(A) Subsurface drains must be installed at least six inches into the massive clay, glacial till or fragipan, and a four-inch diameter or greater perforated pipe must be used and backfilled to or within two inches of the surface with washed stone not larger than the stone used in the absorption trenches or with material specified in 410 I.A.C. 6-8.3 for use in subsurface drains.
(B) Subsurface drains may be employed with conventional trenches only where the soils have a loading rate high enough to allow for rapid movement of water to the drain in order to lower and maintain the water table at a depth of 24 inches below all absorption field trenches. Soils having a loading rate of less than six-tenths gallons per day per square foot shall not be suitable for the installation of a subsurface drain to rapidly lower and maintain a water table. Should a person wish to attempt to use a subsurface drain of any description to lower a water table in soils having a loading rate of less than six-tenths gallons per day per square foot, then such person must demonstrate to the satisfaction of the Health Officer that the proposed subsurface drain can indeed rapidly lower and maintain the water table. To do so, at a minimum, the subsurface drain must be installed at the prescribed depth and location to potentially allow for the private on-site sewage system installation. Not less than two piezometers will then be installed in the central area of the proposed private on-site sewage system. The piezometers must be constructed of four-inch schedule 40 PVC with a secure cap. One shall be installed to a depth of at least 12 inches below the level at which the lowered water table is to be maintained. The second piezometer must be installed as directed by the Health Officer in the surface soils and into the first indication of soil mottling. The piezometers must remain available for review by the Health Officer through at least one high water table period (December through June) to verify that the water table can be lowered and maintained before a permit for the private on-site sewage system will be considered.
(C) A free outfall for the discharge from the subsurface drain shall be provided on-lot. Otherwise, easements for the use and maintenance of any drain used or to be used to transport the water from the subsurface drains or subsurface drain to an outfall located off-lot must be obtained from all owners of adjacent properties through which the underground drain runs to the point of discharge. Copies of the recorded easements must be submitted with the application for a permit to install any private on-site sewage system which has a subsurface drain as a component that discharges off-lot. The use of a legally established, publicly maintained drainage improvement shall be permitted only after written permission for such use is first obtained from the public agency with jurisdiction over such drainage improvement (Surveyor’s office/Drainage Board).
(D) Subsurface drains. Subsurface drains, when required, will be installed around the absorption field area or sand mound on the upslope and sides only. Minimum depth for a subsurface drain shall be 36 inches. This depth shall be measured from the existing ground surface to the bottom of the drain excavation or six inches into compact till, whichever is greater. All drains shall have an approved outlet with a prescribed two and four-tenths inches positive slope or greater for every 100 feet of drain length. Drain outlets to the ground surface shall be fitted with an animal guard approved by the Health Officer.
(Ord. 2012-153, passed 4-16-2012)