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grained sand pack material (100% passing the No. 30 sieve and less than 2% passing the No. 200 sieve) six inches thick must be placed above the sand pack and below the bentonite seal.

(12) Bentonite must be placed above the sand pack using the tremie or other approved method to form a seal at least three feet thick. If pellets or chips are used, sufficient time (usually 4 to 24 hours) must be allotted to allow for sufficient hydration of the bentonite prior to placement of overlying materials.

(13) Grout of cement and bentonite, bentonite alone, or other suitable, low permeability material, if approved by the Department, must completely fill the remaining annular space to the base of the surface seal. The sealing material must set up without being diluted by formation water, and must displace water in the annular space to insure a continuous seal. The sealant must be placed under pressure using a tremie or other method approved by the Department. Backfill of native material to construct the annular seal is prohibited.

(14) A bentonite or concrete surface seal and protective, lockable steel casing must be installed around all monitoring wells and long-term observation wells and piezometers. If a concrete surface seal is constructed, it must extend from below the level of frost action at least to the ground surface. The surface seal must prevent surface water or runoff from ponding around the well casing. The protective steel casing must be set at least six inches lower than the base of the surface seal and extend approximately two inches above the top of the PVC riser. The surface seal must be designed to minimize or eliminate heaving due to frost action. Both the surface seal and the protective steel casing must be designed and constructed so that neither is mechanically coupled to the PVC riser. The diameter of the protective casing must be at least two inches larger than the PVC riser. The protective casing, as well as the PVC riser, must be vented near the top to allow the escape of gasses and the equilibration of water level with atmospheric pressure changes. The protective casing must also have a drain hole at the base. A permanent, distinctive and readily visible marker identifying the well's designation must be affixed to the protective casing or near the well; and a means to locate the well during periods of high snow cover must also be provided. In areas of traffic, bumper guards or other suitable protection for the well are required.

B.Geologic sampling. A boring program is necessary to define site hydrogeology. Borings must be carefully sampled to provide surficial and lithological information.

(1)Borings must be continuously sampled throughout the length of the hole at all locations where surficial stratigraphy and bedrock characteristics have not previously been determined.

(2)In any additional borings not continuously sampled, samples must be taken at five foot intervals, at each stratigraphic change, and at the screened interval in surficial deposits and, in rock, as required by the Department.

(3)At a minimum, the screened interval of each surficial installation must be analyzed.

(4)At well or piezometer clusters, continuous samples must be taken from the surface to the base of the deepest boring. Other wells or piezometer borings in the cluster must be sampled at the screened interval.

(5)Bedrock must be sampled with a standard size NX or larger diameter core barrel. All other materials must be sampled using the split spoon or equivalent method.

Chapter 405: Water Quality Monitoring, Leachate Monitoring, and Waste Characterization

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