NAC445A.530. Submission and approval of engineering report before construction or modification of facility; standards for design.

     1. A supplier of water proposing to:

     (a) Construct a new facility for filtration and disinfection; or

     (b) Make additions to or modify significantly an existing facility for treatment,

Ê must submit an engineering report to the Division or the appropriate district board of health. The report must be approved by the Division or the appropriate district board of health before the supplier begins construction. The report must also describe how the facility will be designed to ensure that it complies with this section and NAC 445A.531.

     2. A new facility for filtration and disinfection must:

     (a) Be designed to attain an average daily effluent turbidity goal of 0.2 units of nephelometric turbidity when using conventional, direct, and diatomaceous earth filtration plants.

     (b) Be free of structural and sanitary hazards.

     (c) Provide for protection against contamination by backflow.

     (d) Provide equipment for measuring and recording flow.

     (e) Provide equipment for measuring and recording the combined filter effluent turbidity.

     (f) Be designed to mitigate the effects of events such as earthquakes, fires, floods, freezing and sabotage that are reasonably foreseeable.

     (g) Provide reasonable access for inspection, maintenance and monitoring of all unit processes.

     (h) Provide for a coagulation process that includes rapid chemical mixing and is based on pilot plant or laboratory scale or equivalent results that demonstrate effectiveness of the coagulant chemicals over the full range of water quality conditions expected.

     (i) Provide for filter-to-waste for each filter unit or addition of coagulant chemicals or organic polymers to the water used for backwashing.

     (j) Provide backwash rates and facilities for surface or subsurface wash using air, water or a combination of these to clean the filter.

     (k) Provide treatment for the removal of solids from filter backwash water if the water is recycled into the treatment process. Recycled backwash water must be returned to the headworks of the treatment plant.

     (l) Make provision for facilities for pretreatment in the design of direct filtration, slow sand filtration or diatomaceous earth filtration plants.

     (m) Provide equipment for disinfection that is of proper size for the full range of expected conditions of flow and capable of feeding accurately at all rates of flow.

     (n) Provide for operation of the treatment plant without frequent shutdowns and start-ups.

     3. As used in this section, “filter-to-waste” means a provision in the filtration process to allow the water that was filtered first to be wasted or reclaimed.

     (Added to NAC by Bd. of Health, eff. 11-29-90; A by Environmental Comm’n by R126-05, 10-31-2005; R194-08, 10-27-2009)