25-10042-000_Letter_re_CCS_Requirement_after_Cu_ALE.pdf

State Water Resources Control Board Division of Drinking Water

August 1, 2025

System No. CA4010832

Attn: Chris Scherle, Water Plant Supervisor Atascadero State Hospital 10333 El Camino Real Atascadero, CA 93422 christopher.scherle@dsh.ca.gov

Subject: CORROSION CONTROL STUDY REQUIREMENT FOLLOWING

COPPER ACTION LEVEL EXCEEDANCE

Dear Mr. Scherle:

The State Water Board Division of Drinking Water (hereinafter “DDW”) received the lead and copper monitoring results from September 2024 for the Atascadero State Hospital (hereinafter “ASH”) public water system. The data shows that the reported copper 90th percentile was 1.95 mg/L which exceeds the 1.3 mg/L copper action level. On December 30, 2024, ASH submitted a corrective action plan describing that it would address the copper action level by replacing parts of the distribution system with elevated levels of copper. Subsequent sampling conducted during June 2025 showed results with a 90th percentile value of 2.00 mg/L. Therefore, the replacement program has proven to not be effective enough to prevent copper action level exceedances.

ASH is required to conduct a corrosion control study (CCS) pursuant to Title 22, CCR, Chapter 17.5. The CCS is due within 18 months of being notified of the requirements; therefore, the CCS is due by February 1, 2027. Requirements for the CCS are listed below.

Corrosion Control Study Procedure.

(a) Each system conducting a corrosion control study shall:

(1) Evaluate the effectiveness of each of the following treatments, and, if appropriate, combinations of the following treatments to identify the CCT for that system:

(A) Alkalinity and pH adjustment;

(B) Calcium hardness adjustment; and mailto:christopher.scherle@dsh.ca.gov

Atascadero State Hospital - 2 - August 1, 2025

(C) The addition of a corrosion inhibitor at a concentration sufficient to maintain an effective residual concentration throughout the distribution system.

(2) Evaluate each of the corrosion control treatments using either pipe rig/loop tests, metal coupon tests, partial-system tests, or analyses based on documentation of such treatments from systems of similar size, water chemistry and distribution system configuration.

(3) Measure the following WQPs in any tests conducted under this subsection before and after evaluating the corrosion control treatments listed above:

(A) Lead;

(B) Copper;

(C) pH;

(D) Alkalinity;

(E) Calcium;

(F) Conductivity;

(G) Corrosion control inhibitor active ingredient (when an inhibitor is used);

(H) Water temperature.

(4) Identify all chemical or physical constraints that limit or prohibit the use of a particular corrosion control treatment and document such constraints with at least one of the following:

(A) 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; and/or

(B) 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.

(5) Evaluate the effect of the chemicals used for corrosion control treatment on other water treatment processes.

(6) Recommend to the DDW in writing the treatment option that the corrosion control studies indicate constitutes CCT for that system on the basis of an analysis of the data generated during each evaluation. The water system shall provide a rationale for its recommendation along with all supporting documentation specified in paragraphs (a)(1) through (5) of this section.

(b) Based on the study conducted pursuant to subsection (a), and a system's recommended treatment alternative, DDW will either approve the corrosion control treatment option recommended by the system, or designate alternative corrosion control treatment(s) from among those listed in paragraph (a)(1) of this section, notify the system of its decision on CCT in writing and explain the basis for its determination. If DDW requests additional information to aid its review, the water system shall provide the information.

Atascadero State Hospital - 3 - August 1, 2025

If you have any questions regarding the information contained in this letter, please contact our office at (805) 566-1326 or email dwpdist06@waterboards.ca.gov.

Sincerely, Jason Cunningham, P.E., District Engineer Santa Barbara District State Water Resources Control Board Division of Drinking Water cc: San Luis Obispo County Environmental Health Department

Atascadero State Hospital - 4 - August 1, 2025

APPENDIX 1 - INITIAL WATER QUALITY PARAMETER MONITORING AND ENTRY

POINT LEAD AND COPPER SAMPLE DATA SHEET

Table 2: Water Quality Parameter – Initial Monitoring Requirements: Entry Point(s) from locations representative of each source after treatment Name of Site

Location of Site

Name of Source Influencing the Site

Number of WQP samples per site

WQP due date

2 samples First 6-month due between November 4, 2021 and December 31, 2021 and Second 6-month due between January 1, 2022 and June 30, 2022

2 samples First 6-month due between November 4, 2021 and December 31, 2021 and Second 6-month due between January 1, 2022 and June 30, 2022

Table 3: Water Quality Parameter – Initial Monitoring Requirements:

Representative Distribution Locations Number of Sites

Location of Site Number of WQP samples per site

WQP due date

10 2 samples First 6-month due between November 4, 2021 and December 31, 2021 and Second 6-month due between January 1, 2022 and June 30, 2022

Table 4: Required Initial Water Quality Parameters pH

Alkalinity

Atascadero State Hospital - 5 - August 1, 2025

Orthophosphate (when an inhibitor containing a phosphate compound is used)

Silica (when an inhibitor containing a silicate compound is used)

Calcium

Conductivity

Water temperature

Atascadero State Hospital - 6 - August 1, 2025

APPENDIX 2 - LEAD AND COPPER MONITORING RESULTS SUMMARY