(A) Limiting layer remediation. If a soil layer has a soil loading rate of zero gpd/ft2, either due to existing conditions, or caused by activity known to compact soil (e.g., vehicular/machine traffic, fill being deposited) deep chisel plowing may be performed to attempt to render the soil suitable. Suitability and loading rate shall be determined by a soil evaluation conducted by a Lake County Licensed Soil Classifier/Scientist in accordance with the requirements of §§ 171.085 through 171.089, after the deep chisel plowing has occurred. Deep chisel- plowing shall be performed as described in this section, based on the conditions of the site.
(1) For soil profiles comprised of 12 inches or more of fill deposited at the surface, chisel plowing shall be performed to a minimum depth of 12 inches.
(2) When one or more suitable surface horizons overlays a thin limiting layer that in turn overlays suitable soil, and the soil loading rate of the soil horizon below the limiting layer is greater than or equal to 0.2 gpd/ft2, chisel plowing shall extend through the limiting layer.
(3) When limiting surface soil horizon(s) overlay suitable soil, chisel plowing shall extend through the limiting soil horizon.
(B) Artificial drainage effectiveness investigation. When a soil evaluation performed in accordance with the requirements of §§ 171.085 through 171.089 establishes that soil is not suitable because it does not meet the requirements of § 171.087(A)(1), the Health Officer may approve an onsite wastewater treatment system when artificial drainage creates conditions such that the depth from the ground surface to the saturated soil is ten inches or more, and the proposed onsite wastewater treatment system meets the requirements of §§ 171.100 through 171.111.
(1) Monitoring. The artificial drainage system shall be installed as proposed, and the saturation depth of the soil shall be monitored, using monitoring wells or piezometers, by an Illinois Licensed Professional Engineer or a Certified Professional Soil Classifier/Soil Scientist and the Lake County Health Department.
(2) Agreement for investigation plan. The construction, installation and location of the monitoring wells or piezometers, and the frequency of observations shall be established through a written agreement between the Health Officer and the onsite wastewater treatment system designer.
(3) Monitoring period. Monitoring shall occur at least weekly during March, April and May with the first reading occurring no later than March 15.
(4) Monitoring data. Monitoring data may be used to establish the limiting layer as follows:
(a) Monitoring data submission. All monitoring data shall be submitted to the Health Officer no more than 60 days after the conclusion of the investigation.
(b) Depth observations and suitability assessment. The drains shall maintain an unsaturated zone of at least ten inches below the ground surface at all times. If at any time, water is observed at a depth shallower than ten inches, a reading shall be conducted two days later. If water is shallower than ten inches at this subsequent reading, the site shall be considered unsuitable for a soil based onsite wastewater treatment system.
(c) Monitoring data validity. Monitoring shall only be valid if the nearest precipitation recording station records a precipitation amount of at least 90% of the historical average during March, April and May. Artificially flooding the soil area being monitored to simulate naturally occurring seasonal saturation shall not substitute for precipitation.
(Ord. [Bd of Health Ord., Art. V], passed 11-12-1996; Ord. [Bd of Health Ord., Art. V], passed 11-12-2013)