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<br /> 51052 Federal Register / Vol. 56, No. 196 / Wednesday, October 9, 1991 / Rules and Regulations
<br /> employees,users of the disposal site, occur if methane levels remain methane problem and to adequately
<br /> and occupants of nearby structures,and unchecked;therefore,the Agency evaluate the alternatives for remedial
<br /> can damage containment structures and believes for safety reasons it is action to alleviate the problem and-to w
<br /> thereby cause the emission of toxic necessary to retain the minimum submit a remediation plan.
<br /> fumes.For this reason,EPA established quarterly frequency for methane The Agency considered the
<br /> an explosive gas criterion in §257.3-8 of monitoring in the final rulemaking.The alternative time frames,ranging from 30
<br /> the original subtitle D Criteria to control Agency believes that methane to 90 days,suggested by the
<br /> the concentration of methane in facility monitoring is critical because it provides commenters.The Agency determined
<br /> structures and at the property boundary. an early warning of potential methane- that 60 days will provide adequate time
<br /> Specifically, §257.3-8 required that the build-up that may lead to explosions, for an owner or operator to develop and
<br /> concentration of methane generated by and that quarterly monitoring accounts place in the operating record a
<br /> the MSWLF not exceed 25 percent of the for the seasonal variations in subsurface remediation plan that would describe
<br /> lower explosive limit(LEL)in facility gas migration patterns. the nature and extent of the problem
<br /> structures(excluding gas control or As mentioned above,EPA also. and the proposed remedy without
<br /> recovery system components)and that it proposed that certain steps be taken if causing undue threat to human health,
<br /> not exceed the LEL itself at the property methane gas levels exceeding the and modified the final rule accordingly.
<br /> boundary.EPA expanded this specified limits are detected.The This 60-day time period is needed to
<br /> requirement in §258.23 of the proposed Agency did not receive any comments provide adequate time for the owner or
<br /> rule by requiring the owner or operator on the proposed§258.23(c)(1)and(2), operator to contact,if necessary,
<br /> to conduct subsurface and facility which required the owner or operator to knowledgeable outside parties to assist
<br /> structure gas monitoring at least take all necessary steps to protect in the development of the remediation
<br /> quarterly to ensure methane control.In human health and immediately notify plan,which should include
<br /> addition,EPA proposed that if methane the State of methane levels detected and determination of the exact location and
<br /> exceeds the limits specified,the owner actions taken.Therefore,EPA retained extent of the methane gas problem,
<br /> or operator must take necessary steps to these provisions as proposed,with determination of the need for and
<br /> ensure protection of human health and minor modifications in keeping with the location of interceptor gas collection
<br /> immediately notify the State of the level self-implementing aspects of today's trenches, and a decision as to whether
<br /> detected and the steps taken to protect final rule.EPA has clarified the rule venting of structures and subsurface gas
<br /> human health.Such steps could include language by requiring the owner or withdrawal is necessary.EPA does not
<br /> evacuation and ventilation of affected operator to notify the State immediately believe that allowing this additional
<br /> buildings.The Agency also proposed when the methane limits have been time compromises the protection of
<br /> that the owner or operator submit a exceeded,and within seven days place human health and the environment
<br /> remediation plan to the States within 14 in the operating record documentation because,under§258.23(c)(1), the owner
<br /> days of the methane limits having been of the methane gas levels detected and a or operator still must take all necessary
<br /> exceeded.This plan must describe the description of the interim steps taken to steps to ensure immediate protection of
<br /> nature and extent of the problem and protect human health.The Agency human health,including interim
<br /> the proposed remedy. believes that seven days is adequate measures,if methane gas levels exceed
<br /> The proposal listed site-specific time for the owner or operator to place the specified limits.Rather,a reasonable
<br /> factors that control the rate and extent the documentation in the operating specific time period for the development
<br /> of gas migration,which should be record.However,the Agency is allowing of a plan facilitates the self-
<br /> considered to determine the type and the State Director to establish implementing nature of today's rule.
<br /> optimal frequency of monitoring(which alternative recordkeeping locations and The Agency also modified the rule to
<br /> in some instances may be more than alternative schedules for recordkeeping require the owner or operator to place
<br /> quarterly).These factors include:soil and notification requirements.The the remediation plan in the operating
<br /> conditions,hydrogeologic conditions Agency included the operating record record and to notify the State.The plan
<br /> surrounding the disposal site,hydraulic provision to ensure that there is proper is then to be implemented once it has i
<br /> conditions surrounding the disposal site, documentation if methane levels are been placed in the operating record.The ,
<br /> and the location of facility structures exceeded and to facilitate citizen suits. Agency added this requirement to the
<br /> relative to property boundaries. EPA received numerous comments final rule to provide a mechanism to ,
<br /> Many commenters criticized the regarding proposed §258.23(c)(3),which ensure that the owner or operator
<br /> minimum frequency of quarterly required the owner or operator to submit develops a remediation plan,when
<br /> monitoring and recommended that a methane remediation plan within 14 necessary,and that the plan is made
<br /> States be allowed to specify the days.Many commenters criticized the available for State and public review.
<br /> monitoring frequency.Some also 14-day period for submitting a The final rule allows Directors of
<br /> suggested that exceptions to quarterly remediation plan as being unrealistically approved States to establish alternative
<br /> monitoring be permitted based on short.Commenters said that plans for recordkeeping locations and alternative c
<br /> climate(either dry or cold),type or interim measures could be submitted in schedules for recordkeeping and c
<br /> quantity of waste disposed,and that time frame to ensure the immediate notification requirements. e
<br /> distance from structures or other protection of human health and the 5 - c
<br /> facilities. environment,but that determination of -The Agency decided to retain the the problem and the exact nature of Under§258.24(a),EPA proposed to 4 c
<br /> minimum quarterly monitoring remediation would take much longer. require that MSWLFs not violate i
<br /> frequency requirement because the Proposed time schedules ranged from 30 applicable Now E
<br /> Agency was not persuaded that dry or to 90 days.The Agency agrees with t
<br /> cold climates,type or quantity of waste these commenters that the 14-day t
<br /> disposed,and location of the facility response time was not a realistic time Section 258.24(b)prop osed to prohibit l
<br /> should be factors for waiving quarterly period to allow an owner or operator to open burning(i.e.,uncontrolled or 1
<br /> monitoring.Catastrophic results may make a complete determination of the unconfined combustion)of solid waste t
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