Hawaii Administrative Rules › Title 11 - DEPARTMENT OF HEALTH › Subtitle 1 - GENERAL DEPARTMENTAL PROVISIONS › Chapter 20 - RULES RELATING TO PUBLIC WATER SYSTEMS › Appendix B - ROUTINE MONITORING FREQUENCY FOR TTHM AND HAA5 (HAR Section 11-20-45.1(c)(2)(A))

Current through June, 2024
Type of System
Minimum Monitoring Frequency
Sample Location in the distribution system
Subpart H system serving at least 10,000
							 persons.
Four water samples per quarter per treatment
							 plant.
At least 25 per-cent of all samples collected each
							 quarter at locations representing maximum residence time. Remaining samples
							 taken at locations representative of at least average residence time in the
							 distribution system and representing the entire distribution system, taking
							 into account number of persons served, different sources of water, and
							 different treatment methods1.
Subpart H system serving from 500 to 9,999
							 persons.
One water sample per quarter per treatment
							 plant.
Locations representing maximum residence
							 time1.
Subpart H system serving fewer than 500
							 persons.
One sample per year per treatment plant during month
							 of warmest water temperature.
Locations representing maximum residence
							 time1. If the sample (or average of annual samples,
							 if more than one sample is taken) exceeds MCL, system must increase monitoring
							 to one sample per treatment plant per quarter, taken at a point reflecting the
							 maximum residence time in the distribution system, until system meets reduced
							 monitoring criteria in HAR §
													11-20-45.1(c)(2)(A)(iv).
System using only ground water not under direct
							 influence of surface water using chemical disinfectant and serving at least
							 10,000 persons.
One water sample per quarter per treatment
							 plant2.
Locations representing maximum residence
							 time1.
System using only ground water not under direct
							 influence of surface water using chemical disinfectant and serving fewer than
							 10,000 persons.
One sample per year per treatment
							 plant2 during month of warmest water
							 temperature
Locations representing maximum residence
							 time1. If the sample (or average of annual samples,
							 if more than one sample is taken) exceeds MCL, system must increase monitoring
							 to one sample per treatment plant per quarter, taken at a point reflecting the
							 maximum residence time in the distribution system, until system meets criteria
							 in HAR §
													11-20-45.1(c)(2)(A)(iv).
1If a system elects to sample more
				  frequently than the minimum required, at least 25 percent of all samples
				  collected each quarter (including those taken in excess of the required
				  frequency) must be taken at locations that represent the maximum residence time
				  of the water in the distribution system. The remaining samples must be taken at
				  locations representative of at least average residence time in the distribution
				  system.
2Multiple wells drawing water from
				  a single aquifer may be considered one treatment plant for determining the
				  minimum number of samples required, with State approval in accordance with
				  criteria developed under HAR §
									11-20-45.1(c)(1)(B).