N.Y. Comp. Codes R. & Regs. tit. 10, APPENDICES, app 5-B, tbl. 2
Well Diameter | |||||||
Water-bearing Formation | Overlying Material | Minimum Casing length or Depth1 | Oversize Drillhole for Grout, Diameter1 | Casing and Grout Placement1 | Cased Portion | Uncased Portion | Well Screen Diameter2(where applicable) |
1. Sand or gravel | Unconsolidated caving material; sand or sand and gravel | 19' minimum; but 5' below pumping level 3 | None required | Grouting not required | 2" minimum | Does not apply | 2" minimum |
2. Sand or gravel | Clay, hardpan, till, silt, or similar material to depth of more than 15' | 5' below pumping level 3 | Casing size plus 2" if pressure placement of grout is used, Casing size plus 4" if gravity placement of grout is used. 4,5,6 | Upper drillhole shall be kept at least one-third filled with clay slurry while driving permanent casing; after casing is in the permanent position, annular space shall be filled with grout 5 | 2" minimum | Does not apply | 2" minimum |
3. Sand or gravel | Clay, hardpan, till, silt, or similar material containing layers of sand or gravel within 15' of ground surface | 5' below pumping level 4 | Casing size plus 2" if pressure placement of grout is used, Casing size plus 4" if gravity placement of grout is used. 4,5,6 | Annular space around casing shall be filed with grout | 2" minimum | Does not apply | 2" minimum |
4. Creviced, shattered or otherwise fractured shale, limestone, igneous, metamorphic or similar rock types or sandstone | Unconsolidated caving material, chiefly sand or sand and gravel to a depth of 19' or more. | Through caving overburden | Non required | Casing shall be firmly seated in rock. Grouting not required | 6" minimum | 6" preferred | Does not apply |
5. Creviced, shattered or otherwise fractured shale, limestone, igneous, metamorphic or similar rock types or sandstone | Clay, hardpan, till, shale, or similar material to a depth of 19' or more | Through overburden | Casing size plus 2" if pressure placement of grout is used, Casing size plus 4" if gravity placement of grout is used. 4,5,6 | Casing shall be firmly seated in rock. Annular space around casing shall be grouted. | 6" minimum | 6" preferred | Does not apply |
6. Creviced, shattered or otherwise fractured shale, limestone, igneous, metamorphic or similar rock types or sandstone | Unconsolidated materials to a depth of less than 19' | 19' minimum | Casing size plus 2" if pressure placement of grout is used, Casing size plus 4" if gravity placement of grout is used.4,6 | Casing shall be firmly seated in rock. Annular space around casing shall be grouted. | 6" minimum | 6" preferred | Does not apply |
Notes for Table 2:
1 In the case of a flowing artesian well, attempts should be made to install and seal the well in a manner that protects the artesian aquifer, prevents erosion of overlying geologic materials, and confines the flow to within the well casing, giving due consideration to practicality, cost, and safety.
2 These diameters shall also be applicable in circumstances where the use of perforated casing is deemed practicable. Well points commonly designated on the trade as 11/4" pipe shall be considered as being 2" nominal diameter well screens for purposes of these regulations.
3 As used in this Table, the term "pumping level" shall refer to the lowest elevation of the water in a well during pumping, determined to the best knowledge of the water well contractor taking into consideration usual seasonal fluctuations and drawdown.
4 Pressure placement includes methods of grout placement using pumps and tremie tubes or using grout displacement through the casing, or otherwise from the bottom up around the casing, with one or more drillable plugs. When pressure placement is used with a borehole diameter of only 2" greater than the casing diameter, casing shall be assembled without couplings unless installed per the "Casing and Grout Placement" technique described on Line "2" of this Table. Gravity placement includes any method that relies on gravity to draw grout, either dry or as a slurry, down into the annular space between the casing and borehole or between an inner casing and outer casing.
5 For wells constructed by cable tool, hollow rod, jetting, or other drilling method where the permanent casing is driven, and where neither temporary casing nor an oversize borehole are used, dry driven grout methods using granular bentonite may be used. These methods use continuous feeding of granular bentonite into a starter hole or continuous mounding around the casing as the casing is driven. Collar flared joints or weld beads extending beyond the outside diameter of the permanent casing shall be used with sufficient spacing to ensure that the grout seal is continuous and extends downward into the saturated zone (i.e., beneath the water table).
6 The oversized borehole for grout placement should be as deep as necessary, based upon local hydrogeologic conditions and potential contaminant sources, to prevent contamination from entering the well. Grout should be placed along the full length of casing, particularly where the presence of non-caving unconsolidated materials, coarse gravel, or creviced, shattered, or fractured rock may result in pathways of contamination to a well water system. Where this is not feasible because of practicality, cost or safety, grout shall be placed at least to a minimum depth of 19 feet. See also Note 1 to Table 1.
N.Y. Comp. Codes R. & Regs. tit. 10, APPENDICES, app 5-B, tbl. 2