The Commonwealth of Massachusetts, Department of Environmental Protection, have allegedly devised more stringent standards in the treatment of on site wastewater through its Title 5, enacted in 1995.
The new code calls for increased separating distances to groundwater of 48" to 60" between the bottoms of infiltration devices and high groundwater (***).  This is, in some cases, reduced by 50% when the effluent is pretreated to a code complying quality which generally means removal of Biochemical Oxygen Demand (BOD), Suspended Solids (SS) and Nitrogen below 20 to 30 ppm.  This severely reduces the availability of organic constituents (BOD's) to act as a barrier in the infiltration devices to remove pathogens, viruses and other biological constituents.

With most of the clogging effect removed in the wastewater, the MA DEP allow a reduction in the separating distance to groundwater for open bottom chamber, gallery, pipe/stone and other infiltration devices.  It appears open bottom Chambers have been approved for use in Massachusetts and other states without testing to evaluate the impact on underlying waters from a device which simply creates a void with open bottom effluent access to underlying soils.  Most chamber devices also have perforations on their sides to enhance effluent delivery to surrounding soils.

Although these open bottom raw septic effluent delivery devices have been approved without testing, the MA DEP requires testing for the Living Filter even though it actually pre treats the effluent prior to discharge into the underlying soils.  The testing would cost approximately $15,000.00 per system for a potential total cost of $500,000.00 to $1,000,000.00 to ascertain that the Living Filter product would provide at least equivalent protection to currently approved systems (conventional pipe and stone trenches, open bottom dumping chambers and galleries, wrapped perforated pipe etc).

The Living Filter comprise the following treatment features between the Septic Tank (Digesting Tank) and underlying soils: (1) Filter Sand, (2) Reinforced Biological Membrane for mechanical filtration and biochemical conversion,
(3) Aggregate for attached microbial growth, (4) Compressed footprint for heat retention, (5) Insulation to elevate temperatures for more complete digestion;
the BIOREN/Living Filter configuration also includes (6) Nitrap^Tm  Filters to reduce nitrate / nitrogen and other undesirable constituents.

Now after more than 10 years of operation at a Condominium Site in South Yarmouth, MA these are the actual readings in the mound (groundwater) directly adjacent (5 lf) and downgradient the BIOREN System.  These test results have been similar during prior years of testing.   Samples were drawn on June 26, 2008 by George Huefelder, RS, Barnstable County Health Dept.   Nitrate as Nitrogen - 0.21 mg/l (maximum contaminant level [MCL] is 10 mg/l), Nitrite as Nitrogen - None Detected (ND),   Ammonia as Nitrogen  - ND,   Phosphorous - 0.07 mg/l ,   Total Kjeldahl Nitrogen (TKN) - 1.3 mg/l,   Total Suspended Solids - ND,   Fecal Coliform < 10 CFU / 100 ml.

It appears the standard applied by many agencies like MA DEP relies on the native soil structure and its flora of bacteria to do the renovation and therefore open bottom devices are acceptable to their standards.
Conventional stone/gravel trenches also deliver raw septic tank effluent to the subterranean soil structure, but comprise large surface areas for attached growth between the delivery conduit and the soil interface adding a treatment aspect not found in many other devices.

There are claims by one or more manufacturers that their chamber devices are innovative, technological marvels, while stating that stone/aggregates do not contribute to the treatment of effluent.  The only apparent innovation may be the multi-angular effluent delivery orifices present on the sides of some of these devices, which manufacturers propose prevent the intrusion of soils.  There are also writings that chamber "technology" has been around for twenty-five years.  I firmly take exception to this statement as I personally was involved in the installation of open bottom dumping chamber devices 33 years ago in East Burke, Vermont.
Also worthy of note is the fact that these chambers failed over 29 years ago.

(***)
The State of Connecticut Department of Public Health requires a separation distance of 18" between bottoms of leaching devices and high groundwater.  This distance is sufficient provided high groundwater is accurately determined and a thorough site investigation is made.  Most systems were built to this standard and thus should allow repairs, in most cases, without having to use pumps and other energy consuming mechanical gadgets.  The net result of the carefully chosen CT DPH standard should result in a (net sum) cleaner environment by conserving energy in addition to huge cost savings to the property owners of Connecticut.
When in close proximity to groundwater we prefer to use our Nitrap Filters to provide a better exchange between the subterranean and surface conditions.

We Recycle Water On Site