4.2B – Operation and Maintenance – Liquid Waste (Including Gray Water) Management
- Provide appropriate receptacles for liquid waste.
- Encourage the proper disposal of gray water. Do not use MSD to store and/or treat gray water. Once gray water is put into a MSD it is no longer considered gray water, but sewage (i.e. black water).
USCG defines gray water as drainage from dishwasher, shower, laundry, bath, and washbasin drains. It does not include drainage from toilets, urinals, hospitals and cargo spaces. Gray water is NOT sewage and may be discharged overboard without passage through an MSD or a holding tank. In fact, draining galley wastes into the MSD is not recommended, because food waste is much more difficult to decompose than the human sewage which the marine sanitation device is intended to handle. If retained, gray water must be included in a separate waste retention capacity for the vessel (source: Coast Guard Regulations, 33 CFR 151.05).
The following list, taken from Clean Water Act, 33 U.S.C. § 312(a)(11) (Table 3-2) describes some of common sources and characteristics of gray water.
- Automatic Clothes Washer: bleach, foam, high pH, hot water, nitrate, oil and grease, oxygen demand, phosphate, salinity, soaps, sodium, suspended solids, turbidity.
- Automatic Dish Washer: bacteria, foam, food particles, high pH, hot water, odor, oil and grease, organic matter, oxygen demand, salinity, soaps, suspended solids, turbidity.
- Sinks, including kitchen: bacteria, food particles, hot water, odor, oil and grease, organic matter, oxygen demand, soaps, suspended solids, turbidity.
- Bathtub and Shower: bacteria, hair, hot water, odor, oil and grease, oxygen demand, soaps, suspended solids, turbidity.
For Marina Owners and Operators
- Prohibit discharges of gray water into marina waters and sensitive ecological areas. Encourage boaters to discharge of gray water outside of marinas, mooring fields, and sensitive ecological areas. If your marina is in an inland lake or area with very little flushing, prohibit the discharge of gray water.
- Where feasible, make sure boaters have a separate, adequately sized holding tank installed for gray water containment. Gray water should be pumped out of tanks and piped or transported to the nearest waste water treatment plant.
- Do not discharge gray water into marina waters, inland lakes, and sensitive ecological areas.
- Make sure you have a separate, adequately sized holding tank installed for gray water containment. Gray water should be pumped out of tanks and piped or transported to the nearest waste water treatment plant.
- NPDES, Central Valley Regional Water Quality Control Board, Memorandum of Understanding with the U.S. Department of Agriculture, Forest Service and Shasta-Trinity National Forest on discharge prohibition for Lake Shasta.
USEPA. 2001. National Management Measures Guidance to Control Nonpoint Source Pollution from Marinas and Recreational Boating. EPA 841-B-01-005. U.S. Environmental Protection Agency, Washington, DC.