Glossary of Terms 80/60 - 80 µg/L (0.080 mg/L) TTHM and 60 µg/L (0.060 mg/L) HAA5. This is MCL for current Stage 1 DBPR compliance using RAA at existing Stage 1 DBPR locations, and eventual MCL during Stage 2 DBPR will also be 80/60 but it will be based on LRAA at new state-approved Stage 2 DBPR locations 40/30 certification - PWS that have: a) collected all required Stage 1 DBPR samples, b) never had any TTHM or HAA5 monitoring violations, and c) did not have any TTHM or HAA5 values (this means all individual samples, not just LRAA or RAA) in a prescribed two-year period that were above 40 µg/L TTHM or 30 µg/L HAA5. For the latter item, the prescribed two-year period depends on system size. The two-year period for systems serving 50,000 or more people can not begin earlier than January 2004, and January 2005 for systems serving <50,000 people. Combined distribution system - one or more wholesale systems interconnected to one or more consecutive systems Consecutive system - a PWS that receives some or all of its finished water from a wholesale system or another consecutive system DBP - disinfection by-product DBP precursor - a substance that is not itself a DBP, but which can react with a disinfectant to produce a DBP (for example, NOM that reacts with free chlorine to produce TTHM) DBPR - DBP Rule, including current Stage 1 DBPR and pending Stage 2 DBPR DOC - dissolved TOC (as opposed to particulate TOC) Dual sample set - means that both a TTHM and HAA5 sample are collected at one location during the same sampling event. Dual sample sets are required for all locations for both IDSE and for Stage 2 DBPR compliance, including all IDSE samples. During compliance monitoring, there will be one exception –groundwater systems serving <10,000 people and surface water systems serving <3,300 will only be required to collect one sample for TTHM and one sample for HAA5 per sample event for the entire PWS, meaning this can be a TTHM and HAA5 sample from the same location or TTHM at one location and HAA5 at a different location. Evaluation Report - Report to be completed by PWS at completion of IDSE. This report summarizes IDSE results, evaluates data from these locations and Stage 1 DBPR locations, and then includes the identification and justification of the locations recommended as future Stage 2 DBPR compliance monitoring points. State must review and approve these proposed locations for Stage 2 DBPR monitoring. HAA - Haloacetic acids, typically referring to chloro, bromo, or mixed chloro-bromo acetic acid compounds. There are nine possible compounds, five of these specific compounds are regulated in drinking water as HAA5. HAA5 - Sum of 5 specific HAAs currently regulated by Stage 1 DBPR and to be regulated by Stage 2 DBPR. Includes mono-, di-, and tri-chloro acetic acid and mono- and di-bromo acetic acid IDSE - Initial Distribution System Evaluation. The component of the Stage 2 DBPR intended to evaluate new locations in the system, particularly focusing on locations where TTHM and HAA5 are highest, to serve as future monitoring locations for the Stage 2 DBPR. IDSE sampling plan - Report submitted prior to initiation of IDSE identifying the locations proposed by the PWS for the IDSE. This report should include data, model results, and other information used by the PWS to justify the locations identified. This report would also propose dates when samples are to be collected (e.g., if August was identified as peak month, PWS might propose collecting samples on second Tuesday of February, April, June, August, October, and December). The PWS must follow a state approved plan when conducting the IDSE, including state approval of location and sampling dates. LRAA - locational running annual average is the average of compliance samples collected at one location for a one year period. For a system collecting four quarterly samples at four monitoring locations, the LRAA is calculated at each of the four locations by averaging four quarterly values, the most recent quarterly value and results from the previous three quarters. Therefore, in this example there will be four LRAA values calculated each quarter, one for each location. Three years after the maximum LRAA for all of the state approved Stage 2 DBPR monitoring locations MCL - Maximum contaminant level. The MCL for TTHM/HAA5 during the current Stage 1 DBPR is 80/60 based on RAA using current Stage 1 DBPR locations. Eventually MCL will be 80/60 based on LRAA at new Stage 2 DBPR locations. Operational evaluation - A series of operational actions and evaluations to be conducted by the PWS whenever the TTHM or HAA5 result (or bromate or chlorite for systems with ozone or chlorine dioxide) for a given quarter would result in an exceedance of the 80/60 LRAA at this location if the result from the current quarter were repeated in the next quarter. For example, if the TTHM results for the previous two quarters were 100 and 80 µg/L, then a result of 71 µg/L or higher will trigger an “operational evaluation”. Details regarding the PWS activities during the operational evaluation will be described in a separate USEPA published Guidance Manual. The events triggering “operational evaluation” were formerly called “significant excursions” in the USEPA Draft version of the Stage 2 DBPR. Some people have also previously referred to these events by the term “significant exceedance”. PWS - Public water system, as defined by USEPA RAA - running annual average, calculated every quarter by taking the average of the current quarterly average and the three previous quarterly averages (i.e., RAA for 2nd quarter of 2005 will be calculated using quarterly average in 1st and 2nd quarter of 2005 along with 3rd and 4th quarters of 2004). Another way to calculate the RAA is to average the LRAA values. SDS - simulated distribution system procedure. Also called a “formation potential”. A test (described in Standard Methods, 5710 C & D) to estimate production of TTHM and other DBPs under conditions similar to those in the distribution system (e.g., pH, temperature, maximum residence time, etc., except typically does not mimic biodegradation from pipe biofilm) Significant exceedance - See “operational evaluation” Significant excursions - See “operational evaluation” Stage “2A” - This term was formerly used during Draft versions of the Stage 2 DBPR to refer to a transition phase prior to 80/60 LRAA compliance at new Stage 2 DBPR locations. However, this transition phase has been dropped in the final version of the Rule, and hence the term "Stage 2A" is no longer needed. Stage “2B” - This term was formerly used in Draft versions of the Rule to refer to the period after "Stage 2A". Both terms "Stage 2A" and "Stage 2B" are no longer relevant and have been removed from the final version of the Rule. Stage 1 DBPR - Current DBPR, including 80/60 RAA at current Stage 1 DBPR monitoring locations. Stage 2 DBPR - Pending DBPR, including IDSE and eventual 80/60 LRAA at new locations selected for Stage 2 DBPR compliance using mostly peak TTHM and HAA5 locations in the distribution system identified during the IDSE. THM - Trihalomethanes, referring to four halogen-substituted methane compounds containing chlorine or bromine, including chloroform (CHCl3), bromodichloromethane (CHCl2Br), chlorodibromomethane (CHClBr2), and bromoform (CHBr3) TOC - Total organic carbon, including both dissolved and particulate TOC TTHM - total THMs, the sum of four regulated chlorine and/or bromine containing THMs VSS - a “very small systems” waiver for the IDSE can be granted by State for systems serving <500 people that have collected all required Stage 1 DBPR samples. State can still choose to require a system that meets these requirements to do an IDSE. All systems that get a VSS waiver will continue to use their Stage 1 DBPR monitoring locations as their compliance locations for Stage 2 DBPR. Wholesale system - PWS that treats source water and delivers some or all of their finished water to another PWS Last Updated: January 26, 2006