020-12 Wyo. Code R. § 12-15 - Finished Water Storage

(a) 2018 TSS, parts 7.0.1-7.0.1(c), general, sizing; 7.0.2-7.0.2(b), general, location of finished water storage structures; 7.0.3, general, protection from contamination; 7.0.4, general, security; 7.0.5, general, drains; 7.0.6, general, stored water age; 7.0.8-7.0.8.2(b), general, access; 7.0.9-7.0.9(e), general, vents; 7.0.10-7.0.10(f), general, roof and sidewall; 7.0.17-7.0.17(c), general, painting and/or cathodic protection; 7.0.18-7.0.18(c), general, disinfection; 7.1.1, treatment plant storage, filter washwater tanks; 7.2-7.2.4, hydropneumatic tank systems; are herein incorporated by reference.

(b) Finished water storage structures shall comply with the following requirements:

(i) Water storage structures shall comply with the following standards for storage tanks, standpipes, ground storage reservoirs that are described in AWWA M42, clearwells, and elevated storage:

(A) AWWA D100;

(B) AWWA D102;

(C) AWWA D103;

(D) AWWA D104;

(E) AWWA D106;

(F) AWWA D107;

(G) AWWA D108;

(H) AWWA D110;

(I) AWWA D115;

(J) AWWA D120; and

(K) AWWA D121.

(ii) All tank and foundation design shall be performed by a Wyoming registered professional engineer. The plans or contractor-furnished information shall be signed and sealed by a Wyoming registered professional engineer.

(iii) All new or modified water storage tanks shall have the inlet and outlet connections separated from each other as much as is practical.

(c) Storage facility designs shall demonstrate:

(i) The average daily demand will require a daily fill of 20 percent of the total storage volume for surface water sources and 10 percent for groundwater sources.

(ii) For designs that demonstrate the storage tank has a small daily demand and a high fire water storage requirement, or the storage tank water age average is greater than two days, the design shall demonstrate that a volume equal to at least 20 percent of the tank volume will be delivered to the storage tank each time pumping is initiated.

(iii) For designs with well systems that provide a minimum of two wells that can supply either the maximum hourly demand or the fire demand, whichever is greater, storage is not required. These systems shall demonstrate that they will provide alternative power for the finished water pumps.

(d) Storage structure design shall eliminate short-circuiting.

(e) The minimum inlet velocity shall be 10 ft/sec unless demonstration of employed mixing system or lower inlet velocity addresses disinfection by-product formation, stratification, stagnation, freezing, and other water age issues.

(f) Overflow and drain lines shall:

(i) Be protected with a mechanical device such as:

(A) A sealed flapper valve or duckbill valve; or

(B) A #24 mesh non-corrodible screen.

(ii) For overflow lines that are protected with a mechanical device, include installation of a #4 mesh non-corrodible screen or finer to prevent the entrance of birds or rodents;

(iii) For overflow lines that are protected with #24 mesh non-corrodible screen, demonstrate prevention of screen clogging that would lead to structural storage tank damage;

(iv) Include installation of the screen within the overflow line at a location that is not susceptible to vandalism and that allows for the overflow line to be operational during an overflow event;

(v) Provide access to the screen with the smallest openings for replacement; and

(vi) Demonstrate that the screen with the smallest openings will be the outermost screen.

(g) Overflow designs shall demonstrate the provisions that will be included to prevent mechanical devices from freezing shut.

(h) Overflow lines shall not be considered as vents and overflow lines shall terminate between 12 and 24 inches above ground surface.

(i) Vents shall be designed to protect the tank from contaminants including but not limited to surface water, stormwater runoff, insects, rodents, and birds.

(i) All openings shall be protected with #24 mesh non-corrodible screen or a combination of #24 mesh and coarser mesh non-corrodible screen.

(ii) The design shall demonstrate consideration of site conditions, freezing, frosting, and provide justification including precautions for snow depth.

(A) The design shall demonstrate consideration of frost-free or frostproof vents; and

(B) The design shall demonstrate consideration of pressure/vacuum, frost-proof release vents that will need to protect openings with #24 mesh non-corrodible screen.

(j) Down-turned vent openings shall be at least 24 inches above the nearest horizontal surface. Non-downturned vents or roof vents must extend a minimum of eight inches from the top of the tank to a #24 mesh screened opening, and the vent opening is to be covered by a protective shroud to the bottom of the screen.

(k) Elevated tanks shall be designed to remove snow via tank geometry to prevent snow build-up clogging vents.

(l) Vent designs shall include calculations that verify the required volume of flow is achievable through the proposed vent pipe and screen combination.

(m) Finished water plant water storage shall comply with the following requirements:

(i) Clearwell storage shall be sized, in conjunction with distribution system storage, to relieve the filter of having to follow fluctuations in water use. Where water is pumped from clearwell storage to the system, an overflow shall be provided.

(ii) If unfinished water is stored in compartments adjacent to finished water, the unfinished and finished water shall be separated by double walls.

(iii) Receiving basins and wetwells shall be designed as finished water storage structures and shall comply with the requirements of this Section.

Notes

020-12 Wyo. Code R. § 12-15

Amended, Eff. 7/26/2023.