Agenda - 09-05-2024; 8-l - Major Subdivision Preliminary Plat Application

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7 blue hatched soil areas with the county health dept and use backhoe pits to evaluate the underlying soils/saprolite to determine the best septic options for these areas. Pretreatment drip are expensive septic systems that may require additional soils work& soil hydraulic conductivity (Ksat)testing and a wastewater engineered design. Unit"UN" on the attached map indicates areas of soils that are less than 13 inches to prohibitive soil characteristics or are unsuitable areas due to landscape position and are generally unsuitable for the type of systems mentioned above. Unit"NE" on the attached map indicates areas that were not evaluated due to existing gravel road and/or large overhead power lines. There are some small overhead power lines on the property that may need to be rerouted when a subdivision is developed. The site plan for each lot must ensure that adequate soil area for system and repair is unaffected by site elements (house placement, driveway, wells, patios, decks, etc.) on that or adjacent lots. The area ultimately designated by the health department on the site plan for the septic system and repair must remain undisturbed(no mechanical clearing, excavation, heavy traffic or other significant site disturbing activities)until authorized by the health department and/or state permitting agency. A lot with initially adequate useable soil area may be rendered unusable as a result of improper site planning and/or disturbance. A field layout of the proposed septic systems may be required as part of the individual lot development process. ORANGE COUNTY REGULATIONS During the subdivision recordation process, Orange County requires a backhoe and backhoe operator to dig pits to evaluate the soils for septic suitability on each lot for subdivisions with 6 or more proposed lots. Any lots/houses proposed with more than 600 gallon per day daily design flow (more than a 5-bedroom house) will require a backhoe and backhoe operator to dig pits for the county heath dept's soils evaluation as well. The cost and coordination of the backhoe and backhoe operator is the responsibility of the septic permit applicant. GENERAL WASTEWATER CONSIDERATIONS Once potentially useable areas are located through vertical borings, the next consideration is the horizontal extent of those areas. The size and configuration of the useable soil area dictate the utility of that area. The size of a subsurface disposal field is determined by: 1)the design flow from the source (120 gallons/bedroom/day in residences), and 2)the long term acceptance rate (LTAR) of the soil (based on the hydraulic conductivity of the soil, a function of the soil's texture, mineralogy, structure,porosity, etc.). The configuration must be such that an efficient layout of disposal lines (on contour) is possible. An additional consideration is the required setbacks for the system from various elements such as wells (50' to 100'), streams and ponds (-80') or more (depending on watershed regulations),property lines (10'), top of embankment (15'), watershed buffers, etc. (see Attachment 1). The utility of a potential useable soil area for a subsurface system is most accurately determined by an on-ground layout of the proposed system. The total area needed for system and repair areas will depend upon the system type, the layout of that system and the total design flow (factors mentioned above). A typical area needed for a 4 bedroom residence is approximately 14,000 to 16,000 ft2 (could be more depending on site features) or 880 to 960 linear feet of conventional line (system and repair) or 1,164 to 1,280 linear feet of low profile chamber line (system and repair). These estimates reference Laws and Rules for Sewage Treatment and Page 2 of 4