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4725.6650 CONSTRUCTION OF MONITORING WELLS.

Subpart 1.

Casing.

Casing for a monitoring well must be steel or plastic casing meeting the standards of parts 4725.2250 to 4725.2650, or stainless steel or flush threaded polyvinyl chloride meeting the standards of this subpart.

A.

A monitoring well may be constructed with flush threaded polyvinyl chloride (PVC) casing if:

(1)

the screen intersects the surface of the water table at the time of installation and the well is constructed so the joint between the two deepest casing sections is above the surface of the water;

(2)

the total depth of the monitoring well is 50 feet or less;

(3)

the monitoring well is completed in unconsolidated materials; and

(4)

the flush threaded PVC casing used meets the standards of ASTM F480-02, and the standards in Schedule 40 as referenced in ASTM Standard D1785-04.

B.

A monitoring well may be constructed with stainless steel casing meeting ASTM Standard A312/A312M-04b, having at least ANSI Schedule 5 for welded joints and ANSI Schedule 40 for threaded joints.

Subp. 2.

Grouting of annular space.

The annular space of a monitoring well must be grouted from ten feet or less above the screen or open bore hole to the established ground surface according to part 4725.3050, except that no cuttings from the bore hole must be added to the grout. Neat-cement or cement-sand grout may terminate at the base of the manhole or vault for an at-grade installation.

Subp. 3.

Exception to drilling fluids.

Drilling fluids used to construct a monitoring well must comply with part 4725.2950, except that a free chlorine residual is not required.

Subp. 4.

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

A monitoring well, that is constructed to monitor contaminants at 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, is exempt from part 4725.2020, subpart 1.

History:

17 SR 2773; 18 SR 1222; 33 SR 211

Published Electronically:

September 2, 2008

Official Publication of the State of Minnesota
Revisor of Statutes