Nebraska Administrative Code
Topic - HEALTH AND HUMAN SERVICES SYSTEM
Title 179 - PUBLIC WATER SYSTEMS
Chapter 25 - LONG TERM 2 (LT2) ENHANCED SURFACE WATER TREATMENT
Section 179-25-019 - PRE-FILTRATION TREATMENT TOOLBOX COMPONENTS

Universal Citation: 179 NE Admin Rules and Regs ch 25 ยง 019

Current through September 17, 2024

019.01 Presedimentation

Systems receive 0.5-log Cryptosporidium treatment credit for a presedimentation basin during any month the process meets the following criteria:

1. The presedimentation basin must be in continuous operation and must treat the entire plant flow taken from a surface water or GWUDI source.

2. The system must continuously add a coagulant to the presedimentation basin.

3. The presedimentation basin must achieve the following performance criteria:
a. Demonstrates at least 0.5-log mean reduction of influent turbidity. This reduction must be determined using daily turbidity measurements in the presedimentation process influent and effluent and must be calculated as follows: log10(monthly mean of daily influent turbidity) - log10(monthly mean of daily effluent turbidity).

b. Complies with Department-approved performance criteria that demonstrate at least 0.5-log mean removal of micron-sized particulate material through the presedimentation process.

019.02 Two-Stage Lime Softening

Systems receive an additional 0.5-log Cryptosporidium treatment credit for a two-stage lime softening plant if chemical addition and hardness precipitation occur in two separate and sequential softening stages prior to filtration. Both softening stages must treat the entire plant flow taken from a surface water or GWUDI source.

019.03 Bank Filtration

Systems receive Cryptosporidium treatment credit for bank filtration that serves as pretreatment to a filtration plant by meeting the criteria in 179 NAC 25-019.03.

25-019.03A Wells with a ground water flow path of at least 25 feet receive 0.5-log treatment credit; wells with a ground water flow path of at least 50 feet receive 1.0-log treatment credit. The ground water flow path must be determined as specified in 179 NAC 25-019.03D.

25-019.03B 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 system must characterize the aquifer at the well site to determine aquifer properties. Systems must extract a core from the aquifer and demonstrate that in at least 90% of the core length, grains less than 1.0 mm in diameter constitute at least 10% of the core material.

25-019.03C Only horizontal and vertical wells are eligible for treatment credit.

25-019.03D For vertical wells, the ground water flow path is the measured distance from the edge of the surface water body under high flow conditions (determined by the 100 year floodplain elevation boundary or by the floodway, as defined in Federal Emergency Management Agency flood hazard maps) to the well screen. For horizontal wells, the ground water flow path is the measured distance from the bed of the river under normal flow conditions to the closest horizontal well lateral screen.

25-019.03E Systems must monitor each wellhead for turbidity at least once every four hours while the bank filtration process is in operation. If monthly average turbidity levels, based on daily maximum values in the well, exceed 1 NTU, the system must report this result to the Department and conduct an assessment within 30 days to determine the cause of the high turbidity levels in the well. If the Department determines that microbial removal has been compromised, the Department may revoke treatment credit until the system implements corrective actions approved by the Department to remediate the problem.

25-019.03F Springs and infiltration galleries are not eligible for treatment credit under 179 NAC 25-019.03, but are eligible for credit under 179 NAC 25-020.03.

25-019.03G Bank Filtration Demonstration of Performance: The Department may approve Cryptosporidium treatment credit for bank filtration based on a demonstration of performance study that meets the criteria in 179 NAC 25-019.03G. This treatment credit may be greater than 1.0-log and may be awarded to bank filtration that does not meet the criteria in 179 NAC 25-019.03A to 25-019.03E.
25-019.03G1 The study must follow a Department-approved protocol 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.

25-019.03G2 The study must include sampling both from the production well(s) and from monitoring wells that are screened and located along the shortest flow path between the surface water source and the production well(s).

Disclaimer: These regulations may not be the most recent version. Nebraska may have more current or accurate information. We make no warranties or guarantees about the accuracy, completeness, or adequacy of the information contained on this site or the information linked to on the state site. Please check official sources.
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