| (a) A landfill must have an approved liner quality control plan prepared under the direction of a licensed professional engineer, and it shall be the basis for the type and rate of quality control testing performance and reported in the soil liner evaluation report as required in §330.341 of this title (relating to Soil Liner Evaluation Report and Geomembrane Liner Evaluation Report). The plan must be included in the site development plan to provide operating personnel adequate procedural guidance for assuring continuous compliance with groundwater protection requirements. The plan must specify construction methods employing good engineering practices for compaction of clay soils to form a liner. Unless alternative construction procedures are approved in writing by the executive director, all constructed liners shall be keyed into an underlying formation of sufficient strength to ensure stability of the constructed lining. The plan shall address the installation and testing of a geomembrane liner, if used. Proposed dewatering plans shall be included. The plan shall include the following information: (1) constructed liner details, where applicable, shall be depicted on cross-sections of a typical cell showing the slope, widths, and thicknesses for compaction lifts. The amount of compaction shall be expressed as a percentage of a predetermined laboratory density; and (2) soil and liner quality-control testing procedures, to include sampling frequency, shall be included in the plan. All field sampling and testing, both during construction and after completion, shall be performed by a person acting in compliance with the provisions of the Texas Engineering Practice Act and other applicable state laws and regulations. The professional of record who signs the soil liner evaluation report or his representative should be on site during all liner construction. Quality control of construction and quality assurance of sampling and testing procedures should follow the latest technical guidelines of the executive director. (b) The liner quality control plan shall also: (1) provide guidance needed for testing and reporting evaluation procedures to the professional who will prepare the soil liner evaluation reports for the facility; (2) specify materials, equipment, and construction methods for the compaction of clay soils to form impermeable liners for the conditions to include the following information: (A) details for the overexcavation and recompaction of the in-situ soils, or the compaction of soils from a borrow source, shall be depicted on cross-sections of a typical cell showing the slope, widths, and thicknesses for compaction lifts; and (B) procedures to be followed when excavations, cells, or disposal areas extend into or have the potential to extend into the groundwater shall be in accordance with the provisions provided in §330.337 of this title (relating to Special Liner Design Constraints); and (3) describe installation methods and quality control testing and reporting following placement for any geomembrane liner that may be required or authorized by the executive director. (c) Soil liner quality control testing frequencies and procedures shall be in accordance with the executive director's most recent guidelines and the following. (1) All field sampling and testing, both during construction and after completion of the lining, shall be performed by a qualified professional experienced in geotechnical engineering and/or engineering geology, or under his direct supervision. (2) All liners should have continuous on-site inspection during construction by the professional of record or his designated representative. (3) The amount of compaction of clay liners shall be expressed as a percentage of a maximum dry density based on a compaction test specified by a licensed professional engineer. The compaction of the clay liner shall have been proven by soils laboratory testing to provide a coefficient of permeability of 1 x 10-7 centimeters per second (cm/sec) or less. (4) The liner quality control plan shall define the frequency of testing for each of the test procedures listed in subparagraphs (A) - (F) of this paragraph. These frequencies shall be expressed in numbers of tests per specific area of liner per lift or specific thickness of liner, unless an alternative frequency is approved by the executive director. In addition, unless otherwise approved by the executive director, all soil tests performed on any in-situ or constructed soil liners shall be in accordance with the standards in subparagraphs (A) - (E) of this paragraph: (A) laboratory permeability tests. Permeability tests shall be run using tap water or .05 Normal (N) solution of calcium sulfate (CaSO4 ) and not distilled water. All test data must be submitted on permeability tests regardless of test method used. At a minimum, the calculations of the last data set reported for each sample and the resultant coefficient of permeability shall be reported as supporting data. Tests shall be either constant head with back pressure (Appendix VII of Corps of Engineers Manual, EM 1110-2-1906; American Society of Testing and Materials (ASTM) D5084, "Measurement of Hydraulic Conductivity of Saturated Porous Materials Using a Flexible Wall Permeameter,") or falling head (Appendix VII of Corps of Engineers Manual, EM1110-2-1906); (B) sieve analysis +1, 200, -200 sieves; (ASTM D422 or ASTM D1140, as applicable); (C) Atterberg limits (ASTM D4318); (D) moisture-density relationships (ASTM D698 or any executive director approved modified test whose compactive effort matches the on site-construction equipment); (E) moisture content (ASTM D2216); and (F) thickness verification. (5) All soils used as constructed liners must have the following minimum values verified by testing in a soils laboratory: (A) plasticity index--equal to or greater than 15; (B) liquid limit--equal to or greater than 30; (C) percent passing 200 mesh sieve (-200) equal to or greater than 30%; (D) percent passing one-inch screen--100%; and (E) coefficient of permeability less than or equal to 1 x 10-7 cm/sec. (6) Permeability tests for proving the suitability of soils to be used in constructing clay liners shall be performed in the laboratory using the procedures and guidance of paragraph (4)(A) of this subsection. Field quality control must be provided by field density tests based on predetermined moisture-density compaction curves, Atterberg limits, and laboratory permeabilities of undisturbed field samples of compacted liner soils, unless an alternative plan is approved by the executive director. (7) Field permeability testing of in-situ soils or constructed soil liners shall be in accordance with ASTM D5093 for those soil liners that are in the floor of the excavation and a variation of the Boutwell STEI field permeability test approved by the executive director for the sidewalls, or in accordance with guidance furnished by the executive director. (8) All quality control testing of soil liners shall be performed during the construction of the liner. In no instance shall any quality control field or laboratory testing be undertaken after completion of liner construction, except for that testing which is required of the final constructed lift, confirmation of liner thickness, or cover material thickness. (9) All soil testing and evaluation of either in-situ soil or constructed soil liners shall be complete prior to installing the leachate collection system or, if no leachate collection system is required, prior to adding the one foot of protective cover on the area under evaluation. (d) Soil and liner density shall be expressed as a percentage of the maximum dry density and at the corresponding optimum moisture content specified as appropriate by a licensed professional engineer experienced in geotechnical engineering. These soils so compacted must upon testing either in the laboratory or as a test pad in the field demonstrate a coefficient of permeability no greater than 1 x 10-7 cm/sec. (e) Unless alternative construction procedures have prior written approval by the executive director, all constructed soil liners shall be keyed into an underlying formation of sufficient strength to ensure stability of the constructed lining. (f) Each soil liner evaluation report shall be prepared in accordance with the approved liner quality control plan. Any deviation from the approved plan must have prior written approval from the executive director. (g) Soil liners shall not be compacted with a bulldozer or any track-mobilized equipment unless it is used to pull a pad-footed roller. All soil liners shall be compacted with a pad-footed or prong-footed roller only. The maximum clod size of the compacted liner soils shall be approximately one inch in diameter. In all cases soil clods shall be reduced to the smallest size necessary to achieve the coefficient of permeability reported by the testing laboratory and to destroy any macrostructure evidenced after the compaction of the clods under density-controlled conditions. (h) The liner soil material shall contain no rocks or stones larger than one inch in diameter or that total more than 10% by weight. Rock content shall not be a detriment to the integrity of the overlying geomembrane. |
