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Partial Facility Closure Plan for
B-20 Detonation Area
March 1994
Section 3
Implementation of Corrective Action
Closure of the B-20 OB/OD area is being conducted in compliance with an EPA Compliance Order to CSSA dated June 30, 1993. The compliance order required CSSA, the operator of the B-20 area, to immediately cease operation of the unit and to prepare and implement a closure plan for the unit in accordance with the applicable regulations. This section presents the regulatory framework applicable to the closure of the B-20 site and an outline of the proposed closure procedure that conforms to the regulatory requirements for the unit.
In November 1980, CSSA submitted a RCRA Part A permit application for hazardous waste management activities at the facility. Accordingly the facility is considered an interim status hazardous waste facility under RCRA. However, the B-20 OB/OD area was not included as a hazardous waste management area in the Part A permit application, or in subsequent hazardous waste activity notifications. CSSA had ceased operations at the B-20 site at the time of the Part A application and did not resume demolition activities until 1984. From the 1950's or 1960's until 1987 (with a hiatus in activities between 1980-1984 as stated above), CSSA used the B-20 site to treat and dispose of reactive water explosives which are classified as hazardous wastes for reactivity (EPA waste number D003). During an inspection in January 1993, EPA determined that the B-20 site was a hazardous waste thermal treatment unit and did not have interim status since it was not included in the Part A permit application. A subsequent EPA compliance order in June 1993 required CSSA to prepare and implement a closure plan for the B-20 site.
Based on the nature of its operation, the B-20 site is considered a thermal treatment unit (40 Code of Federal Regulations (CFR) 265 Subpart P). As a hazardous waste treatment unit, the B-20 unit is regulated both under federal and state regulations. The following are brief descriptions of federal and state regulations applicable to closure of the B-20 site. The EPA compliance order for the B-20 unit requires that a closure plan for the unit be prepared in accordance with the 40 CFR 265 Subpart G and Title 31 Texas Administrative Code (TAC) Chapter 335.
The federal regulations which specify closure requirements for interim status hazardous waste facilities are established in 40 CFR 265 Subpart G. These regulations establish the closure performance standards, post closure requirements, and financial assurance requirements. The state regulations governing industrial solid wastes and municipal hazardous wastes are established at 31 TAC Chapter 335 Subchapters A, E, and S. Specifically, 31 TAC 335.118(a)(ii) requires that is a compliance order to cease receiving waste and/or close a units is issued, as in the case of the B-20 site, a closure plan must be prepared. The closure plan should be prepared in accordance with 40 CFR 265.112 (31 TAC 335.118). In accordance with 40 CFR 265.112 (31 TAC 335118), the closure plan should be submitted to the EPA Administrator (Texas Natural Resource Conservation Commission, TNRCC Executive Director) for approval. The owner/operator (o/o) of the unit must treat, remove and/or dispose of onsite of all hazardous wastes within 90 days after receiving the final volume of wastes or the approval of the closure plan, whichever is later (40 CFR 265.113). Similarly, all closure activities must be completed within 180 days. However, the o/o may request an extension of closure periods allowed under the regulation.
At the completion of the closure activities, the o/o must submit a closure report to the Administrator along with a certification from an independent registered professional engineer (40 CFR 265.115 and 116). The report should also include a survey plat of the unit. If residual waste constituents remain at the unit, the o/o should prepare a post-closure care plan and deed record the area (40 CFR 265.117, 118, and 119; and 31 TAC 335.560 and 566). The unit must be managed in accordance with the approved post-closure care plan.
The closure requirements in 31 TAC 335 Subchapters A and S apply to closure of both industrial solid waste and municipal hazardous waste. In addition, the closure requirements apply to the closure of areas which have received unauthorized releases such as spills. The closure regulations establish the obligation for closure and remediations and specify the mechanisms to evaluate the closures and remediations. In addition to the closure and remediation requirements as outlined in 31 TAC 335.8 pertaining to the risk reduction standards, any treatment, storage, or disposal facility is also subject to the provisions in subchapter E which incorporate federal regulations at 40 CFR 265 by reference.
Risk reduction standards established at 31 TAC 335 Subchapter S apply to closure and remediation of solid waste management units (including hazardous waste management units). These regulations define three closure standards based on the level of risk posed by residential contamination at the end of site closure. The risk reduction standard 1 is the equivalent of clean closure and requires that all waste constituents at the site be removed to background levels. Post-closure care is not required under standard 1. The risk reduction standard 2 requires that the waste constituents be removed to health-based levels that eliminate substantial current or future risks to human health or the environment. Post-closure deed recordation is required. The risk reduction standard 3 requires removal of waste constituents to levels that allow site management with controls during post-closure period to eliminate any substantial risk posed by the residual contamination. Site controls must be maintained during a post-closure period.
For all three standards, a final report to the Executive Director to show that the closure was completed according to the approved closure plan should be submitted (31 TAC 335.8). Furthermore, if post-closure care is determined necessary, a post-closure care plan should be prepared and implemented, and the site should be deed recorded with the local authorities noting the waste management boundaries and site history (31 TAC 335.8(b) and 335.553).
The closure performance standard specified in 40 CFR 265 and 31 TAC 335 is the o/o must close the facility in a manner that: (1) minimizes the need for further maintenance, and (2) controls, minimizes, or eliminates post closure escape of hazardous constituents to protect human health and the environment. This overall closure performance standard is met by implementing the standard specified in the risk reduction rules.
Risk reduction standard 1 requires that all waste constituents at the site be removed to background levels for inorganic constituents and to below detection limits or practical quantitation limits (PQLs) for organic constituents. Preliminary data collected from the site indicates some hazardous waste constituents may still remain at the site. Because of the large area of the B-20 site, removal of all hazardous constituents may not be feasible and standard 1 is not selected fro closure at this time.
Risk reduction standard 2 requires that the waste constituents at the site be removed to health-based levels that eliminate any substantial current or future risks to human health or the environment. Based upon preliminary data, this standard may be achievable at the B-20 site. however, this standard will not be selected at this time. The increased flexibility inherent to standard 3 is needed due to the limited nature of the preliminary data. However, this plan will be amended to closure under risk reduction standard 2 if the results from the remedial investigation indicate that standard 2 may be achieved.
The risk reduction standard 3 requires removal of waste constituents to levels that allow site management and engineered controls to eliminate any substantial risk posed by the residual contamination. Continuing post-closure care is required to maintain the controls. Based on the review of the preliminary investigation data, standard 3 was chosen as the closure performance standard for the B-20 site. Some hazardous waste residues were found at the site. A more complete investigation is needed to establish site conditions. If hazardous waste residues are found throughout the site, the baseline risk assessment required under standard 3 will be used to establish media specific contaminant concentrations. Standard 3 requires that the closure must be permanent or achieve the highest degree of long-term effectiveness, balance cost-effectiveness and long-term effectiveness, and achieve the media cleanup requirements listed at 31 TAC 335.563.
Under the standard 3, the following activities are included in the closure activities (31 TAC 335.553):
Closure investigation to define type and extent of contamination,
Baseline risk assessment (baseline RA) to determine the current and future risks at the site and establish cleanup criteria,
Corrective measures study (CMS) to evaluate potential remedies for the site,
Implementation of the remedial action approved by the Executive Director, and
Final closure report, certification, and deed recordation.
The regulations at 31 TAC 335.563 establish media specific cleanup levels for carcinogens and systemic toxicants that are identified as chemicals of concern in the baseline RA. Standard 3 also establishes cleanup levels that are protective of air and waters at the site taking into account the site conditions and any engineering controls that may be employed. At the completion of closure efforts, a post-closure care plan is required, if determined necessary, in accordance with 31 TAC 335.565. The site will be deed recorded as required in 31 TAC 335.566.
The risk reduction standard 3 achieves cleanup levels for wastes and waste residues that are identified in the baseline RA to pose unacceptable exposure risks. In addition, the standard also requires engineering controls and post-closure care to minimize risks associated with any residual contamination. Thus, compliance with risk reduction standard 3 achieves the closure performance standard established at 40 CFR 265.111 which includes minimization of the need for further maintenance and protection of human health and the environment to the extent determined necessary in the baseline RA.
Therefore, based on the above evaluation, the attainment of risk reduction standard 3 at the B-20 site will comply with the closure requirements under both the federal and the state regulations.
The B-20 site will be closed to achieve risk reduction standard 3 described in section 3.2. The closure procedures specified in standard 3 include a remedial investigation, baseline risk assessment, corrective measures study, closure action design and implementation, and preparation of closure certification report and site deed recordation. The closure procedures specific to the B-20 site are described in detail in later sections. The following is an overview of each of the closure procedures with emphasis on objective of the closure procedure.
The remedial investigation activities will include characterization of surface and subsurface soils, surface water and sediment for wastes and waste residues. These activities will include surface soil sampling, soil borings for subsurface investigation, and sampling of surface waters and sediments at the site. Geophysical methods, such as a magnetometer survey, will be employed for subsurface mapping at the site. Field screening methods will also be utilized to characterize the site. The remedial investigation activities are described in detail in section 4.
The remedial investigation activities will be conducted in accordance with the quality assurance project plan (QAPP) included as appendix C to this document. A project health and safety plan will be prepared after acceptance of the proposed investigation action. At the completion of the remedial investigation, a remedial investigation report will be prepared in accordance with 31 TAC 335.553(b)(1). The report will describe the procedures and findings of the investigation including nature, extent and distribution of wastes and waste residues in environmental media of concern. The report may also recommend additional field investigation if the data collected are found insufficient to conduct the closure procedures described below.
If the results of the remedial investigation indicate concentrations of contaminants at this site are below the risk reduction standard 2 MSCs (or if such levels can easily be achieved), the EPA and TNRCC will be notified and requested to allow closure of the B-20 site under standard 2.
A baseline RA will be conducted using the data collected during the preliminary investigation and the remedial investigation. Additional data for the baseline RA may be collected, if found necessary, at the conclusion of the remedial investigation. The baseline RA will evaluate the human health risks present in the event no remedial activities are conducted at the B-20 site. Standard exposure factors will not be used in the baseline RA as provided for in 335.563(e)(2), as land use other than residential is more appropriate based on historical, current and probable future use, and the effectiveness of institutional controls. The results of the baseline RA will be presented in a report in accordance with 31 TAC 335.553(b)(2).
The baseline RA for the B-20 site includes selection of chemicals of concern, exposure assessment, toxicity assessment, characterization of human health risks for exposure pathways, and uncertainty analysis. Using the baseline RA, hazard index and cancer risks for the chemicals of concern will be calculated for present exposure scenarios. The calculated values of hazard index and cancer risks will be used to establish the site cleanup levels in accordance with 31 TAC 335.563(b) and (c). A detailed description of the baseline RA procedures that may be used for the B-20 site is presented in section 5.
If the baseline RA determines that no unacceptable exposure risks exist at the site for the current land-use scenarios, no further remedial actions may be performed at the site. A no-further-action (NFA) document will be prepared for the site for approval by the EPA and the TNRCC. Upon the approval of the NFA document, and deed recordation, the site will be considered closed in accordance with the approved closure plan.
Based on the results of the baseline RA, any need for remedial action at the B-20 site to achieve with the closure performance standard will be determined. If a remedial action is found necessary, a CMS will be conducted to evaluate the relative capability, effectiveness, implementability and cost of remedial technologies applicable to the site to achieve the cleanup levels to meet the requirements of the risk reduction standard 3. The CMS evaluation will be conducted using the procedures listed in 31 TAC 335.563, and a CMS report will be prepared to present the evaluation process and the findings in accordance with 31 TAC 335.553(b)(3). A more detailed discussion of the CMS for the B-20 site is presented in section 6.
A final closure report will be identified using the findings of the CMS. This closure action will be implemented at the B-20 site with the approval of the EPA and the TNRCC. A closure action work plan will be prepared to describe the methods, procedures, and schedule of activities that may be performed during the implementation of the closure action. This work plan will also include any construction design drawings and details that may be necessary to implement the closure action. The closure action is discussed in more detail in section 7.
The implementation of the closure action will be monitored and documented to verify that it met the requirements of risk reduction standard 3 and the closure performance standard. Closure verification samples may be collected to confirm that the cleanup levels were achieved.
Upon the completion of the closure action, a final closure report will be prepared to describe the procedures and results of closure action. The report will be certified by an independent professional engineer registered in the State of Texas. The closure report will be submitted to the EPA and TNRCC for review and approval according to 31 TAC 335.553(b)(4). Furthermore, the site will be deed recorded with the county authority in accordance with 31 TAC 335.566.
The closure report will also include a post-closure plan, if one is deemed necessary for the site. Post-closure care may be necessary at the B-20 site if engineering controls and maintenance activities are required to manage any residual contamination at the site after the completion of closure action. The management of residual contamination may be required to ensure that no exposure risks in excess of the closure performance standard for risk reduction standard for risk reduction standard 3 exist at the site during the post-closure period. The requirements of the final closure report and certification are further discussed in section 8.
Closure contingency activities may be necessary for the B-20 site in the event the closure performance standard selected for the site (section 3.2) can not be achieved. Such activities may be implemented outside the closure procedures presented in section 3.3. These activities may include partial closure, interim measures and post-closure care.
The contingency activities may be implemented if unexpected site conditions such as unexploded and unstable ordnances are discovered that inhibit the implementation of closure actions to achieve the closure performance standard. Under such conditions, a partial closure of the B-20 unit may be conducted and a post-closure care program installed. Site conditions that pose imminent threat to human health and the environment may require remediation measures (interim measures) outside the normal sequence of the closure procedure.
If implementation of closure contingency activities is necessary, a closure contingency plan will be prepared describing the contingency activity and the procedures. In addition, the closure plan, closure cost estimate, and schedule may also be modified to include the contingency actions. The contingency plan will be implemented as approved by the EPA and the TNRCC.
An additional contingency may exist based on the results of the remedial investigation. If the results of the investigation indicate risk reduction standard 2 closure requirement may be met, a closure plan amendment will be filed with the EPA and TNRCC to use standard 2 as the closure performance standard. If achievable, standard 2 is preferable because it is more protective of human health and the environment.