Or. Admin. Code § 690-220-0115 - Unhydrated Bentonite and Method of Placement
(1) When abandoning a pre-existing well with
unhydrated bentonite the Water Supply Well Constructor shall provide additional
notification to the Regional Well Inspector or the Well Construction Program
Coordinator in Salem by fax, e-mail or telephone 72 hours prior to starting
abandonment work.
(a) In case of an
emergency, the additional notification is not required; however, the Water
Supply Well Constructor shall notify the Department prior to beginning
abandonment work as required in OAR
690-205-0200.
(2) Unhydrated
bentonite used in the abandonment of water supply wells shall meet the
following requirements:
(a) Specifically
designed for use in water supply wells; and
(b) Within industry tolerance for dry western
sodium bentonite; and
(c) Free of
polymers that promote bacterial growth; and
(d) Manufactured to be 3/8-inch or 3/4-inch;
and
(e) National Sanitation
Foundation (NSF) approved or have a swell index greater than 15 milliliters
(ml) per 2 grams (gm).
(3) Powdered bentonite, bentonite grout or
bentonite slurry shall not be used to abandon water supply wells.
(4) Unhydrated bentonite shall only be used
to abandon water supply wells when in contact with water having less than 800
parts per million (ppm) total dissolved solids (TDS).
(a) Unhydrated bentonite may be used to
abandon water supply wells exceeding 800 ppm TDS if the bentonite manufacturer
provides documentation that their product can be used in water that exceeds 800
ppm TDS.
(A) Prior Department approval is
required before placement.
(B) The
bentonite manufacturer's documentation and Department approval shall be
submitted with the Water Supply Well Report as required in OAR
690-205-0210.
(b) In all cases, the
TDS shall be reported on the Water Supply Well Report as required in OAR
690-205-0210.
(5) Water supply wells
with casing that is at least four inches in diameter and less than eight inches
in diameter may be abandoned with unhydrated bentonite to a maximum well depth
of 700 feet, if being placed through water. Unhydrated bentonite may be used
deeper with prior Department approval.
(6) Water supply wells with casing that is at
least four inches in diameter and less than eight inches in diameter may be
abandoned with unhydrated bentonite to a maximum well depth of 1000 feet, if
being placed through air. Unhydrated bentonite may be used deeper with prior
Department approval.
(7) Water
supply wells with casing that is at least eight inches in diameter may be
abandoned with unhydrated bentonite to a maximum well depth of 1200 feet, if
being placed through water. Unhydrated bentonite may be used deeper with prior
Department approval.
(8) Water
supply wells with casing that is at least eight inches in diameter may be
abandoned with unhydrated bentonite to a maximum well depth of 1500 feet, if
being placed through air. Unhydrated bentonite may be used deeper with prior
Department approval.
(9)
Unhydrated bentonite shall be screened across a minimum 1/4-inch mesh screen
during placement to minimize the introduction of bentonite dust into the
sealing interval. The resulting seal shall be free of voids or bridges.
(10) A sounding or tamping tool
shall be used in the sealing interval during placement to measure the fill rate
and to break up possible bridges or cake formations.
(11) Unhydrated bentonite shall be poured at
the manufacturers recommended rate in the water- filled portion of the
drillhole and shall not be less than two minutes per 50 pound sack.
(12) In a dry sealing interval, (above the
water level), bentonite shall be hydrated from land surface to a minimum depth
of 50 feet below land surface. Unhydrated bentonite shall be hydrated with
potable water in maximum ten foot lifts to ensure activation.
(13) The estimated and actual volume of
sealing material used shall be calculated and reported on the Water Supply Well
Report as required by OAR
690-205-0210.
Notes
Stat. Auth.: ORS 183, 536, 537 & 540
Stats. Implemented: ORS 183, 536, 537 & 540
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