SECTION 252:626-7-2. Surface water

  A surface water source includes all streams, natural lakes, springs, and artificial reservoirs or impoundments within the drainage basin above the point of intake.

(1)   Quantity.

(A)   The quantity of water must be adequate to:

(i)   meet the projected water demand, including anticipated growth of the service area as shown by calculations based on the extreme recorded drought, and

(ii)   compensate for losses such as silting, evaporation, seepage, etc.

(B)   Criteria for evaluating adequacy are outlined below:

(i)   where water is drawn from a flowing stream, the minimum recorded stream flow, less water demand of other users, plus off-stream storage must exceed the estimated future water demand, and

(ii)   where water is drawn from a reservoir or lake, the average inflow for a period including the driest recorded period plus the effective storage capacity must exceed the estimated future demand for the maximum recorded drought period.

(2)   Quality.

(A)   Bacterial quality.

(i)   Waters containing coliform bacteria counts averaging less than 5,000 per 100 ml in any 1 month and not exceeding this number in more than 20 percent of samples examined in the same month require flocculation, sedimentation, filtration, and disinfection.

(ii)   Waters that contain coliform bacteria counts exceeding 5,000 per 100 ml in over 20 percent of samples examined during any 1 month, but less than 20,000 per 100 ml in over 5% of the samples examined in the same month, require pre-sedimentation, flocculation, sedimentation, filtration, disinfection, or at least 30 days of off-stream storage.

(iii)   Waters that contain coliform bacteria counts in excess of 20,000 per 100 ml in more that 5% of the samples examined in any 1 month are considered unsuitable for use as a source water supply unless they can be brought into conformance by prolonged preliminary storage or other reliable means.

(B)   Physical quality. Surface water containing an excessive amount of suspended material requires pre-sedimentation and possibly other preliminary treatment prior to conventional treatment.

(3)   Hydrologic studies.

(A)   Use stream flow and weather records for contributing or adjacent watersheds for estimating the safe yield of a source. Empirical formulas and ratios in published literature are not satisfactory criteria for judging the adequacy of a source unless supported by hydrologic data obtained from the specific watershed.

(B)   Perform a study of all hydrologic factors that affect and determine the safe yield of a proposed surface water supply. Use data from the U.S. Weather Bureau, the U.S. Geological Survey or Climatological Survey to estimate watershed run-off.

(4)   Safe yield. When the demand for water is greater than the minimum rate of flow in the stream from which the water is to be taken, an impounding reservoir is required. Evaluate the factors disclosed by the hydrologic data by the use of a mass diagram or other equivalent method and include in the design report.

(5)   Reservoir and lake sanitation. Protection of the watershed is required for municipal water supply reservoirs. Control the marginal shoreline land by purchase or ordinance. The ordinance must describe the water district boundaries and enforcement rules for the protection of the water supply and include but not be limited to:

(A)   regulating the public health aspects of water supply, waste and sewage disposal, and recreational activities,

(B)   regulating the building of structures within the controlled area,

(C)   regulating aquatic activities involving body contact with the water, and

(D)   clearing of timber, brush and debris.

(6)    Off-stream reservoirs.

(A)   Provide for site preparation where applicable:

(i)   removal of brush and trees to high water elevation,

(ii)   protection from floods during construction, and

(iii)   plugging of all wells which will be inundated, in accordance with OWRB requirements.

(B)   Restrict body contact recreational activities wherever water quality or public health may be adversely affected.

(7)   Intake structures.

(A)   General. Intake structure design must provide for:

(i)   location of the structure an adequate distance from existing or potential source(s) of pollution to protect the water quality,

(ii)   location of the structure to obtain the best quality of raw water,

(iii)   the intake to meet the ultimate capacity of the water treatment plant,

(iv)   release of undesirable water to prevent it from entering the treatment plant,

(v)   temporary barriers to allow dewatering for inspections and maintenance,

(vi)   protection against damage to the structure caused by dragging anchors, etc.,

(vii)   ports located above the bottom of the stream, lake or impoundment, but at sufficient depth to be kept submerged at low water level,

(viii)   where shore wells are not provided, a diversion device capable of keeping fish or debris from entering intake structure,

(ix)   the operating floor must be above the 100-year flood level and be accessible at all times, and

(x)   in the case of Zebra mussel presence, an infiltration gallery may be used. See Appendix B for design guidelines.

(B)   River intakes.

(i)   Site. Locate intakes so that a continuous supply of water is ensured.

(ii)   Headworks structure. Design the intake to protect pumps from sand and to minimize silting or obstruction by deposits of bed load. If the headworks are constructed on permeable material, the design must take into account the anticipated effect of underflow and hydrostatic uplift pressure.

(C)   Reservoir or lake intakes. Locate inlets or gates in the intake structure so they are accessible for inspection and maintenance.

(i)   Fixed inlet structures. Design intake structure for water withdrawal from at least three (3) separate levels of the lake or reservoir. Install the top inlet below the water surface at normal pool elevation.

(ii)   Floating structures. Design for water withdrawal at selected depths. Multiple length suction pipes, provisions for addition or removal of extension pipe to the pump suction are acceptable design. Other designs will be considered on a case-by-case basis.

(8)   Trash racks and screens. Provide a trash rack or screen at the inlets to any intake structure. The port area design must limit the net velocity through the racks to not more than 2 ft/s during normal operation for bar racks having 1-1/2 inch spacing and larger, and must not exceed 0.5 ft/s for fine screens of 2-inch. Precede fine screens with coarse screens or bar racks. Use mechanical rakes or other devices to clean the bars. On small intakes, hand rakes can be used.

(9)   Shore wells. Shore wells must:

(A)   have electrical controls protected from flooding,

(B)   be accessible during a 100-year flood,

(C)   be designed to resist flotation,

(D)   be equipped with removable or traveling screens before the pump suction well,

(E)   provide for chemical introduction into the raw water transmission main,

(F)   be equipped with intake valves and provisions for backflushing or cleaning, and

(G)   have provisions for withstanding surges.

(10)   Infiltration lines as a raw water source.

(A)   Infiltration lines may be used where geological conditions preclude the possibility of developing an acceptable drilled well.

(B)   The water supplier must control the area around infiltration lines for a minimum distance of 600 feet from the lines.

(C)   Flow in the lines must be by gravity to the collecting well.

(D)   Water from infiltration lines is considered surface water and treatment equivalent to surface water supplies is required.

(11)   Off stream reservoirs. When constructing an off stream reservoir assure that:

(A)   water quality is protected by controlling runoff into the reservoir,

(B)   dikes are structurally sound and protected against erosion,

(C)   intake structures and devices meet requirements of this chapter, and

(D)   point of influent must be separated from the point of withdrawal.

[Source: Added at 18 Ok Reg 1612, eff 6-1-01; Amended at 25 Ok Reg 2304, eff 7-11-08]