Version History for U.S. Geological Survey Open-File Report 2022-1023 Compilation and Evaluation of Data Used to Identify Groundwater Sources Under the Direct Influence of Surface Water in Pennsylvania By Eliza L. Gross, Matthew D. Conlon, Dennis W. Risser, and Chad E. Reisch ----------------------------------------------------- Posted online May 9, 2022 ----------------------------------------------------- Revised and reposted June 15, 2023 as version 2.0 In the section, “Abstract,” in the third paragraph, the third sentence: A subset (4,018 wells consisting of 3,842 non-GUDI wells and 175 GUDI wells) of the PADWIS database, which originally included data for 12,147 groundwater sources (11,812 non-GUDI wells and 335 GUDI wells), was created for an analysis and includes only community wells evaluated in accordance with the SWIP. changed to The PADWIS database originally included data for 12,147 groundwater sources (11,812 groundwater sources not under the direct influence of surface water (non-GUDI) wells and 335 GUDI wells). A subset (4,018 wells consisting of 3,842 non-GUDI wells and 175 GUDI wells) of the PADWIS database was created for an analysis and includes only community wells evaluated in accordance with the SWIP. In the section, “Introduction,” in the first paragraph, the fourth sentence: Although hydrologists consider groundwater and surface water as a single resource (Winter and others, 1998), GUDI is defined by the PADEP as, “any water beneath the surface of the ground with the presence of insects or other macroorganisms, algae, organic debris or large diameter pathogens such as Cryptosporidium and Giardia lamblia, or significant and relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity or pH which closely correlate to climatological or surface water conditions” (Pennsylvania Department of Environmental Protection, 2002a,b). changed to Although hydrologists consider groundwater and surface water as a single resource (Winter and others, 1998), for the purposes of this report GUDI is defined as, “any water beneath the surface of the ground with the presence of insects or other macroorganisms, algae, organic debris or large diameter pathogens such as Cryptosporidium and Giardia lamblia, or significant and relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity, or pH which closely correlate to climatological or surface-water conditions” (Pennsylvania Department of Environmental Protection, 2002a,b). in the second paragraph, the first sentence: Groundwater sources that do not meet Pennsylvania’s regulatory definition for GUDI (groundwater sources not under the direct influence of surface water [non-GUDI] or groundwater) should not be as prone to pathogenic contamination. changed to Groundwater sources that do not meet Pennsylvania’s regulatory definition for GUDI are considered groundwater sources not under the direct influence of surface water (non-GUDI) or groundwater, and these sources should not be as prone to pathogenic contamination. In the section, “Purpose and Scope,” the paragraph: This report documents the following components of data compilation and evaluation: (1) a review of file information for 43 public water-supply system wells (hereafter referred to as wells) from the PADEP Northcentral and Southcentral regions to evaluate SWIP and Microscopic Particulate Analysis (MPA) in GUDI determinations, (2) the addition of attributes to PADWIS including spatial anthropogenic (land cover and PADEP region) and naturogenic (geologic and physiographic, hydrologic, soil characterization, and topographic) data that could be potential indicators of GUDI designation or the presence of contaminants in MPA results, which resulted in the creation of three datasets (PADWIS database, PADWIS database subset, and MPA database subset) to be used for analysis (Gross, 2022), and (3) statistical summary and correlation analysis to evaluate existing GUDI sources in the databases with respect to hydrogeologic and source-construction characteristics that are currently utilized in the assessment methodology. changed to This report documents the following components of data compilation and evaluation: (1) a review of file information for 43 public water-supply system wells (hereafter referred to as wells) from the PADEP Northcentral and Southcentral regions to evaluate the SWIP and Microscopic Particulate Analysis (MPA) in GUDI determinations, (2) the addition of attributes to the PADWIS database including spatial anthropogenic (land cover and PADEP region) and naturogenic (geologic and physiographic, hydrologic, soil characterization, and topographic) data that could be potential indicators of GUDI designation or the presence of contaminants in MPA results, which was the impetus for the creation of three datasets (PADWIS database, PADWIS database subset, and MPA database subset) to be used for analysis (Gross, 2022), and (3) statistical summary and correlation analysis to evaluate existing GUDI sources in the databases with respect to hydrogeologic and source-construction characteristics that are currently utilized in the SWIP assessment methodology. In the section, “Review of Case Files for 43 Wells,” in the first paragraph, the first sentence: Case files associated with 43 selected wells in the PADWIS database were reviewed to (1) verify and compile missing data values for attributes in the PADWIS database and identify additional data not included in the PADWIS database that might help to explain a well’s susceptibility to surface-water influence, and (2) provide a better understanding of how the SWIP was applied in practice, since the application of professional judgement is not captured in PADWIS. changed to Case files associated with 43 selected wells in the PADWIS database were reviewed to: (1) verify and compile missing data values for attributes in the PADWIS database and identify additional data not included in the PADWIS database that might help to explain a well’s susceptibility to surface-water influence, and (2) provide a better understanding of how the SWIP steps were applied in practice to generate data needed to evaluate wells. the second sentence: The distribution of GUDI wells across PADEP regions is uneven, with more than half (56 percent) of GUDI wells located within the Northcentral region and just one GUDI well in the Southeast region (fig. 2). changed to The distribution of GUDI wells across PADEP regions is uneven, with more than half (56 percent) located within the Northcentral region and just one in the Southeast region (fig. 2). the third sentence: The complex physical settings can be highly variable among wells across the state and available site-specific data could make implementation of a uniform evaluation approach for GUDI difficult. changed to The complex physical settings can be highly variable among wells across the state, and limited site-specific data make implementation of a uniform evaluation approach for GUDI difficult. the third sentence: Differences in the application of professional judgement could strongly affect the likelihood that a well is classified as GUDI and might be a factor contributing to the uneven percentage of GUDI wells across PADEP regions (fig. 2). changed to The complex physical settings can be highly variable among wells across the state, and limited site-specific data make implementation of a uniform evaluation approach for GUDI difficult. This is likely a contributing factor explaining the uneven percentage of GUDI wells across the state (fig. 2). the fourth sentence: Differences in the application of professional judgement are also linked to complex physical settings that can be highly variable among wells. was removed. in the second paragraph, the last sentence: In the Northcentral region, we examined case files of wells that had been classified as GUDI without undergoing 6 months of monitoring—a practice that does not seem consistent with the SWIP—and which is described in greater detail in PADEP documentation (Pennsylvania Department of Environmental Protection, 2001, 2002b). changed to In the Northcentral region, case files were examined that had been classified as GUDI without undergoing 6 months of monitoring. (Pennsylvania Department of Environmental Protection, 2001, 2002b). In the section, “Data Availability,” the second sentence of the first paragraph: Although the PADWIS database includes most of the criteria used for the SWIP, such as major aquifer type, static water level, or whether the aquifer is confined (Pennsylvania Department of Environmental Protection, 2001, 2002b), it does not provide sufficient information to show how the determination was made for classifying a well as GUDI. changed to Although the PADWIS database includes most of the criteria used for the SWIP, such as major aquifer type, static water level, or whether the aquifer is confined (Pennsylvania Department of Environmental Protection, 2001, 2002b), it does not provide sufficient information to show what data were utilized to classify a well as GUDI. the third sentence of the first paragraph: For example, the SWIP STATUS attribute (table 1) in the PADWIS database indicates if an evaluation was completed, but this attribute does not provide results for the SWIP monitoring or the total risk factor scores from any collected MPA samples, so it is impossible to know which, if any of the SWIP monitoring criteria or guidelines (Pennsylvania Department of Environmental Protection, 2001,2002b) were utilized during the evaluation. changed to For example, the SWIP STATUS attribute (table 1) in the PADWIS database indicates if an evaluation was completed, but this attribute does not provide results for the SWIP monitoring or the total risk-factor scores from any collected MPA samples, so it is not known which, if any, of the SWIP monitoring criteria or guidelines (Pennsylvania Department of Environmental Protection, 2001, 2002b) were utilized during the evaluation. the fourth sentence of the first paragraph: was removed. the fifth sentence of the first paragraph: As a result, some PADWIS attributes could have QC verification performed using information in the well files to change incorrect values to correct values or to fill in missing values. changed to As a result, some PADWIS attributes could have verification performed using information in the well files to change incorrect values to correct values or to fill in missing values. the last sentence of the second paragraph: According to PADEP’s Guidance for Surface Water Identification Protocol, static water level in the well is a necessary attribute for GUDI classification (Pennsylvania Department of Environmental Protection, 2001). changed to According to PADEP’s SWIP, static water level in the well is a necessary attribute for determining if a source is susceptible to surface-water influence (Pennsylvania Department of Environmental Protection, 2001). the first sentence of the third paragraph: Additional variables of importance to the classification of a well as GUDI or non-GUDI include the spatial coordinates that define a well’s location (LATITUDE and LONGITUDE attributes, table 1). changed to Other variables of importance to determine if additional monitoring and evaluation are needed on a source include the spatial coordinates that define a well’s location (LATITUDE and LONGITUDE attributes, table 1). the second sentence of the third paragraph: Spatial coordinates for 11 wells in the Southcentral region were found in files associated with the wells, and spatial coordinates listed in the files for 9 of these 11 wells differed by 130 to 14,800 feet (ft) from the spatial coordinates provided in the PADWIS database. changed to Spatial coordinates for 11 wells in the Southcentral region were found in files associated with the wells, yet the spatial coordinates listed in the files for 9 (82 percent) of these 11 wells differed by 130 to 14,800 feet (ft) from the coordinates provided in the PADWIS database. the second sentence of the fourth paragraph: For example, the distance (threshold distance of 200 ft) from a well to the nearest surface-water feature, such as a flowline, water feature, or water body, is not an attribute available for assessment in the PADWIS database (Pennsylvania Department of Environmental Protection, 2016), but this is an attribute that may require a well to be identified for further evaluation of well integrity criteria or required to conduct SWIP monitoring. changed to For example, the distance (threshold distance of 200 ft) from a well to the nearest surface-water feature, such as a flowline, water feature, or water body, is not an attribute available for assessment in the PADWIS database (Pennsylvania Department of Environmental Protection, 2016), but this is an attribute that may require a well to be identified for further evaluation. the first sentence of the fifth paragraph: Pearson correlation coefficients, which are derived from data (water-quality parameters, precipitation, and local surface water conditions) collected by PADEP during the 6-month SWIP monitoring program, that are considered high (> 0.40) can be used to classify a well as GUDI or to elicit MPA testing, but these results are not included in the PADWIS database despite providing important information about perceived risk. changed to Pearson-correlation coefficients, which are derived from data (water-quality parameters, precipitation, and local surface-water conditions) collected by the water system during the 6-month SWIP monitoring program, that are considered high (> 0.40) can be used to classify a well as GUDI or to elicit MPA testing, but these results are not included in the PADWIS database. In the section, “Application of the Surface Water Identification Protocol,” the first sentence of the first paragraph: The SWIP consists of three steps: (1) screening for sources susceptible to surface-water influence on the basis of aquifer type and well characteristics, (2) monitoring for 6 months to evaluate the Pearson correlation results among water level, precipitation, or stream stage with selected water-quality parameters, and (3) sampling for particulates and organisms with an MPA. changed to The SWIP consists of up to three steps: (1) screening for sources susceptible to surface-water influence based on aquifer type and well characteristics, (2) monitoring for six months to evaluate the Pearson-correlation results among water level, precipitation, or stream stage with selected water-quality parameters, and (3) sampling for particulates and organisms with an MPA. the first sentence of the second paragraph: File review of selected wells showed that the SWIP is usually followed, but for some sources the GUDI determination in practice is much more complex and cannot be easily summarized in a database such as PADWIS. changed to File review of selected wells showed that for some sources the GUDI determination in practice is much more complex and cannot be easily summarized in a database such as PADWIS. the first sentence of the third paragraph: As expected, review of the well files shows that hydrogeologic judgement is a factor in all three steps of the SWIP, but its effect is difficult to quantify. changed to Review of the well files shows that application of a uniform evaluation approach for GUDI is difficult because of highly variable site-specific factors that need to be considered in applying the SWIP steps, but its effect is difficult to quantify. the second sentence of the third paragraph: Judgement is especially notable in the evaluation of results from the 6 months of SWIP monitoring because the Pearson correlation results among the monitored parameters are commonly moderate (close to but not exceeding 0.40). changed to This is especially notable in the evaluation of results from the 6 months of SWIP monitoring because the Pearson-correlation results among the monitored parameters are commonly moderate (close to but not exceeding 0.40). the fifth sentence of the third paragraph: In some of these cases, the presence of bacteria and other organisms was used as an indication of surface-water influence and as evidence to classify the source as GUDI; in other cases, the well was not classified as GUDI because the MPA sample showed low risk of surface-water influence and the presence of bacteria was deemphasized because the source could be treated by disinfection. changed to In some of these cases, the presence of bacteria and other organisms was used as an indication of surface-water influence and as evidence to classify the source as GUDI; in other cases, despite the presence of bacteria, the source was not classified as GUDI given the low-risk MPA results in addition to the implementation of disinfection treatment practices. the fourth paragraph: In general, the file review suggests a somewhat different approach to classification of some wells as GUDI in the Northcentral region than in the Southcentral region. In the Northcentral region, the presence of any indicator organisms in the MPA sample was used as evidence supporting a GUDI classification, even if the total MPA risk factor score was low. This may be an acceptable rationale, but it seems to differ from the approach used in the Southcentral region on the basis of review of 11 well files in that office. In the Southcentral region, 8 of 12 wells in carbonate rock had moderate Pearson correlation results and low MPA risk (or no MPA sample) and were not classified as GUDI. was removed. the first sentence of the fifth paragraph: Findings about the implementation of the SWIP in the Southcentral and Northcentral regions from the examination of well files are further summarized in the following sections. changed to Implementation of the SWIP in the Southcentral and Northcentral regions is further summarized in the following sections based on the examination of well files. In the section, “Examination of Case Files for 19 Wells Classified as Groundwater Under the Direct Influence of Surface Water in Southcentral Pennsylvania,” the first sentence of the first paragraph: Files for 19 Southcentral region wells classified as GUDI were reviewed. PADWIS included SWIP STATUS attributes for these wells, indicating that the steps of the protocol had been completed for the wells, but it was apparent from the file review that data from different steps were given different weighting based on hydrogeologic judgement. changed to Files for 19 Southcentral region wells classified as GUDI were reviewed. PADWIS included SWIP STATUS attributes for these wells, indicating that the steps of the protocol had been completed for the wells, but it was apparent from the file review that data from different steps were given different weighting. the first sentence of the first bullet point: GUDI classification was indicated by all three SWIP steps–For 12 of the 19 wells reviewed (63 percent), the initial screening step showed the wells were highly susceptible to surface-water influence, 6 months of monitoring showed moderate Pearson correlation results among water-quality parameters with bacteria present in samples, and the MPA results indicated moderate or high risk (total risk factor score of 10 or greater). changed to GUDI classification determined by all three SWIP steps.—For 12 (63 percent) of the 19 wells reviewed, the initial screening step showed the wells were highly susceptible to surface-water influence, six months of monitoring showed moderate Pearson-correlation results among water-quality parameters with bacteria present in samples, and the MPA results indicated moderate or high risk (total risk factor score of 10 or greater). the last sentence of the first bullet point: The three SWIP steps each supported classification of the wells as GUDI. changed to Data from the three SWIP steps supported classification of the wells as GUDI. the first sentence of the second bullet point: GUDI classification was indicated by monitoring – For 2 of the 19 files reviewed (11 percent), the screening step showed that although the wells had a high susceptibility to surface-water influence, the MPA results indicated low risk (total risk factor score lower than 10), so the GUDI determination was made on the basis of results from 6 months of monitoring that showed Pearson correlation results between turbidity and precipitation greater than 0.4 with the presence of bacteria. changed to GUDI classification determined by monitoring.—For 2 (11 percent) of the 19 files reviewed, the screening step showed that although the wells had a high susceptibility to surface-water influence, the MPA results indicated low risk (total risk factor score lower than 10), so the GUDI determination was made on the basis of results from six months of monitoring that showed Pearson-correlation results between turbidity and precipitation greater than 0.4 with the presence of bacteria. the last sentence of the second bullet point: Thus, two of the three SWIP steps supported classification of the wells as GUDI. changed to Thus, data generated from two of the three SWIP steps supported classification of the wells as GUDI. the first sentence of the third bullet point: GUDI classification was indicated by susceptibility and professional judgement – For 1 of the 19 wells reviewed (5 percent), the screening step showed the well had a high susceptibility to surface-water influence, but there were no high Pearson correlation results between water-quality parameters and precipitation during 6 months of monitoring, and the MPA result indicated low risk (total risk factor score less than 10). changed to GUDI classification determined by susceptibility and existing data from other wells in the same well field.—For 1 (5 percent) of the 19 wells reviewed, the screening step showed the well had a high susceptibility to surface-water influence, but there were no high Pearson-correlation results between water-quality parameters and precipitation during six months of monitoring, and the MPA result indicated low risk (total risk factor score less than 10). the last sentence of the third bullet point: In this case, although only one of the SWIP steps supported classification as GUDI, the well was classified as GUDI along with the other supply wells in the well field. changed to In this case, existing data from other wells in the same well field was used to classify the well as GUDI. In the section, “Examination of Case Files for 11 Wells Not Classified as Groundwater Under the Direct Influence of Surface Water in Southcentral Pennsylvania,” the last sentence of the first paragraph: The files were reviewed to determine if the SWIP was followed consistently, find out why they were designated as groundwater (non-GUDI) instead of GUDI, and identify key factors that might be used to distinguish GUDI from non-GUDI wells prior to monitoring. changed to The files were reviewed to determine: (1) how the SWIP steps were utilized, (2) to examine the data used to assign a source classification, and (3) to identify key factors that might be used to distinguish GUDI from non-GUDI wells prior to monitoring. the first sentence of the second paragraph: The review of files for the 11 non-GUDI wells in the Southcentral region showed more ambiguity in the determination than for the 19 GUDI wells in the region previously discussed, but it was apparent from the file review that PADEP hydrogeologists were following the SWIP steps. changed to The review of files for the 11 non-GUDI wells in the Southcentral region showed more ambiguity in the determination than for the 19 GUDI wells. the second sentence of the second paragraph: Hydrogeologic judgement was applied during the process, especially in evaluating the monitoring results and determining when to require MPA sample collection. was removed. the introductory phrase of the first bullet point: Non-GUDI classification was determined by an MPA result indicating low risk changed to Non-GUDI classification determined by low-risk MPA result.— the last sentence of the first bullet point: The non-GUDI classification appears to have been based heavily on an MPA result indicating low risk (total risk factor score lower than 10) even though results from the 6 months of SWIP monitoring and presence of bacteria could have been used to support classification as GUDI. changed to The non-GUDI classification appears to have been based heavily on an MPA result indicating low risk (total risk factor score lower than 10). the introductory phrase of the second bullet point: Non-GUDI classification was indicated by monitoring and low bacteria counts changed to Non-GUDI classification determined by monitoring and low bacteria counts. the introductory phrase of the third bullet point: Non-GUDI classification assumed to be determined by professional judgement changed to Non-GUDI classification determined by other factors the last sentence of the third bullet point: It is possible that the professional(s) responsible for guiding these wells through the SWIP steps considered the lithology (AQUIFER LITHOLOGY attribute in PADWIS database; see table 1) of the Wills Creek and Jacksonburg Formations in which these wells are completed to be shale instead of carbonate-rock aquifers, thus resulting in these two wells being classified as non-GUDI. changed to Since these wells were coded as being in the Wills Creek and Jacksonburg Formations, it is possible that they were determined to be in shale instead of carbonate-rock aquifers. In the section, “Examination of Case Files for 13 Wells Classified as Groundwater Under the Direct Influence of Surface Water in Northcentral Pennsylvania,” the first sentence of the first paragraph: Files associated with 13 GUDI wells in the Northcentral region were examined to understand why more wells in this region than in other regions had been classified as GUDI without requiring 6 months of SWIP monitoring. changed to Files associated with 13 GUDI wells in the Northcentral region were examined to understand why wells in this region had been classified as GUDI without requiring six months of SWIP monitoring. the fourth sentence of the first paragraph: Although it may have been available elsewhere, documentation fully explaining the reasoning behind the classification of two of the 13 wells (15 percent) as GUDI could not be found in the files associated with the wells. changed to Although it may have been available elsewhere, documentation fully explaining the reasoning behind the classification of 2 (15 percent) of the 13 wells as GUDI could not be found in available files associated with the wells. the introductory phrase of the first bullet point: GUDI classification was indicated by susceptibility and default changed to GUDI classification potentially determined by susceptibility the second and third sentence of the first bullet point: Once it came to the point in the process at which the operator(s) would be required to conduct 6 months of monitoring, five of these wells were abandoned, and the water-system operator began to filter the water from the sixth well prior to its dissemination. These six wells were then classified as GUDI in the PADWIS database without 6 months of SWIP monitoring or the collection of MPA samples, most likely because the water-system operators perceived that the wells would likely fail the monitoring and MPA testing. changed to Prior to conducting six months of monitoring, five of these wells were abandoned, the water-system operator began to filter the water from the sixth well prior to its dissemination, and all six wells were classified as GUDI in the PADWIS database. the last sentence of the first bullet point: Therefore, the SWIP STATUS attribute value of “Completed - Monitoring Not Required” in the PADWIS database is misleading because the 6 months of monitoring was required, but was not conducted, so these wells were essentially classified as GUDI by default. was removed. the introductory phrase of the second bullet point: GUDI classification was determined by unclear methods changed to GUDI classification potentially determined by monitoring and susceptibility the first sentence of the second bullet point: For four of the 13 wells for which files were reviewed (21 percent), the classification of the wells as GUDI was not clearly documented in the files associated with the wells. changed to For 4 (21 percent) of the 13 wells for which files were reviewed, the classification of the wells as GUDI was not clearly documented in the available files associated with the wells. the second sentence of the second bullet point: At two of these wells, 6 months of SWIP monitoring was completed, and the GUDI classification for these two wells seems to have been based on moderate Pearson correlation results during the monitoring period, even with MPA results indicating low risk (total risk factor score lower than 10). changed to At two of these wells, six months of SWIP monitoring was completed, and the GUDI classification for these two wells seems to have been based on moderate Pearson-correlation results during the monitoring period. the introductory phrase of the third bullet point: GUDI classification was indicated by all three SWIP steps changed to GUDI classification determined by susceptibility, high bacteria counts, and high-risk MPA result In the section, “Pennsylvania Drinking Water Information System,” the first sentence of the fifth paragraph: In addition to differences in the number of wells classified as GUDI among regions, the SWIP STATUS attribute in the PADWIS database (Pennsylvania Department of Environmental Protection, 2016) indicates 98 of the 335 GUDI wells (approximately 29 percent) were potentially designated as such without receiving the 6 months of SWIP monitoring; most of these wells (85 percent) are in the Northcentral region (fig. 3). changed to The SWIP status attribute in the PADWIS database (Pennsylvania Department of Environmental Protection, 2016) indicates 98 (approximately 29 percent) of the 335 GUDI wells were designated GUDI where SWIP monitoring was not required. Most of these wells are in the Northcentral region (fig. 3). the second sentence of the fifth paragraph: Of these 98 wells classified as GUDI without receiving SWIP monitoring, 78 (80 percent) had a SWIP finalization date (SWIP FINAL attribute) between 1991 and 2000, compared to only 13 wells (13 percent) with a SWIP finalization date between 2003 and 2012; thus, indicating the practice of classifying wells as GUDI without SWIP monitoring occurred more frequently in the early days of the program, that is, prior to 2001. changed to Of the 98 wells without SWIP monitoring requirements, 78 (80 percent) had a SWIP finalization date between 1991 and 2000, indicating the classification of wells as GUDI without required SWIP monitoring occurred prior to 2001. the third, fourth, fifth, sixth, seventh, and eighth sentences of the fifth paragraph: No data were available for the remaining 7 wells (7 percent) for the SWIP FINAL attribute in the PADWIS database. The last well classified as a GUDI source without receiving SWIP monitoring had a SWIP finalization year of 2012 (Pennsylvania Department of Environmental Protection, 2016). It should be noted that of these 98 wells, only 13 of the wells (13 percent) have a SOURCE AVAILABILITY attribute describing them as permanent; 80 of them (82 percent) are listed as abandoned; the other five wells (5 percent) are designated as reserve wells. Also, the ACTIVITY STATUS attribute in the PADWIS database for six of these 13 wells indicates that they are inactive; the remaining seven wells are classified as active. For the seven GUDI wells designated as permanent and active, it is not apparent how the GUDI determinations were made without the benefit of SWIP monitoring. Available data in the PADWIS database are insufficient to understand why these seven wells were classified as GUDI without SWIP monitoring, but it is possible that the wells had structural defects or poor water quality, which would have increased the likelihood for a GUDI designation and perhaps agreement by the water-system operator to bypass additional testing and provide adequate treatment. were removed. the ninth and tenth sentence of the fifth paragraph: In addition, the PADEP’s Guidance for Surface Water Identification Protocol (Pennsylvania Department of Environmental Protection, 2001) indicates that MPA testing may be conducted for susceptible sources prior to the SWIP monitoring; thus, an initial MPA sample may have indicated a moderate or high risk of susceptibility to surface water influence. Several of these wells were examined in greater detail in the “Application of the Surface Water Identification Protocol” subsection of the “Review of Case Files for 43 Wells” section. changed to In addition, the PADEP’s Guidance for Surface Water Identification Protocol (Pennsylvania Department of Environmental Protection, 2001) indicates that MPA testing may be conducted for susceptible sources prior to the SWIP monitoring; thus, an initial MPA sample may have indicated a moderate or high risk of susceptibility to surface-water influence. In the section, “Pennsylvania Drinking Water Information System Database Subset,” the first sentence of the first paragraph: A subset of the PADWIS database was extracted to include only community wells that have undergone the SWIP to determine a source classification of GUDI or non-GUDI to ensure that all the sources included in the study analysis had been through a comparable evaluation process and were subject to as consistent a protocol as possible (Pennsylvania Department of Environmental Protection, 2010). changed to A subset of the PADWIS database was extracted to include only community wells that were indicated in the database to have undergone the SWIP to determine a source classification of GUDI or non-GUDI; this was an effort to only include sources in the study analysis that had been through a comparable evaluation process to receive GUDI or non-GUDI classification (Pennsylvania Department of Environmental Protection, 2010). In the section, “Microscopic Particulate Analysis Database Subset,” the first sentence of the second paragraph: A digital database of 2,327 MPA results for samples collected between 1990 and 2014 was provided by PADEP. changed to A digital database of 2,327 MPA results for samples collected from public water-supply systems between 1990 and 2014 was provided by PADEP. the second sentence of the second paragraph: This database included analytical results from samples collected since the introduction of the SWIP in the early 1990s and contained results for bio-indicator counts and associated risk factor scores for groundwater samples collected from public water-supply systems. changed to This database included analytical MPA results determined from methods in US Environmental Protection Agency (1992), including bioindicator counts and associated risk-factor scores for groundwater samples. All samples were collected and analyzed after the introduction of SWIP in the early 1990s. the first sentence of the ninth paragraph: The regional distribution of the 631 wells with associated MPAs is similar to that of the total amount of GUDI wells, with the Northcentral and Southcentral regions having the highest number of wells with MPAs (fig. 7). changed to The regional distribution of the 631 wells with associated MPAs is like that of the total amount of GUDI wells, with the Northcentral and Southcentral regions having the highest number of wells with MPAs (fig. 7). the second sentence of the ninth paragraph: Unlike the geographic distribution of total GUDI wells, the Southeast region had just one GUDI well (fig. 3), but this region had 89 wells (89 of 631; 14 percent) with MPAs, with 26 of the MPAs exceeding zero and only two of the MPAs classified as moderate or high risk (fig. 7). changed to Unlike the geographic distribution of total GUDI wells, the Southeast region had just one GUDI well (fig. 3). The Southeast region had 89 (14 percent) of 631 wells with MPAs, with 26 (29 percent) of the 89 MPAs exceeding zero and only 2 (2 percent) of the 89 MPAs classified as moderate or high risk (fig. 7). the third sentence of the ninth paragraph: The Northcentral region, which had the highest number of total GUDI wells (186 of 335; 56 percent), also had the highest number of wells with MPAs (276 of 631; 44 percent), with 58 of those 276 (21 percent) MPAs exceeding zero and 22 (8 percent) MPAs classified as moderate or high risk (fig. 7). changed to The Northcentral region, which had the highest number of total GUDI wells (186 [56 percent] of 335), also had the highest number of wells with MPAs (276 [44 percent] of 631). In the Northcentral region, 58 (21 percent) of 276 MPAs exceeded 0, and 22 (8 percent) of 276 MPAs were classified as moderate or high risk (fig. 7). In the section, “Anthropogenic Data,” the last sentence of the first paragraph: These radii are not necessarily assumed to be actual contributing areas to the well, but data compiled for these areas are considered to be representative of land-surface characteristics near the wellhead. changed to These radii are not necessarily assumed to be actual contributing areas to the well, but data compiled for these areas are representative of land-surface characteristics near the wellhead. In the section, “Naturogenic Data,” the first sentence of the first paragraph: Geologic data include major aquifer types (Miles and Whitfield, 2001; Soller and Packard, 1998) and physiographic provinces (Pennsylvania Bureau of Topographic and Geologic Survey, 2008) in Pennsylvania (fig. 4) used to characterize GUDI well occurrence or presence of contaminants in MPA results in specific bedrock types and geographic areas. changed to Geologic data include major aquifer types (Miles and Whitfield, 2001; Soller and Packard, 1998) and physiographic provinces (Pennsylvania Bureau of Topographic and Geologic Survey, 2008) in Pennsylvania (fig. 4) used to characterize GUDI well occurrence or presence of bioindicators in MPA results in specific bedrock types and geographic areas. the sixth sentence Wells were assumed to be completed in the major aquifer type at the well’s spatial coordinates without regard to well or bedrock depth; therefore, the “carbonate,” “crystalline”, and “siliciclastic” classifications do not account for overlying surficial deposits, and likewise, major aquifer types classified as “surficial” do not account for underlying bedrock geology changed to Wells were assumed to be completed in the major aquifer type at the well’s spatial coordinates without regard to well or bedrock depth. Therefore, the “carbonate,” “crystalline,” and “siliciclastic” classifications do not account for overlying surficial deposits, and major aquifer types classified as “surficial” do not account for underlying bedrock geology. In the section, “Availability of Data Associated with the Surface Water Identification Protocol,” the last sentence of the fourth paragraph: Data describing the criteria listed in table 6, including the number of criteria met by each well, were included in further statistical analyses to determine if these criteria are a statistically significant measure of a well being GUDI. changed to Data describing the criteria listed in table 6, including the number of criteria met by each well, were included in further statistical analyses to determine if these criteria are a statistically significant measure of a well having been designated as GUDI. In the section, “Microscopic Particulate Analysis Database Subset,” the third sentence of the fourth paragraph: Of the bio-indicator variables, the risk factor, sample count, and presence or absence variables for algae, rotifers, and diatoms had the highest positive correlations with both MPA total risk factor scores and assigned hazard-level scores, suggesting that these bio-indicators are more commonly present in MPA samples with high risk-factor and hazard-level scores than bio-indicators such as insects/crustacea, plant debris, giardia, or coccidia. changed to Of the bioindicator variables, the risk-factor score, sample count, and presence or absence variables for algae, rotifers, and diatoms had the highest positive correlations with both MPA total risk-factor scores and assigned hazard-level scores, suggesting that these bioindicators are more commonly present in MPA samples with high risk-factor and hazard-level scores than bioindicators such as insects/crustacea, plant debris, giardia, or coccidia. In the section, “Limitations of the Data,” the second and third sentence of the first paragraph: As previously explained, detailed case file review showed that the SWIP was usually followed, but for some sources the GUDI determination was based on professional judgement by the PADEP. Factors considered in these judgements could not be easily summarized in a database such as PADWIS. changed to As previously explained, detailed case-file review showed the SWIP steps were typically utilized to generate data needed to evaluate wells, but for some wells the evaluation approach was based on other factors such as complex physical setting or other available data that could not be easily summarized in a database such as PADWIS. the last sentence of the first paragraph: Review of the files for specific wells shows that hydrogeologic judgement was a factor in the overall evaluation, but its effect was difficult to quantify and compare among regions. was removed. the first sentence of the second paragraph: In addition, analysis of the PADWIS database showed discrepancies among regions in compiling data describing well characteristics and site-specific attributes. changed to In addition, analysis of the PADWIS database showed differences among regions in compiling data describing well characteristics and site-specific attributes. the fifth sentence of the second paragraph: Including Pearson correlation coefficients calculated by PADEP during the SWIP as an attribute in the PADWIS database would be useful for understanding why a well was classified as GUDI. changed to Including Pearson-correlation coefficients calculated by PADEP during the SWIP as an attribute in the PADWIS database could be useful for understanding why a well was classified as GUDI. the first sentence of the third paragraph: Detailed review of the files for specific wells showed data discrepancies between well files and the corresponding well record in the PADWIS database, which may indicate inaccurate transfer of data. changed to Detailed review of the files for specific wells indicated there were some differences between well files and the corresponding well record in the PADWIS database, which might have contributed to an inaccurate transfer of data. In the section, “Summary,” the last sentence of the first paragraph: Most of the data were provided by the Pennsylvania Department of Environmental Protection (PADEP), including source data derived from PADEP case files, a source information database for public water-supply systems, and Microscopic Particulate Analysis (MPA) results and associated water-quality data for public water-supply systems. changed to Most of the data were provided by the Pennsylvania Department of Environmental Protection (PADEP), including source data derived from PADEP case files, a source information database for public water-supply systems, and Microscopic Particulate Analysis (MPA) results and associated water-quality data for public water-supply wells. the second sentence of the second paragraph: Review of file information for these 43 wells showed that, although the SWIP steps are usually followed, for some sources the GUDI determination is complex and cannot be easily summarized. changed to Review of file information from these 43 wells showed that, for some sources, the GUDI determination is too complex to be easily summarized in a database. the third sentence of the second paragraph: File review also showed that hydrologic judgement is a factor in all three steps of the SWIP, but its effect is difficult to quantify. changed to File review also showed that complex physical setting and available site-specific data may influence all three steps of the SWIP, but the effect on GUDI determination is difficult to quantify. the last sentence of the second paragraph: For example, data may indicate, but not precisely prove, that a well is GUDI and result in a well being classified as GUDI anyway, which seemed to be the case for more of the wells classified as GUDI in the Northcentral region than in the Southcentral region. was removed. the fourth sentence of the third paragraph: MPA results for 631 wells were compiled, along with data for associated water-quality constituents and properties (including alkalinity, chloride, Escherichia coli, fecal coliform, nitrate, pH, sodium, specific conductance, sulfate, total coliform, total dissolved solids, total residue, and turbidity) populated from the PADEP Bureau of Laboratories, Sample Information System for 49 to 367 of the 631 wells. changed to MPA results for 631 community and non-community wells were compiled, along with data for associated water-quality constituents and properties (including alkalinity, chloride, Escherichia coli, fecal coliform, nitrate, pH, sodium, specific conductance, sulfate, total coliform, total dissolved solids, total residue, and turbidity) populated from the PADEP Bureau of Laboratories, Sample Information System. Data describing associated water-quality constituents and properties were available for varying amounts (between 49 to 367) of the 631 wells that had MPA results. the first sentence of the fourth paragraph: Data on the major aquifer type in which a well is completed, the physiographic province in which it is located, and construction data for wells in the PADWIS database subset and MPA database subset were analyzed using the Kruskal-Wallis test to evaluate differences among groups. changed to Data describing the major aquifer type in which a well is completed, the physiographic province in which it is located, and construction data for wells in the PADWIS database subset and MPA database subset were analyzed using the Kruskal-Wallis test to evaluate differences among groups. the first sentence of the fifth paragraph: Spearman’s rank correlation coefficient (rho) was used to characterize available data that best identify a community well as being GUDI or result in a contaminated MPA, which could potentially result in a GUDI determination. changed to: Spearman’s rank correlation coefficient (rho) was used to characterize available data that best identify a community well as being GUDI or a community or non-community well with a contaminated MPA result, which could potentially be the cause of a GUDI determination. the last sentence of the fifth paragraph: The PADEP region variables illustrate potential differences in the implementation of the Safe Drinking Water Program in Pennsylvania across PADEP regions. changed to The PADEP region variables illustrate potential affects that a complex physical setting and available site-specific data can have on the implementation of a uniform evaluation approach for GUDI across the state. the last sentence of the sixth paragraph: Of the bio-indicator variables, the risk factor, sample count, and presence or absence variables for algae, rotifers, and diatoms had the highest positive correlations with both MPA total risk factor scores and assigned hazard-level scores, suggesting that these bio-indicators are more commonly present in MPA samples with high risk-factor and hazard-level scores than bio-indicators such as insects/crustacea, plant debris, giardia, or coccidia. changed to: Of the bioindicator variables, the risk-factor score, sample count, and presence or absence variables for algae, rotifers, and diatoms had the highest positive correlations with both MPA total risk-factor scores and assigned hazard-level scores, suggesting that these bioindicators are more commonly present in MPA samples with high risk-factor and hazard-level scores than bioindicators such as insects/crustacea, plant debris, giardia, or coccidia. the first sentence of the last paragraph: On the basis of the results of the several analyses described in this report, broad conclusions can be drawn regarding site-specific well characteristics and anthropogenic and naturogenic factors that could be responsible for a well being designated as GUDI, but the accuracy of these results is dependent on the quality of the data being analyzed. changed to Based on the results of the analyses described in this report, broad conclusions can be drawn regarding site-specific well characteristics and anthropogenic and naturogenic factors that could be responsible for a well being designated as GUDI, but the accuracy of these results is dependent on the quality of the data being analyzed. the second sentence of the last paragraph: Detailed review of well files showed that the SWIP steps are usually followed, but for some sources, the GUDI determination in practice is much more complex and cannot be easily summarized in the PADWIS database. changed to Detailed review of well files showed that the SWIP steps are usually followed, but for some sources, the GUDI determination in practice is more complex than what can be easily summarized in the PADWIS database.