AN APPROACH FOR INTEGRATION OF FACILITY CLOSURES WITH CERCLA RESTORATION AT THE INEEL IDAHO CHEMICAL PROCESSING PLANT
Doug Greenwell, Rene R. Rodriguez, Annette L. Schafer
LMITCO
Richard L. Henry
Parsons
ABSTRACT
There are 285 facilities within the Idaho Chemical Processing Plant (ICPP) at the Idaho National Engineering and Environmental Laboratory (INEEL) that are co-located with 95 release sites regulated under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). The evaluation of CERCLA sites inside an active complex poses regulatory and technical challenges beyond the traditional scope of the CERCLA process. The long-term closure strategy of the ICPP will involve integration of cleanup decisions across several regulatory programs so that all closure goals are consistent with final Remedial Action Objectives (RAOs) that will be published in a CERCLA Record of Decision (ROD) by September 1998. An approach taken at the INEEL involves identifying the facility closure projects most likely to be inconsistent with the RAOs and cumulatively evaluating the long-term impact of residual soil contamination left behind as a result of conducting CERCLA cleanups and facility closures within the same active complex. It is anticipated that implementing this strategy will require optimizing decision variables such as closure design, worker exposure, and cost.
INTRODUCTION
The ICPP at the INEEL is a former spent nuclear fuel reprocessing plant that consists of 285 facilities presently scheduled for deactivation and closure between the years 1998 and 2044. These facilities include permitted units and facilities to be closed under other programs, such as the Resource Conservation and Recovery Act (RCRA), facility deactivation, and Decontamination and Decommissioning (D&D). A Remedial Investigation/Feasibility Study (RI/FS) is underway to study and identify cleanup options for 95 release sites that are co-located with the 285 facilities and are regulated under CERCLA. The evaluation of CERCLA sites inside an active complex poses regulatory and technical challenges beyond the traditional scope of the CERCLA RI/FS process. The challenge arises because operational facilities may leave hazardous substances behind after facility closure that could potentially contribute to an overall increase in risk to human health or the environment. Because of this, the long-range cleanup strategy of the ICPP extends beyond the CERCLA scope and includes the ICPP facilities to the extent that facility closure goals are consistent with the CERCLA cleanup decisions. The extent of remediation and the facility closure design must be cost effective while remaining protective of human health and the environment. This paper outlines an approach for integrating facility closures with CERCLA restoration at the ICPP.
In order to address the complex problem of integrating facility closures with CERCLA cleanup actions within the same active complex, the Environmental Restoration Program has proposed a two-phased approach termed the Comprehensive Facility Closure Evaluation (CFCE). The CFCE approach is proposed for future use as the remaining operational facilities approach the end of their useful life. The approach begins with Phase I which consists of a screening process for all 285 facilities that will identify those posing the most potential to adversely impact ICPP-wide comprehensive risk. Phase II consists of further screening and evaluation of possible groundwater impacts from migration of residual soil contamination left behind from a facility closure, using a simplified version of the RI/FS fate and transport model. This is an optimized risk-based closure procedure that evaluates the potential risk contribution from a facility closure design to the comprehensive ICPP-wide risk. Optimization objectives include minimizing cost and meeting final CERCLA RAOs. The decision variables include the maximum release rate allowed from each closed facility and the risk reduction achieved by remediation at each existing CERCLA site, as well as worker exposure and cost.
INEEL AND ICPP BACKGROUND
The INEEL, is located about 40 miles west of Idaho Falls, Idaho and occupies about 890 square miles on the northwestern portion of the Eastern Snake River Plain. The Eastern Snake River Plain is a relatively flat, semiarid, sagebrush desert terrain. Drainages within and around the Eastern Snake River Plain recharge the Snake River Plain Aquifer that underlies the region. The top of the aquifer is located within basalt lava flows about 450 feet below the ICPP and is overlain by other lava flows and sedimentary interbeds. The upper surface of the basalt flows beneath the ICPP is covered with about 45 feet of alluvium deposited by the Big Lost River.
Because of soil and groundwater contamination resulting from operations, the INEEL was placed on the National Priorities List in November 1989. A Federal Facilities Agreement/Consent Order was negotiated between the U. S. Department of Energy (DOE), the U. S. Environmental Protection Agency (EPA), and the Idaho Department of Health and Welfare (IDHW) to direct cleanup activities at the INEEL. These activities are being conducted to address past releases under CERCLA.
The ICPP, located in the south-central area of the INEEL, began operations in 1952. Historically, spent nuclear fuel from defense projects was reprocessed to separate reusable radioactive materials from by-products of nuclear reaction. This process continued through 1992 when it was phased out. Liquid waste generated from this activity is stored in an underground tank farm. This liquid waste was and still is treated using a calcining process to convert the liquid to a more stable granular form. Calcined solids are stored in underground stainless-steel bins. The new mission for the ICPP is to receive and temporarily store special nuclear fuel and radioactive waste for future disposition.
COMPREHENSIVE FACILITY CLOSURE EVALUATION
The DOE has the responsibility to conduct remedial activities at the ICPP that assure compliance with CERCLA. Additionally, the DOE is responsible for the deactivation and D&D of facilities at the ICPP in a manner consistent with RCRA as well as DOE guidance and other regulations. An integration strategy across all regulatory programs is needed to evaluate, and where necessary, optimize cleanup actions in such a way that when evaluated together, residual contamination left behind by CERCLA actions, D&D projects, and RCRA closures are not inconsistent with final CERCLA RAOs over time and location. This concept is graphically depicted in Figure 1.
Fig. 1. Risk Profile Showing Potential Impact To RAO From A Hypothetical Facility Closure.
The CFCE procedure described in this paper is proposed for use by ICPP facility owners at the planning stage of a facility closure project. The approach features a screening process with facility exit criteria so that only high threat facilities are kept for further evaluation, a groundwater fate and transport methodology, performance criteria, and documentation required to verify that contaminants left in place at closed facilities do not cause the comprehensive ICPP-wide risk thresholds to be exceeded. The CERCLA RAOs will become the not-to-exceed-performance-criteria in surface soil, perched water, and aquifer groundwater agreed to in the Record of Decision (ROD) which will be finalized in September 1998. The RAOs define the measurement criteria against which the risks posed by contaminants left in place at a closed facility will be compared to determine if the comprehensive ICPP-wide risk thresholds will be exceeded. Additional risk from contaminants left in place at a closed facility must not exceed the risk thresholds for surface soils, perched water, and the aquifer. The RAOs are written to protect a hypothetical future on-site resident beginning in the year 2095, which is the period that INEEL land use documents have identified when institutional control by the DOE can no longer be assumed.
The CFCE process, consisting of Phase I (Stage 1) and Phase II (Stages 2 through 5), is intended as a site and facility management tool that utilizes CERCLA methodology and objectives to achieve a negotiated level of protectivess across the ICPP for all future cleanup actions. The CFCE protocol is not meant to define the facility closure process but instead promote a consistent approach to facility closures by way of identifying supporting documentation that would be necessary to demonstrate that facility closure goals are not inconsistent with CERCLA RAOs.
The CFCE process is comprised of two phases consisting of five stages:
Phase I
Phase II
CFCE PHASE I
Phase I consists of a screening process that eliminates co-located facilities not expected to contribute significantly to the comprehensive ICPP-wide risk. The CFCE Phase I process is designated Stage 1, Pre-Closure Screening, and includes four qualitative screening steps that systematically identify and exit facilities that clearly pose insignificant negative impact to the comprehensive ICPP-wide risk. The Phase I process includes the following steps:
The closing facility may exit the CFCE process provided that the criteria in the four stage 1 screening steps are met. Thereafter, the exiting facility is only subject to the requirements established by its respective closure organization, such as D&D, and the facilities are no longer required to integrate their activities with the CERCLA ER program.
Using the CFCE Phase I screening process, 79 of the 285 ICPP facilities were identified as containing CERCLA hazardous substances that could potentially impact human health or the environment and the ICPP-wide comprehensive risk following facility closure. These facilities include processing buildings, storage facilities, Tank Farm facilities, process waste or transfer lines, and other facilities. The 206 facilities that were determined to not pose a CERCLA risk exited the CFCE process. The remaining 79 facilities are potentially subject to the CFCE Phase II process.
CFCE PHASE II
Phase II consists of further evaluation of those sites considered having the potential to contribute to comprehensive ICPP-wide risk. This phase is an optimized risk-based closure procedure that evaluates and compares the potential risk contribution from a closed facility to the overall plant risk. The purpose of the CFCE Phase II process is to provide a flexible facility closure evaluation procedure that will allow the facility owner organization to assess the additional risk that may result from leaving contaminants in place at closed ICPP facilities. The end product of a CFCE assessment will be summarized and included in the CERCLA 5-year review of the ROD. The support documentation will present evidence that indicate that deactivation and D&D end states do not significantly impact comprehensive ICPP-wide risk and is not inconsistent with CERCLA RAOs. The CFCE Phase II process consists of three evaluation stages (stages 2 - 4).
Stage 2 of the CFCE process is termed Initial Facility Closure Planning. As a facility nears the end of its mission, a facility closure planning meeting will be held with the CERCLA Environmental Restoration program to discuss the contaminant sources present at the closing facility, the potential impact of the closing facility on the site-wide comprehensive risk, and possible source reduction or engineering control measures planned to remove or mitigate releases of contaminants from the closed facility to the environment. The Initial Facility Closure Planning stage provides an additional exit step to further reduce the number of facilities that must undergo the full CFCE evaluation process. Under Stage 2, a closing facility can exit the CFCE process one of two ways:
If a facility is eliminated from the CFCE process by exit screening, the facility owner organization would be required to provide evidence that support this result to the INEEL CERCLA ER program. One of the following documents must be provided that shows how the facility will not impact comprehensive ICPP-wide risk:
Facilities that do not exit the CFCE process either in Phase I or Stage 2 of Phase II must demonstrate that the risk posed by the closing facility will not exceed comprehensive ICPP-wide risk thresholds established in the final ROD. The risk posed by these facilities will be quantitatively evaluated in Stage 3 of the CFCE process.
Stage 3 (Facility Closure Design) of the CFCE Phase II process involves the performance of a risk assessment to determine if the proposed facility closure design will achieve the "not to exceed" performance criteria specified by the CERCLA RAOs in the final ROD. All available historical information concerning the facility will be collected and reviewed to establish a basis for the closure design. The closure design must consider the contaminant sources, source strength, contaminants of concern, contaminant release mechanisms and flux rates, and exposure pathways and routes so that risks from potential releases are minimized.
Demonstrating compliance with the CERCLA RAOs involves an evaluation of possible exposure to facility contaminants via air, soil, and groundwater pathways. In order to maintain flexibility in the CFCE process, using the same risk assessment techniques employed in the ICPP RI/FS are not strictly required. This allows the use of future improvements in risk evaluation and modeling techniques to be adopted, so long as they are applicable and consistent with the approach used to establish the comprehensive ICPP-wide risk. The incremental risk contribution from the closed facility will be compared to the ICPP-wide risk to determine if the closure design provides adequate protection of human health and the environment.
The CERCLA RAOs consist of two main performance criteria. The first aims at establishing health-based exposure limits to site-related contaminants in surface soil. The location for compliance with these criteria is at each facility. The second is more complex and involves assessing the impact to groundwater quality from migration of contaminants left in place after a facility closure. Unlike the first criteria, compliance with the second is demonstrated at the ICPP south boundary which is the negotiated point of compliance. At this location, adverse impacts to groundwater quality resulting from residual soil contamination anywhere on the ICPP cannot lead to contaminant concentrations that exceed the maximum contaminant limits (MCLs), or other EPA recommended health based levels. At this time, the groundwater flow and contaminant transport model used in the RI/FS will serve as the analytical tool to demonstrate consistency with the groundwater CERCLA RAO. During the RI/FS, a three dimensional model with capability of including transient effects (such as those caused by very large fluctuations in infiltrating water volumes originating at the surface in the form of percolation ponds, Big Lost River, irrigation, and sewage ponds and in the subsurface in the form of an injection well) was necessary. Although computationally intensive, this modeling effort was very successful in predicting contaminant concentrations as a function of location and time in the aquifer.
Applying the traditional forward modeling approach, which uses the RI/FS model to evaluate the effects of multiple facility closures over time, would require a monumental effort. An innovative groundwater modeling approach for facility closure, which consists of a simplified numerical method that features convolution and superposition methods with representative site hydrogeologic conditions to evaluate grouping of facilities, would be preferred. This approach can be used because of the elimination of transient conditions in the vadose zone by removal of the anthropogenic water sources during CERCLA remediation or facility closures and subsequent draining to steady-state moisture conditions. The equations solved by the numerical model become linear and the results scaleable in time and space.
The following steps are necessary to apply the computationally abbreviated approach:
If the closure design evaluated during Stage 3 reduces the risk from the closed facility such that ICPP-wide comprehensive risk is not significantly impacted, the facility can proceed to Stage 4, Closure Implementation. If the closure design does not provide suitable risk reduction, one of the following actions will be taken:
Stage 4, Closure Implementation, involves implementing the final facility closure design. When the facility closure is complete, the closed facility enters Stage 5, Post-Closure Monitoring and Maintenance. The CERCLA ER program will perform post-closure monitoring and maintenance. The results of the monitoring and maintenance will be evaluated during the CERCLA 5-year reviews for the ICPP. The CERCLA ER program will use the post-closure monitoring data to demonstrate that the facility closure is not inconsistent with the CERCLA RAOs. Documentation describing the final facility closure design, its implementation, and the final as-builts will be provided to the CERCLA ER program to substantiate the effectiveness of the facility closure at minimizing impacts to comprehensive site risks. The following documentation is required by the CERCLA Environmental Restoration Program for closure design, implementation, and monitoring.
REFERENCES