Dairy wash water is not usually considered a dairy sanitation problem. If not carefully managed, however, dairy wash water can contaminate both groundwater and surface water sources.

The amount of wash water generated varies with milking preparation, equipment used, and the number of cows. A 100-cow, free-stall operation may use anywhere from 100 to 1000 gallons of water per day in the milking center alone.

Milking center wash water is contaminated with organic matter, nutrients, chemicals, and microorganisms. Poorly designed or mismanaged wash water disposal systems can contaminate groundwater and surface water with ammonia, nitrate, phosphorus, detergents, and disease-causing organisms. If not managed properly, these contaminants can be carried directly into a well or can leach through the soil to cause groundwater contamination. Surface water can also be contaminated by manure, milk solids, ammonia, phosphorus, and detergents.

The goal of Home·A·Syst is to help you protect the groundwater that supplies your drinking water.

• It will take you step-by-step through your milking center wash water treatment practices.
• It will rank your activities according to how they might affect the groundwater that provides your drinking water supplies.
• It will provide you with easy-to-understand risk rankings that will help you analyze your milking center wash water treatment practices.
• It will help you determine which of your practices are reasonably safe and effective, and which practices might require modification to better protect your drinking water.

Milking Center Wash Water Treatment

These terms may help you make more accurate assessments when completing worksheet 10. They may also help clarify some of the terms used in fact sheet 10.

Land application: Application of wash water to croplands and pastures by irrigation equipment or a liquid manure spreader.

Slow surface infiltration: Application of wash water at one end of a gently sloping grass filter strip or terrace so that it is treated as it slowly flows through the plant-soil system. A portion of the flow percolates to groundwater, and some is used by vegetation.

Soil permeability: The quality that enables the soil to transmit water or air. Slowly permeable soils have fine-textured materials, like clays, that permit only slow water movement. Moderately or highly permeable soils have coarse-textured materials, like sands, that permit rapid water movement.

Step 2: Look at your rankings for individual activities.

• High risk practices (1's) pose a high risk of polluting groundwater.
• Moderate-to-high risk practices (2's) are inadequate protection in many circumstances.
• Low-to-moderate risk practices (3's) provide reasonable groundwater protection.
• Low risk practices (4's) are ideal; should be your goal despite cost and effort.

Any shaded rankings require immediate attention. Some concerns you can take care of right away; others could be major or costly projects, requiring planning and prioritizing before you take action. The long-term goal of the Home·A·Syst program is to improve homestead practices and structures so that they are classed as low risk. Activities classed as low risk generally reflect best management practices.

Transfer any activities that you ranked in the shaded areas in step 1 to the "High-Risk Activities" on pages 2-3 of worksheet 12.

Step 3: Read fact sheet 10, Improving Milking Center Wash Water Treatment, if you haven't already. Consider how you might modify your homestead practices to better protect your drinking water.

The Homestead Assessment System is a cooperative project of Washington State University Cooperative Extension, Washington Department of Ecology, and the U.S. Environmental Protection Agency Region X.

Home·A·Syst team members: Christopher F. Feise and Edward B. Adams, WSU Cooperative Extension Water Quality Coordinators; James D. LaSpina, Homestead Assessment System Project Associate.

Milking Center Wash Water Technical Reviewers: Ronald E. Hermanson, WSU Cooperative Extension; Andy Werkhoven, Dairy Farmer; Anne Schwartz, Washington Tilth; John A. Gillies, USDA-Soil Conservation Service; Philip A. KauzLoric, Washington Department of Ecology; John W. Bernard, WSU Cooperative Extension.

Adapted for Washington from material developed by the Wisconsin, Minnesota, and Kansas Extension Services and Farm·A·Syst Programs. Washington Home·A·Syst development was supported by the National Farmstead Assessment Program.

Issued by Washington State University Cooperative Extension, and the U.S. Department of Agriculture in furtherance of the Acts of May 8, and June 30, 1914. Cooperative Extension programs and policies are consistent with federal and state laws and regulations on nondiscrimination regarding race, color, religion, national origin, gender, age, disability, and gender preference. Evidence of noncompliance may be reported through your local Cooperative Extension office. Trade names have been used to simplify information; no endorsement is intended. Published September 1993. Subject Code 376. A. EB1746-W10