5 Colo. Code Regs. § 1002-11.11

Current through Register Vol. 47, No. 11, June 10, 2024

Section 5 CCR 1002-11.11 - GROUNDWATER RULE

11.11(1)General Applicability and Definitions

(a) For all groundwater systems, the supplier must comply with the requirements specified in this rule.

(i) For the purposes of this rule, a "GROUNDWATER SYSTEM" means any public water system that meets one or more of the following criteria:

(A) The system only uses groundwater sources.

(B) The system uses both surface water and groundwater sources and does not combine the groundwater sources and surface water sources before treatment.

(I) This rule only applies to the groundwater sources.

(II) Systems that combine groundwater sources with surface water sources before treatment are not considered groundwater systems.

(C) The system is a consecutive system that receives finished water from a groundwater system.

11.11(2)Minimum Disinfection Treatment Requirements

(a)Applicability for Minimum Disinfection Treatment Requirements

(i) The supplier must comply with the requirements specified in this section, 11.11(2), unless one or more of the following conditions apply:

(A) The groundwater system is operating under a disinfection waiver and the supplier is required to comply with 11.13.

(B) The groundwater system has only hand-pumped wells and the supplier is required to comply with 11.12.

(C) The groundwater system has hand-pumped wells and other sources and the supplier is required to comply with this section, 11.11(2), for the groundwater sources that are not hand-pumped wells and with 11.12 for the groundwater sources that are hand-pumped wells.

(D) The groundwater system is a consecutive system that only supplies finished groundwater received from a wholesale system and therefore supplier is required to comply with 11.11(2)(b)(i)(B)(II-III), 11.11(2)(c)(i)(B), 11.11(2)(c)(i)(C), 11.11(2)(d)(i)(B-C), and 11.11(2)(e)(ii).

(b)Treatment Technique Requirements for Minimum Disinfection Treatment

(i) The minimum disinfection treatment technique requirements are as follows:

(A) When a groundwater source is used to supply water to the public, the supplier must disinfect the water using a chemical treatment method.

(B) When a groundwater source is used to supply water to the public, the supplier must maintain a residual disinfectant concentration at each entry point and throughout the distribution system.

(I) At each entry point, the residual disinfectant concentration must be greater than or equal to (>=) 0.2 mg/L.

(II) In the distribution system, the residual disinfectant concentration must be greater than or equal to (>=) 0.2 mg/L.

(ii) No later than December 31, 2015, the supplier may apply to the Department for an extension for complying with the treatment technique requirements specified in 11.11(2)(b)(i)(B)(III).

(A) In the application, the supplier must include all of the following information:

(I) An explanation of why the supplier is unable to comply with the treatment technique requirements specified in 11.11(2)(b)(i)(B)(III).

(II) A distribution system disinfectant residual data analysis demonstrating the inability to comply with the treatment technique requirements specified in 11.11(2)(b)(i)(B)(III).

(III) An engineering report prepared by a professional engineer registered in the state of Colorado demonstrating that capital improvements are necessary to comply with the treatment technique requirements specified in 11.11(2)(b)(i)(B)(III).

(IV) A proposed schedule for completing the system modifications.

(B) The Department shall consider the following criteria when determining if an extension will be granted:

(I) The supplier submitted a complete application that included the information specified above;

(II) The supplier has complied with the monitoring requirements specified in 11.17 in the last 36 months; and

(III) The supplier has not incurred an MCL violation specified in 11.17(9) in the last 36 months.

(iii) The Department will only grant an extension for up to four years.

(iv) If the supplier receives written Department-approval for an extension, the supplier must:

(A) Continue to comply with the treatment technique requirements specified in 11.11(2)(b)(i)(B)(II) and is subject to the violation specified in 11.11(2)(d)(i)(B) until the capital improvements are completed or the extension expires, whichever comes first; and

(B) Comply with any Department-specified requirements.

(c)Monitoring Requirements for Minimum Disinfection Treatment Technique Requirements

(i) To determine compliance with the minimum disinfection treatment technique requirements, the supplier must monitor the residual disinfectant concentration.

(A) At each entry point, the supplier must monitor the residual disinfectant concentration at least once each week that water is supplied to the public from that entry point.

(I) If any entry point residual disinfectant concentration result is less than (<) 0.2 mg/L, the supplier must increase the residual disinfectant concentration monitoring frequency at that entry point to at least once every 24 hours from the time of discovery until the residual disinfectant concentration is greater than or equal to (>=) 0.2 mg/L.

(B) In the distribution system, the supplier must, at a minimum, monitor the residual disinfectant concentration at the same time and at the same sampling locations as the total coliform samples collected under 11.16(4) and 11.16(5).

(C) The supplier must measure the residual disinfectant concentration as free chlorine unless the supplier uses a disinfection process that results in a monochloramine residual disinfectant, then the supplier must measure the residual disinfectant concentration as total chlorine. If the supplier uses a different type of chemical disinfectant (e.g., ozone or chlorine dioxide), the supplier must measure the appropriate residual disinfectant concentration.

(d)Treatment Technique Violations for the Minimum Disinfection Treatment Requirements

(i) The following constitute disinfection treatment technique violations:

(A) At any entry point, the residual disinfectant concentration is less than (<) 0.2 mg/L for more than 72 hours after the time of discovery.

(B) In the distribution system:

(I) If the supplier collects greater than or equal to (>=) 40 residual disinfectant concentration samples per month, the residual disinfectant concentration is less than (<) 0.2 mg/L in more than 5 percent of the samples collected.

(II) If the supplier collects greater than (>) one but less than (<) 40 residual disinfectant concentration samples per month, the residual disinfectant concentration is less than (<) 0.2 mg/L in more than one sample collected.

(III) If the supplier collects greater than (>) one but less than (<) 40 residual disinfectant concentration samples per month, the residual disinfectant concentration is less than (<) 0.2 mg/L in more than 5 percent of the samples collected in each month for two consecutive months that the system supplies water to the public.

(IV) If the supplier collects only one residual disinfectant concentration sample per monitoring period, the residual disinfectant concentration is less than (<) 0.2 mg/L.

(e)Response to Treatment Technique Violations for the Minimum Disinfection Treatment Requirements

(i) In the event of an entry point treatment technique violation as specified in 11.11(2)(d)(i)(A), the supplier must:

(A) Notify the Department as soon as possible but no later than the end of the next business day.

(B) Determine and resolve the failure that resulted in the treatment technique violation.

(C) No later than 48 hours after the resolution of the failure, document all of the following:

(I) The date, time and duration of the failure.

(II) The cause of the failure.

(III) The steps taken to correct the failure.

(IV) What steps will be taken to prevent future failures.

(D) Submit the documentation specified above in 11.11(2)(e)(i)(C) if required by the Department.

(E) Distribute Tier 2 public notice as specified in 11.33.

(ii) In the event of a distribution system treatment technique violation as specified in 11.11(2)(d)(i)(B-C), the supplier must:

(A) Notify the Department no later than 48 hours after the violation occurs.

(B) Distribute Tier 2 public notice as specified in 33.

11.11(3)Requirements for 4-Log Treatment of Viruses

(a)Applicability for 4-Log Treatment of Viruses

(i) For any new or existing groundwater source that is treated to at least 4-log treatment of viruses at the entry point, either by choice or because the supplier is required to as specified in 11.38(3)(a)(i)(D) or 11.11(6), the supplier must comply with the requirements specified in this section, 11.11(3).

(A) If the supplier is subject to the requirements specified in this section, 11.11(3), the supplier is not required to meet the source water monitoring requirements specified in 11.11(4) and 11.11(5).

(b)Notification of 4-Log Treatment of Viruses

(i) The supplier must submit notification that the system is providing at least 4-log treatment of viruses at the entry point(s).

(A) The submission must include engineering, operational, or other information that the Department requests to evaluate the submission.

(c)Treatment Technique Requirements for 4-Log Treatment of Viruses

(i) The supplier may use one of the following to comply with the 4-log treatment of viruses treatment technique requirements, as approved by the Department:

(A) Chemical disinfection.

(B) Alternative treatment methods.

(ii) If the supplier uses chemical disinfection to comply with the 4-log treatment of viruses treatment technique requirements, the supplier must maintain the Department-approved residual disinfectant concentration at the Department-approved location(s) that represent treated water at the entry point.

(iii) If the supplier uses a Department-approved alternative treatment method to comply with the 4-log treatment of viruses treatment technique requirements, the supplier must operate the alternative treatment according to Department-specified requirements.

(d)Monitoring Requirements for 4-Log Treatment of Viruses

(i) To determine compliance with the 4-log treatment of viruses treatment technique requirements, the supplier must:

(A) Begin monitoring no later than 30 days after placing the source in service.

(B) Monitor at the Department-approved location and/or according to the Department-specified requirements.

(ii) If the supplier uses chemical disinfection to comply with the 4-log treatment of viruses treatment technique requirements, the supplier must also:

(A) For a system that supplies greater than (>) 3,300 people, continuously monitor the residual disinfectant concentration at the Department-approved location(s).

(I) If there is a failure in the continuous monitoring equipment, the supplier must monitor the residual disinfectant concentration by collecting grab samples every four hours until the continuous monitoring equipment is returned to service.

(a) The supplier must resume continuous residual disinfectant concentration monitoring no later than 14 days after the equipment failure.

(B) For a system that supplies less than or equal to ([LESS THAN EQUAL TO]) 3,300 people, monitor the residual disinfectant concentration daily by collecting grab samples at the Department-approved location(s).

(I) The supplier must collect a daily grab sample during the hour of peak flow or at another time specified by the Department.

(II) If any daily grab sample result is less than (<) the Department-approved residual disinfectant concentration, the supplier must monitor the residual disinfectant concentration every four hours until it is greater than or equal to (>=) the Department-approved residual disinfectant concentration.

(III) Alternatively, the supplier may monitor continuously as specified in 11.11(3)(d)(ii)(A).

(C) When a groundwater source is used to supply water to the public, record the lowest residual disinfectant concentration monitored each day.

(iii) If the supplier uses a Department-approved alternative treatment method to comply with the 4-log treatment of viruses treatment technique requirements, the supplier must monitor according to Department-specified requirements.

(e)Treatment Technique Violation and Response for 4-Log Treatment of Viruses

(i) If the supplier fails to provide at least 4-log treatment of viruses at the Department-

approved location and/or according to the Department-specified requirements and the failure is not corrected within four hours from the time of discovery, a 4-log treatment of viruses treatment technique violation occurs.

(ii) In the event of a 4-log treatment of viruses treatment technique violation, the supplier must:

(A) Notify the Department as soon as possible but no later than the end of the next business day.

(B) Distribute Tier 2 public notice as specified in 11.33.

(f)Discontinuing Monitoring for Compliance With 4-log Treatment of Viruses Requirements

(i) The supplier may submit a request to discontinue the monitoring requirements for 4-log treatment of viruses. If the Department determines that monitoring for a source is no longer necessary, the Department shall document the decision in writing and the supplier may discontinue monitoring that source as specified in 11.11(3)(d).

(A) If the supplier has received Department-approval to discontinue monitoring as specified in 11.11(3)(d), the supplier must continue monitoring the source water as specified in 11.11(4) and 11.11(5) and meet the minimum residual disinfectant concentration requirements specified in 11.11(2).

11.11(4)Triggered Source Water Monitoring

(a)Applicability for Triggered Source Water Monitoring

(i) The supplier must conduct triggered source water monitoring if:

(A) The supplier does not provide at least 4-log treatment of viruses (using inactivation, removal, or a Department-approved combination of 4-log inactivation and removal) at the entry point to the distribution system for each groundwater source as specified in 11.11(3); and

(B) The supplier is notified that a sample collected under 11.16 is total coliform-positive and the sample was not invalidated under 11.16(7).

(ii) The supplier is not required to conduct triggered source water monitoring if either of the following conditions are met:

(A) The Department determines and documents in writing that the routine total coliform-positive sample collected under 11.16, was caused by a distribution system deficiency and not by the source water.

(B) The supplier collected the routine total coliform-positive sample collected under 11.16 at a location that meets Department criteria for distribution system conditions that will cause total coliform-positive sample results and therefore the total coliform-positive sample result was not caused by the source water.

(I) No later than 30 days after receiving the total coliform-positive sample result, the supplier must submit documentation that demonstrates the sample location met Department criteria.

(b)Monitoring Requirements for Triggered Source Water Monitoring

(i) The supplier must collect triggered source water monitoring samples no later than 24 hours after being notified of a total coliform-positive sample collected under 11.16.

(A) If the supplier experiences circumstances beyond their control that prevent the supplier from collecting the source water samples, the Department may extend the 24-hour limit on a case-by-case basis.

(I) If the Department approves the extension, the Department shall specify how much time the supplier has to collect the source water samples.

(ii) The supplier must collect at least one triggered source water monitoring sample from each groundwater source that was in use at the time the total coliform-positive sample was collected. These samples must be collected at the well, before any treatment is applied.

(A) If the system's configuration does not allow for the supplier to sample at the well itself, the Department may:

(I) Approve the collection of triggered source water monitoring samples at a location that represents the water quality of that well or a location after treatment; and/or

(II) Require that sampling equipment be installed at the well itself.

(B) For systems with more than one groundwater source, the Department may approve collection of the triggered source water monitoring samples from a representative groundwater source(s).

(I) The representative source(s) must supply water to the section of the distribution system where the total coliform-positive sample was collected.

(II) If required by the Department, the supplier must submit, for approval, a triggered source water monitoring plan to use a representative source(s).

(a) The triggered source water monitoring plan must identify which source(s) the supplier intends to use for representative sampling of groundwater sources. For each representative source identified, the supplier must identify each total coliform sampling location that the source represents in the system's sampling plan specified in 11.16(3).

(C) For a groundwater system supplying less than or equal to ([LESS THAN EQUAL TO]) 1,000 people that uses E. coli as a fecal indicator for triggered source water monitoring, the supplier may use a triggered source water monitoring sample to meet both the repeat sampling requirements specified in 11.16(5), and the triggered source water monitoring requirements. If the repeat sample collected from the groundwater source is E. coli-positive, the supplier must comply with the requirements in 11.11(4)(d).

(iii) The supplier must have all groundwater source samples analyzed for the presence of one of the following fecal indicators: E. coli, enterococci, or coliphage.

(c)Additional Triggered Source Water Monitoring Requirements for Consecutive and Wholesale Systems

(i) For consecutive systems, no later than 24 hours after being notified of the sample result,

the supplier responsible for the consecutive system must notify all of their wholesalers of a total coliform-positive sample result collected under 11.16.

(ii) A wholesale system that receives notification from a consecutive system it serves that a sample collected under 11.16 is total coliform-positive, the wholesaler must sample all of its groundwater source(s) as specified above in 11.11(4) no later than 24 hours and analyze the samples for a fecal indicator under 11.46(2)(b and e).

(d)Response to Triggered Source Water Monitoring Fecal Indicator-Positive Sample Results

(i) If the supplier has a fecal indicator-positive triggered source water monitoring sample result, that is not invalidated under 11.11(4)(e)(i), the supplier must:

(A) Notify the Department and initiate consultation no later than 24 hours after being notified of the fecal indicator-positive initial triggered source water monitoring sample result.

(B) Distribute Tier 1 public notice as specified in 11.33.

(I) For all consecutive systems supplied by the groundwater source that tested positive for a fecal indicator, the supplier responsible for the consecutive system must also distribute Tier 1 public notice to its consumers as specified in 11.33.

(C) No later than 24 hours after being notified of the fecal indicator-positive triggered source water monitoring sample result, the supplier must collect five confirmation samples from the same source unless the Department requires the supplier to implement corrective action as specified in 11.11.

(I) If the supplier collects more than one triggered source water monitoring sample at the location required to meet the total coliform repeat sampling requirements specified in 11.16, the supplier may use any of those triggered source water monitoring samples that were E. coli-negative toward complying with the five required confirmation samples.

(II) If one or more of the confirmation samples is fecal indicator-positive, the supplier must implement corrective action as specified in 11.11(6).

(D) For a wholesale system, notify all consecutive systems that are supplied by that source of the original fecal indicator-positive sample result no later than 24 hours after being notified of the sample result and meet the requirements of 11.11(4)(d).

(e)Sample Invalidation for Triggered Source Water Monitoring

(i) At the supplier's request, the Department may invalidate a fecal indicator-positive triggered source water monitoring sample based on one of the following conditions:

(A) The supplier submits written notice from the laboratory that improper sample analysis occurred.

(B) The Department determines and documents in writing that there is substantial evidence that the fecal indicator-positive triggered source water monitoring sample result is not related to source water quality.

(ii) If the Department invalidates a fecal indicator-positive triggered source water monitoring sample result, the supplier must collect a replacement source water sample no later than 24 hours after being notified by the Department of the invalidation.

(A) The replacement sample must meet all triggered source water monitoring requirements specified in 11.11(4). Additionally, the replacement sample must be analyzed by the laboratory for the same fecal indicator as the invalidated source sample.

(B) If the supplier experiences circumstances beyond their control that prevent the supplier from collecting the source water sample(s), the Department may extend the 24-hour limit on a case-by-case basis.

(I) If the Department approves the extension, the Department shall specify how much time the supplier has to collect the replacement source water samples.

11.11(5)Assessment Source Water Monitoring

(a)Applicability for Assessment Source Water Monitoring

(i) If required by the Department, the supplier must comply with the assessment source water monitoring requirements specified in this section, 11.11(5).

(A) To determine if assessment source water monitoring shall be required, the

Department may request that the supplier provide information that will enable the Department to complete a hydrogeologic sensitivity assessment.

(I) "HYDROGEOLOGIC SENSITIVITY ASSESSMENT" means a determination of whether a groundwater system obtains water from hydrogeologically sensitive settings. The following describe sensitive settings that can increase the risk of fecal contamination:

(a) Aquifers that exist in an area with high population densities combined with onsite wastewater treatment systems.

(b) Aquifers in which viruses may travel faster and further than bacteria (e.g. alluvial or sand aquifers).

(c) Shallow, unconfined aquifers.

(d) Aquifers with thin or absent soil cover.

(e) Areas where wells have previously been identified as having fecal contamination.

(f) Sensitive aquifers.

(ii) For new sources, the Department may require the supplier to begin assessment source water monitoring before the new source supplies water to the public.

(b)Monitoring Requirements for Assessment Source Water Monitoring

(i) Department-determined assessment source water monitoring requirements may include, but are not limited to:

(A) Collection of a groundwater source sample(s) each month the system supplies water to the public for a total of at least 12 samples for each groundwater source.

(B) Collection of groundwater source samples from each well unless the supplier obtains written Department approval to conduct representative sampling.

(I) "REPRESENTATIVE SAMPLING" means samples are collected at one or more wells within the groundwater system that are representative of multiple wells used by that system because the wells draw water from the same hydrogeologic setting.

(C) Collection of groundwater source samples at a location before any treatment of the groundwater source, unless the Department approves a sampling location after treatment.

(D) Collection of groundwater source samples at the well itself unless the system's configuration does not allow for sampling at the well itself and the Department approves an alternative sampling location that is representative of the water quality of that well.

(E) Analysis of assessment source water monitoring samples for the presence of E. coli, enterococci, or coliphage.

(F) Collection of a standard sample volume of at least 100 ml for fecal indicator analysis for assessment source water monitoring samples.

(ii) If the supplier is required to conduct assessment source water monitoring, the supplier may use triggered source water monitoring samples collected under 11.11(4) to meet the requirements of assessment source water monitoring.

(c)Response to Assessment Source Water Monitoring Fecal Indicator-Positive Sample Results

(i) If an assessment source water monitoring sample result is fecal indicator-positive, the supplier must:

(A) Distribute Tier 1 public notice as specified in 11.33.

(B) If required by the Department, implement corrective action as specified in 11.11(6).

11.11(6)Corrective Action for Source Water Fecal Indicator-Positive Monitoring Results

(a)Applicability

(i) The supplier must comply with the requirements specified in this section, 11.11(6), if:

(A) A confirmation triggered source water monitoring sample result collected under 11.11(4)(d)(i)(C) is fecal indicator-positive; or

(B) The supplier is required to by the Department after either:

(I) A fecal indicator-positive initial triggered source water monitoring sample collected under 11.11(4)(b)(i-ii) or 11.11(4)(c)(ii); or

(II) A fecal indicator-positive assessment source water monitoring sample collected under 11.11(5)(b).

(b)Corrective Action Requirements

(i) The supplier must implement one or more of the following corrective actions:

(A) Correct all significant deficiencies.

(B) Provide an alternative source of water.

(C) Eliminate the source of contamination.

(D) Provide treatment that reliably achieves at least 4-log treatment of viruses at the Department-approved location for the groundwater source.

(ii) The Department may specify interim measures at any time pending completion of corrective action to protect public health.

(iii) No later than 30 days after receiving written notice from a laboratory of a fecal indicator-positive confirmation triggered source water monitoring sample result collected under 11.11(4)(d)(i)(C) or receiving direction from the Department to complete corrective action as specified in 11.11(6)(a)(i)(B), the supplier must consult with the Department regarding the appropriate corrective action, unless the Department specifies which corrective action the supplier must implement.

(iv) No later than 45 days after receiving written notice from a laboratory of a fecal indicator-positive confirmation triggered source water monitoring sample result collected under 11.11(4)(d)(i)(C) or receiving direction from the Department to complete corrective action as specified in 11.11(6)(a)(i)(B), the supplier must submit a corrective action plan for approval.

(A) The corrective action plan must include the actions the supplier will take to address the fecal indicator-positive groundwater source sample(s) and a proposed schedule for completing the actions.

(v) Any changes the supplier makes to a Department-approved corrective action plan and schedule must be approved by the Department.

(vi) No later than 120 days, or earlier if required by the Department, after receiving written notice from a laboratory of a fecal indicator-positive confirmation triggered source water monitoring sample result collected under 11.11(4)(d)(i)(C) or receiving direction from the Department to complete corrective action as specified in 11.11(6)(a)(i)(B), the supplier must either:

(A) Have completed the Department-approved corrective action plan including any Department-specified interim measures; or

(B) Be in compliance with a Department-approved corrective action plan and schedule including any Department-specified interim measures.

(vii) No later than 30 days after completing any corrective action under 11.11(6)(b), the supplier must notify the Department of the completed corrective action.

(c)Treatment Technique Violation and Response for Corrective Action

(i) If the supplier fails to comply with the requirements specified in 11.11(6)(b), a corrective action treatment technique violation occurs.

(ii) In the event of a corrective action treatment technique violation, the supplier must:

(A) Notify the Department no later than 48 hours after the violation occurs.

(B) Distribute Tier 2 public notice as specified in 11.33.

5 CCR 1002-11.11

38 CR 07, April 10, 2015, effective 4/30/2015

41 CR 11, June 10, 2018, effective 6/30/2018

41 CR 23, December 10, 2018, effective 12/30/2018

43 CR 07, April 10, 2020, effective 4/30/2020

43 CR 17, September 10, 2020, effective 9/30/2020

45 CR 24, December 25, 2022, effective 1/14/2023