Section 58.01.13.204 - DESIGN CRITERIA FOR TAILINGS IMPOUNDMENTS01.Engineered Liner System. In addition to meeting the general liner requirements in Subsection 200.06.b., the engineered liner system plans and specifications must provide for the following. a. Geomembrane liners with a minimum thickness of sixty (60) milli-inches (one point five (1.5) mm) or equivalent liners approved by the Department.b. A system to limit hydraulic head over the geomembrane liner that preserves the integrity and long-term performance of the liner system and includes the following: i. A system to reduce excess pore pressure within the tailings; andii. A plan for managing the depth, area, and volume of process water occurring above the tailings surface and in direct contact with the liner, including thresholds and contingency measures to manage excess accumulation of process water in the facility.c. Monitoring points that will provide for early detection of discharges of pollutants.02.Enhanced Containment Criteria. An enhanced level of containment may be required by the Department for all of the tailings impoundment or for a portion thereof after considering the following factors:a. The anticipated characteristics of the material to be deposited;b. The characteristics of the soil and geology of the site;c. The methods employed and degree to which the hydraulic head on the liner is minimized;d. The extent of and methods used for material stabilization and recycling or neutralization of process water;e. Area and volume of process water;f. The depth from the surface to all ground water;g. The methods employed in depositing the impounded material; andh. The proximity to surface water and the ground water interactions with surface water.03.Tailings Treatment. Tailings impoundments are restricted to a maximum of fifty (50) mg/L WAD cyanide concentration in the liquid fraction unless otherwise approved by the Department.Idaho Admin. Code r. 58.01.13.204