Annual background leakage shall be calculated as follows:
Annual reported leakage shall be calculated as follows:
Annual unreported leakage shall be calculated by deducting annual background leakage and annual reported leakage from average baseline real loss.
Months taken to survey whole system shall be calculated by dividing average length of mains by average leak detection survey frequency.
Each part represents the amount of the system that can be surveyed each month, such that the number of parts in a system is equal to the number of months needed to survey the whole system.
Unreported leakage per part of system shall be calculated by dividing annual unreported leakage by months taken to survey whole system.
Rate of rise of leakage per part of system shall be calculated by dividing rate of rise of leakage by months taken to survey whole system.
Monthly water lost due to backlog of unreported leakage shall be calculated as follows:
Monthly unreported real loss with intervention shall be the sum of monthly water lost due to backlog of unreported leakage, monthly water lost from rising leakage in never surveyed parts of the system, and monthly water lost from rising leakage in previously surveyed parts of the system.
Monthly unreported real loss without intervention shall be calculated as follows:
Water saved in month of implementation shall be calculated by deducting monthly unreported real loss with intervention from monthly unreported real loss without intervention.
Value of water loss reduced in each month shall be calculated as follows:
(water loss occuring without intervention - water loss occuring with intervention) x Marginal cost of water in each time step
Present value of water loss reduced each month shall be calculated as follows:
Cost of leak detection during each month shall be the product of average leak detection survey frequency in miles surveyed each month and average cost of leak detection surveying per mile.
Average volume per leak per year shall be calculated as follows:
Volume of leakage from mains per leak per year shall be calculated as follows:
Volume of leakage from service connections per leak per year shall be calculated as follows:
Leaks found per part of the system is calculated for each month as follows:
Cost of leak repair during each month shall be calculated as follows:
Total leak detection and repair cost for each month shall be the sum of cost of leak detection during each month plus cost of leak repair during each month.
Present value of cost for each month shall be calculated as follows:
Present value of net benefit in month of implementation shall be calculated by deducting present value of cost for each month from present value of benefit for each month.
Present value of net benefit over 30 years is the sum of present value of net benefit in month of implementation summed from January 1, 2022, through December 31, 2051.
The Benefit to cost ratio until 2028 is the sum of present value of benefit for each month from January 2022 through December 2027 divided by the sum of the present value of cost for each month from January 2022 through December 2027.
Cal. Code Regs. Tit. 23, § 982
Note: Authority cited: Sections 1058, 10608.34, Water Code. Reference: Article X, Section 2, California Constitution; Section 116275, Health and Safety Code; Sections 102, 104, 105, 350, 516, 1846, 10608.12 and 10608.34, Water Code.