Clay Hill 
Constructed Wetland Wastewater Facility

Water is 

a renewable resource

Construction  ---Our wetland is modeled after US EPA and TVA construction protocol.  It consists of four wetland cells 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 then laid down about 6 inches of sand in the bottom of each trench.  We lined each cell with continuous EPDM rubber sheeting, essentially forming a watertight tank.  The system was designed to allow water to flow from cell to cell by gravity.  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.  The sump allows us to adjust the level of water in the bed by using a stand pipe.  Once we had completed the plumbing, we 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.  While the emergent plants in the cells, go dormant during winter, the water hyacinth is native to Brazil and it continues to grow in our winter months.  In fact, water hyacinth grows and multiplies at a phenomenal rate, even during winter, removing any remaining nutrients from the water before it is eventually pumped into the Joan White Howell Environmental Education Center's 250-gallon display aquarium.  Overflow water 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. 

 

Published 26 August 2005                                          Last modified  11 February 2007                                                © Clay Hill Memorial Forest 2005