(a)   Subdivisions. The owner shall submit plans and specifications of the sewage treatment system where such is required, together with the plans and specifications of the proposed water supply system, to the Health Department for approval, and such plans and specifications shall be approved prior to the start of any construction or building.
   The Health Director shall develop procedures to evaluate subdivisions served by on-site sewage treatment systems, consistent with the Land Subdivision and Development Ordinance and Facilities Standards Manual.
   Prior to construction on any lot, it shall be necessary to apply for and obtain a permit from the Health Department, and such permit shall be issued in accordance with the standards at the time the application is made. The Health Department shall take into consideration the specific proposal and the previous findings, but shall not be obligated by those findings should it later be determined that a health hazard would result by allowing installation of a soil absorption system.
   (b)   Individual Lots. A permit for construction of an onsite sewage treatment system on an individual lot or property shall be issued after completion of a satisfactory evaluation which indicates that such a system can be installed and is expected to perform in a sanitary manner so as not to create a health hazard.,
   (c)   Evaluation. Soil evaluation reports submitted for onsite sewage treatment system approval shall contain detailed soil/site investigations, as described in subsection (g) hereof. Evaluations shall indicate whether or not the soils meet the criteria specified herein for the installation of the type of on-site sewage treatment system proposed. In addition to information gathered during the soils and geotechnical investigation, the topography, available area, proximity to ground and drinking water supplies, proximity to bodies of water, rates of water absorption by the soil horizon proposed for use, or a combination of any of the above, shall also be considered in such evaluation. If absorption rate problems are suspected, percolation tests or other infiltration tests may be required, but their results shall not be presumptive, prima-facie or conclusive evidence as to the suitability for effluent absorption. Soil reports shall be field reviewed by the Health Department unless administratively denied or deemed approved. Backhoes are required for Health Department soil/site evaluations and verifications of private sector submitted soil/site evaluations unless waived by the Health Department.
   (d)   Plot and Structure Identification. A plot, prepared by the applicant, is to accompany all applications for permits to construct on-site sewage treatment systems and must show accurately:
         (1)   The dimensions of the property.
         (2)   Proposed and/or existing structures and driveways.
         (3)   Underground utilities.
         (4)   Adjacent sewage treatment systems.
         (5)   Bodies of water.
         (6)   Drainageways and floodplains.
         (7)   Wells and springs within a 200-foot radius of the edge of the proposed onsite sewage treatment system.
   (e)   Physical Features.
      (1)   Pad and trench soil absorption systems shall not be placed on slopes greater than twenty-five percent.
      (2)   Placement of subsurface soil absorption systems in disturbed soil is prohibited.
      (3)   Outside of the Limestone Overlay District no onsite sewage treatment system shall be placed closer than 100 feet from the low point of a sinkhole nor closer than fifty feet from the outer edge of a sinkhole. Sinkholes will be considered to exist with or without knowledge of the size, orientation or presence of subterranean voids, since the surface collapse evidences subsidence into such a void. Distances from rock outcrops may be imposed and additional geologic information required in accordance with a geotechnical report, as described in Section 6.150 of the Loudoun County Facilities Standards Manual, where limestone or other environmentally critical rock formations are encountered.
      (4)   Within the Limestone Overlay District no onsite sewage treatment system shall be placed closer than 100 feet from the rim of a sinkhole/swallet/closed depression, from a cave opening, or from a perennial sinking stream. Nor shall an onsite sewage treatment system be placed closer than fifty feet from a rock outcrop, or underground solution channel within 45 feet of the surface. Such setback may be reduced by up to fifty percent if a geophysical study, as required by Section 4-1905 of the Revised 1993 Zoning Ordinance, as amended, conducted in accord with Section 6.151 of the Facilities Standards Manual, concludes that the risks of collapse and groundwater contamination are non-existent or insignificant for the proposed location and use. No setback reduction shall be allowed for any perennial sinking stream, nor for any sinkhole, swallet, closed depression or cave opening that receives an intermittent or perennial sinking stream. No onsite sewage treatment system shall be placed closer than: (1) one hundred (100) feet from a developed spring, measured from the first emergence of the spring or (2) two hundred (200) feet from a developed spring when the first emergence of the spring is downslope from the proposed sewage disposal system. However, for a lot of record existing on February 17, 2010, an onsite sewage treatment system for a principal residential structure may be permitted within the setback if it is constructed in compliance with all recommendations of the geophysical study and such system is sited on the lot so as to be located as far from the feature as is feasible. No such onsite sewage treatment system shall be allowed if the geophysical study shows subsidence or groundwater contamination poses a serious risk to public health or safety or to the safety of residents or users of the residential structure unless the design of the system is certified, both structurally and geotechnically, by a professional engineer.
   (f)   Soil Profiles.
      (1)   Depth of profile hole. The minimum depth of the profile hole shall be six feet, or deep enough to verify all stand offs unless prevented or made unnecessary by some physical feature of the soil, such as redoximorphic features, rock or when a potential horizon is found at a lesser depth. When a potential soil horizon is considered for use, the soil evaluation shall be extended below the soil horizon, with potential for use, to insure that there is no interference with seasonal water tables, lithic rock, paralithic rock or other impervious strata within the vertical offset limitation.
      (2)   Number and location of profile holes. A minimum of five holes is necessary to determine the design requirements of an area for the placement of any soil absorption area. Holes shall be evenly placed to bound the area under consideration with one hole installed in the center. If more than one area is required in which to install the soil absorption area, each area shall be evaluated with at least three soil borings. The actual area and number of borings necessary shall be determined on a case-by-case basis.
   (g)   Requirements for a detailed soil/site evaluation. Detailed soil-site evaluation reports generated for any proposed on-site sewage treatment system are required by and are to be submitted to the Health Department. A detailed investigation may also be required by the Health Director for specialized land use applications such as solid waste operations, composting facilities or other similar uses.
   The detailed soil/site evaluation report should include the following, where appropriate, unless determined by the Health Director, at the request of the developer, to be inapplicable based upon sound engineering principals:
      (1)   Results of field investigation.
         A.   A map, drawn to 1:2,400 scale (1 inch = 200 feet) and larger, as requested on a sheet twenty-four inches by thirty-six inches. Where small tracts are involved, an eight by eleven-inch sheet may be acceptable, provided it complies with all other requirements set forth herein.
         B.   Existing water supplies within 100 feet of the property and 200 feet of sewage treatment systems on the property.
         C.   The location of all borings and backhoe pits. Test holes/pits are to be numbered and located dimensionally, including surface elevations.
         D.   The location of all numbered proposed on-site soil absorption areas, if applicable. All soil absorption areas must be shown on contour and delineated by five borings or pits. In addition, site locations within the Limestone Overlay District and those underlaid by limestone/limestone conglomerate, shall be examined in cross section to a depth of 45 feet minimum, using technology such as electrical resistivity, to determine the presence of karst features. Karst features, such as voids and solution channels, may be grounds for denial of the site.
         E.   The following items as they relate to the proposal, if required:
            1.   The landscape type and position, the slope, topography and the surface drainage.
            2.   The soil morphology, including the texture, color, structure, consistency, depth, lithologic discontinuities, boundaries, etc.
            3.   The permeability, internal drainage and perched water tables.
            4.   The parent material and associated problems.
            5.   Restrictive strata.
         F.   The soil evaluation form.
      (2)   The following items shall be required in the report when soil absorption areas are proposed:
         A.   Depth of installation, type of system, relative suitability and modifications.
         B.   Recommendations and conclusions for repairing existing malfunctioning on-site sewage treatment systems.
         C.   Potential impacts on ground and surface water.
      (3)   Field logs. Soil profile descriptions taken from soil boring/backhoe pits shall include:
         A.   The boring/pit number.
         B.   The depth, thickness and description of each horizon, including paralithic and lithic contacts encountered.
         C.   Locations of all samples taken and analyses to be conducted on each sample.
         D.   The depth to perched water and/or the ground water table if observed (or if indicated by soil color patterns).
         E.   The name of the person responsible for the description and sampling.
      (4)   Field testing. If field tests, such as percolation tests or other permeability tests, have been conducted, the results shall be included.
         A.   Percolation tests.
         B.   Permeability tests, including a description of the profile.
         C.   Piezometer observations, including readings, depth, date of readings, rainfall data and soil profile (if available for the site).
      (5)   Laboratory data. Laboratory data produced to support the report shall be included.
(Ord. 94-05. Passed 2-16-94; Ord. 10-02. Passed 2-17-10; Ord. 10-05. Passed 5-4-10; Ord. 17-03. Passed 1-19-17.)