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newSchoolWorks.com › VoTechWorks › Agriculture, Environment & Public Service › Water / Wastewater Operator › Water and Wastewater Regulations › Lesson 4
AGR-WATE71-06 · Lesson 4 · 12.5 clock hours · theory

Lead and Copper Rule and Disinfection Byproduct Rules

Objective. Students will explain the monitoring, action level, and public notification requirements of the Lead and Copper Rule and the Stage 2 Disinfectants and Disinfection Byproducts Rule.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a licensed professional in the field or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

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Lead and Copper Rule Overview

The Lead and Copper Rule (LCR) is a federal regulation under the Safe Drinking Water Act, administered by the U.S. Environmental Protection Agency (EPA) and enforced by state drinking water programs. Its purpose is to minimize exposure to lead and copper in drinking water, primarily because these metals can leach into water from household plumbing, solder, and service lines — not from the original source water or treatment plant itself. Lead exposure is especially dangerous for children and pregnant women, causing developmental and neurological harm. Copper at high levels causes gastrointestinal illness.

Action Levels and How They Work

The LCR does not set a maximum contaminant level (MCL) for lead or copper in the traditional sense. Instead, it establishes action levels (ALs). If results exceed an action level, the utility must take specific corrective steps.

These action levels are evaluated using the 90th percentile of tap water samples collected from targeted sampling sites. A system exceeds the action level when the 90th percentile result is greater than the AL — not when any single sample exceeds it.

Sample Site Selection

The LCR requires utilities to sample at first-draw tap water sites — meaning water that has sat in the pipes for at least six hours without being used. Sites are selected based on their likelihood of having high lead or copper exposure. Priority goes to homes with lead service lines, homes with lead solder installed after 1982, and homes with copper pipes with lead solder. Each system must maintain a tiered list of sampling sites and collect a required minimum number of samples based on system size.

Calculating the 90th Percentile

To determine whether the action level is exceeded, follow these steps:

1. Collect the required number of first-draw samples.

2. Rank all results from lowest to highest.

3. Multiply the total number of samples by 0.90 and round up to the next whole number.

4. The result at that position in the ranked list is the 90th percentile value.

5. Compare the 90th percentile value to the action level.

For a ten-sample set, the 90th percentile position is the 9th result (10 × 0.90 = 9.0, so position 9).

Public Notification and Corrective Action

If the 90th percentile exceeds the lead or copper action level, the utility must:

Public notification requirements have specific timeframes and formats set by EPA and state regulations. Operators must know their state's deadlines.

Stage 2 Disinfectants and Disinfection Byproducts Rule

When utilities disinfect water using chlorine or chloramines, chemical reactions with naturally occurring organic matter in the water can form disinfection byproducts (DBPs). The Stage 2 D/DBP Rule targets two main groups:

These byproducts are associated with increased cancer risk and adverse reproductive outcomes with long-term exposure.

Locational Running Annual Average (LRAA)

The Stage 2 rule uses the locational running annual average (LRAA) rather than a system-wide average. Each monitoring location in the distribution system is evaluated individually. The LRAA is calculated by averaging the four most recent quarterly sample results at each specific location. If the LRAA at any single location exceeds the MCL, the system is in violation — even if the system-wide average is acceptable. This is more protective than Stage 1, which used a single system-wide average.

Required Response When DBP Levels Are Exceeded

If an LRAA at any location exceeds the TTHM or HAA5 MCL, the utility must:

Safety Considerations

When collecting tap water samples, operators must follow standard sampling protocols and avoid contamination. When working with disinfectant chemicals (chlorine gas, sodium hypochlorite, chloramines), always wear appropriate PPE: chemical-resistant gloves, splash goggles, and a face shield when handling concentrated solutions. If chlorine gas is in use at the facility, know the location of the self-contained breathing apparatus (SCBA) and emergency evacuation routes. Follow lockout/tagout (LOTO) procedures when performing maintenance on chemical feed systems. Never mix chlorine with ammonia-based compounds outside of a controlled, engineered chloramination process.

Key Takeaway

Operators must understand both rules deeply because non-compliance can result in state enforcement action, fines, and most importantly, public health harm. Accurate sampling, correct 90th percentile calculation, timely reporting, and proper public notification are all operator responsibilities that appear on licensing exams.

Key terms8

Action Level (AL)A concentration of lead or copper in drinking water that, if exceeded at the 90th percentile of tap water samples, triggers required corrective actions by the utility; not the same as a maximum contaminant level.
90th PercentileA statistical value used in the Lead and Copper Rule; calculated by ranking sample results from lowest to highest and selecting the value at the 90th percentile position, used to determine if an action level is exceeded.
First-Draw SampleA tap water sample collected after water has stood in the plumbing for at least six hours without use, designed to capture water most likely to contain leached lead or copper.
Disinfection Byproducts (DBPs)Chemical compounds formed when disinfectants such as chlorine react with naturally occurring organic matter in water; regulated because of potential long-term health risks including cancer.
Total Trihalomethanes (TTHMs)A group of regulated disinfection byproducts including chloroform and related compounds; the MCL under the Stage 2 D/DBP Rule is 0.080 mg/L evaluated as a locational running annual average.
Haloacetic Acids (HAA5)A group of five regulated disinfection byproduct acids formed during chlorination; the MCL under the Stage 2 D/DBP Rule is 0.060 mg/L evaluated as a locational running annual average.
Locational Running Annual Average (LRAA)The average of the four most recent quarterly sample results at a single monitoring location in the distribution system, used under the Stage 2 D/DBP Rule to evaluate compliance at each individual site.
Corrosion Control TreatmentA water treatment strategy, such as pH adjustment or addition of corrosion inhibitors, used to reduce the leaching of lead and copper from pipes and plumbing into drinking water.

Worked examples4

1. A community water system collects 10 first-draw lead samples as required under the LCR. The results in µg/L are: 2, 4, 5, 7, 9, 12, 14, 18, 22, 30. Does the system exceed the lead action level?
  1. Step 1 – Rank the results from lowest to highest: 2, 4, 5, 7, 9, 12, 14, 18, 22, 30.
  2. Step 2 – Determine the 90th percentile position: multiply the number of samples by 0.90. 10 × 0.90 = 9.0. Because the result is a whole number, use position 9.
  3. Step 3 – Identify the value at position 9 in the ranked list: the 9th value is 22 µg/L.
  4. Step 4 – Compare the 90th percentile result to the lead action level of 15 µg/L (0.015 mg/L). 22 µg/L > 15 µg/L.
Answer: The 90th percentile result is 22 µg/L, which exceeds the lead action level of 15 µg/L. The system must initiate required corrective actions and notify the state.
2. A different system collects 10 first-draw lead samples with results in µg/L: 1, 2, 3, 4, 5, 6, 8, 10, 13, 20. Does this system exceed the lead action level?
  1. Step 1 – Rank the results from lowest to highest (already ranked): 1, 2, 3, 4, 5, 6, 8, 10, 13, 20.
  2. Step 2 – Determine the 90th percentile position: 10 × 0.90 = 9.0. Use position 9.
  3. Step 3 – Identify the value at position 9: the 9th value is 13 µg/L.
  4. Step 4 – Compare to the lead action level: 13 µg/L < 15 µg/L.
Answer: The 90th percentile result is 13 µg/L, which does not exceed the lead action level of 15 µg/L. No corrective action is triggered for lead, though monitoring must continue.
3. A monitoring location in a distribution system has the following quarterly TTHM results over one year (in µg/L): Q1 = 62, Q2 = 78, Q3 = 88, Q4 = 74. Does the LRAA at this location exceed the TTHM MCL?
  1. Step 1 – Identify the four quarterly results: 62, 78, 88, and 74 µg/L.
  2. Step 2 – Calculate the average (LRAA): add all four values. 62 + 78 + 88 + 74 = 302.
  3. Step 3 – Divide by 4: 302 ÷ 4 = 75.5 µg/L.
  4. Step 4 – Compare the LRAA to the TTHM MCL of 80 µg/L. 75.5 µg/L < 80 µg/L.
Answer: The LRAA at this location is 75.5 µg/L, which is below the TTHM MCL of 80 µg/L. This location is currently in compliance, but the operator should monitor the trend since Q3 was 88 µg/L.
4. At another location, quarterly HAA5 results (in µg/L) are: Q1 = 55, Q2 = 64, Q3 = 70, Q4 = 61. Does the LRAA exceed the HAA5 MCL?
  1. Step 1 – List the four quarterly HAA5 results: 55, 64, 70, 61 µg/L.
  2. Step 2 – Sum the results: 55 + 64 + 70 + 61 = 250.
  3. Step 3 – Divide by 4 to get the LRAA: 250 ÷ 4 = 62.5 µg/L.
  4. Step 4 – Compare to the HAA5 MCL of 60 µg/L. 62.5 µg/L > 60 µg/L.
Answer: The LRAA at this location is 62.5 µg/L, which exceeds the HAA5 MCL of 60 µg/L. The system is in violation at this location and must report to the state and issue public notification.

The math in this lesson1

Learners rank ten lead results and find the 90th percentile value, 22 µg/L, against the action level.
S-ID.2
Brush up in the math halls at newSchoolWorks.com:
In class: Guided reading of the Lead and Copper Rule action levels for lead and copper; students work through the sample site selection criteria and calculate whether a 90th percentile result exceeds the action level using a provided data set. · Review of the Stage 2 D/DBP Rule: students identify which disinfection byproducts are regulated (total trihalomethanes and haloacetic acids), the locational running annual average concept, and required response when levels are exceeded. · Role-play: one student acts as the state compliance officer, another as the utility operator; the operator must explain their system's LCR monitoring plan and DBP results and answer compliance questions.
Materials: EPA Lead and Copper Rule summary, Stage 2 D/DBP Rule fact sheet, sample monitoring data sets, action level reference card, role-play scenario cards
Check: Students correctly calculate the 90th percentile result from a ten-sample data set and state whether it exceeds the action level; 100% accuracy required on this calculation.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

Regulations and Compliance
1. Under the Lead and Copper Rule, what concentration represents the action level for lead in drinking water?
Regulations and Compliance
2. A system collects 10 first-draw lead samples. To find the 90th percentile result, the operator should look at which position in the ranked data set?
Sampling and Monitoring
3. Which type of sample is required under the Lead and Copper Rule to capture water most likely to contain leached metals?
Regulations and Compliance
4. Under the Stage 2 D/DBP Rule, compliance with the TTHM and HAA5 MCLs is evaluated using:
Regulations and Compliance
5. The MCL for total trihalomethanes (TTHMs) under the Stage 2 D/DBP Rule is:
Regulations and Compliance
6. A utility's 90th percentile copper result from LCR sampling is 1.1 mg/L. What is the correct conclusion?
Treatment Processes
7. Disinfection byproducts such as TTHMs and HAA5 are formed primarily when:
Regulations and Compliance
8. When a utility's LRAA for HAA5 exceeds the MCL at one monitoring location, which of the following actions is required?
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