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Frequently Asked Questions

Lead and Copper Sampling Guidance

This guidance is for water system operators and sampling agents with specific questions on Lead and Copper sampling, and does NOT include the many other requirements required by these rules. Please refer to the additional information links and contacts at the end of this fact sheet for other questions and compliance requirements.

  • Why aren’t all the sampling sites on the Analysis Request Form?
    When a water system submits 10 or more samples in rounds 1 and 2 and achieves 90th percentile values below the action levels, they are put on a reduced sampling schedule. In these cases, the number of samples needed is reduced by half and the analysis request form will only show half the total number of sites for the system.

    Please note that if a site has been made inactive, it will not show on the analysis request form; you may request an inactive site be made active and it will appear on your form. You may contact us at any time for a copy of your full site list.

    Your sampling sites are selected to represent a variety of locations in your distribution system. The Master Sampling Schedule lists even numbered sites one round and odd numbered sites the next round. YOU MAY CHOOSE TO SAMPLE AT ANY ACTIVE SITE unless otherwise directed by DWGB.

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  • How do I add or change a sampling site?
    You can add a new sampling site at any time, provided that it meets the requirements of a sampling location. You can find this information on the Lead and Copper sampling instructions Adobe Acrobat Reader Symbol. You should always submit a site change request BEFORE you take your routine Lead and Copper samples. This will ensure that DWGB has the newly updated sampling sites in our database and will be able to accept the sampling results. In order to add a site, DWGB needs to receive your request in writing by email, fax or regular mail. DWGB will review the requested site change and notify you when the change has been made

    If a street or a room is renamed and/or renumbered, or if the use of a room changes and the description is no longer accurate, you can contact us with the update in writing. We will make the change and notify you when it has been completed.

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  • Can I sample at fewer locations?
    Since the number of required samples is based on the population, you need to update the DWGB with any population change first. We will then look at the number of required samples based on the updated population. If we make the change, we will notify you when it has been completed so that you will be able to obtain an updated Master Sampling Schedule.

    The number of required sampling sites is based on the total population served using the information found in our database. If you have a seasonal system it may be appropriate to consider requesting a change in the sampling schedule to a time when the residency rate is highest.

    You should make an assessment of your ability to sample a sufficient number of sites during a projected sampling quarter. Prior to, or after the scheduled sampling period, you may request a change based on seasonal residence.

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  • Why is our Master Sampling Schedule wrong or holding old data?
    If you ever notice a discrepancy on your Master Sampling Schedule, please contact the Lead and Copper program. In some instances the issue can be resolved by simply bringing it to our attention.

    When systems are on an accelerated reduced schedule, the Master Sampling Schedule cannot accurately reflect the correct sampling period. In any case we would be happy to look up and explain the particulars for your water system.

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  • What is an action level and a 90th percentile value?
    The specified action level for Lead is 0.015 milligrams per liter (mg/L) and the action level for Copper is 1.3 mg/L.

    These action levels represent the concentration of Lead or Copper in drinking water above which a water system may be required to complete corrective actions such as installing treatment.

    Compliance with the Lead and Copper rule is determined by comparing the 90th percentile of results (which is a statistical calculation performed by DES) with the established Federal Action Level (“AL”). These calculations are found online within your public water system information page. Please be aware that if the 90th percentile exceeds the AL for either Lead or Copper in the first round, you must stop additional sampling and we will be in contact with further instructions.

    The goal is to ensure that no more than 10 percent of the population served has Lead or Copper present in amounts above the action level by comparing it to the calculated 90th percentile value.

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  • What am I supposed to do for Routine Water Quality?
    If the results from the compliance samples indicate an exceedance after the treatment is installed, the system must collect routine water quality samples to determine why the treatment is not working correctly.

    At a minimum, the routine water quality measurements include pH and alkalinity taken at the Distribution Entry Point(s) every two weeks; also once every quarter from at least one distribution site (the number of distribution sites sampled is based on population).

    The information that should be reported quarterly to the DWGB includes water system name, PWS ID, collector’s name and collection dates, followed by the biweekly measurements of temperature, pH and alkalinity.

    DWGB has a Routine Water Quality Reporting formMicrosoft Word Symbolavailable for your use. You may use your own form provided all the required information is included.

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  • Can we just resample at one bad site?
    Most often the answer is no, but there are circumstances where this could be allowed.

    Adding one more sample result would not change the 90th percentile calculation enough to achieve levels of Lead and/or Copper below the action level(s).

    If you believe that one of the samples taken signifies a temporary or otherwise non-representational result you can submit your reasons with a request to invalidate the sample for consideration. You must have time remaining in your compliance period to resample.

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  • Why should I sample early in my compliance period?
    Many systems exceed the Lead and/or Copper action levels due to improper sampling technique. If your water system samples early in their compliance period, then time remains for you to collect a second set of samples during the same period which can be used additionally for compliance purposes. In the Lead and Copper program, we can accept the results of a second set of samples taken in the same compliance period and then recalculate the 90th percentile based on the total number of samples taken within that period. This may result in a 90th percentile below the Action Levels, depending on the sampling results.
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