(Written by Jack Milarch – NMHBA EVP/CEO – Originally published in the August 2006 Housing Journal)

New Septic Tank Regs – Revisited

Those of you interested in the new septic tank regulations that have been in place for nearly a year will remember that the board which passed these new rules promised they would revisit them after they’d been in effect long enough for us to see how things are going in the field. Staff of NM Environment Department recently began that process of review.

Our builder members and those who install and service septic tanks have been accumulating their observations and comments on the new regulations, and on July 24th and again on July 25th we met with Ana Marie Ortiz, NMED Groundwater Bureau Chief, and her staff to present our opinion of what should be changed.

  • DRAIN FIELD LENGTH – We asked that the maximum drain field line length be extended by five feet. The current regulation has a maximum length of 150 feet and when installers use some drain field materials, 150 feet falls just short of the length of line needed for the typical three-bedroom home. When that happens, installers are forced to install a second drain line. We feel the addition of another five feet onto any one line will solve this problem and keep installations efficient. NMED staff countered that a drain longer than 150 feet may not work because of soil settlement or poor installation practices. After much discussion NMED staff agreed this change makes sense and they will join us in recommending the change to their board.
  • GALLONS PER DAY CAPACITY – The current (and past) regulations about drain field sizing and approved products all revolve around the assumption that a typical three-bedroom home (5 people) needs a drain field capable of dissipating 375 gallons-per-day (GPD). This industry “standard” was developed many years ago, long before low water usage fixtures became the norm for installation in new homes. The “sound science” that is always called upon to be the benchmark for debate on all drain field products and configurations is in fact based on this arbitrary 375 GPD dissipation requirement. In addition, there is a feeling among longtime observers of septic tank installations here in desert New Mexico that surface evaporation isn’t given proper recognition. For these reasons we are asking that the gallons-per-day dissipation (absorption) requirement be reduced to 250 GPD for a three-bedroom house. NMED staff counters that all systems need extra capacity for unusual “surge” flows, and 250 GPD isn’t enough. Again, we believe actual field observations should be relevant to this issue and, when the water used by most families is measured, it almost always comes out to less than 75 gallons per person per day, including outside and irrigation uses which never make it into the septic tank. We believe 50 GPD per person includes enough surge capacity for typical use. NMED staff is studying this proposal and they have not made a decision whether to support or oppose this change.
  • INSPECTION ON SALE OF EXISTING HOMES – We are hearing that the new provision requiring an inspection of the septic tank before the sale of an existing home is unpopular with some home sellers. Our association promoted this controversial new requirement on the theory that existing home owners should be doing their part to clean up our state’s ground water and that checking to be sure those old systems were working properly was appropriate from many points of view. We asked NMED staff if they felt this was helping to clean up our ground water, and they said emphatically “yes” – that this requirement is exposing many illegal and failed systems and causing them to be repaired or replaced.
  • SPACE FOR ALTERNATE DRAIN FIELD – We are asking NMED to review their long standing requirement that every lot onto which a septic tank drain field system is installed have open space sufficient for a replacement drain field. Observation of many home sites over many years suggests that home owners have no idea they should be keeping the original alternate drain field space open for future use. Over the years, sheds, driveways, room additions, etc. take up the lot space, especially on the smaller lots. The requirement for an alternate drain field site makes installations on difficult terrain lots unnecessarily complicated. Installers tell us that digging out failed systems and amending the soil to allow installation in the same place is more the norm anyway. NMED staff didn’t have time to discuss this suggestion at these meetings and will set up additional meetings for more discussion.

If you have comments on these items or other issues with the new septic tank regulations, please send them by email to info@nmhba.org so we can take your comments into account as we work toward a presentation to the Environment Improvement Board on additional changes to New Mexico’s new septic tank regulations.