Section 410. Portable equipment and diversions

A. Needs. Portable equipment (pumps or generator sets) shall be acceptable to satisfy the continuous operability requirements where, under critical conditions imposed by rush hour traffic, multiple pumping station failures, etc., the portable equipment transportation, connection and starting can be accomplished within allowable time periods.

1. Portable pumping equipment shall have the following provisions:

a. Pumping units shall have capability to operate between the wet well and the discharge side of the station.

b. Each station served by portable pumping equipment shall facilitate rapid and easy connection of lines.

2. Numbers of portable units and their pumping implementation capabilities that are simultaneously available to service pumping stations, which are provided continuous operability through the use of portable equipment, shall conform to the following, whichever shall yield the greater number:

a. The number shall be the maximum number of pumping stations (dependent on portable equipment for continuous reliability) that are on the same radial extremity (single source feed) of any electrical distribution circuit from the point of the radial extremity's intersection with circuitry that has alternate feed.

b. The number shall be equal to 5.0% of the number of pumping stations (dependent on portable equipment for continuous reliability).

3. Volume and head capabilities (pumps) or power watts (generators) of portable equipment shall be capable, singly or in combination, of operating the largest pump station dependent on portable equipment for continuous reliability.

B. Submittals. Plans and specifications for a pump station submitted to the area engineer proposing to use portable equipment to meet continuous operability requirements shall be accompanied by a completed "Portable Equipment for Sewage Pump Stations" form. A list of this information is included in 9VAC25-790-990.

1. The design submitted for sewerage systems that utilize portable equipment to meet the continuous operability requirements for sewage pump stations shall include the following information: (i) an inventory of the owner's portable equipment (pumps or generators) which lists numbers of units, capacities, storage locations, and assignment of this equipment by the owner; and (ii) an analysis of response times based on geographical locations within the owner's sewerage system service area.

2. The response time analysis should be based upon a work crew responding to an alarm from the pump station during the hour of the day that the peak flow to that station is expected to be received.

C. Controlled diversion. The provision of a high-level wet well-controlled diversion may be considered for pump stations of all reliability classes.

1. If a high-level wet well-controlled diversion is utilized, the overflow elevation shall be such that the maximum feasible storage capacity of the wastewater collection system shall be used before the controlled diversion is used. When a controlled diversion is utilized at a Reliability Class I pumping station, it shall be to a storage detention basin or tank. The storage volume shall be sized in accordance with the pump station's operating conditions and the constraints and conditions applicable to the owner's repair and maintenance capabilities. The storage volume shall provide, without overflow, not less than six hours detention capacity at the anticipated flow diversion rate.

2. Additional storage volume, or provisions for protection against overflows in critical areas, may be required.

Historical Notes

Former 12VAC5-581-470 derived from Volume 18, Issue 10, eff. February 27, 2002; amended and adopted as 9VAC25-790-410, Virginia Register Volume 20, Issue 09, eff. February 12, 2004.

Statutory Authority

§ 62.1-44.19 of the Code of Virginia.