203360 ASSESSMENT OF THE OTA ALTERNATIVE FOR REMEDIATION OF THE ONSITE AREA OF LIPARI LANDFILL Introduct ion We have reviewed the Congressional Office of Technology Assessment (OTA) report entitled "A Review of EPA's Decision Under the Superfund Program for an Onsite Cleanup of the LiPari Landfill". The approach as outlined in OTA's report would consist of the following sequential steps: 1. Dewatering of the contained or "onsite" portion of the LiPari site 2. Enhanced volatilization 3. Partial excavation of contaminated materials 4. Backfilling of the excavated area with clean(ed) soil 5. Onsite treatment (incineration) of the excavated contaminated materials 6. Flushing of the contaminated soil This approach is estimated by OTA to cost approximately $65 million. The advantages associated with this increase in cost over the $8.9 million batch flushing alternative selected by EPA in the Record of Decision (ROD) are reported by OTA to be a decrease in the time required for clean-up of the site (estimated by OTA to be 5-7 years as opposed to the 15 years for the selected flushing alternative) and an increase in reliability, effectiveness, and certainty of the remedy. Our comments concerning OTA's approach are organized to address the six sequential steps which comprise this approach. o o •~v; . a> rH o J 0 . I o 1 272429 125 iiiiiiiinininiiii 1. Dewatering of the Containment As outlined in the "Final Draft Report - Onsite Feasibility Study for LiPari Landfill" (FS) prepared by the REM II team and dated August 1985, dewatering of the Upper Cohansey within the containment system is a feasible step. This conclusion was reached based upon the results of the hydrogeologic investigation of the LiPari Landfill in February and March 1985 and the successful extraction of over one million gallons of leachate from the containment by IT Corporation during September and October 1984. The major cost components for completing this step are as follows: o Capital costs for extraction wells, holding tank, prefabricated building and contingencies: $920,000. o Operation and maintenance costs including personnel, power, vapor- phase carbon, and off—site treatment of one pore volume at a per­ mitted industrial waste treatment facility: $880,000. o Total cost • $1.8 million. Dewatering time was estimated in the Feasibility Study at 6 months utilizing 10 extraction wells at a combined rate of 40 gallons per minute. This time period could be approximately halved utilizing 20 extraction wells at a combined rate of 80 gallons per minute without suffering yield loss in the extraction wells or pressurizing the containment system. This analysis is presented in more detail in later sections of this report which address flushing. 2. Enhanced Volatilization After an initial site dewatering, OTA proposes using an enhanced volatilization technique to extract volatile organics from the landfill prior to the commencement of the proposed partial excavation. This ±2ti 2 126 technique would utilize a combination forced air/vacuum system to extract the volatile organics and other gases and direct them to an on-site treatment system, presumably a vapor-phase carbon adsorption unit. OTA did not provide any details as to (1) the estimated costs for such a system other than to note it is "relatively inexpensive" or (2) the time period over which this system would be required to operate to extract enough volatiles before beginning excavation. Our comments concerning this system are: Based on experience with enhanced volatilization at a site in California, this technique was demonstrated to be effective in collecting compounds which volatilize at ambient temperatures in homogeneous soil. The effectiveness is dependent on establishing a "central flow path" consisting of air extraction and air inlet wells installed just above groundwater. The system as proposed will be operated at a negative internal pressure. Theoretically, a concentration gradient could be created by displacing the equilibrium gradient such that, in time, groundwater contaminants would also be volatilized into the soil and similarly be extracted by the wells. Enhanced volatilization has also been applied at three California sites with demonstrated recovery rates of 1 to 2 pounds per day, 25 pounds per day, and 200 pounds per day, respectively. However, these systems have been used at industrial sites where the toxic compounds are well defined and limited in number in homogeneous soil, unlike the conditions at LiPari where a wide variety of chemical compounds exist and the fill material is heterogeneous. Other experience to date has mainly revolved around two pilot systems. In one field experiment a homogeneous sandy soil in the unsaturated zone was contaminated with "low" concentrations of volatiles. After 17 weeks of operation over 99 percent of the volatiles were reported to have been re­ moved. In the second field demonstration a sandy soil in the unsaturated zone was contaminated with "high" concentrations of volatiles. In this instance "good" recovery was achieved after 12 months. Costs for using this technique over a 10 acre site were estimated in the $100,000-5200,000 range excluding a vapor recovery/treatment system. • r* */ ±w i 127 Although enhanced volatilization appears promising there are uncertainties regarding the length of time that such a system would be operated to effectively minimize public health risks during any excavation event at LiPari. In California, the systems researched have been designed to be coupled with groundwater treatment. However, the benefits of- implementa­ tion are questionable with respect to the time required to significantly decrease public health risks or reduce contaminant levels prior to excavation. If an enhanced volatilization system were to be coupled at the LiPari site with the groundwater treatment (i.e., flushing) system, then the operation of the two media treatment systems could be conducted concurrently. A combined treatment system may improve the overall cleanup by maximizing the removal of contaminants within the two media of transport. Implementation of an enhanced volatilization system may reduce the amount of risk encountered during excavation at LiPari. Some of the volatiles currently within the interstices of the landfill would be removed and therefore not be dispersed as the landfill is opened and excavated. This is particularly important with regard to methane generated within the site which during an excavation process would give rise to concern about fire and/or explosions. It is anticipated that some volatile compounds will not be removed by the enhanced volatilization process and therefore still be made available to the atmosphere as the landfill material is disturbed through excavation. This release of volatiles will be greatest in those portions of the landfill where, because of short-circuiting or channeliza­ tion due to the heterogeneous makeup of the fill, volatile organics have not been removed by the enhanced volatilization process. The quantity of these volatiles and associated health risks to on-site workers and the nearby residents cannot be accurately defined because of the varied nature of the materials disposed at the LiPari landfill during the 13 year operating history. Accordingly, at the time of excavation, measures to reduce the amount of volatilization must be implemented. Several techniques are discussed in the following section. 128 The capital cost to install an enhanced volatilization system at LiPari with a battery of thirty-six 6-inch PVC wells, varying from 20 to 35 feet deep at the minimal spatial distances of 100 feet apart would be approximately $150,000-$200,000. Additional costs for a vapor phase carbor recovery system utilizing granular activated carbon to treat the contaminated air prior to discharge to atmosphere is estimated at $100,000 resulting in a total cost estimate of $250,000 to $300,000. This estimate does not include operating and maintenance costs which would be dependent principally on carbon replacement requirements to meet ambient air quality criteria. 3. Partial Excavation of the Containment System The OTA report recommends, that only a portion of the LiPari Landfill be excavated and subsequently treated on-site, based on the assumption that only about 6 acres of the total 15 acre LiPari site was used originally as a landfill. Furthermore, OTA states "enough is known about the movement of the underground water to estimate what parts of the site area might be highly contaminated." "It should be possible to establish criteria for certain key contaminants so that areas with higher concentrations can be designated for excavation." Extent of Onsite Contamination: Examining this approach, the spatial distribution of LiPari's "indicator contaminants" may be utilized to ascertain which portions of the containment system are in fact con­ taminated. As noted in the Onsite Feasibility Study (FS), 13 indicator compounds were selected for the LiPari site based on concentration, mobility, and toxicity. These compounds were: bis (2-chloroethyl) ether; 1.2, dichloroethane; methylene chloride; toluene; benzene; phenol; chromium; nickel; lead; mercury; selenium; arsenic; and silver. Table 1 and Figure 1 indicate the distribution of these contaminants within the 15 acre containment system. It is apparent from the information presented that the extent of con­ tamination is more widespread than the original six acre landfill. Each of < o 129 TAAU I oismieuTion or ttoic*n4 oencAis vimm nc omvAiiMNr $vsu« lutlcitar