Section 327IAC8-2.6-17. Prefiltration treatment toolbox components; requirements for microbial toolbox components; enhanced treatment for Cryptosporidium

   (a) A PWS may receive a 0.5-log Cryptosporidium treatment credit for a presedimentation basin during any month the process meets the following criteria:

(1) The presedimentation basin must:

(A) be in continuous operation; and

(B) treat the entire plant flow taken from a:

(i) surface water; or

(ii) ground water under the direct influence of surface water;

source.

(2) The PWS shall continuously add a coagulant to the presedimentation basin.

(3) The presedimentation basin must achieve the following performance criteria:

(A) Demonstrate at least 0.5-log mean reduction of influent turbidity that:

(i) is determined using daily turbidity measurements in the presedimentation process influent and effluent; and

(ii) must be calculated according to the following formula:

Reduction = log₁₀ (monthly mean of daily influent activity) - log₁₀ (monthly mean of daily effluent turbidity).

(B) Comply with performance criteria approved by the commissioner that demonstrate at least 0.5-log mean removal of micron-sized particulate material through the presedimentation process.

  (b) A PWS may receive an additional 0.5-log Cryptosporidium treatment credit for a two (2)-stage lime softening plant if:

(1) chemical addition and hardness precipitation occur in two (2) separate and sequential softening stages prior to filtration; and

(2) both softening stages must treat the entire plant flow taken from a:

(A) surface water; or

(B) ground water under the direct influence of surface water;

source.

  (c) The following determine if a PWS is eligible for Cryptosporidium treatment credit for bank filtration:

(1) A PWS may, as follows:

(A) Receive Cryptosporidium treatment credit for bank filtration that serves as pretreatment to a filtration plant by meeting the conditions under subdivision (2).

(B) Not receive the Cryptosporidium treatment credit for bank filtration if the system is using bank filtration when it begins source water monitoring under 40 CFR 141.701(a), as incorporated by reference in section 8(a)(1) of this rule, but the system shall collect samples as described in 40 CFR 141.703(d), as incorporated by reference in section 8(a)(3) of this rule.

(C) Not receive Cryptosporidium treatment credit for bank filtration under this section for springs or infiltration galleries but may be eligible for credit under section 18(c) of this rule.

(2) The following conditions shall determine the applicability of the Cryptosporidium treatment credit for bank filtration:

(A) Wells with a ground water flow path of at least:

(i) twenty-five (25) feet receive a 0.5-log treatment credit; and

(ii) fifty (50) feet receive a 1.0-log treatment credit.

The ground water flow path must be determined according to clause (D).

(B) Only wells in granular aquifers are eligible for treatment credit. Granular aquifers are those comprised of sand, clay, silt, rock fragments, pebbles, or larger particles, and minor cement. A PWS shall:

(i) characterize the aquifer at the well site to determine aquifer properties; and

(ii) extract a core from the aquifer and demonstrate that in at least ninety percent (90%) of the core length, grains less than one and zero-tenths (1.0) millimeters in diameter constitute at least ten percent (10%) of the core material.

(C) Only horizontal and vertical wells are eligible for treatment credit.

(D) The ground water flow path for a:

(i) vertical well is the measured distance from the edge of the surface water body under high flow conditions, as determined by the:

(AA) one hundred (100) year floodplain elevation boundary; or

(BB) floodway;

as defined in Federal Emergency Management Agency flood hazard maps, to the well screen; and

(ii) horizontal well is the measured distance from the bed of the river under normal flow conditions to the closest horizontal well lateral screen.

(E) Turbidity monitoring requirements and conditions are as follows:

(i) A PWS shall monitor each wellhead for turbidity at least once every four (4) hours while the bank filtration process is in operation.

(ii) If monthly average turbidity levels, based on daily maximum values in the well, exceed one (1) NTU, the PWS shall:

(AA) report this result to the commissioner; and

(BB) conduct an assessment within thirty (30) days to determine the cause of the high turbidity levels in the well.

(iii) If the commissioner determines that microbial removal has been compromised, the commissioner may revoke treatment credit until the PWS implements corrective actions approved by the commissioner to remediate the problem.

(F) Cryptosporidium treatment credit for bank filtration may be:

(i) approved by the commissioner based on a demonstration of performance study that must:

(AA) follow a protocol approved by the commissioner and must involve the collection of data on the removal of Cryptosporidium or a surrogate for Cryptosporidium and related hydrogeologic and water quality parameters during the full range of operating conditions; and

(BB) include sampling both from the production well or wells and from monitoring wells that are screened and located along the shortest flow path between the surface water source and the production well or wells; and

(ii) greater than 1.0-log and can be awarded to bank filtration that does not meet the criteria under clauses (A) through (E).

(Water Pollution Control Division; 327 IAC 8-2.6-17; filed May 7, 2010, 9:30 a.m.: 20100602-IR-327080198FRA)