Construction  ---Our wetland is modeled after US EPA and TVA construction wetlands.  It consists of four wetland that are each 10 ft wide and 40 feet long.  We excavated the cells with a bulldozer to a depth of about 4-5 feet with a very slight grade (less than one inch in 40ft).  We put 6 inches of sand in the bottom of each trench covered this with EPDM rubber sheeting, forming a watertight tank.  The cells are connected to one another by PVC pipes that pass through the EPDM liner at bulkhead fittings.  At the effluent (low) end of each cell we placed a sump allowing us to adjust the level of water in the bed with stand pipes.  We then placed 18" of river gravel in each bed.  The gravel serves as habitat for the microorganisms that perform much of the work of the system. It also serves as anchorage for the roots of irises, cattail, and other emergent plants that remove nutrients from the water. Once the water passes through the fourth bed it flows into a buried 800-gallon storage tank.  This tank is normally nearly empty.  It serves as an overflow for water during a substantial rain event. When water fills the tank, it is pumped to a tank in our greenhouse.  There are three greenhouse tanks, each 100-gallon capacity.  These tanks have water hyacinth (a floating, fast growing tropical plant with a very extensive root system.  Overflow from these tanks is pumped into a 250-gallon display aquarium.  Overflow from this joins our wastewater stream and enters into the first of two 1500-gallon septic tanks.  These tanks serve to settle any solids from the wastewater stream before it enters into the first cell of the wetland.  At this point the water has made one circuit on Clay Hill's Round River..