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

 Department of Energy 

 Carlsbad Field Office 

 P. O. Box 3090 

 Carlsbad, New Mexico 88221 

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/Carlsbad 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 related to panel closures: 

• The New Mexico Environment Department (NMED) will be responsible for approval of 

the design and construction of the panel closure system at WIPP. 

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

In addition to the original requests, DOE/CBFO is also recommending that permanent closure of 

panels be delayed to allow gas monitoring, with installation 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 letter. 

In October 2002, DOE/CBFO asked EPA to modify Condition 1 of the WIPP Certification decision 

by agreeing that NMED is responsible for final review and approval of the design and construction 

of the panel closure system at WIPP, while recognizing that EPA must be satisfied the new closure 

design will not adversely affect compliance with the long-term performance criteria. The 2002 

submittal included details of a revised panel closure 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/CBFO asked that NMED approve the installation of 

the explosion wall component of the approved “Option D” closure as required by the Hazardous 

Waste Facility Permit (HWFP), but to extend the time period for completing the remainder of the 

closure activities until NMED and EPA rendered their respective final decisions on the request to 

modify the approved final panel closure system design. 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/CBFO’s first recertification application. 
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On March 29, 2006, EPA rendered its recertification decision and as a result DOE/CBFO is 

resubmitting the request to modify Condition 1 of the Final Rule. DOE/CBFO has also requested 

that NMED now consider the proposed new design submitted 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 system in the WIPP facility is to control volatile 

organic compound (VOC) emissions during the operating life of the facility, and, thus, to protect the 

health and safety of workers. In addition, the closure is designed to contain any possible explosion 

associated with a hypothetical build up of flammable gases. There are no long-term design 

requirements or performance specifications for these closures, beyond the necessity to demonstrate 

that they will not have an adverse affect on long-term performance. 

The currently approved panel closure design (“Option D”) specified in Condition 1 involves 

installation of a concrete block “explosion isolation wall”, removal of the Disturbed Rock Zone 

along a section of the panel access drift, and emplacement 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-evaluated 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 underground, 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 influencing the short- or long-term performance of the 

repository. The analyses that accompany this letter demonstrate that the long-term performance of 

the repository is not sensitive to the closure design, within a broad range of likely closure 

permeability values, and specifically demonstrate that impacts to the predicted long-term 

performance of the repository associated with the installation of the revised closure design are 

negligible compared to the currently prescribed Option D design. 

The HWFP issued by NMED specifies panel closure requirements that comply with the requirements 

of the New Mexico hazardous waste regulations during the operational, closure and 30-year postclosure periods of the repository. Because the panel closure specifications cover only the operational 

and closure periods and because long-term performance is insensitive to this design, DOE/CBFO 

believes that NMED, tasked with regulating hazardous waste disposal in New Mexico, should have 

responsibility for final approval of the panel closure system design. DOE/CBFO therefore requests 

that the EPA modify Condition 1 of the WIPP Certification decision to acknowledge that NMED is 

responsible for regulating the design and construction of the panel closure system at WIPP, provided 

that DOE demonstrates there are no long-term impacts on performance. DOE/CBFO suggests that 

such a change might be made on the following basis: 
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• DOE/CBFO will implement a panel closure system as approved by the NMED 

• DOE/CBFO will demonstrate, by an appropriate impact assessment, that the panel closure 

system proposed to NMED does not adversely affect the 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 panel closures. To this end, the details of the 

redesign and its performance are included in the enclosed Compact Disk (CD). The CD includes the 

following attachments. 

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

provides a description of the proposed design and demonstrates its adequacy to meet requirements of 

the Resource Conservation and Recovery Act during the operational period. This design report has 

been certified by a Professional Engineer registered in New Mexico. Attachment A was transmitted 

to NMED in October 2002 as part of the Permit Modification Request to change the Closure Plan 

contained in the HWFP. 

Attachment B, Effective Permeability of the Redesigned Panel Closure 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 range 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 repository. 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 repository associated with the installation of the WPC are 

negligible compared to the currently prescribed Option D design. This attachment also includes a 

new impact analysis specifically designed to evaluate the effects of the new closure. 

Attachment D, Further Assessment of the Short-term Stability of the 12 Foot Explosion Isolation 

Wall, dated June 30, 2006, evaluates the continued stability 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 calculations. 

Attachment E, Panel Closure System History, provides information regarding the various submittals 

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 requested modification of Condition 1 of the 
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Certification Decision. The description of the revised 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 delayed to allow the October 2002 Class 3 to be 

amended to address long-term monitoring of combustible 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 monitoring 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 remain 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 for any closure beyond the steel bulkheads. On the 

other hand, if the observed gas concentrations exceed 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. DOE/CBFO will provide EPA copies of future 

submissions to NMED on monitoring as the are developed. 

Attachment G is a Class 1* Permit Modification Request (PMR) submitted to NMED to extend the 

closure schedules for Panels 1 through 3, while NMED 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 Permitted Facility identifies physical 

alternations which must be made in Panel 3 for safety reasons. 

We appreciate your timely consideration of this request. Should you require further information, 

please contact Daryl Mercer of my staff at (505) 234-7452/8172. 

 Sincerely, 

 David C. Moody 

 Manager 

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

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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