N.Y. Comp. Codes R. & Regs. tit. 10, § 74.4 – Sewerage facilities.

(a) A community sewerage system is required when:
1. (1) a subdivision is located in an existing sewer district or service area;
2. (2) a subdivision is reasonably accessible to an existing sewer district or service area. This requirement shall apply in the absence of proof satisfactory to the department that the developer cannot effect arrangements for the installation and/or connection of the sewerage system to the existing sewer district or service area facilities;
3. (3) the soil percolation rate is lower than 60 min/in.;
4. (4) the subdivision consists of 50 lots or more;
5. (5) the subdivision consists of 200 or more residents in the aggregate;
6. (6) a minimum separation of two feet cannot be maintained between the lowest part of the leaching system and the highest elevation of the top of the zone of water saturation, rock, hardpan or other impermeable material at all times of year; or
7. (7) an approved comprehensive study exists.
(b) Only subsurface leaching systems utilizing a septic tank may be employed on an individual basis in lieu of the provision of a community system. Septic tanks shall be designed and installed so that they are readily accessible for inspection and cleaning. Where individual water supply and sewage disposal systems are to be installed on a single lot, the minimum lot area shall be 20,000 square feet.
(c) When a community system is required and where the soil is suitable, interim individual sewerage systems may be permitted by the commissioner, provided that:
1. (1) dry sewers are designed and installed consistent with the community sewerage plan;
2. (2) plumbing is installed from the house to the dry sewer to facilitate individual connection to the community system; and
3. (3) such community sewerage service will be operative in five years.
(d) The relevant provisions of Bulletin 1^* entitled New York State Health Department Standards for Waste Treatment Works will be the basis upon which all plans, specifications and reports for sewerage systems, individual or community, will be reviewed for approval by the department.