A cross connection is connection between a potable (drinking) water system and water from an unsafe or unknown source. A common place in wastewater collection systems where this can occur is on the seal water line for a lift station pump. When potable water is used as the seal water supply and a no protection is in place, a direct cross connection exists. Without protection, wastewater from inside the pump could enter and contaminate the potable water system. Several devices for controlling cross connections exist.
The use of these devices is related to the “degree of hazard” that exists to the potable water system. An air gap device offers the highest degree of protection and is commonly used in wastewater applications.
Several excellent programs are available to train operators about the dangers of cross connections and the devices used for control cross connections.
At the start of a sewer construction project, the inspector should obtain two sets of the plans for the project. One copy is the working plan that will be used to guide the construction project. The other copy is known as the “asbuilt” plans. Any daily construction that deviates from the working plan should be recorded on the as-built plan by the inspector. This plan then becomes the true record of where stub-outs and taps are placed, where lines and manholes are located, etc.
The as-built plans reflect what actually exists underground. Because of this fact, they are invaluable to the collection system operators. When a project is completed, the asbuilt plans are submitted to the project engineer who either
files them directly or has a revised drawing made. These plans should always be kept available to collections system workers.
All too often few or no maps exist of the wastewater collection system. Although some collections workers may feel that this offers “job security”, the headaches brought about by not having proper plans to work with probably offsets this feeling.