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System pressure sensor locations shall be chosen such that localized transient gradient fluctuations which are not reflective of the overall system hydraulic gradient conditions are avoided. Choice of the best location may have to be made based on hydraulic analysis results.

Easy accessibility to the pressure sensor vault location is also an important consideration. The vaults shall be located near existing roadways (away from residential front yards) or suitable access road shall be provided.

Where possible the vault should be built with the top of the slab slightly above grade.

The vault shall be of reinforced concrete construction complete with access hatch, vent pipes, ladder, sump, etc., and shall be sized to house all the components required viz:

(a) Circuit breaker load center (240/120V, 1Ø, 3W with main breaker and six 1P, 15-amp branch circuit breakers in NEMA 3R enclosure).

(b) Telemetering cabinet (with power supply, line protector and three FS transmitters – one transmitter for pressure to the pump station, and one transmitter for pressure and one transmitter for flood alarm to the WSSC Control Room).

(c) Pressure gauge and pressure transmitter.

(d) Sump pump with union, check valve and gate valve.

(e) Flood alarm switch.

(f) Ventilating fan.

(g) Lights (wall mounted).

The vault shall be membrane waterproofed. Pressure sensor vault details are shown in Drawing DG-02-12.

Meterbase and service disconnect (circuit breaker) shall be mounted on service pole in case of overhead electrical service and on a pedestal in case of underground electrical service. The service disconnect circuit breaker shall be mounted in a lockable NEMA 4 stainless steel enclosure. Service pole or service pedestal shall be located approximately 10 feet from the vault. Location and other requirements shall be coordinated with the power company. The same pole or pedestal shall also be used for telephone service. Service conduit to the load center inside the vault, telephone service conduit to the telemetering cabinet, and all conduit inside vault shall be PVC coated rigid galvanized steel.

Freezing of water in the sump discharge pipe is to be prevented. The sump pump discharge shall be taken through the side of the vault to a suitable nearby location so that discharge is free and flows toward drainage. If this is not feasible, pump discharge shall be terminated in a perforated drain tile in a gravel pocket. A small hole drilled in the discharge pipe, above the gate valve, will also be helpful in preventing freezing. (Amended during 2019 codification; 28-ME-DG-02 § 23.4)