The maximum contaminant level for turbidity is applicable to all suppliers of water using surface water sources, or ground water sources under the direct influence of surface water, in whole or in part. Until June 29, 1993, the maximum contaminant level for turbidity in drinking water, when measured at a representative entry point to the distribution system, is: 1 turbidity unit (TU), as determined by a monthly average pursuant to Regulation .12 of this chapter, except that 5 or fewer turbidity units may be allowed if this higher level of turbidity does not: Interfere with disinfection, Prevent maintenance of an effective disinfectant agent throughout the distribution system, and Interfere with microbiological determinations; 5 turbidity units (TU) based on an average of two samples collected on consecutive days. The Approving Authority may set turbidity performance requirements for filtration technologies other than conventional filtration treatment, direct filtration, slow sand filtration, or diatomaceous earth filtration as set forth in 40 CFR §141.173. If the Approving Authority has determined that a system shall install filtration and the system installs filtration after June 29, 1993, then the requirements of §B of this regulation shall continue to apply until filtration is installed. The turbidity standards for systems using a surface water source or a ground water source under the direct influence of surface water are as follows: Suppliers of water at all systems shall meet the turbidity requirements in 40 CFR §§141.70—141.75; Suppliers of water at systems serving 10,000 or more individuals shall meet the additional turbidity requirements in 40 CFR §141.173(a); and Beginning January 1, 2005, suppliers of water at systems serving fewer than 10,000 individuals shall meet the additional turbidity requirements of 40 CFR §§141.550— 141.553. Notwithstanding §A of this regulation, all unfiltered systems that are monitoring in accordance with the criteria to avoid filtration found in 40 CFR §§141.70—141.75 are subject only to the turbidity requirements of 40 CFR §§141.70—141.75.