PURPOSE: This rule establishes maximum contaminant levels and monitoring requirements for turbidity.

1. (1) Applicability.

   1. (A) This rule applies to all public water systems that use surface or ground water under the direct influence of surface water. Requirements and compliance dates vary depending on system size.
   2. (B) The department strongly encourages systems serving less than ten thousand (10,000) people and using surface water or groundwater under the direct influence of surface water to strive to meet the maximum contaminant levels (MCLs) and turbidity standards in section (3) of this rule, since it is likely that federal regulations will require these systems to meet the more stringent standards in 2003.
   3. (C) Beginning September 1, 2000, any water treatment plant proposed for construction or major modification must be designed to meet the turbidity requirements in section
2. (3) of this rule.

3. (2) Systems Serving Less Than Ten Thousand (10,000) People.

   1. (A) The MCLs for Turbidity.

      1. 1. The turbidity level must be less than

or equal to 0.5 turbidity units in at least ninety-five percent (95%) of the measurements taken each month.

1. 2. The turbidity level must at no time

exceed five (5) turbidity units in any one (1) confirmed measurement.

1. (B) The frequency of sampling shall be as set forth in 10 CSR 60-4.080(3).
2. (C) If the result of a single turbidity measurement exceeds the MCL established in subsection (2)(A), the measurement must be confirmed by resampling, preferably within one (1) hour. The resample result must replace the original sample result for determining compliance with subsection (2)(A) of this rule.
3. (D) If any confirmed sample result exceeds five (5) turbidity units, the supplier of water must notify the department by the end of the next business day and give notice as required by 10 CSR 60-8.010(1)(A)3.
4. (E) The department, on a case-by-case basis, may allow a system to operate at an MCL for turbidity of 1.0 turbidity units in at least ninety-five percent (95%) of the measurements taken each month if the following criteria are met: the total percent removal and inactivation of Giardia lamblia is ninetynine and nine-tenths percent (99.9%), required treatment is provided, the treatment facilities are properly operated, none of the treatment units are malfunctioning due to mechanical failure or incorrect construction, the system is in compliance with all of the disinfection requirements of 10 CSR 60- 4.055(1)–(4), the treatment facilities are providing ninety-nine percent (99%) Giardia cyst removal and the system cannot meet the turbidity MCL of 0.5 turbidity units due to raw water quality, iron, manganese or similar compelling factors. The request to operate at the higher turbidity MCL must be made in writing and be accompanied by an engineering report which includes the results of full scale particle or Giardia cyst removal studies, operational test data, water analyses results, a report of the sanitary survey of the treatment facilities and any other information that the department may require to assure that the criteria of this rule are met. Approval of the engineering report is the approval to operate at the higher turbidity MCL.

1. (3) Systems Serving Ten Thousand (10,000) or More People.

   1. (A) The turbidity levels and other requirements in section (2) apply to these systems until January 1, 2002.

   2. (B) Beginning January 1, 2002—

      1. 1. Turbidity must be equal to or less

than 0.3 turbidity units in at least ninety-five percent (95%) of the measurements taken each month; and

1. 2. There must be no more than one (1)

turbidity unit in any one (1) confirmed measurement.

1. (C) The frequency of sampling shall be as set forth in 10 CSR 60-4.080(3).
2. (D) If any confirmed sample result exceeds five (5) turbidity units, the supplier of water must notify the department by the end of the next business day and give notice as required by 10 CSR 60-8.010(1)(A)3.

3. (E) Filtration Sampling Requirements for Surface Water Systems Serving More Than 10,000 People.

   1. 1. A public water system subject to the

requirements of 10 CSR 60-4.055(6) that provides conventional filtration treatment must conduct continuous monitoring of turbidity for each individual filter using an approved method in 10 CSR 60-5.010 and must calibrate turbidimeters using the procedure specified by the manufacturer. Systems must record the results of individual filter monitoring every fifteen (15) minutes.

1. 2. If there is a failure in the continuous

turbidity monitoring equipment, the system must conduct grab sampling every four (4) hours in lieu of continuous monitoring, until the turbidimeter is repaired and back on-line. A system has a maximum of five (5) working days after failure in the continuous monitoring equipment to repair the equipment before the system is in violation.

1. (F) Lime Softening.

   1. 1. A system that uses lime softening may

acidify representative samples prior to analysis using a protocol approved by the department. 10 CSR 60-4

1. 2. Systems that use lime softening may

apply to the department for alternative exceedance levels for the levels specified in 10 CSR 60-7.010(7)(B) if they can demonstrate that higher turbidity levels in individual filters are due to lime carryover only and not due to degraded filter performance.

1. (G) Filtration Technologies Other Than Conventional Filtration Treatment.

   1. 1. A public water system may use a fil-

tration technology other than conventional filtration if it demonstrates to the department, using pilot plant studies or other means, that the alternative filtration technology, including direct filtration, in combination with disinfection treatment that meets the requirements of 10 CSR 60-4.055, consistently achieves 99.9 percent removal and/or inactivation of Giardia lamblia cysts and 99.99 percent removal and/or inactivation of viruses, and 99 percent removal of Cryptosporidium oocysts, and the department approves the use of the filtration technology.

1. 2. For each approval, the department

will set turbidity performance requirements that the system must meet at least 95 percent of the time and that the system may not exceed at any time at a level that consistently achieves 99.9 percent removal and/or inactivation of Giardia lamblia cysts, 99.99 percent removal or inactivation of viruses, or both, and 99 percent removal of Cryptosporidium oocysts.

AUTHORITY: section 640.100, RSMo Supp. 1999.* Original rule filed May 4, 1979, effective Sept. 14, 1979. Amended: Filed April 14, 1981, effective Oct. 11, 1981. Amended: Filed July 12, 1991, effective Feb. 6, 1992. Amended: Filed Feb. 1, 1996, effective Oct. 30, 1996. Amended: Filed Dec. 15, 1999, effective Sept. 1, 2000. *Original authority: 640.100, RSMo 1939, amended 1978, 1981, 1982, 1988, 1989, 1992, 1993, 1995, 1996, 1998, 1999.