Clarification of Regulation Requirements for New Construction
& Expansion of Existing Buildings

In February 2008, the New Hampshire Department of Environmental Services issued new administrative rules concerning the design, installation, and replacement of individual septic systems.

Env-Wq 1002.29 “Expansion” means an increase in the design flow, based on Env-Wq 1008.03, over the existing design flow for an existing flow for a structure or an increase in the size of the footprint or ridgeline of an existing or former structure.

Env-Wq 1004.15 Relocation or Expansion of Existing Buildings; Replacement of Demolished or Burned Buildings.
  (a) Replacement of a building that has burned or otherwise been demolished, reconstruction of a building in a new location, or an existing structure, shall be considered new construction which requires submission of a new application; including plans and specifications, in accordance with Env-Wq 1003, unless all of the following are true:

(1) As compared to the structure it is replacing, the new structure will have:

1. The same footprint;
2. The same ridgeline;
3. The same usable space; and
4. The same use; and

(2) A valid construction and operating approval exists for the existing total sewage load, as determined by Env-Wq 1008.03.

DES interprets these conditions as follows:

1. The same footprint means that the foundation of the new structure is in the exact same location, and conforms to the same dimensions as the foundation of the structure it replaces. Any expansion of the foundation dimensions would require submission of new septic plans to DES.

2. The same ridgeline means that the structure can be no higher than the structure it replaces. Any increase in the height of the structure would require submission of new septic plans to DES.

3. The same usable space means that, while there can be some reconfiguration of the interior of the structure from what previously existed, the actual usable, livable space in the new structure may not be greater than that of the former structure. This means that the room configurations may change, and the ceiling height in some rooms may be different, but the overall living space in the structure must remain unchanged, or new septic plans must be submitted to DES.

4. The same use means that the building must be used for the same purposes as the former structure. For example, a residential structure cannot be changed to a commercial structure without submission of new septic plans to DES.

Finally, a valid construction and operational approval for the existing septic system, issued by DES, must exist.

If all of these conditions are met, then reconstruction of the structure on the property can begin without the necessity of further septic permits from DES.

For Further Information
If you have any questions concerning septic systems, contact DES Subsurface at (603) 271-3501, or PO Box 95 - 29 Hazen Drive, Concord, NH 03302-0095; (603) 271-3711; Fax: (603) 271-6683; www.des.nh.gov/ssb/.