I strongly support the…

I strongly support the proposed changes to the section 8. 7 of the Code regarding the expansion of leaching chamber models to include units known in the industry as "low profile" chambers.

The addition of low profile chambers to the Code will result in reduced costs for chamber systems when these models are used in lieu of the taller leaching chamber units. Low profile chambers are nominally 200 mm tall, whereas the the codified chamber models (commonly referred to a "standard" model chambers because they are the same height as the stone aggregate in a conventional trench) are 300 mm tall. Low profile chamber models are less expensive than than "standard" model chambers simply because they are made with less plastic than the "standard" units. The 33% decrease in height also results in the need to use approximately 33% less material to backfill around and between chamber rows in trench and bed installations when the lower profile models are specified and installed. In systems which project above grade, use of low profile chambers will result in lower-profile mounds, which will not only reduce costs but also result in a lower "mound" on the site, which is a distinct benefit from an aesthetic perspective. Finally, and quite importantly, use of low profile chambers allows for installation of the chamber row in the trench at a higher profile in the soil. It is universally accepted that oxygen is critical to the breakdown of organics in residential-strength wastewater. Oxygen levels in the soil are reduced as the depth of soil increases. In other words, the oxygen levels decrease as the depth of the soil column increases. Low profile chambers allow for the receiving soil interface (at the bottom of the trench excavation) to be located higher in the soil profile. This results in greater treatment of the wastewater as compared to taller chambers which will be located 100 mm deeper into the ground.

One section in the Code that was not proposed to be changed is section 8.7.3.2.(1)(c). Presently this section requires trenches to be "not less than "600 mm in depth". This specification should be revised to allow for the trench bottom to be higher in the soil profile when using low profile model chambers, while allowing for equal depths of cover material over all of the systems. I recommend that the minimum depth be specification be changed from 600 mm to 500 mm. This will allow low profile chambers to carry the same amount of cover material as required of all trench media, but will raise the infiltrative surface (bottom of the trench) by 100 mm. Organic breakdown within the low profile chamber trenches will be enhanced in system which provide an elevated infiltrative surface (bottom of the trench).