(a) All requests for a variance or an exemption shall be in a form prescribed by and submitted in writing to the department. Suppliers of water may submit a joint request for variances or exemptions when they seek similar variances or exemptions under similar circumstances. The department shall act on any request for a variance or an exemption submitted pursuant to section 5-1.90, 5-1.91 or 5-1.92 of this Subpart within 90 days of receipt of the request.

(b) Requests for exemptions to the filtration requirements outlined in section 5-1.30(b) of this Subpart must be made by June 29, 1992, except for systems with groundwater sources determined to be directly influenced by surface water. For systems with groundwater sources directly influenced by surface water the request for an exemption must be submitted no later than six months after notification of the determination of direct influence. Before an exemption to a filtration requirement can be granted, the supplier of water must demonstrate to the department that the granting of the exemption will not pose an unreasonable risk to public health and that the system is in compliance with sections 5-1.30(c)(5), (c)(8), (g) and 5-1.52 tables 3, 6, 9 and 11 of this Subpart.

(c) Systems with unfiltered surface water sources or groundwater sources directly influenced by surface water must have a disinfection capability that achieves at least 99 percent inactivation of Giardia lamblia cysts before an exemption to a filtration requirement can be granted.