City of Troy, MO Building and Installation of Lift Stations

This Chapter covers guidelines for construction of submersible non-clog or grinder pump stations. In addition to the following guidelines, the design and installation shall also conform to Missouri Department of Natural Resources regulations (10 CSR 21.8). Lift stations include precast concrete or reinforced fiberglass wet well and valve chamber complete with base, piping, access doors, and electronic controls. The pump and controls shall have name plates.

Figures 1 to 3 included as attachments to this Chapter show details of the wet well and valve chamber. The wet well, valve chamber and associated piping shall be constructed as shown in the figures.

Section 515.020 Accessibility.

[R.O. 2006 §515.020; Ord. No. 796A §1, 3-15-1996]

The pumping station shall be readily accessible by maintenance vehicles during all weather conditions. The road shall be minimum two (2) inch Type I aggregate shaped and rolled on top of six (6) inch two and one-half (2½) to three (3) inch base rock. The lift station shall be located off the trafficway of streets and alleys.

Section 515.030 Pumps.

[R.O. 2006 §515.030; Ord. No. 796A §1, 3-15-1996]

At least two (2) pumps shall be provided. A minimum of three (3) pumps shall be provided for stations handling flows greater than one (1) MGD. If only two (2) pumps are provided, they should have the same capacity. Each shall be capable of handling flows twice the expected maximum flow.

For pumping wastewater from single residences or when a minimum velocity of two (2) fps cannot be achieved in a four (4) inch diameter discharge pipe, a grinder pump shall be used. In other cases, non-clog submersible pumps can be used.

Except where grinder pumps are used, pumps shall be capable of passing spheres of at least three (3) inches in diameter, and pump suction and discharge piping shall be at least four (4) inches in diameter.

Submersible pumps shall be readily removable and replaceable without dewatering the wet well or disconnecting any piping in the wet well. A hoist shall be furnished to lift the pump.

Bar racks shall be provided to protect pumps from clogging or damage. Where a bar rack is provided, a mechanical hoist shall also be provided.

Electrical systems and components in the wet well shall be suitable for hazardous locations (National Electrical Code, Class I, Group D, Division I location). In addition, equipment located in the wet well shall be suitable for use under corrosive conditions. Each flexible cable shall be provided with watertight seal and separate strain relief. A fused disconnect switch located above ground shall be provided for all pumping stations. When the equipment is exposed to weather, it shall meet the requirements of weatherproof equipment.

Electrical supply and control circuits shall be designed to allow disconnection at a junction box located at, or accessible from, the outside of the wet well. Terminals and connectors shall be protected from corrosion by location outside of the wet well or by watertight seals.

The motor control center shall be located outside the wet well and be protected by a conduit seal to prevent the atmosphere in the wet well from gaining access to the control center. The seal shall be NEC Class 1, Division 2, Group D.

Pump motor power cords shall be designed for flexibility and serviceability under conditions of extra hard usage and shall meet the requirements of the Mine Safety and Health Administration for trailing cables.

Section 515.040 Controls.

[R.O. 2006 §515.040; Ord. No. 796A §1, 3-15-1996]

The control system shall be of the encapsulated float type. The electrical equipment shall be suitable for hazardous locations (National Electrical Code, Class I, Group D, Division I location). The control shall be located in a NEMA type 3R enclosure.

In small stations, the pump shall automatically alternate.

There will be an alarm for the following conditions:

Power failure;

High water level;

Low water level;

Seal leakage; and

Pump motor overheating.

A local audio/visual alarm or telemetered alarm shall be provided. Use of a local or telemetered alarm will be decided by the City Engineer.

Section 515.050 Piping and Valves.

[R.O. 2006 §515.050; Ord. No. 796A §1, 3-15-1996]

Suitable shutoff and check valves shall be placed on the discharge line of each pump. The check valve shall be located between the shutoff valve and the pump. Check valves shall not be placed on the vertical portion of the discharge piping.

The shutoff valve shall be quarter-turn, permanently lubricated eccentric type with resilient faced plug. End connections shall be flanged. Valves shall be lever operated and equipped with position indicator. The valve shall be as manufactured by DeZurik or equal.

Check valve shall be swing disc type with outside lever and spring. End connections shall be flanged. The valve shall be as manufactured by Clow Valve or equal.

Valves shall not be located in the wet well. There will be a separate valve chamber where the check and shutoff valves are installed.

Accumulated water in valve chamber shall be drained to the wet well.

Lift station piping shall be Ductile Iron ANSI A21.50, Class 52. Joints shall be flanged, ANSI A21.10. The piping, valves and supports shall be coated with one (1) coat epoxy primer and two (2) coats of polyemide cured epoxy glass enamel.

The system control floats shall be mercury float switches suspended in the wet well. The operational sequence will be as follows:

High level alarm

Lead pump on (on rise)

Lag pump on (on rise)

Both pumps off (on fall)

Low level alarm.

Section 515.060 Wet Well.

[R.O. 2006 §515.060; Ord. No. 796A §1, 3-15-1996]

The wet well size and control setting shall be appropriate to avoid heat build up in the pump motor due to frequent starting and to avoid septic conditions due to excessive detention time.

The time between starts for the pump shall not be less than fifteen (15) minutes. The volume of the wet well between start and stop elevations shall be sized to provide the above mentioned duration between starts. A maximum detention time of twenty (20) minutes shall be allowed at average design flowrate to prevent septic conditions in the wet well.

Ventilation shall be provided in the wet well. A four (4) inch vent with return bend shall be used as shown in Figure 2.

The wet well shall be constructed of precast reinforced concrete (ASTM C76). Water proofing shall be as per manhole water proofing.

Section 515.070 Access Doors.

[R.O. 2006 §515.070; Ord. No. 796A §1, 3-15-1996]

Access doors shall be heavy duty, single leaf, steel hatches with galvanized steel channel frame and one-quarter (¼) inch thick diamond plate cover. The door shall be designed for three hundred (300) pound/square foot live load and watertightness. A holding arm shall be provided when door is fully open. Door shall open to ninety degrees (90°) and lock automatically in that position. A flush, spring loaded locking device capable of unlocking from the interior without a key shall be provided. The door shall be as manufactured by Bilco Company or equal.

Section 515.080 Approval By City Engineer.

[R.O. 2006 §515.080; Ord. No. 796A §2, 3-15-1996]

Prior to the construction or installation of any such lift station, the specifications for said lift station shall be submitted to the City Engineer and be approved in writing by him/her.

Section 515.090 Warranty.

[R.O. 2006 §515.090; Ord. No. 796A §3, 3-15-1996]

Any lift station thereafter built or installed in the City of Troy shall carry a warranty by the person building or installing said system for a period of one (1) year after the date of completion of the installation and acceptance by the City.