Observation and Shut Off Station Requirements, Nutrient Management Act, 2002 and Regulation 267/03, As Amended

Under the Nutrient Management Act, 2002 and Regulation 267/03, as amended, all new or expanding permanent liquid nutrient storage facilities must have two levels of groundwater protection. These two levels of protection are achieved by:

• the construction of the floor and walls of the tank or earthen storage, and
• either the native soil below and around the tank or earthen storage, or if found inadequate, a compacted soil or synthetic liner.

Professional engineers are responsible for ensuring that the design of nutrient storages meet the required two levels of protection.

Nutrient storage facilities constructed below or partly below ground level normally require a perimeter foundation drain. The foundation drain minimizes the hydrostatic pressure (water pressure) pushing in on the storage walls and/or upward on the footings and floor.

While perimeter foundation drains are effective in reducing hydrostatic pressure, they can drain away nutrients if a leak occurs in the storage structure. To manage this risk, the Regulation specifies that foundation drains around the perimeter of a permanent nutrient storage facility must be routed through an observation and shut-off station. This is a requirement for all new or expanding permanent nutrient storages regardless of size, or whether the nutrient stored is in a liquid or solid form.

An observation and shut-off station, shown in Fig. 1, is a chamber with a shut-off mechanism to intercept the flow of liquids from a perimeter drain. It is used to monitor the quality of the liquid collected in the drain before it is discharged to the environment. Should a liquid sample indicate the presence of nutrients contained in the storage facility, it is discharge to the environment can be prevented using the shut-off mechanism. The contaminated liquid can either be pumped back into the storage facility or treated.

Text Equivalent of Diagram

Figure 1. An observation and shutoff station is used to provide access to the discharge from a perimeter drain. Possible contaminated flow can be observed and blocked. Steps can then be taken to address the situation.

Remember, if surface water is allowed to enter an observation and shut-off station, a 50-metre flow path setback is required between the storage facility and observation and shut-off station.

OMAFRA recommends that non-perforated pipes be used between the foundation drain and the observation and shut-off station. The outlet pipe of the observation station must be non-perforated within 15 metres from any nutrient storage facility, or at least a minimum of three metres past the station, whichever is the greatest.