buildings that are located adjacent to potential sources of chlorinated solvents
Rubicon is conducting several phases of investigation at a former 6-acre chemical distribution facility that had 12 underground storage tanks (USTs) containing petroleum hydrocarbons and chlorinated solvents. The USTs were removed in the 1980s. Rubicon initiated subsurface investigations at the site in 2001 in association with the closures of a former clarifier and the former RCRA Storage Area. The initial investigations led to the development of a Consent Agreement between DTSC and the client. Rubicon is responsible for conducting all activities related to Resource, Conservation, and Recovery Act (RCRA) Facility Investigation (RFI) and the Corrective Measures Study (CMS). Prior to any field work, we developed a HASP, SAP, QAPP, Community Profile, and data management plan. To date, more than 100 soil borings, 17 ground water monitoring wells, and 95 soil vapor points have been completed to define the extent of soil, soil vapor, and ground water contamination. We have performed several rounds of soil vapor surveys to assess the potential for indoor air vapor intrusion followed by modeling using Johnson & Ettinger code. To mitigate vapor-phase VOCs, Rubicon designed, permitted, and installed a soil vapor extraction/treatment (SVET) system that was approved for operation by DTSC. The system consists of 16 vapor extraction wells and a 250-long trench connected to a 1,000 scfm blower. The VOCs are treated with four 8,000-lb granular-activated carbon vessels. Rubicon performed a comprehensive monitoring of the system including noise measurements to comply with DTSC’s CEQA (California Environmental Quality Act) requirements. Rubicon continues to operate and maintain the SVET system through weekly and quarterly monitoring events. To date, we have recovered 8,000 lb of VOCs. To protect potential receptors, we have performed two rounds of indoor air sampling and analysis combined with ambient air sampling and soil vapor-phase VOC measurements for source identification. We performed risk assessment on a quarterly basis to assure compliance with the CEQA requirements with respect to the soil vapor extraction system. All of our activities have been approved by DTSC prior to implementation. Rubicon has performed a treatability study to evaluate the use of chemical oxidation as an interim remedial approach for ground water. The results of the test are positive and Rubicon is currently planning field-scale pilot tests. Investigations at the facility are on-going with DTSC’s oversight.
Assessment of the potential impact of large scale pumping of a water district in northern California on migration of chemicals at impacted facilities
At this 47-acre property located adjacent to the San Francisco Bay, Rubicon has performed extensive characterization and interim remediation. Ground water is less than 5 feet from the surface and the site is underlain by a shallow zone and a deeper water-bearing zone. The principal chemicals of potential concern include ethylene dibromide (EDB), 1,2-dichloroethane (1,2-DCA), and elemental phosphorus. We designed, constructed, and operated two hydraulic control systems to contain the plume in conformance with the compliance monitoring program approved by the RWQCB. Under an order by the RWQCB, San Francisco Bay Region, in 2002, we developed the Final Remedial Action Alternatives and Cleanup Standards which was approved by the RWQCB for implementation. The selected remedial action alternatives included dual phase extraction from the two water-bearing zones to address the contaminated vapor-phase and water-phase VOCs and capping of the area impacted by elemental phosphorus. The capping is complete and the DPE was implemented in phases.
Recently, we developed a ground water flow model capable of simulating the potential hydrologic impact of pumping from the Alameda County Water District (ACWD) wells on the ground water flow regime at the site. Specifically, the ground water flow model is intended to be sufficiently flexible to predict water level changes resulting from extraction from any of the ACWD wells located in the vicinity of the site. Furthermore, the ground water flow model can be used as a predictive tool to develop alternative ground water extraction scenarios at the site in the event that ACWD activities affect the existing hydraulic control maintained by the current ground water extraction and treatment system.
Since early 1960s, the ACWD has been engaged in the restoration of the ground water aquifers of the Niles Cone Basin that have been degraded by salt water intrusion. To accomplish this objective, the ACWD has implemented extensive pumping programs in the Newark aquifer and Centerville-Fremont aquifer. Pumping from these aquifers, particularly at high flow rates, may impact the ground water flow regime within the Niles Cone Basin. Our modeling was intended to evaluate the potential impact of ACWD pumping programs on the flow regime at the site. The simulations demonstrated that depending on the pumping rate and distance from the site, certain extraction schemes would not significantly impact the site. The results are currently being reviewed by the RWQCB, San Francisco Bay Region.
Remedial design and optimization for an aerospace company in Southern California
Rubicon was retained to design and optimize a system for full-scale remediation of a facility (the Site) that is impacted by trichloroethene, Freon 113, and 1,4-dioxane. A hydraulic barrier for plume containment and in-situ chemical oxidation (ISCO) for source removal were selected as the principal ground water remedial technologies. Our modeling objectives included design and optimization of hydraulic barrier and ISCO injection spacing and rates; prediction of plume behavior under regional and stressed conditions; and evaluation of effectiveness of the remedial system. To achieve the stated objectives, we reviewed the characteristics of the Site, developed a Site Conceptual Model (SCM), selected a groundwater/transport code, calibrated the model, and performed predictive simulations. Subsequently, we verified the model behavior by the results of the full-scale implementation of the remediation system.
We constructed a three-dimensional ground water model to simulate the flow regime in a 6-layer aquifer system using MODFLOW. Prior to applying MODFLOW, we used Analytic Element approach (MODAEM) to establish boundary conditions. The groundwater model domain includes the Site and approximately 7,000 feet from the property boundaries to the north, east, south, and west. Vertically, the model domain extends from the ground surface to the bottom of the Beta Aquifer encountered at about 250 feet below grade. Simulation results showed that extracting a total of 40 gallons per minute (gpm) from 4 wells at the downgradient site boundary will contain the plume. Our model not only considered on-site extraction/injection conditions, it also included large-scale (~ 2,000 gpm) pumping from the City wells. We applied Parameter Estimation by Sequential Testing (PEST) for calibrating the flow model. The model was also applied to evaluate extraction/injection scenarios and to assess if full or partial reinjection aided in plume capture, accelerated remediation progress, and reduced life-cycle project costs. We showed that because of access constraints, reinjection did not significantly improve the plume capture. However, reinjection would reduce the cost of water replenishment. Knowing the characteristics of the oxidant (sodium persulfate, sodium hydroxide, and ferric iron) and the flow regime, using MT3DMS, we performed oxidant injection simulations to simulate the transport and degradation of ISCO oxidant. Using the degradation characteristics of the oxidant and the ground water flow regime, our simulations demonstrated that 28 amendment wells at an approximate spacing of 35 feet would be sufficient to deliver the oxidant at a rate of 1 to 2 gallon per minute (gpm). Figure 4 shows the breakthrough curves for the oxidant for three cases: 1) advection; 2) advection and dispersion; and 3) advection, dispersion, and degradation. The results demonstrated that in the presence of advection, dispersion, and degradation, the oxidant front reaches a distance of approximately 45 feet. The Radius of Influence (ROI) of the oxidant has been estimated from the increase in Oxidation Reduction Potential. The field application results show an ROI of 10 to 60 feet in the 60-Foot Sand. The model is a dynamic tool that will be utilized during the site remediation process.
Our most recently designed/installed system is a dual phase extraction (DPE) system for a site impacted with VOCs. Ground water and soil vapor is extracted and routed to the treatment compound. Ground water is treated with an air stripper. Extracted soil vapor and air stripper off-gas is treated using a thermal oxidation unit with an acid scrubber.