set backs are 10 feet from property lines and 10 feet from any
structure and 75 feet from any wells (there is one across the street). Two other factors
impact the design; when the
site was originally subdivided and recorded; and, the type of system chosen. The
results of the percolation tests are level 3 equal to 45
minutes per inch, which is good.
this rate the absorbtion field must have 100 feet of line per bedroom.
For a four bedroom home you would need 200 feet.
Because of the date when
the lot was recorded a 50% reduction is possible for a gravity fed
system. However, no point in pushing
the limit. There is a
system called a ATU system that aerates the waste in the primary tank
increasing the rate of bacterial
breakdown. This system
would also allow you to reduce the standard field size by 50%.
For these reasons we chose an Eljen GSF Septic Waste Disposal System. Established in 1970, Eljen Corporation created the world’s first
prefabricated drainage system for foundation drainage and erosion
The Eljen GSF Geotextile Sand Filter System is a cost-effective upgrade
from other septic technologies. Comprised of a proprietary two-stage
Bio-Matt™ pre-treatment process, the GSF Modules apply a
better-than-secondary aerobic effluent to the soil, increasing the
soil’s ability to accept the effluent. The result is superior treatment
in a smaller soil absorption area.
Primary Treatment Zone
Perforated pipe is centered above the GSF Module to distribute septic
effluent over and into corrugations created by the cuspated core of the
Septic effluent is filtered through the Bio-Matt fabric. The GSF
Module’s unique design provides increased surface area for biological
treatment that greatly exceeds the Module’s footprint.
air channels within the GSF Module support aerobic bacterial growth on
the Module's geotextile fabric interface, surpassing the surface area
required for traditional absorption systems.
An anti-siltation geotextile fabric covers the top and sides of the GSF
Module and protects the Specified Sand and soil from clogging, while
maintaining effluent storage within the Module.
Secondary Treatment Zone
Effluent drips into the Specified Sand layer and supports unsaturated
flow into the native soil. This Specified Sand/soil interface maintains
soil structure, thereby maximizing the available absorption interface in
the native soil. The Specified Sand supports nitrification of the
effluent, which reduces oxygen demand in the soil, thus minimizing soil
clogging from anaerobic bacteria.
The Specified Sand layer also protects the soil from compaction and
helps maintain cracks and crevices in the soil. This preserves the
soil’s natural infiltration capacity, which is especially important in
finer textured soils, where these large channels are critical for
• Native soil provides final filtration and allows for groundwater recharge.