When Can Eljen GSFs Be Used – and Why Should They Be a Consideration?
According to the PA DEP Alternate On-Lot listing for the Eljen Geotextile Sand Filter, the system may be used for:
- New construction or repair
- Sites described in Chapter 73 (other than IRSIS)
- Shallow Limiting Zone sites (with LZ’s ≥10” to seasonal high water table or redoximorphic features AND ≥16” to rock)
Absorption Area Sizing Reductions
In addition to the above siting criteria, when the limiting zone is ≥20” AND the perc rate is between 3 and 60 min/in, a reduction in absorption area size of up to 40% can be taken. This can be a particularly valuable feature of Eljen on challenging sites with limited area. Please see the related section on taking reductions “without taking a reduction.”
Bed Length:Width Ratio
One advantage to Eljen is in the requirements for bed configuration. As has been the case for many years, with other elevated absorption areas incorporating fine aggregate (i.e., elevated sand mounds), the bed length:width ratio for Eljen beds on sites with slopes less than 8% is not specified. This allows flexibility in the siting of Eljen systems, particularly in repairs. For example, there are numerous instances where Eljen has been used in narrow absorption areas where the bed is completely off-contour. Please see related section on bed length:width ratio and when 4:1 IS NOT required.
Clearly, the wisdom in designing systems off-contour is tempered by the perc rate of the soil and other site-specific considerations but there are repairs where no other legitimate option is available!
End Feed and Oddly Shaped / Unique Bed Configurations
The listing for Eljen states that in the case of sites with LZs ≥20″, “Distribution of effluent to the individual laterals shall be by a central manifold extending into the absorption area from the delivery pipe or header or from an end feed manifold. The pressure distribution design shall consist of a minimum of 2 laterals. The overall length of the laterals may exceed 51 feet.”
For Shallow LZ sites, the listing states that, “Distribution of effluent to the individual laterals shall be by a central manifold extending into the absorption area from the delivery pipe or header or by an end feed manifold. The pressure distribution design shall consist of a single lateral or single pair of laterals placed on the same contour. The overall length of the laterals may exceed 51 feet.”
The fact that Eljen beds can be fed from a manifold placed at the end of the bed allows for some unique bed layouts (primarily in repair situations) as shown in the examples below:
Aesthetics and Cost
Significant cost savings (and a dramatic improvement in appearance compared to the typical sand mound) can be realized with the need for only 12″ of sand under Eljen modules on sites with LZs of 10” and up. Coupled with sizing reductions on faster perc-ing soils and considerably less materials of construction are necessary! With the minimal maintenance requirements (see below), the long-term costs of Eljen ownership can be significantly less than that of competing systems.
No Maintenance Agreement Required!
Most other treatment technologies approved in PA that reduce or remove fine aggregate from the construction of the absorption area also require some form of annual (or bi-annual) maintenance in order to keep them functioning properly. Eljen has the same maintenance requirements as conventional absorption area systems in PA, largely consisting of periodic septic tank pumping.
American Made by Eljen Corp., multi-year recipient of the of the US Department of Labor’s HIRE Vets Platinum Medallion