**CBFO:OSO:DM:KJB:06-0381:UFC5486** 

### Department of Energy

Carlsbad Field Office
P. O. Box 3090 Carlsbad, New Mexico 88 221



### November 22, 2006

**Juan Reyes, Director**

**Radiation Protection Division 1200 Pennsylvania Ave. NW** 

**Room 556C Washington DC, 20460** 

**Dear Mr. Reyes:**

**On October 7, 2002, the Department of Energy/Carlsb ad Field Office (DOE/CBFO) requested**  **Environmental Protection Agency (EPA) approval of a proposed change to the design of the panel**  **closures at the Waste Isolation Pilot Plant (WIPP). This letter renews DOE/CBFO’s 2002 request for**  **EPA to review and approve two proposed actions rela ted to panel closures:** 

• **The New Mexico Environment Department (NMED) will b e responsible for approval of**  **the design and construction of the panel closure sy stem at WIPP.** 

• **A new design may be used for the panel closures.**

**In addition to the original requests, DOE/CBFO is a lso recommending that permanent closure of**  **panels be delayed to allow gas monitoring, with ins tallation of final panel closures depending on the**  **results of that monitoring. Background information and the major documents that support these**  **requests are described in the remainder of this let ter.** 

**In October 2002, DOE/CBFO asked EPA to modify Condi tion 1 of the WIPP Certification decision**  **by agreeing that NMED is responsible for final revi ew and approval of the design and construction**  **of the panel closure system at WIPP, while recogniz ing that EPA must be satisfied the new closure**  **design will not adversely affect compliance with th e long-term performance criteria. The 2002**  **submittal included details of a revised panel closu re design that was submitted to NMED with a**  **request to have the new design approved for use in closing the WIPP panels.** 

**On November 12, 2002, DOE/CBFO also informed EPA of its request to NMED to extend the panel**  **closure schedule for Panel 1. Specifically, DOE/CB FO asked that NMED approve the installation of**  **the explosion wall component of the approved “Optio n D” closure as required by the Hazardous**  **Waste Facility Permit (HWFP), but to extend the tim e period for completing the remainder of the** 

**closure activities until NMED and EPA rendered thei r respective final decisions on the request to**  **modify the approved final panel closure system desi gn. By letter dated December 26, 2002, NMED**  **approved a delay of final closure until a time “not later than five years after completion of the**  **explosion isolation wall.” In a subsequent letter in 2005 NMED approved a similar delay for Panel**  **2. In a November 15, 2002 letter, EPA advised DOE/ CBFO that EPA was deferring review of the**  **proposal until a decision had been issued on DOE/CB FO’s first recertification application.** **CBFO:OSO:DM:KJB:06-0381:UFC5486**

**Juan Reyes -2-**

**On March 29, 2006, EPA rendered its recertification decision and as a result DOE/CBFO is**  **resubmitting the request to modify Condition 1 of t he Final Rule. DOE/CBFO has also requested**  **that NMED now consider the proposed new design subm itted in October 2002, and is attaching to**  **this letter information on the proposed new design, and its predicted performance. The proposed**  **panel closure design is the same as that submitted in October 2002. The supporting documentation**  **has been updated with a new impact analysis of the long-term effect of the revised closure design on**  **repository performance.**

**As you know, the purpose of the panel closure syste m in the WIPP facility is to control volatile**  **organic compound (VOC) emissions during the operati ng life of the facility, and, thus, to protect the**  **health and safety of workers. In addition, the clo sure is designed to contain any possible explosion**  **associated with a hypothetical build up of flammabl e gases. There are no long-term design**  **requirements or performance specifications for thes e closures, beyond the necessity to demonstrate**  **that they will not have an adverse affect on long-t erm performance.** 

**The currently approved panel closure design (“Optio n D”) specified in Condition 1 involves**  **installation of a concrete block “explosion isolati on wall”, removal of the Disturbed Rock Zone**  **along a section of the panel access drift, and empl acement of a concrete monolith composed of** 

**Salado Mass Concrete in that section of the access drift. After several years of experience with**  **WIPP as an operational facility, we have re-evaluat ed a number of its engineering and construction**  **aspects. This effort included detailed planning to install the Option D closures in Panel 1 and a**  **parallel analysis of alternative closure designs. As a result of this re-evaluation, we believe a**  **redesign of the panel closure system is warranted. The redesigned panel closure (called the WIPP**  **Panel Closure (WPC)) is constructible in the WIPP u nderground, will be much simpler and**  **significantly less expensive to build, will reduce the risk of accidents and industrial injury to**  **construction workers, and will reduce the potential for disruption of waste emplacement activities.** 

**All of these benefits will accrue without influenci ng the short- or long-term performance of the**  **repository. The analyses that accompany this lette r demonstrate that the long-term performance of**  **the repository is not sensitive to the closure desi gn, within a broad range of likely closure**  **permeability values, and specifically demonstrate t hat impacts to the predicted long-term**  **performance of the repository associated with the i nstallation of the revised closure design are**  **negligible compared to the currently prescribed Opt ion D design.** 

**The HWFP issued by NMED specifies panel closure req uirements that comply with the requirements**  **of the New Mexico hazardous waste regulations durin g the operational, closure and 30-year post**  **closure periods of the repository. Because the pan el closure specifications cover only the operationa**  **l and closure periods and because long-term performan**  **ce is insensitive to this design, DOE/CBFO believes that NMED, tasked with regulating hazardou**  **s waste disposal in New Mexico, should have responsibility for final approval of the panel clos**  **ure system design. DOE/CBFO therefore requests that the EPA modify Condition 1 of the WIPP Certifi**  **cation decision to acknowledge that NMED is responsible for regulating the design and construct**  **ion of the panel closure system at WIPP, provided that DOE demonstrates there are no long-term impact**  **s on performance. DOE/CBFO suggests that such a change might be made on the following basis:** **CBFO:OSO:DM:KJB:06-0381:UFC5486**

**Juan Reyes -3-**

• **DOE/CBFO will implement a panel closure system as a pproved by the NMED** 

• **DOE/CBFO will demonstrate, by an appropriate impact assessment, that the panel closure**  **system proposed to NMED does not adversely affect t he long-term performance of the repository** 

**This Notification of Proposed Change to Condition 1 requires that EPA be fully cognizant of the**  **CBFO’s Permit modification request to NMED for pane l closures. To this end, the details of the**  **redesign and its performance are included in the en closed Compact Disk (CD). The CD includes the**  **following attachments.**

**Attachment A,** Design Report for a Revised Panel Closure System a t the Waste Isolation Pilot Plant

**, provides a description of the proposed design and d**  **emonstrates its adequacy to meet requirements of the Resource Conservation and Recovery Act during t**  **he operational period. This design report has been certified by a Professional Engineer registere**  **d in New Mexico. Attachment A was transmitted to NMED in October 2002 as part of the Permit Modif**  **ication Request to change the Closure Plan**

**contained in the HWFP.**

**Attachment B,** Effective Permeability of the Redesigned Panel Clos ure System, **provides estimates of the permeability of the WPC as a function of time.**  **Specifically, it demonstrates the permeability of**

**the new closures will be between 10 -15**  **m 2**  **and 10 -19**  **m 2**  **throughout the regulatory period. This range is significant because it is consistent with the ra**  **nge of panel closure permeability evaluated in**

**Attachment C.**

**Attachment C,** Panel Closure Impact Assessment Documentation, **evaluates the impacts of panel closures on the long-term performance of the reposi**  **tory. This analysis report is prepared pursuant to 40 CFR Part 191, Subparts B and C, and 40 CFR Part**  **194. The report demonstrates that impacts to the predicted long-term performance of the reposito**  **ry associated with the installation of the WPC are negligible compared to the currently prescribed Opt**  **ion D design. This attachment also includes a new impact analysis specifically designed to evalua**  **te the effects of the new closure.**

**Attachment D,** Further Assessment of the Short-term Stability of t he 12 Foot Explosion Isolation Wall, **dated June 30, 2006, evaluates the continued stabi lity of the explosion isolation walls**  **constructed in Panel 1. Since some time has passed since the initial request to extend the time for** 

**final closure construction and installation of the explosion wall component of the Option D design,** 

**the DOE/CBFO has conducted additional calculations to ensure the explosion wall component will**  **continue to function as required for an additional period while the revised closure design is being**  **reviewed. Attachment D provides these new calculat ions.** 

**Attachment E,** Panel Closure System History **, provides information regarding the various submit tals**  **and responses pertaining to panel closures from the time of the Compliance Certification Application**  **submittal in 1996 up to the present.**

**Attachment F is a courtesy copy of the October 2002 Planned Change Request that provided a**  **revised design for the panel closure system and req uested modification of Condition 1 of the** **CBFO:OSO:DM:KJB:06-0381:UFC5486**

**Juan Reyes -4-**

**Certification Decision. The description of the rev ised panel closure system design was also provided** 

**to NMED in 2002 as a Class 3 PMR.**

**In addition to the requests in the original October 2002 submittal, DOE/CBFO is further requesting**  **that permanent closure of Panels 1, 2, and 3 be del ayed to allow the October 2002 Class 3 to be**  **amended to address long-term monitoring of combusti ble gases potentially generated by degradation**  **of the emplaced waste. DOE/CBFO is requesting that NMED allow DOE/CBFO to install a**  **temporary steel bulkhead and utilize existing monit oring equipment to continue to measure the**  **concentrations of volatile organic compounds until final NMED action is taken on the October 2002**  **Class 3. Ultimately, if the gas concentrations rem ain low, as we expect, then we intend to delay**  **installation of the permanent panel closures until repository closure. In this case we would review**  **the design of panel closures as well as the need fo r any closure beyond the steel bulkheads. On the**  **other hand, if the observed gas concentrations exce ed certain action levels related to the lower**  **explosive limits of hydrogen and methane, then more frequent monitoring or installation of an**  **approved panel closure design will be required. DO E/CBFO will provide EPA copies of future**  **submissions to NMED on monitoring as the are develo ped.** 

**Attachment G is a Class 1* Permit Modification Requ** **est (PMR) submitted to NMED to extend the closure schedules for Panels 1 through 3, while NME**  **D reviews the original October 2002 Class 3**

**PMR.**

**Attachment H provides the “Notice of Planned Change ,” submitted to NMED in accordance with the**  **WIPP HWFP. The Notice of Planned Change to the Per mitted Facility identifies physical** 

**alternations which must be made in Panel 3 for safe ty reasons.** 

**We appreciate your timely consideration of this req uest. Should you require further information,**  **please contact Daryl Mercer of my staff at (505) 23 4-7452/8172.** 

**Sincerely,**

**David C. Moody Manager** 

**Enclosure CBFO:OSO:DM:KJB:06-0381:UFC5486** 

**Juan Reyes -5-**

**cc: w/enclosure I. Triay, EM**  **F. Marcinowski, EM S. White, EPA-ORIA**  **C. Byrum, EPA-ORIA T. Peake, EPA-ORIA**  **S. Ghose, EPA-ORIA N. Stone, EPA-Region VI**  **J. Bearzi, NMED S. Zappe, NMED**  **J. Fox, Pecos Management Inc.**

**cc: w/o enclosure** **V. Daub, CBFO * ED** **G. Basabilvazo, CBFO ED M. Rose, CBFO ED**  **R. Raaz, WTS ED D. Kessel, SNL ED** 

***ED denotes electronic distribution CBFO:OSO:DM:KJB:06-0381:UFC5486** 

**Juan Reyes -6-**

**bcc: w/o enclosure** **D. Mercer, CBFO * ED** **B. Kehrman, WRES ED S. Kouba, WRES ED**  **W. Most, WRES ED R. Chavez, WRES ED**  **D. Streng, WRES ED R. Steger, CTAC ED**  **A. Chavez, WRES ED E. Vugrin, SNL ED** 

***ED denotes electronic distribution**