36.21.805    SEAL/MATERIALS

(1) The intent of this rule is to provide protection to the ground water at least equal to the soil or rock profile penetrated by the borehole or excavation. More stringent standards set by other local, state, or federal agencies shall be followed when applicable.

(2) Acceptable seals for rotary or dug holes [air, fluid, auger (solid and hollowstem) , backhoe] include:

(a) above the water table:

(i) neat cement grout or Portland cement concrete,

(ii) bentonite clay grout,

(iii) cuttings slurry grout,

(iv) compacted clay cuttings,

(v) pre-wetted granular or powdered bentonite,

(vi) compacted asphaltic concrete,

(vii) other materials or methods with board approval;

(b) below the water table:

(i) neat cement grout, tremied or pumped,

(ii) bentonite clay grout, tremied or pumped,

(iii) cuttings slurry grout, tremied or pumped,

(iv) bentonite pellets or chips,

(v) other materials or methods with board approval.

(3) For driven wells acceptable seals are granular or powdered bentonite.

(4) Jetted methods are not allowed for monitoring well use without board approval.

History: 37-43-202, MCA; IMP, 37-43-202, MCA; NEW, 1988 MAR p. 2503, Eff. 11/24/88; AMD, 1997 MAR p. 65, Eff. 1/17/97.