OAR 340-073-0055: Dosing Assemblies: Effluent Pumps, Controls and Alarms

(1) Design and equipment must emphasize ease of maintenance, longevity, and reliability of components and must be proven suitable by operational experience, test, or analysis acceptable to DEQ. (2) Easy means of electrical and plumbing disconnect must be provided. All apparatus must be constructed and installed to facilitate ease of service without having to alter any other component. (3) Component materials must be durable and corrosion-resistant such as Type 316 stainless steel, suitable plastics, or 85-5-5-5 bronze. (4) Pumps, Controls, and Alarms. All pumps, controls and related apparatus must be field tested under working conditions and found to operate and perform satisfactorily. Electrical components used in onsite systems must comply with applicable requirements of the State of Oregon Electrical Code and the standards in this rule. (a) Motors must be continuous-duty with overload protection. (b) Pumps must have durable impellers of bronze, cast iron, or other materials approved by DEQ. (c) Submersible pumps must be provided with an easy, readily accessible means of electrical and plumbing disconnect and a noncorrosive lifting device to remove the pump for servicing. (d) Except where the agent specifically authorizes it in writing by the agent, the pump must be placed within a corrosion-resistant screen or vault with a filtering device that extends into or above the tank's service access manhole. The screen or filtering device must have at least 12 square feet of surface area, with 1/8-inch openings. In lieu of the screen, the agent may allow other methods with equal or better performance for preventing suspended solids from passing to the pump. (e) Pumps must be automatically controlled by float switches with a minimum rating of 12 amps at 115 volts A.C. or by a DEQ-approved, equally reliable switching mechanism. Except as otherwise required in this division, the switches must be installed so that no more than 20% of the design flow is discharged each cycle. The pump "off" level must be set to maintain the liquid level above the top of the pump or to the designer and pump manufacturer's specifications. (f) An audible and visual high water level alarm with manual silence switch must be located in or near the building served by the pump. Only the audible alarm may be user- cancelable. The switching mechanism within a dosing tank or chamber controlling the high water level alarm must be located so that at time of activation the tank has a remaining volume equal to 1/3 or more of the system's design flow, as measured below the invert of the inlet, for effluent storage. The alarm and pump must be on separate circuits. Commercial applications using duplex pumps are not subject to the 1/3 storage reserve requirement. (g) When a system has more than one pump, DEQ may require the pumps to be wired into the electrical control panel to function alternately after each pumping cycle. If either pump should fail, the other pump will continue to function while the high water level alarm activates. A cycle counter must be installed in the electrical control panel for each pump. (h) All pump installations must be designed with adequate sludge storage volume below the effluent intake level of the pump. (i) All commercial systems with a design flow greater than 600 gallons must be constructed with two or more alternating pumps unless otherwise authorized in writing by DEQ. Controls must be provided such that an alarm will signal when one of the pumps malfunctions. (j) All pumps serving commercial systems must be operated through a pre-manufactured electrical control panel. There must be a means of monitoring pump performance with elapsed-time meters and cycle counters. (k) Where multiple pumps are operated in series, an electrical control panel must be installed to prevent the operation of a pump or pumps preceding a station that experiences a high level alarm event.