1. (2) For any reporting year that includes more than one standard, each applicable standard shall be multiplied by the number of days for which the standard applies pursuant to Water Code section 10609.4 that occur in the reporting period.

   1. (A) The supplier submits supporting information meeting the criteria described in subdivision (e); and
   2. (B) The associated water use, for any individual variance, represents 5 percent or more of the budget associated with the standard described in section 966(c)(1).

   (b)(1) An urban retail water supplier may, in calculating its urban water use objective, include budgets for variances identified in paragraph (2) for residential indoor use, if:

2. (2) Variances may be requested for water use associated with any of the following:

   1. (A) Significant use of evaporative coolers
   2. (B) Significant fluctuations in seasonal population.

3. (c) Variances available pursuant to subdivision (b) shall be calculated as follows:

   1. (1) A variance for water use associated with evaporative coolers (V_EC) represents the volume of water evaporative coolers used on operating days. Operating days (N_DAYS) are days when the average temperature in the supplier's service area was greater than 78 degrees Fahrenheit for at least one hour. V_EC shall be calculated by multiplying the number of evaporative coolers in the service area (N_EC) by the number of operating days (N_DAYS), the average daily evaporative cooler operating hours (H_O), and the average daily evaporative rate (R_EC). This formula is expressed mathematically follows:

      1. (A) The number of evaporative coolers in the service area (N_EC) may be estimated based on a representative sample of customers meeting the criteria specified in paragraph (D).

      2. (B) The evaporative cooler operating hours (H_O) may be a daily average based on a sample meeting the criteria specified in paragraph (D). A supplier shall use the service area average operating hours or the daily maximum operating hours, whichever is lower.

         1. (i) The service area wide average operating hours shall equal the average of all operating hours based on the sample.
         2. (ii) The service area daily maximum operating hours shall equal the number of hours in a day when the temperature was above 78 degrees Fahrenheit within the supplier's service area.

      3. (C) The evaporative cooler evaporation rate (R_EC) may be a daily average based on a sample meeting the criteria specified in paragraph (D). R_EC, in gallons per hour, shall be calculated by multiplying the average air exchange rate of the evaporative cooler units within the supplier's service areas (CFM), in cubic feet per minute, by the average daily difference in hourly wet and dry bulb temperatures (ΔT_Bulb), in degrees Fahrenheit, and by a representative efficiency rate of 80 percent. To convert the heat absorbed, in British Thermal Units, to the volume of water evaporated by the coolers, in gallons, that product shall be divided by 8700. This formula is expressed mathematically as follows:

         

         The average air exchange rate of the evaporative cooler units within the supplier's service areas (CFM) and the average daily difference in hourly wet and dry bulb temperatures (ΔT_Bulb) shall be calculated according to the Department's Methods for Estimating Residential Cooler Water Consumption and Prevalence using Account-Level Water and Energy Consumption Data (published April 15, 2022), which is hereby incorporated by reference, or an alternative method that the supplier has demonstrated to the Department, in coordination with the Board, to be equivalent, or superior, in quality and accuracy.

      4. (D) For the purposes of this section, the sample must represent at least 10,000 residential connections, or ten percent of residential connections, whichever is smaller.

      V_EC = N_EC x N_DAYS x H_O x R_EC

   2. (2) A variance for water use associated with seasonal populations (V_SP), in gallons, shall be calculated by multiplying the number of dwelling units associated with seasonal occupancy (N_DU) by the occupancy rate (R_O) and by the residential indoor use standard for the given time period (S_indoor). This formula is expressed mathematically as follows:

      1. (A) The number of dwelling units associated with seasonal occupancy (N_DU) shall be calculated according to the Department's Methods for Estimating Seasonal Populations with Water and Energy Data (published by June 22, 2022), which is hereby incorporated by reference, or an alternative method that the supplier has demonstrated to the Department, in coordination with the Board, to be equivalent, or superior, in quality and accuracy.

      2. (B) The occupancy rate (R_O) shall be calculated by dividing the average number of seasonally occupied rooms (R_S) by the average number of rooms occupied by permanent residents (R_P) and multiplying the quotient by the average number of people per permanently occupied household (H_P) and the average number of days households are seasonally occupied (S_DAYS). This formula is expressed mathematically as follows:

         

         The average number of days households are seasonally occupied (S_DAYS) shall be calculated according to the Department's Methods for Estimating Seasonal Populations with Water and Energy Data (published June 22, 2022), which is hereby incorporated by reference, or an alternative method that the supplier has demonstrated to the Department, in coordination with the Board, to be equivalent, or superior, in quality and accuracy.

      3. (C) Notwithstanding subdivision (b)(1)(B), a supplier is eligible for the variance for water use associated with seasonal populations if the supplier uses detailed daily or hourly Advanced Metering Infrastructure (AMI) data to effectively identify dwelling units with seasonal population and the associated water use represents 1 percent or more of the budget associated with the standard described in section 966(c)(1). If the supplier uses detailed daily or hourly AMI data, then the occupancy rate (R_O) shall be calculated by multiplying the water used by seasonally occupied homes (W_SO) by the supplier's residential service area population (P) and dividing the product by the water used for permanently occupied homes (W_PO). The quotient shall be multiplied by the average number of days households are seasonally occupied (S_DAYS). This formula is expressed mathematically as follows:

         

         The average number of days households are seasonally occupied (S_DAYS) shall be calculated according to the Department's Methods for Estimating Seasonal Populations with Water and Energy Data (published June 22, 2022), or an alternative method that the supplier has demonstrated to the Department, in coordination with the Board, to be equivalent, or superior, in quality and accuracy.

      V_SP = N_DU x R_o x S_indoor

4. (d) An urban retail water supplier may request a temporary provision to respond to negative impacts to wastewater collection, treatment, and reuse systems, if the supplier shows to the satisfaction of the Board that meeting the objective pursuant to section 966 would require adhering to the applicable residential indoor standard identified in Water Code section 10609.4 and that meeting the budget for efficient residential indoor use is causing challenges within wastewater collection, treatment, and reuse systems.

5. (e) In order to receive approval for a variance or a temporary provision, an urban retail water supplier must submit to the Board, in a machine-readable format for review and approval by the Executive Director, or the Executive Director's designee, a request that includes information quantifying and substantiating each request; information demonstrating that the water applicable to the request is water delivered by the supplier; information verifying that the approval of the request would not jeopardize the ability of a permittee within the supplier's service area to comply with existing permit requirements; and information describing and supporting the methodology the supplier will use to estimate the parameters described in subdivision (c), including the number of households sampled and the total number of residential connections, as reported to the Board pursuant to Health and Safety Code section 116530.

   1. (1) Approved variances or temporary provisions submitted between July 1 and October 1 may be included in the associated budget for the prior state fiscal year.
   2. (2) Approved variances or temporary provisions submitted between October 2 and June 30 may be included in the associated budget for the current state fiscal year.
   3. (3) Approved variances and temporary provisions may be included in the associated budget for up to five years. Variance and temporary provision approval constitutes approval of both methodology and data. Unless otherwise specified in section 975, a supplier may use the same data for each year or update the data annually in accordance with the approved variance or temporary provision methodology.

(a)(1) Each year, a supplier shall calculate its budget for residential indoor water use (R_indoor), in gallons, by multiplying the applicable standard (S_indoor) described in Water Code section 10609.4, subdivision (a) by the supplier's residential service area population (P), and by the number of days in the year. This formula is expressed mathematically as follows:

R_indoor = S_indoor x P x days in year

Note: Authority cited: Sections 1058, 10609.2 and 10609.20, Water Code. Reference: Article X, Section 2, California Constitution; Section 51201, Government Code; and Sections 102, 104, 105, 350, 1122, 1123, 1124, 1846, 1846.5, 10608.12, 10609.2, 10609.4 and 10609.10, Water Code.

History

1. New section filed 9-30-2024; operative 1-1-2025 (Register 2024, No. 40). For prior history, see Register 87, No. 10.