OPERATION AND MAINTENANCE .1 General Considerations

The designer of a stormwater pump station should pay careful attention to the affect that design features have on operation and maintenance. The design should facilitate and minimize the cost of operation and maintenance without adding unreasonably to construction costs. The design also should minimize the possibility of malfunctions and stations becoming inoperable.

Primary design considerations or measures to help minimize operation and maintenance costs include:

• ensuring proper hydraulic design,

• providing for debris trapping and removal,

• providing for sediment handling or control and removal,

• considering appropriate pump type for given conditions,

• accounting for the experience of local maintenance personnel, and

• maintaining consistency with existing maintenance capabilities.

12.4.2 Safety

All elements of the pump station should be thoroughly reviewed for safety during operation and maintenance. Particular attention should be given to all safety features in order to maintain a safe working environment. All safety features included in the design and construction of

pumping stations must be in accordance with the prescribed local, state and national safety laws and codes. Safety features include:

• ladders, stairwells, railings and other access points for use by maintenance and operations personnel in accordance with OSHA and local standards,

• guards and railings placed around all access holes and openings and all mechanical equipme nt with which the operator might come into contact including belt drives, gears, chain drives, rotating drive shafts and other moving parts,

• adequate space for the operation and maintenance of all equipment,

• warning signs near dangerous machinery and safety rules posted in appropriate locations throughout the station,

• paying particular attention to providing proper and reliable lighting especially when there is moving equipment,

• rubber mats provided in front of all electrical equipment where there is a possibility of electric shock,

• electrical equipment properly insulated and grounded,

• switches and controls of the non-sparking type,

• proper drainage to eliminate the possibility of slippery surfaces,

• a telephone to permit an operator to maintain regular contact with the main office,

• air testing and monitoring equipment in order to assure a safe environment within the station,

• ventilation systems to minimize the dangers of explosions and those arising from pollutants,

• fire extinguishers throughout the station in case of emergency,

• permanent traffic warning signs, and

• temporary traffic control, if access is limited.

An entry plan should be developed as part of the operation and maintenance procedures for each pump station. The plan should identify measures to be taken prior to and during any visit to the pump station, including monitoring of environmental conditions, especially air quality. All measures should conform with current OSHA requirements.

12.4.3 Access to the Pump Station Site

Personnel safety is a paramount concern, so access should not interfere with vehicular traffic.

If right-of-way or other physical restrictions preclude construction of a dedicated service road or driveway, temporary barricades and signs should be placed during inspection and maintenance in conformance with the National Manual for Uniform Traffic Control Devices.¹⁴

12.4.4 Removal of Collected Debris and Sediment

Normal operation of the collection system will result in a build up of debris on trash racks, gratings and screens and sediment in the storage unit and sump. The build- up of debris may cause the bearings, impellers and bowls to be damaged reducing the pump efficiency and often resulting in failure.

An operation and maintenance schedule should identify a frequency of inspection to identify the need for debris and sediment removal.

12.4.5 Provision for Replacing Pumps

Pumping stations should be designed for easy maintenance and/or removal and replacement of pumps. The alternatives usually are a permanent hoist in the station or use of mobile hoisting equipment.

12.4.6 Typical Problems

The following is a list of design practices that can result in unnecessary maintenance requirements:

• poor siting of the station making access difficult,

• inadequate erosion control and slope stability measures producing excessive sediment and resulting in excessive wear of pump equipment,

• inadequate wet well dimensions causing vortexing or cavitation leading to excessive noise and wear,

• improper orientation of pumps causing vortexing, noise and wear, and

• poor trash handling resulting in clogging.

Generally, if the considerations and criteria discussed in this manual are followed, the potential for significant maintenance problems will be minimized.

12.4.7 Troubleshooting

Table 12-1 identifies some specific problems, their likely cause(s), and possible mitigation measures.

Table 12-1. Pump operation problems and typical solutions

Condition Likely Cause Mitigation/Avoidance On and off sensor levels

incorrectly set

• Adjust sensors to activate at design levels

• Check sensors during pump testing

Clogged intake • Provide trash rack and frequent cleaning Frequent flooding of road

low point

Inadequate pump capacity • Add pump(s),

• replace pumps, or

• add storage unit On and off sensor levels

incorrectly set

• Adjust sensors to activate at design levels

• Check sensors during pump testing

Inadequate usable storage • Increase storage unit capacity

Rapid cycling

Excessive pump size • Increase storage unit capacity, or

• Add low flow pump Cavitation or vortexing • Increase submergence

and pump clearances, or

• add baffles/vortex suppressors Excessive noise/vibration

Incorrectly aligned pump • Check installation and adjust alignment Excessive wear on pumps Rapid cycling, cavitation or

vortexing

See rapid cyc ling and excessive noise/vibration Overheating of pumps Rapid Cycling See rapid cycling

Sump pump failure Low fluidity of sump sediment.

Provide flushing system

12.4.8 Inspection and Maintenance Schedule

The highway agency should develop a maintenance log that includes:

• the required frequency of inspection,

• an inspection check list, and

• routine maintenance measures.

12.4.9 Monitoring

By necessity, highway stormwater pumps must operate automatically. There are numerous components that may be subject to failure. With only one or two pump stations, it may be efficient enough to rely on local highway maintenance offices to manually monitor the condition of the stations. As the number of stations in an agency’s inventory increase, it becomes feasible and desirable to use some kind of automated monitoring system. Typical features to monitor include:

• high water in the wet well,

• number of starts for each motor,

• cumulative operation time of each pump,

• leakage in dry well (for dry-pit stations),

• debris levels/amounts,

• sediment levels,

• motor/engine failure,

• ambient temperature,

• temperature of bearings and motor wiring,

• smoke,

• gases, and

• unauthorized entry.

The simplest type of automated warning system is a flashing light or siren that relies on locals to call in to a listed number. Preferred systems allow remote telemetering of any of the above alarms, or data, to a monitoring station.

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