Montana Administrative Register Notice 17-422 No. 16   08/26/2022    
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                                          OF THE STATE OF MONTANA


In the matter of the amendment of ARM 17.36.345, 17.38.101, 17.38.209, Department Circular PWS-5 regarding ground water under the direct influence of surface water determinations, and section 3.2.2 and Appendix A of Circular DEQ-1 regarding standards for public water supply systems














            TO: All Concerned Persons


            1. On May 27, 2022, the Department of Environmental Quality (department) published MAR Notice No. 17-422 pertaining to the public hearing on the proposed amendment of the above-stated rules at page 713 of the 2022 Montana Administrative Register, Issue No. 10.


            2. The department has amended the rule text of ARM 17.36.345, 17.38.101, and 17.38.209 as proposed.


            3. The department has amended section 3.2.2 and Appendix A of department Circular DEQ-1 as proposed.


            4. The department has made changes to Circular PWS-5 as originally proposed in MAR Notice No. 17-422, 2022 Montana Administrative Register, Issue No. 10, based on the comments that the department received during the public comment period.


 5. The department has thoroughly considered the comments received. A summary of the comments and the department's responses are as follows:


COMMENT 1: One commenter stated that Circular PWS-5 is well-written and does a great job of being clear and concise. The commenter noted that many extraneous descriptions and details have been removed, making the Circular more understandable.

RESPONSE 1: The department appreciates the comments.


COMMENT 2: One commenter identified a typographical error in section 4 and suggested a correction. 

RESPONSE 2: The department believes that this comment relates to an earlier draft and that the typographical error has been corrected in the final Circular.


COMMENT 3: The department received two comments that identified a typographical mistake in the first sentence of section 4.2.

RESPONSE 3: The department agrees and has made the following change to section 4.2:


An MPA testing is used to determine if surface water organisms are present in subsurface water sources.


COMMENT 4: One public water system operator raised concerns about the potential effects of the Circular on the commenter's public water supply system. The commenter explained how the commenter's system had gone through the evaluation process for groundwater under the direct influence of surface water (GWUDISW) and had received a negative result in the microscopic particulate analysis (MPA). The commenter believed that this result should be sufficient.  The commenter further noted that the commenter's system would not have the financial ability to install chlorination, as it was already struggling to cover the costs associated with other system repairs.

RESPONSE 4: The department cannot comment directly on how individual systems may be affected, since each GWUDISW review is a case-by-case evaluation. The area around a source and the source itself will change over time, which may make a source susceptible to contamination. 

Under its duties as a primacy state, the department is required to conduct sanitary surveys at every public water supply system every three or five years, depending on the type of system. During the sanitary survey, the department must evaluate the adequacy of the source to provide safe drinking water. 40 C.F.R. § 141.401. If the sanitary survey or other information (such as sample results) indicates that conditions around the source have changed in such a way to make the source more susceptible to contamination, then it is important that the source be reevaluated as necessary based on that new condition. This process has existed in previous editions of Circular PWS-5 and remains unchanged in the new edition. To clarify this process, the department has modified section 4.3.2 of the Circular as follows:


DEQ will evaluate and classify any water system that the water system owner has chosen to modify the source, the nearest surface water, or the area around the source, beginning with completion of a PA.  If modifications have occurred to the source, to the area around the source, or to the nearby surface water, DEQ will complete a new GWUDISW evaluation, starting with a new PA based on the changed circumstances.


As for the potential costs to the system caused from receiving a GWUDISW classification, sources that are classified as GWUDISW pose a risk to public health. To correct this problem, a system may decide to use an alternate water source, make appropriate modifications to remove the surface water influence, or meet the applicable filtration and disinfection requirements of the Surface Water Treatment Rule and DEQ-1. These are existing rules that are required as part of the department's primacy agreement with EPA and remain unchanged in this rulemaking. 

In the nearly thirty years that the department has been making GWUDISW determinations, only 42 water sources have been classified as GWUDISW, while 3,238 have been classified as groundwater. Thus, only 1.3% of water sources have been classified as GWUDISW. 


COMMENT 5:  One commenter stated that the MPA method does not designate a source as having a low-, moderate-, or high-risk of surface water influence that corresponds with the risk of Giardia or Cryptosporidium contamination. Rather, the commenter noted, the MPA result assigns a relative risk score based on ranges of indicators observed.

RESPONSE 5:  The department agrees that the MPA results are reported as a points score that correspond to a relative risk.  To reduce confusion, the department has modified the Circular in response to this comment to refer to the MPA result score in points, rather than relative risk. 

The department has modified section 4.2 as follows:


In addition to the organism counts found in the sample, the MPA results provide a designation of low-, moderate-, or high-risk of surface water influence are converted to a points score. The MPA scores, as defined by the Consensus Method, are as follows:


Low- risk

< 9 points

Moderate- risk

10–19 points

High- risk

>20 points


All subsurface water sources to be tested must be completely constructed and able to operate. DEQ may require the test source or, for systems with more than one source, other sources to be operating before or during the test. For subsurface water sources that are artificially recharged by surface water, the MPA must be completed during a recharge event.

In most circumstances, two MPAs must be completed—one in May or June and one in August or September. If, however, the first MPA result is moderate or high risk 10 or more points, a second test is not needed for classification and will not be conducted. DEQ may also require additional tests in circumstances in which there is low confidence in the accuracy of a test result. 


The department also has modified section 4.3.2 as follows:


Any subsurface water source with one or more moderate- or high-risk MPA results of 10 or more points will be classified as GWUDISW, except in cases where it is highly probable the surface water indicators did not originate from the water source. A classification of a subsurface water source as GWUDISW based on a moderate- or high-risk MPA result score of 10 or more points is final for that configuration of the source. 


COMMENT 6:  One commenter disagreed with the proposed approach of using a single MPA with a moderate- or high-risk finding to classify a subsurface source as GWUDISW. The commenter noted that the MPA is a non-standard subjective analytical method that lacks thorough quality assurance/quality control. The commenter also noted that the economic and operational implications of misclassifying a source as GWUDISW are significant and stated that primary reliance on the MPA would subject the regulated community to an overly conservative approach without adequate opportunity to question or allow for verification of the finding. Finally, the commenter provided several reasons why a single MPA result should not be the sole deciding factor in whether a source is GWUDISW. 

RESPONSE 6: The requirement that a water source with one MPA test result with 10 or more points (moderate- or high-risk) be classified as GWUDISW is not new to this version of the Circular. Section 7, PWS-5 (2008 ed.) ("If results of any MPA test indicate moderate or high risk then the source will be considered to be under the direct influence of surface water unless there are mitigating factors associated with well construction or other human activities."). In adopting the 2008 Circular, the department and Board of Environmental Review determined that an MPA test result of 10 or more points (both moderate- and high-risk results) indicates that a source has an unacceptable potential to adversely affect public health. Response to Comments Nos. 19 and 21, Notice of Amendment and Adoption, No. 17-273, 2008 MAR page 2625 (Dec. 24, 2008). While the commenter mentioned the economic and operational implications to the water system that can result from a GWUDISW classification, there are also health and economic implications for people who are exposed to untreated surface water. The department continues to believe that this approach appropriately balances the risk to human health from contaminated water. 

Further, the presence of surface water indicators in subsurface water, without another explanation, during one MPA is strong evidence that the water source is influenced by surface water and poses a risk to human health. The MPA is a representative water sample, and it is improbable that the MPA test was collected on the only day when surface water indicators are present.  Once a water source has one MPA test result of 10 points or more, further sampling will not change the fact that surface water indicators have been found in that source. While subsequent MPA samples may have results with fewer than 10 points, this will be after the direct surface water influence has already been established. When the surface water influence is not continuous, it is nearly impossible for the water system to predict that influence (if the system is even aware that it has occurred) and to modify operations to not serve the contaminated water. If surface water influence can happen once, it can happen again, often unpredictably and in a way to which the system is unable to respond. Thus, finding surface water indicators in subsurface water sources, even in just one MPA at quantities that score 10 or more points, is reason to classify the source as GWUDISW.

As the commenter notes, the MPA consensus method has some limitations. Nevertheless, it remains the recommended analytical method by EPA, see Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems Using Surface Water Sources 2-7 and 2-8 (March 1991), (Guidance Manual), and is the leading tool available to directly test whether surface water organisms are able to travel to the subsurface water source. As with all laboratory analyses, the quality of the sample being analyzed will affect the test results and their subsequent interpretation, which is why the new Circular requires the department staff to collect all MPA samples.

Finally, the MPA is not conducted in a vacuum. The MPA would be conducted only after the preliminary assessment and other information available to the department indicated a susceptibility of direct surface water influence. 

The department acknowledges, however, that there may be some issue that would cause the MPA test result to not correctly describe the risks associated with the source.  The department has modified section 4.3.2 in response to this comment to provide an exception in certain instances where the surface water indicators are caused by something other than the source water. Given the health risks associated with surface water contamination, as discussed above, it is necessary that this exception apply only in instances in which it is highly probable—that is, clear and convincing—that the surface water indicators were caused by something other than the direct influence of surface water.

Any subsurface water source with one or more moderate- or high-risk MPA results of 10 or more points will be classified as GWUDISW, except in cases where it is highly probable the surface water indicators did not originate from the water source. A classification of a subsurface water source as GWUDISW based on a moderate- or high-risk MPA result score of 10 or more points is final for that configuration of the source. 


COMMENT 7:  One commenter stated that the department should not exclude significant and relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity, or pH, noting that those characteristics were part of the GWUDISW definition. The commenter also noted that such water quality information may be used to determine that a source is not GWUDISW. The commenter also provided an example in which water quality parameters were used as a deciding factor even though surface water algae appeared in an MPA result.

RESPONSE 7:  The department has been managing this rule for over two decades.  Initially, the department implemented this rule by first requiring hydrogeologic assessments and water quality analyses for water sources identified as susceptible by the preliminary assessment, as these analyses were cheaper and potentially easier for the water system to complete. Nevertheless, MPAs frequently were required because the hydrogeologic assessments and water quality analyses were insufficient to make a confident determination. This experience led the department to move directly to MPA tests and use those results as the basis of determination. Moving to the MPA first provides faster, more definitive answers that save the system time and money, while being more protective of public health.  

Hydrogeologic assessments and water quality analyses can provide important corroborating information in the GWUDISW evaluation process, and the department will consider all available information to understand the hydrogeologic system around the water source to make a determination. However, the MPA still provides the best evidence of direct surface water influence. As EPA notes, water quality parameters "would not give a direct indication of whether pathogens originating in surface water were present, but could indicate whether the water chemistry was or was not similar to a nearby surface water and/or whether source water chemistry changed in a similar pattern to surface water chemistry."  Guidance Manual 2-11.  The water quality data is best used in a supporting role and not as deciding factor. 

As for the example provided by the commenter, the department believes that such situations would be adequately addressed in the changes to section 4.3.2 described in response to comment 6 above.


COMMENT 8:  One commenter stated that section 4.3.1 should include allowances for reevaluating a source due to temporary events, such as flooding of a wellhead or spring box. The commenter noted that flooding would not be reason to classify the water as GWUDISW because it is an event-driven and correctable situation.

RESPONSE 8:  Floods may overtop a wellhead or spring box and directly introduce contaminants to drinking water systems. In such cases, it is understood that the flooded well would not be classified as GWUDISW but would be handled as an emergency event by the system. Floods may have other impacts on sources, however. Floods may raise the water table near or around a well, which could introduce contaminants into the source. Floods also may erode the riverbank or even alter the river course, which could change the distance between the source and the surface water. While these effects could be short lived and restricted to the flooding event, they also could change the hydraulic system around the water source. Flooding is a significant enough event to warrant reviewing the water source again, so the department has left this section of the Circular unchanged.


COMMENT 9:  One commenter noted that it was incorrect to use the term "certified laboratory" in section 4.2 because there is no certification program for MPA laboratories or analysts.

RESPONSE 9:  The department agrees and has modified section 4.2 of the Circular in response to this comment as follows:


The public water system shall be responsible for coordinating with a certified laboratory capable of conducting the MPA to secure the sample kit, shipping the samples to the certified laboratory, and paying for analysis and shipping costs.


COMMENT 10:  One commenter suggested wording changes to section 4.2 to indicate that MPA sampling, rather than the MPA analysis itself, would be conducted by department staff.

RESPONSE 10:  The department agrees and has modified section 4.2 of the Circular in response to this comment as follows:


All MPA sample collection must be conducted by DEQ staff. 


COMMENT 11:  One commenter suggested wording changes in section 1 to remove references to viruses and bacteria, noting that viruses and bacteria are not included in the federal or state definitions of GWUDISW and stating that their presence in groundwater does not imply risk of contamination of the water by Giardia or Cryptosporidium.

RESPONSE 11:  The department agrees and has modified section 1 of the Circular in response to this comment as follows:


Direct influence of surface water is that influence that causes a risk of pathogenic organisms (primarily large pathogens such as Giardia lamblia, and Cryptosporidium, viruses, and bacteria) to transfer from a surface source water to a subsurface drinking water source.


COMMENT 12:  EPA Region 8 recommended that the department take a holistic approach to GWUDISW screening and expand on the elements of the preliminary assessment when assessing if additional evaluation is appropriate. The commenter recommended that the department take into account all readily available information in the department's initial screening of the source, including pieces of information contained within a hydrogeologic assessment and a water quality analysis. The commenter supported the flexibility provided in sections 4 and 4.1.1 of the Circular.

REPSONSE 12:  The department agrees that a holistic approach is necessary. The preliminary assessment is a screening tool that separates those sources that are easily recognized as groundwater.  All other water sources will undergo further review.  This review will involve all available information and may include a site visit.  This review will be used to create a conceptual model of the hydraulics of the water source, and the level of effort will vary depending on the complexity of each water source.  The department has modified section 4 of the Circular in response to this comment to more explicitly describe the scope of information that may be considered, as follows: 


As described in this section, DEQ evaluates all subsurface water sources using a preliminary assessment (PA) and, if necessary, a microscopic particulate analysis (MPA). DEQ also may rely on other relevant materials, including but not limited to, photos of the water source and surrounding topography, well logs, aquifer test results, annular seal installation reports, geologic maps, groundwater studies, water quality data, historic rainfall data, river gauging data, engineering drawings, and other documents. A hydrogeologic assessment may be done as appropriate on a case-by-case basis. If necessary, a microscopic particulate analysis (MPA) will be conducted pursuant to this section


In response to this comment, the department also has modified section 4.3.1 to remove any misleading language about the holistic approach adopted in sections 4.1.1 and 4.1.2. The department has also modified this section to refer to the MPA points score, as discussed in response to comment 5:


A source may be classified as ground water if either (1) the subsurface water source scores less than 40 points on the PA; 2) if the PA score is more than 40 points and upon further review it is found that DEQ determines that direct surface water influence is not likely; or 3(2) if both MPAs indicate a low risk score fewer than 10 points


COMMENT 13:  EPA Region 8 recommended that GWUDISW evaluations be repeated or reviewed, as appropriate. The commenter noted that sanitary surveys offer the department the opportunity to confirm or update information used within the GWUDISW evaluation.

REPSONSE 13:  The department agrees, as discussed above in response to comment 4, and has modified the Circular in response to this comment. The department has modified section 4.1 as follows:


The GWUDISW evaluation process begins with a PA. All PAs must be completed by DEQ as part of a site visit. DEQ will score water sources according to the criteria and score in the table below.


The department has modified section 4.3.1 as follows:


DEQ will, as part of regularly scheduled sanitary surveys, inspect every source for any changes in and around the source. If such changes have occurred, a new PA will be completed. DEQ may reevaluate a ground water classification upon changes to the source environment, water quality, or construction. Examples of such changes include, but are not limited to, flooding of the source, moving of an existing surface water body, installation of a new artificial surface water body closer to the water source, E. coli positive sample results, or reconstruction of a spring box. In any of these cases, the process begins with a new PA based on the new configuration. 


COMMENT 14:  EPA Region 8 commented on section 2.2, which provides that the department may exclude from the preliminary assessment temporary surface water bodies that are unlikely to harbor or transport surface water organisms to the ground water.  The commenter recommended not preemptively excluding these surface water features, noting that they may be temporary surficial expressions of underlying permanent groundwater features.  The commenter included examples of cut-off walls associated with infiltration galleries and groundwater collection boxes that can be utilized to artificially raise groundwater elevations in certain locations for water collection.

RESPONSE 14:  The department considered this comment but left the Circular unchanged. Section 2.2 of the Circular only excludes those features "that contribute little or no water to the subsurface." A surficial expression of groundwater, as suggested by the commenter, would contribute water to the subsurface, meaning that such features would be considered a surface water body on the preliminary assessment form.  


COMMENT 15:  EPA Region 8 recommended that section 3 be reworded to include a broader list of potential sources to underground water, including springs, infiltration galleries, and horizontal wells. The commenter noted that the set of examples provided could lead to misinterpretation of which sources would be evaluated.

RESPONSE 15:  This comment revealed an ambiguity in the section that the department has corrected. The intent of section 3 is not to list all potential sources but to emphasize that sources that are available to serve a public water supply system are subject to evaluation, even if those sources are not actively supplying water to the system. For instance, emergency wells and backup wells may not actively supply water to the system but are connected to the system and have the potential to introduce contamination to the system if they are used. The department has modified section 3 of the Circular in response to this comment as follows:


This Circular applies to all public water supply systems with a subsurface water source (e.g., wells, springs, horizontal wells, infiltration galleries, etc.). Each subsurface source that serves a public water supply system must be evaluated and classified as ground water or GWUDISW. Sources that are available to serve a public water supply system—including, for example and without limitation, lag wells, emergency wells, and backup wells—are subject to the requirement of this Circular.


COMMENT 16:  EPA Region 8 recommended evaluating total coliform and E. coli violations in the preliminary assessment Question 4, as done in the 2008 edition of the Circular.

RESPONSE 16:  The 2008 edition of PWS-5 included consideration of violations of the maximum contaminant level (MCL) for total coliform. EPA removed the MCL for total coliform in 2016 with adoption of the Revised Total Coliform Rule. Likewise, the E. coli samples are not included in the 2008 edition because that edition predated EPA's adoption of the Groundwater Rule in 2009. It is the department's opinion that E. coli-positive samples are a better indicator of surface water risk than total coliform results. The department has left preliminary assessment Question 4 unchanged.


COMMENT 17:  EPA Region 8 recommended modifications to Question 7 of the preliminary assessment, which concerns the construction characteristics of the source. The commenter recommended (1) evaluating whether a two-inch annular space between the borehole and the outer casing is present to be more consistent with industry best practices; (2) using cement bond log information, if applicable and available, to qualify the seal in areas where cement grout is utilized; and (3) considering the presence of a pitless adaptor and its disturbance and impact to the annular seal.

RESPONSE 17: The department considered this comment but decided to leave Question 7 unchanged. Montana's well drillers' rules and the department design standards in DEQ-1 both require a 1 1/2-inch annular space, meaning that most sources would fail the commenter's proposed revision of 2 inches. Designing a question that most sources would fail undermines the screening value of the preliminary assessment review, and the department believes that the difference between the two is negligible. Cement bond log information is generally not available for most wells. If that information is available, the department may consider it under section 4. Pitless adaptors are very common in Montana, and the department's experience in administering the rule in Montana has revealed that they are not a factor for surface water influence. Those few cases in which a leaking pitless adaptor contributed to negative water quality (i.e., E. coli samples) were identified and resolved as significant deficiencies under the Groundwater Rule. 

To the extent that the commenter recommends changes to specific design criteria, such recommendations are outside the scope of this PWS-5 rule making.


COMMENT 18: EPA Region 8 commented that the term "static water level" in Question 9 of the preliminary assessment implied only well completions in unconsolidated sediments. The commenter recommended that the department provide additional information regarding confined conditions in bedrock wells and wells with artesian pressures.

RESPONSE 18:  "Static water level" means the ambient water level elevation in a cased well where the aquifer has not been stressed. Willis D. Weight, Hydrogeology Field Manual 738 (2008). The definition of static water level is purely an observation and does not include any aquifer interpretation, so it includes all aquifer types (e.g., unconfined, confined, porous media, fractured, etc.).  The static water level reported on the well logs is used to answer Question 9 from the preliminary assessment. The department has left preliminary assessment Question 9 unchanged.



BY: /s/  Edward Hayes                               BY: /s/  Christopher Dorrington   

EDWARD HAYES                                      CHRISTOPHER DORRINGTON

Rule Reviewer                                            Director

                                                                    Department of Environmental Quality


            Certified to the Secretary of State August 16, 2022.


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