Best Technical Guidance (BTG) – BTG is a powerful regulatory tool which may provide SEOs the ability to address malfunctions. The application of BTG is limited to allowing a variance of horizontal isolation distances to allow for repair of malfunctioning on-lot systems when necessary. It has been brought to DEP’s attention that BTG is not always being applied in accordance with the regulations and policy. The following are two (2) examples of inappropriate use of BTG:
- BTG does not allow for a variance in the vertical isolation distance to a limiting zone (LZ). If you are looking to replace a malfunctioning on-lot sewage system and there are unsuitable soil conditions (<20” to the LZ or <10” to a SHWT / <16” to a rock LZ for a spray field) for a conventional system, you may not use BTG to overcome this limitation. For example, if you have a LZ at 17” and you need 20” of suitable soil for a sand mound, you may not add an additional 3” of sand to overcome this issue under the guise of BTG. You should look to replace the malfunction with either a shallow limiting zone alternate system, a small flow treatment facility or a holding tank. The use of a technology on LZs that the technology is not approved for would require review by the Department and if appropriate, classification as an experimental system.
- BTG does not allow for modification to the design of the system. The alternate systems classified by the Department are classified based on an approved design. Any changes to the design require the Department to review and classify the altered design. For example, if you are looking to modify the minimum length to width ratio design requirement of the absorption area, you would submit the design to the Department for review and if appropriate, classification as an experimental system.