OAR 340-094-0060: Design Criteria

(1) If a municipal solid waste landfill is subject to 40 CFR, Part 258 as provided in 40 CFR, §258.1, the owner or operator shall comply with landfill design criteria in 40 CFR, Part 258, Subpart D. Except as otherwise provided in OAR 340, division 94, any person who designs, constructs, expands or modifies any municipal solid waste landfill must do so in conformance with the design requirements of this rule. (2) Plan Design Requirements. In addition to the requirements of 40 CFR, Part 258, Subpart D, unless an exemption has been granted under OAR 340-093-0070(4), and in addition to the requirements of OAR 340-093-0070, detailed plans and specifications for landfills shall include but not be limited to: (a) Topographic maps which show natural features of the site; the location and design of all pertinent existing and proposed structures, such as berms, dikes, surface drainage control devices, access and on-site roads, water and waste water facilities, gas control devices, monitoring wells, fences, utilities, maintenance facilities, shelter and buildings; legal boundaries and property lines, and existing contours and projected finish grades. Unless otherwise approved by the Department, the scale of the plan drawings shall be no greater than one inch equals 200 feet, with contour intervals not to exceed five feet. Horizontal and vertical controls shall be established and tied to an established bench mark located on or near the site. Where the Department deems it essential to ensure compliance with OAR 340, divisions 93 through 96, the bench mark shall be referenced to the Oregon State Plane Coordinate System, Lambert Projection; (b) A minimum of two perpendicular cross section drawings through the landfill. Each cross section shall illustrate existing grade, excavation grade, proposed final grade, any additions for groundwater protection, water table profile and soil profile. Additional cross sections shall be provided as necessary to adequately depict underlying soils, geology and landfill contours, and to display the design of environmental protection devices or structures; (c) A description of the design assumptions and methods used to forecast flows and to determine the sizing of pumps, pipes, ditches, culverts and other hydraulic equipment used for the collection, treatment and disposal of leachate and for the control of surface drainage; (d) A detailed operations plan pursuant to OAR 340-094-0040(11)(b) and timetable which describes the proposed method of operation and progressive development of trenches and/or landfill lifts or cells. (3) Leachate. In addition to the requirements of 40 CFR, Part 258, Subpart D, any person designing or constructing a landfill shall ensure that leachate production is minimized. Where required by the Department, leachate shall be collected and treated or otherwise controlled in a manner approved by the Department. Leachate storage and treatment impoundments shall be located, designed, constructed and monitored, at a minimum, to the same standards of environmental protection as municipal solid waste landfills. (4) Gas Control. No person shall establish, expand or modify a landfill such that: (a) The concentration of methane (CH4) gas at the landfill exceeds 25 percent of its lower explosive limit in facility structures (excluding gas control or gas recovery system components) or its lower explosive limit at the property boundary; (b) Malodorous decomposition gases become a public nuisance. (5) Surface Drainage Control. Each permittee shall ensure that landfill is designed and constructed so that drainage will be diverted around or away from active and completed operational areas. (6) Additional Requirements to Protect or to Monitor Potential Threats to Groundwater. When a person applies to construct a new or expanded landfill cell at a municipal solid waste landfill, the Department shall evaluate the need to provide protection to groundwater in addition to the requirements of 40 CFR, Part 258, Subpart D. The Department shall also evaluate whether the specific conditions at the site require an enhanced ability to monitor potential threats to groundwater in addition to the requirements in 40 CFR, Part 258, Subpart E. The evaluation shall be based on site-specific data, including but not limited to location, geography, hydrogeology and size of the site. To assist in the Department’s evaluation, the applicant shall provide necessary relevant data. The Department may require a secondary leachate collection system, and/or leak detection system, or other design or technology providing equivalent protection to the environment if the Department determines that: (a) There is significant potential for adverse impact to groundwater from the proposed cell; or (b) Additional measures are necessary to provide adequate monitoring of potential threats to the groundwater.