Okla. Admin. Code § 252:656-7-1

Current through Vol. 41, No. 19, June 17, 2024

Section 252:656-7-1 - Pump station design

(a) Required design factors for pumping stations are:

(1)Emergency plan. Provide an emergency plan for handling sewage should the lift station completely fail. Required emergency operations are in 252:656-7-4.

(2)Separate wells. Wet and dry wells must be completely separated, each with its own entrance.

(3)Equipment accessibility and safety. Provide a suitable stairway or ladder for dry wells and for wet wells with bar screens or mechanical equipment. Adequate provision must be made to effectively protect maintenance personnel from hazards. Equipment for confined space entry in accordance with OSHA and regulatory agency requirements must be provided for all wastewater pumping stations. The design of the system must protect the pump station controls and appurtenances from unauthorized access and vandalism. Provide a building or other form of protection such as fencing or access hatches with locks. The design of the system must prevent unauthorized access or vandalism to control system and equipment.

(4)Equipment removal. Provide for removal of pumps, motors, and other mechanical and electrical equipment during all weather conditions.

(5)Dry well dewatering. Provide a sump pump in dry wells to remove leakage or drainage. The discharge pipe shall terminate above the overflow level of the wet well and include a check valve located near the pump. Do not connect water ejectors to a potable water supply. Slope all floor and walkway surfaces to the sump. Pump seal water shall be piped to the sump.

(6)Flood Protection. Wastewater pumping stations structures and electrical and mechanical equipment shall be protected from physical damage by the 100 year flood and shall not be located in a flood way. Wastewater pumping stations shall remain fully operational and accessible during the 25 year flood. Regulations of state and federal agencies regarding flood plain obstructions shall be followed.

(7)Buoyancy. Where high groundwater conditions are anticipated, buoyancy of the wastewater pumping station structures shall be considered and, if necessary, adequate provisions shall be made for protection.

(8)Pump station accessibility and security. The pumping station must be readily accessible by maintenance vehicles during all weather conditions and must be located off the traffic ways of streets and alleys.

(b) Pump requirements are:

(1)Multiple units. Provide at least two pumps. With any pump out of service, the remaining pump(s) must have the capacity to handle maximum sewage flows.

(2)Protect against clogging. Pump stations with screening devices shall provide for the storage and disposal of the collected material. Provide a suitable bypass where screening is installed.

(3)Pump openings. Pumps, other than grinder type pumps,shall be capable of passing a 3-inch sphere. Suction piping shall be at least 4 inches in diameter. Suction lines to dry wells shall include suitable shut-off valves to allow pump removal.

(4)Priming. Locate pumps so they will operate under a positive suction head under normal conditions.

(5)Intake. Each pump shall have an individual intake and be designed to avoid turbulence near the intakes.

(6)Pumping rates. Size pumps to prevent hydraulic surges.

(c) Force main requirements are:

(1)Diameter. Force mains shall be at least 4 inches in diameter and provide at least 2 fps velocity.

(2)Air relief valve. Install air relief valves at high points in force mains.

(3)Termination. Terminate force mains not more than 2 feet above the flow line of the receiving manhole, and design them to reduce splashing and erosion.

(4)Design pressure. Design the force main and fittings, including reaction blocking, to withstand normal pressure and pressure surges (water hammer).

(5)Stream crossings. Force main construction used for stream crossings must meet applicable requirements of OAC 252:656-5-4.

(6)Design friction losses. Calculate friction losses through force mains with the Hazen and Williams formula (or equivalent), using these C values:

(A) Unlined iron or steel - 100

(B) All other lined ductile iron - 120

(C) PVC - 140

(7)Separation from water mains. Refer to OAC 252:656-5-4(c).

(8)Controls. Locate the control system so it is not affected by turbulence of incoming flow or pump suction. Provide automatic alternation of constant speed pumps at each cycle.

(9)Valves. Place suitable shutoff valves on suction and discharge lines of each pump. Place a check valve or equivalent on each discharge line, between the shut-off valve and the pump. Shut-off valves are not required on the suction side of pumps that can be removed from service without discharging.

(10)Wet wells. Wet well size and control settings shall be appropriate to meet the chosen manufacturer's recommended cycling times and to avoid heat buildup in the pump motor due to frequent starting and not to exceed 30 minutes between pump off to pump on to avoid septic conditions due to excessive retention time. The effective volume of the wet well shall be based on design average flow and a filling time not to exceed 30 minutes unless the facility is designed to provide flow equalization. Slope wet well floors to the pump intake at least 1 to 1 (1:1). Covered wet wells shall have provisions for air displacement to the atmosphere.

(11)Ventilation. Adequate ventilation shall be provided for all pump stations. Where the pump room is located below ground surface, mechanical ventilation is required. There shall be no interconnection between wet well and dry well ventilation systems. If the wet well must be entered to service mechanical equipment, forced ventilation is required, independent of dry well ventilation. Ventilation equipment switches shall be well marked and located at the entrance to the dry well. Intermittent operation ventilation systems shall be interconnected with the lighting system. The fan wheel(s) shall be fabricated from non-sparking material.

(A)Wet wells. Ventilation may be either continuous or intermittent. Mechanical ventilation is required if screens or mechanical equipment requiring maintenance and/or inspection are located in a wet well. Continuous ventilation shall provide at least 12 complete air changes per hour. Intermittent ventilation shall provide at least 30 complete air changes per hour. Air shall be forced into, rather than exhausted from, the wet well. Wet wells not designed for access shall have provision for air displacement to the atmosphere. The top of the pumping station shall be located higher than the 100-year flood.

(B)Dry wells. Provide adequate ventilation for all dry wells. Ventilation may be either continuous or intermittent. Continuous ventilation shall provide at least six complete air changes per hour; intermittent ventilation shall provide at least 30 complete air changes per hour. Ventilation equipment switches shall be marked and located at the entrance to the dry well.

(12)Water supply interconnection. There shall be no direct connection between any potable water supply and sewage pumps or piping.

(13)Pressure testing/leakage testing. Test the installed pipe for leakage in accordance with the applicable ASTM standard specifications. The design working pressure of the pipe must not exceed 2/3 of the rated pressure of the pipe. Specify the applicable ASTM standard to be used.

Okla. Admin. Code § 252:656-7-1

Added at 17 Ok Reg 1140, eff 6-1-00; Amended at 18 Ok Reg 2019, eff 6-11-01; Amended at 23 Ok Reg 937, eff 6-15-06; Added at 28 Ok Reg 1282, eff 7-1-11