(1) 
All lots to be served by septic systems shall require soil evaluation tests in order to assess soil percolation rates and the relative suitability of soil conditions under the current regulation requirements.
(2) 
Each lot shall contain sufficient square footage to meet minimum health requirements.
(3) 
General Requirements. Prior to large lot subdivision approval the applicant shall specify the proposed means of sewage disposal for the large lot subdivision. Every large lot subdivision shall have a method of sewage disposal which is reliable, safe, and meets all of the requirements of the state and county health regulations.
(4) 
Individual On-Site Sewage Systems. The land divider may choose to designate individual on-site sewage systems as the means for sewage disposal in a large lot subdivision unless a public sewer system is available. If the large lot subdivision is to be served by an individual on-site sewage disposal system, each system shall be entirely contained on the same lot as the dwelling which it is intended to serve or on other land on which the lot owner possesses an easement interest. Prior to large lot subdivision approval, the environmental services section shall determine whether soils on each lot will safely accommodate individual on-site systems if such systems are properly constructed and managed. If conditions are found to be unsuitable for individual on-site sewage systems, or such systems cannot be accomplished consistent with state and county health regulations, individual on-site sewage systems shall not be allowed. When individual on-site sewage systems are to serve a large lot subdivision's sewage disposal needs, this shall be so stated on the final large lot subdivision map. It shall be the responsibility of each individual lot owner to obtain required on-site sewage disposal systems pursuant to the state and county health regulations.
(5) 
Community On-Site Sewage Systems. When the Lewis County environmental services section determines that individual disposal systems to serve each lot are unsuitable, and a public sewer system is not available, the land divider may, if feasible, install an on-site community disposal system. The on-site community sewage system need not serve lots which can accommodate individual on-site sewage disposal systems. Prior to large lot subdivision approval the community system shall be constructed by the land applicant in accordance with engineering plans approved by all public agencies of jurisdiction. The large lot subdivision lot owner's association, or an approved public utility that is qualified to operate and maintain on-site sewage systems, shall manage the community disposal system. Maintenance and operation of the system shall be consistent with all state health and environmental requirements. When an on-site community sewage system is to be utilized to serve the large lot subdivision's disposal needs, the system shall be entirely within the subdivision or large lot subdivision boundaries or on land controlled by the system ownership.
(6) 
Public Sewer System. When a public sewer system is available to serve the large lot subdivision, then all lots shall utilize the sewer system to satisfy its sewage disposal requirements in compliance with Lewis County Board of Health Ordinance H-98-326, and as amended, Section 12 (LCC § 8.40.070).
(7) 
Large lot subdivisions contiguous to lakes, streams, or other bodies of water shall be required to take the following precaution to prevent pollution of said bodies of water from septic tank effluent: A setback line from the ordinary high water mark consistent with state health law shall be established, within which no part of a sewage storage, treatment or disposal facility shall be established.
(Ord. 1169 § 1, V, X, 2000; Ord. 1269 § 5, 2016)
(1) 
Lots which exceed the minimum land area requirements of "The Sewage System Rules and Regulations of the Lewis County Board of Health" for individual wells and septic systems do not need to be served by an approved public water supply system; provided, that the large lot subdivision meets the following: Prior to the final approval of the large lot subdivision the applicant shall demonstrate to the environmental services section that a potable water source is available to serve all lots. If the environmental health officer is uncertain regarding the ability of the water source to provide long-term safe and adequate water to the subdivision, the applicant shall be required to conduct a water source study completed by a qualified professional.
(a) 
Prior to large lot subdivision approval, subdivisions proposing individual wells for source water may be required to drill one well per plat. The demonstrated well shall provide at least 400 gallons per day as evidenced in a pump test or well driller's log. The quality of water shall be approved by the Lewis County environmental services section, including location and construction as per well log, site plan and/or site visit, bacteria, nitrates, and possibly arsenic. If the water source does not meet these standards, such fact shall be a basis to deny the large lot subdivision if no other means of providing water to the large lot subdivision can be accomplished.
(2) 
Approved Public Water System. An approved public water system shall be provided to each lot with less than the minimum gross land area required by current on-site regulations for individual septic systems and wells. The applicant shall provide a public water supply facility and a complete water distribution system and may dedicate it to a large lot subdivision lot owner's association, or a public agency if a satellite maintenance agency approved by the Lewis County environmental services section is unavailable. The dedication shall include a water supply and distribution system which includes the well, reservoir and/or treatment system and the land upon which they are located or upon land which the lot owner's association shall have control and shall grant utility easements for the distribution system. The applicant may retain ownership of the system or dedicate it to a responsible person, either of which shall operate and maintain the system consistent with state requirements if a satellite management system is unavailable.
(3) 
Subdivision Water Supply System - Commitment. An approved public water system which has been developed and approved to serve a large lot subdivision shall be reserved for the exclusive use of the large lot subdivision; provided, that service connections located outside of the subdivision, in excess of those required to serve the total number of lots within the large lot subdivision, may be authorized by the entity or person owning the system. The public water system must also demonstrate substantial compliance with Chapter 246-290 or 246-291 WAC, as now or hereafter amended, including monitoring data on record, satisfactory construction records and plans on file, and not under any compliance or enforcement order. The public water system shall also demonstrate adequate water rights, if required, from the Washington State Department of Ecology.
(Ord. 1169 § 1, V, Y, 2000; Ord. 1269 § 5, 2016)