Description of Corrosion Control Treatment Requirements

PURPOSE: This rule describes the corrosion control treatment requirements which are applicable to all water systems under 10 CSR 60-15.020. (1) Based upon the results of lead and copper tap monitoring and water quality parameter monitoring, small- (serving fewer than three thousand three hundred (3,300) persons) and medium-size (serving three thousand three hundred one to fifty thousand (3,301–50,000) persons) water systems exceeding the lead or copper action level shall recommend installation of one (1) or more of the corrosion control treatments listed in subsection (3)(A), which the system believes constitutes optimal corrosion control for that system. The department may require the system to conduct additional water quality parameter monitoring in accordance with 10 CSR 60-15.080(2) and perform corrosion control studies as described in this rule to assist the department in reviewing the system’s recommendations. (2) The department may require any small- or medium-sized systems that exceed the lead or copper action level to perform corrosion control studies under section (3) of this rule to identify optimal corrosion control treatment for the system. (3) Performance of Corrosion Control Studies. (A) Any public water system performing corrosion control studies shall evaluate the effectiveness of each of the following treatments and, if appropriate, combinations of the following treatments to identify the optimal corrosion control treatment for that system: 1. Alkalinity and pH adjustment; 2. Calcium hardness adjustment; and 3. The addition of a phosphate or silicate based corrosion inhibitor at a concentration sufficient to maintain an effective residual concentration in all test tap samples. (B) The water system shall evaluate each of the corrosion control treatments using either pipe rig/loop tests, metal coupon tests, partial-system tests or analyses based on documented analogous treatments with other systems of similar size, water chemistry and distribution system configuration. (C) The water system shall measure the following water quality parameters in any tests conducted under this section before and after evaluating the corrosion control treatments listed in paragraph (3)(A)1. of this rule: 1. Lead; 2. Copper; 3. pH; 4. Alkalinity; 5. Calcium; 6. Conductivity; 7. Orthophosphate (when an inhibitor containing a phosphate compound is used); 8. Silicate (when an inhibitor containing a silicate compound is used); and 9. Water temperature. (D) The water system shall identify all chemical or physical constraints that limit or prohibit the use of a particular corrosion control treatment and document these constraints with at least one (1) of the following: 1. Data and documentation showing that a particular corrosion control treatment has adversely affected other water treatment processes when used by another water system with comparable water quality characteristics; or 2. Data and documentation demonstrating that the water system has previously attempted to evaluate a particular corrosion control treatment and has found that the treatment is ineffective or adversely affects other water quality treatment processes. (E) The water system shall evaluate the effect of the chemicals used for corrosion control treatment on other water quality treatment processes. (F) On the basis of an analysis of the data generated during each evaluation, the water system shall recommend to the department, in writing, the treatment option that the corrosion control studies indicate constitutes optimal corrosion control treatment for that system. The water system shall provide a rationale for its recommendation along with all supporting documentation specified in this section. (4) Based upon consideration of available information including, where applicable, studies performed under section (3) of this rule and a system’s recommended treatment alternative, the department shall either approve the corrosion control treatment option recommended by the system or designate alternative corrosion control treatment(s) from among those listed in subsection (3)(A) of this rule. When designating optimal treatment, the department shall consider the effects that additional corrosion control treatment will have on the water quality parameters and on other water quality treatment processes. (5) The department, in writing, shall notify the system of its decision on optimal corrosion control treatment and explain the basis for this determination. If the department requests additional information to aid its review, the water system shall provide the information. (6) Each system shall properly install and operate throughout its distribution system the optimal corrosion control treatment designated by the department. (7) The department shall evaluate the results of all lead and copper tap samples and water quality parameter samples submitted by the water system and determine whether the system has properly installed and operated the optimal corrosion control treatment designated by the department. Upon reviewing the results of tap water and water quality parameter monitoring by the system, both before and after the system installs optimal corrosion control treatment, the department shall designate— (A) A minimum value or a range of values for pH measured at each entry point to the distribution system; (B) A minimum pH value measured in all tap samples. That value shall be equal to or greater than 7.0, unless the department determines that meeting a pH level of 7.0 is not technologically feasible or is not necessary for the system to optimize corrosion control; (C) If a corrosion inhibitor is used, a minimum concentration or a range of concentrations for the inhibitor measured at each entry point to the distribution system and in all tap samples, that the department determines is necessary to form a passivating film on the interior walls of the pipes of the distribution system; (D) If alkalinity is adjusted as part of optimal corrosion control treatment, a minimum concentration or a range of concentrations for alkalinity, measured at each entry point to the distribution system and in all tap samples; (E) If calcium carbonate stabilization is used as part of corrosion control, a minimum concentration or a range of concentrations for calcium, measured in all tap samples. (F) The values for the applicable water quality control parameters listed in this section shall be those that the department determines to reflect optimal corrosion control treatment for the system. The department may designate values for additional water quality control parameters determined by the department to reflect optimal corrosion control for the system. The department shall notify the system, in writing, of these determinations and explain the basis for its decisions. (8) All systems optimizing corrosion control shall continue to operate and maintain optimal corrosion control treatment, including maintaining water quality parameters at or above minimum values or within ranges designated by the department under section (7) of this rule for all samples collected under 10 CSR 60-15.080(4)–(6). Compliance with this section shall be determined every six (6) months, as specified under 10 CSR 6015.080(4). A water system is out of compliance with the requirements of this section (8) for a six (6)-month period if it has excursions for any department-specified parameter on more than nine (9) days during the period. An excursion occurs whenever the daily value for one (1) or more of the water quality parameters measured at a sampling location is below the minimum value or outside the range designated by the department. Daily values are calculated as follows. The department shall have discretion to delete results of obvious sampling errors from this calculation. (A) On days when more than one (1) measurement for the water quality parameter is collected at the sampling location, the daily value shall be the average of all results collected during the day regardless of whether they are collected through continuous monitoring, grab sampling, or a combination of both. (B) On days when only one (1) measurement for the water quality parameter is collected at the sampling location, the daily value shall be the result of that measurement. (C) On days when no measurement is collected for the water quality parameter at the sampling location, the daily value shall be the daily value calculated on the most recent day on which the water quality parameter was measured at the sample site. (9) The department, upon its own initiative or in response to a request by a water system or other interested party, may modify its determination of the optimal corrosion control treatment or optimal water quality control parameters. A request for modification by a system or other interested party shall be in writing, explain why the modification is appropriate and provide supporting documentation. The department may modify its determination where it concludes that the change is necessary to ensure that the system continues to optimize corrosion control treatment. A revised determination shall be made in writing, setting forth the new treatment requirements, explaining the basis for the department’s decision and providing an implementation schedule for completing the treatment modifications. AUTHORITY: section 640.100, RSMo 2000.* Original rule filed Aug. 4, 1992, effective May 6, 1993. Amended: Filed Aug. 14, 2001, effective April 30, 2002. *Original authority: 640.100, RSMo 1939, amended 1978, 1981, 1982, 1988, 1989, 1992, 1993, 1995, 1996, 1998, 1999.