BEST MANAGEMENT PRACTICES FOR CONTROL OF STORM WATER RUNOFF AT A LARGE DAIRY

An over 1000-head dairy farm in the largest watershed in the State of Michigan was designed to drain excess water to an agricultural ditch that flowed into a bayou and then to the primary river of the watershed, the Grand River. This farm was also of particular concern since a portion is located in the 100-year floodplain and approximately 30 miles upstream of one of the State's primary beach resorts.The original farm was built prior to 1980 and has since undergone a number of changes. Similar to many farms constructed in the past, excess water generated at the facility was looked at from a transport and disposal perspective and not from an environmental perspective. The farm is situated at the edge of a steep incline and was designed to channel water down the incline to an agricultural drain located at the bottom of the slope. A washroom utilized by farm employees and a drain associated with cleaning nursery equipment discharged directly onto site soils at separate locations near the top of the slope. The farm also contained numerous areas where rainwater that ran toward the agricultural drain came into contact with nutrient rich material including: silage storage areas, partially covered feed alleys, exercise lots, calf hutch areas, and livestock alleys. Finally, natural springs located along the slope added to the volume of water that needed to be transported offsite.Surface drains located throughout the facility collected the majority of the runoff. Some of the flow was directed to a sedimentation/infiltration area prior to flowing down the slope and into the agricultural ditch. The remainder of the runoff captured by the surface drains flowed to a conduit located at the top of the incline and was severely eroding the soils at the outlet. Due to sediment accumulation and the addition of impervious surfaces associated with facility expansion, the sedimentation/infiltration area was being short-circuited and runoff entering the agricultural ditch allegedly contained pollutants in excess of State standards.As a result of the alleged “release” and in the anticipation of new State discharge requirements, the farm was retrofitted so that any form of “dirty” surface water discharge could be eliminated: the washroom and nursery sinks were connected to a new septic system, the storm water runoff pathways were mapped, separated, and designated as “dirty” storm water and “clean” storm water, and a clay lined “dirty” storm water retention pond was constructed in conformance with NRCS standards and replaced the separation/filtration area. The pond was designed to store rainfall runoff resulting from precipitation generated during the winter months, plus the runoff generated from a 25-year, 24-hour storm event. The “dirty” storm water is now used to hydrate manure in the pits under the freestalls and the excess is applied onto nearby fields via two center pivot systems. Also, an unlined “clean” storm water detention pond was constructed to store runoff from a 5-year, 24-hour storm event and a riprapped spillway for the “clean” storm water detention pond was designed for circumstances when the design storm event was exceeded. The area around a natural spring that was located in an exercise lot was tiled and the flow was channeled, via a solid tile, north towards the agricultural ditch. The agricultural ditch was filled and a drain tile was installed to facilitate infiltration so overland/channelized flow could be avoided. In addition to the above mentioned tasks and since the majority of the earthwork took place in the 100-year floodplain of the Grand River, permits had to be obtained from the State and local authorities.These changes were completed by the end of November 2001. However, keeping the “clean” storm water runoff from contacting/transporting nutrient rich material has proved operational problematic. In 2003 the operator directed us to prepare a plan to combine the ponds into one so that all storm water runoff will be managed through irrigation. The new pond was completed in 2003.