Advanced Treatment and At-Grade
The At-Grade effluent treatment and disposal system is a method of accomplishing the final treatment and disposal of effluent from an advanced sewage treatment plant. The At-Grade is arranged utilizing pressurized distributional laterals above virgin ground surface. The pressurized pipe is supported 1.5 inches above ground surface utilizing feet spaced every meter along the length of the pipe. The pressurized lateral is then covered with a 4 – 6 inch insulated shield. The entire assembly is then covered with 12 inches of vertical wood chip cover or leaf mold or peat moss. The width will vary between 3 and 6 feet depending on slope and terrain variables.
Freezing is avoided by adequate cover, proper time dosing, and proper drainage of pipe. All of these parameters are site specific and require specialized training to accomplish this task. A variance from Alberta Municipal Affairs is required prior to installing any At-Grade system.
A typical At-Grade will perform at a rate 4.3 times better than any subsoil absorption method. By variance code we are able to distribute 3.25 gallons per lineal foot to achieve an expectable absorption rate. Within 2 – 6 years, the entire area of the At-Grade will become infiltrated by local flora and fauna, blending it in with the surrounding terrain. The efficiency of the At-Grade is expected to improve as time passes, decomposition and growth in the area aid in the absorption/distribution of water. At-Grades out perform all other methods of final treatment in high water table areas and tight clay soils.
At-Grades perform best in treed areas where protection from wind and vehicles is greatest. The vegetation in the forest provides the best infiltration available. Areas with sloping terrain are preferred, but level areas are also acceptable.
