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4725.7450 ENVIRONMENTAL BORE HOLES.

Subpart 1.

Construction.

An environmental bore hole must be constructed, repaired, maintained, and sealed according to the general standards in parts 4725.2010 to 4725.3875. In addition, an environmental bore hole that is cased must be constructed to conform to the monitoring well requirements in parts 4725.6650 to 4725.6850.

Subp. 2.

At-grade bore holes.

An environmental bore hole cased and completed at-grade must conform to part 4725.6850.

Subp. 3.

Sealing.

An environmental bore hole that is not in use or that serves as a potential or actual source of contamination must be sealed according to this chapter.

Subp. 4.

Exception to sealing requirements.

An environmental bore hole less than 50 feet in depth, in an unconsolidated formation, and not encountering a confining layer may be sealed by removing the casing and screen and allowing the bore hole to collapse, except for a flowing boring which must meet the requirements of part 4725.3850.

A.

The bore hole must not encounter pollution or contamination or have been installed to detect pollution or contaminants.

B.

The collapse must not be induced other than by removal of the screen or casing.

C.

The portion of the bore hole that does not collapse must be sealed immediately upon removal of the casing as specified in part 4725.3850 with bentonite grout, neat-cement grout, or cement-sand grout.

Subp. 5.

Screen or open hole across an unconsolidated formation and bedrock contact.

An environmental bore hole may be constructed to test contaminants without extracting water, or to vent, recover vapor, or sparge contaminants from the water surface, by placing a screen or open hole across the contact of an unconsolidated formation and bedrock according to part 4725.6050, subpart 3.

History:

17 SR 2773; 33 SR 211

Published Electronically:

September 2, 2008

Official Publication of the State of Minnesota
Revisor of Statutes