Percolation Testing Rates

Percolation Testing Rates and the Identification of Limiting Zones Policy
A failed percolation test will be considered as evidence of the existence of a limiting zone, in cases where no limiting zone was identified during test pit evaluation, in accordance with the conditions outlined here, and will be used in the process of determining site suitability and for permit issuance.
  • When a 36" percolation test failed and a subsequent 60" percolation test was performed in the same location and also failed, the limiting zone will be assumed to be at 36".
  • When a percolation test has been conducted at 36" and 60" simultaneously at the same location, and the 60" percolation test fails but the 36" test passes, the limiting zone will be assumed to be at 60".
  • This policy is not intended to conflict with applicable sub-surface sand filter provisions.
Discussion
  1. The definition of a Limiting Zone is found in Title 25, Chapter 71, § 71.1, Limiting Zone (iii): "A rock formation, other stratum, or soil condition which is so slowly permeable that it effectively limits downward passage of effluent". In discussion with DEP and soil experts the exact meaning or intent of this text has never been adequately explained.
  2. The suitability of the soil to pass effluent, determined by a percolation test, has accepted maximum and minimum percolation rate limits.
  3. Percolation rates that fall outside of a specified range of rates established in Title 25, Chapter 73, § 73.16, TABLE A, and considered to be unacceptable for use of a specific technology.
  4. The current regulations do not specifically address this issue.
  5. The CCHD successfully used this argument as the basis for denying the issuance of a sewage permit.
  6. CCHD has been acting in accordance with the rationale described above for a period of years.
This policy will serve as the basis for applicable decisions made by the CCHD relative to site suitability and permit issuance.