There are several potential areas where a dairy farm can contaminate the local ground water unless specific design criteria are taken to prevent this threat. Dairy Development International, LLC (DDI) has designed the dairy complex to have zero-discharge to the local ground water.
The following design characteristics have been implemented:
- Milk house wastewater is completely contained.
- All rainwater is directed away from areas where cattle reside.
- Manure is prevented from escaping from barns.
- The manure transport system is secure.
- The manure storage system is leak proof.
- Silage leachate is controlled.
In addition to these operational issues, DDI has implemented monitoring and prevention systems:
- Monitoring wells installed.
- Monitoring pipes under the floor of the liquid storage system.
- 400,000 gallon secondary containment around the liquid storage system
- A containment berm placed downstream to prevent a catastrophic spill from entering a surface water system.
The only discharge from the DDI Dairy Complex is domestic sewage that is handled through a standard septic system. The hydraulic load of the septic system is expected to be less than 300 gallons per day and has been approved by the Cortland County Heath Department.
Milk house wastewater
Wastewater from the parlor and the milk house contains a high COD (Chemical Oxygen Demand) and must not enter either ground water or surface water directly. All of this wastewater at DDI is pumped to the manure flow gutter and incorporated with the main manure flow. There is no external discharge on site.
The DDI dairy complex receives approximately 40 inches (1 meter) of precipitation per year. One roofline of a barn (438’ long and 48’ wide) represents 70,000 ft3 (523,000 gallons) of water. It is important that this water enters the local ground water without biological contamination. All roof lines have French drains made of large rock to facilitate the drainage of this water. Furthermore, there are no outside animal areas that allow the mixing of manure and rainwater. Except for the rainwater that enters the liquid storage system, all rainwater that falls on the site will remain free of biological contaminants associated with housing dairy cattle.
The barns are designed to ensure that manure does not escape from the alleys. Alleys with cows in them will be automatically and continuously scraped. At the outside end of the alley, the last 10 feet has a 1% rise to ensure inward flow of manure. Furthermore, six feet has been added to each barn so that the alley scraper mechanisms are completely enclosed in the barn. These alley scrapers will move all manure to the center of the barn where it will enter a gravity flow system. To ensure that the alley scrapers work through freezing weather, the floors have a heating system installed to keep them above freezing.
Manure transport system
Manure from the barn floors is moved to a concrete gutter in the middle of each barn. The gutters are connected by HI-Q double walled plastic pipe. From each barn to the next (north to south) there is a foot drop in elevation. Also, in each gutter there are step dams to ensure manure mixing. The milk house wastewater enters the flow gutter at the head of the system. At the end of the system is a 17,000-gallon concrete collection pit. Manure will flow through this system without mechanical devices.
|Figure 1. Concrete flow gutter
||Figure 2. HI Q Pipe connecting buildings
From the 17,000-gallon collection pit, manure will be pumped through a 6” PVC line to the anaerobic digester, which is poured in-place concrete. To ensure no leakage, this 6” PVC line will be surrounded by a 10” PVC line. Once the manure enters the anaerobic digester, it will slowly move through the digester taking approximately 20-30 days. From the effluent chamber of the digester, manure will be pumped to an elevated solids separator. These lines are exposed and a leak will be readily detected. The solids from the separator will fall to a concrete containment area or directly into a truck for off-site transport. The liquids from the separator will flow over the side of the liquid storage container through exposed pipes. By loading the liquids over the top of the container, the risk of accidental evacuation through the filling port is eliminated.
Manure storage system
The liquid storage system selected for the DDI Dairy Complex is a SlurryStore structure. This structure has a diameter of 162’ and is 19’ tall. The capacity of the structure is 391,600 ft3. The structure has glass fused to steel and all exposed steel is protected with a cathodic system.
The unloading system for the SlurryStore structure has double valves to ensure that accidental discharge does not occur. The interior valve is a slide valve and the exterior valve is a knife valve.
Silage leachate has one of the highest CODs on a dairy farm. DDI has implemented an AgBag system for storing fermented forages. The AgBag Pads have a road fabric base with gravel and crushed stone on top. Because the bags are sealed and silage is not in contact with rain, the issues of silage leachate are eliminated.
Figure 7. Ag Bag Pad
To ensure that an unforeseen problem does not go undetected, DDI has installed ground water monitoring wells. These wells are intended to monitor ground water level and direction of flow as well as water quality. On May 18, 2001, the baseline ground water level was between 1144 and 1147 feet above sea level. The depth of ground water was approximately 18 feet. The baseline nitrate concentrations were below 3 mg/L, which is well below the federal guidelines for safe drinking water. These wells will be periodically monitored to ensure that the ground water around the DDI Dairy Complex is safe.
Liquid storage system monitoring system
The base of the liquid storage system is concrete. In the highly unlikely event that a crack would develop in that concrete that allows manure to escape, DDI has implemented a leak detection system. At four locations around the SlurryStore structure, drain tile was placed under the floor and emptied into an exposed container. These containers will be periodically examined to ensure that no manure has escaped from the floor.
400,000 gallon secondary containment
Around the SlurryStore Structure, DDI has built a containment area with an extremely low perk rate. Should a minor spill ever occur, this containment area would provide time to clean up the spill without contaminating ground water. This containment represents approximately 13% of the total volume of the storage system.
Figure 8. Secondary containment
The area around the DDI Dairy Complex slopes to the south with a natural shallow valley. It is conceivable that a complete evacuation of the liquid storage system during a time of frozen ground (no infiltration) that liquid manure could reach the West Branch of the Tioughnioga River. To ensure that this possibility would not exist, a berm was built in this natural shallow valley such that the area between the berm and the liquid storage structure would contain 3 million gallons.
Figure 9. Soil for containment berm