(a)   Depth and size. The maximum cover over a tank containing wastewater shall not exceed 48 inches. In no case shall septic tank capacity be less than 750 gallons.
   (b)   Location. Tanks shall not be placed in concave areas or drainage ways. Tanks shall be protected with controlled backfill when shrink-swell soil or rock is present. If water table indications are observed or measured above penetrations or tank seams, a water table reduction system must be installed to lower the water table below the seam or penetration.
   (c)   Structural Soundness. Tanks shall be structurally sound as determined by an engineer design with appropriate safety factors, and watertight verified through appropriate testing and compliance monitored by the Health Department. All tanks shall be designed and certified by a professional engineer, licensed and qualified to perform structural design in the Commonwealth of Virginia. The engineer shall contemplate all reasonably expected loading conditions, including burial depth, tank full to top of riser, an empty tank installed with water table at top of ground, vehicular traffic and any other reasonable expected loading conditions. The manufacturer shall certify that all tanks manufactured meet the engineer design. Tanks may only be installed in accordance with the design standards specified.
   (d)   Buoyancy. Septic tanks and pump chambers shall implement buoyancy controls where seasonal water table is a concern.
   (e)   Penetrations. All tank lids shall be manufactured with the first section of risers pre-cast into the top of the tank. Risers shall terminate a maximum of six inches below finished grade. Manufacturers shall install watertight boots at all penetrations. Boots for all tanks must meet ASTM C-923. Boots for concrete tanks must meet ASTM C-923 and have a clamp assembly to resist pipe deformation.
   (f)   Tank Testing. All tanks shall be watertight, including inlet and outlet pipe penetrations, and the riser assembly. The installer shall, on all watertight tanks, complete one of the following tests during, or in conjunction with a Health Department or other approved construction inspection. In high water table conditions the Health Director is authorized to require a water tightness test of the entire treatment and conveyance system.
      (1)   Water test procedure. A water test is to be performed by installing the tank, connecting inlet and outlet piping, installing risers as necessary, and filling with water above tank top outer surface into the riser for 24 hours. The tank penetrations and seams must be visible. The water level is to be marked in the riser. The tank is to be refilled to the mark and observed for one hour. If the level has not dropped the tank passes.
      (2)   Vacuum test procedure. A vacuum test is performed by plugging inlet and outlet piping, installing risers, and using a vacuum pump to pull a negative pressure of two and one half (2.5) inches of mercury. The tank must hold this vacuum for five minutes with no more than a 10% variation in pressure.
         If tanks fail either test, repairs must be completed using manufacturer approved materials and the test repeated until satisfactory.
(Ord. 09-19. Passed 12-15-09; Ord. 17-03. Passed 1-19-17.)