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Source Water Assessment Plan - State of Missouri

Drinking Water Source Water Assessment Plan

Revised December 28, 2000
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Missouri Department of Natural Resources
Public Drinking Water Program


Figure 1 ground water example Appendix A advisory committee members
Figure 2 surface water example Appendix B public comments
Figure 3 example priority area Appendix C public meeting announcements
Figure 4 example interstate source water area Appendix D sources of contaminant information
    Appendix E list of potential contaminants and contaminant sources
    Appendix F List of Acronyms

Purpose of this Document

The purpose of this document is to describe the state of Missouri’s plan for developing and implementing requirements of the Safe Drinking Water Act (SDWA) Amendments of 1996 (P.L. 104-182) for state Source Water Assessment Programs [sections 1453 and 1428(b)].  The ultimate goal of this program is to protect public drinking water sources from contamination and provide safe drinking water.

Source Water Assessments include defining the geographic areas that may influence the quality of drinking water sources, and then identifying potential contamination sources in those areas.  Drinking water sources include public wells, springs, impoundment intakes, and river intakes. The area that may influence the quality of a water source is known as the source water area. As an example, the source water area for a drinking water lake may include the watershed upstream of the intake.  Source water areas are discussed more thoroughly in Section III.  Potential contamination sources are discussed in Section IV.

Public water supplies are encouraged to develop individual Source Water Protection Programs.   These Source Water Protection Programs can take advantage of the information resulting from the state’s Source Water Assessments.  Voluntary Source Water Protection Programs can further protect drinking water sources by reducing the presence of contaminants in the source water area or reducing the source’s susceptibility to those contaminants.  Source water protection includes wellhead and watershed protection.  Source water area delineations, potential contaminant inventories, and susceptibility determinations provided by the state can be used by local groups as the first steps of their own source water protection plans.  Results of source water assessments may also be used by the Department to improve the state’s program to prioritize and encourage source water protection.

The responsibility of developing and implementing this plan lies with the Public Drinking Water Program (PDWP) within the Division of Environmental Quality (DEQ) of the Missouri Department of Natural Resources (DNR).  This plan was formally submitted to EPA on February 6, 1999.  This revised plan is being submitted in response to the comments provide by EPA.


The 1996 SDWA Amendments place a strong emphasis on public awareness and involvement.  The state is required to involve the public in the development of this Source Water Assessment Program and make the assessment results available to the public.  This is intended to encourage the development of local Source Water Protection Programs.  EPA encourages involvement of public interest groups, public health groups, vulnerable populations, business groups, local governments, conservation groups, water suppliers, and others.

PDWP established a technical advisory committee and a citizens advisory committee to provide input in the development of this source water assessment plan.  Groups that were invited to participate on the committees are listed in Appendix A. The first committee meetings were held in August 1998.  The content of the technical advisory committee and the public advisory committee were so similar that it was decided the committees would henceforth meet jointly.  There are several changes from previous drafts throughout this plan that resulted from comments of the advisory committees.  A summary of the committees’ comments and PDWP’s responses is included in Appendix B. Committee members are updated periodically of revisions to this plan.  The committee convened in December 1998 to review the plan before it was submitted to EPA and in January 2000 to review this revised plan. The committee agreed to meet periodically to address source water assessments.  Future meetings will be scheduled around milestones in the implementation of this plan, or at least on an annual basis.

Six public meetings were held around the state.  The purpose of these meetings was to present this plan to anyone among the general public who is interested. 54 people attended these meetings. Comments on the plan raised during these public meetings and PDWP’s responses are summarized in Appendix B. A news release advertising these meetings is included in Appendix C.  These news releases were distributed through the Missouri Link to approximately 500 print and broadcast media outlets.  KRES radio out of Moberly and KJEL radio out of Lebanon are among the news agencies that are confirmed to have distributed the news release.  These are both regional radio stations with large geographic listening areas.  The news release was also published in at least four newspapers with a total circulation of over 45,000 readers.  Flyers were distributed to all the advisory committee members, Missouri Water and Wastewater Conference section chairs, and 23 regional Retired Senior Volunteer Program (RSVP) contacts.  Many committee members carried the meeting announcements on to other members of their organizations and affiliates.  Additional flyers were also distributed to public water systems that showed an interest in source water protection, district Health Department offices, local University Extension offices, and news agencies in the cities where meetings were held.

PDWP is also taking advantage of any additional opportunities to publicize the source water assessment plan.  Articles have been published in the Water and Wastewater Digest, Protecting Missouri’s Natural Resources newsletter, and the Missouri Groundwater Quarterly.  A brief presentation was given to the Water Quality Coordinating Committee on July 21, 1998, the Safe Drinking Water Commission on July 30, 1998, the Missouri Groundwater Association on September 18, 1998, the Clean Water Commission on September 23, 1998, the Missouri Water and Wastewater Conference on September 29, 1998, the PDWP regional office workshop on December 2, 1998, and the Mid Missouri GIS Users Group on January 20, 1999. The draft plan and public meeting announcements were originally available on the CARES (Center for Agricultural, Resource, and Environmental Systems) Internet site (, which currently provides public access to pertinent public drinking water GIS data. The CARES site will be utilized extensively to distribute the final results of the source water assessments.  Announcement of the public meetings and a link to the CARES site is also on the Missouri Watershed Information Network Internet site.  Missouri’s revised source water assessment plan will be posted on the Department’s own Internet site at (modified with new URL).



Groundwater is a vital resource for the citizens of Missouri, particularly those in the central and southern parts of the state where plentiful, high-quality groundwater is available. There are over 3800 active or proposed public wells in Missouri and another 600 public wells that are currently inactive.  The location of each public well has been recorded in a Geographic Information System (GIS). A geographic information system is a computerized database that has the ability to draw maps.  The GIS system has been used to produce a map for each public well showing a ½-mile radius as an interim source water area.  Figure 1 is an example of one of these maps.  In order to produce more accurate source water assessments, the Public Drinking Water Program will replace these interim source water areas with source water delineations based on the hydrogeologic information available for each well.  To do this, PDWP will employ a combination of the methods described in the Missouri Wellhead Protection Program and EPA’s Guidelines for Delineation of Wellhead Protection Areas. PDWP will delineate 1, 5, and 10-year time-of-travel areas for each well as recommended in the Missouri Wellhead Protection Program. The 1-year and 5-year time-of travel areas will be shown to illustrate the predicted groundwater movement.  The 10-year time-of-travel area will be used as the source water area on which assessments will be based.  PDWP would like to thoroughly conduct a hydrogeologic study of each well to accurately define each source water area.  This is nearly impossible given the limited resources and time frame.  The state of Missouri is requesting the eighteen-month extension offered by EPA.  This would give Missouri two and a half years to complete the assessments after EPA approves this plan.

To some degree, all public water supply wells are susceptible to contamination.  However, the risk of contamination varies greatly, depending on well construction, well location, aquifer type and depth, and many other factors.  Source water areas are intended to represent the areas that provide recharge to water-supply wells, and where the introduction of contaminants could reasonably be expected to affect the quality of water produced from the wells.  One approach to doing this is to determine the size of the drawdown cone, which extends from a well while it is being pumped.  Another is to also consider the regional potentiometric gradient as well as the drawdown cone to determine the area of contribution for the well.  In many aquifers, particularly artesian aquifers having low storage coefficients, the cone of depression and area of contributions can be very large, literally extending in all directions from the pumped well for more than a mile.

The wellhead areas delineated under this project will be crude estimates of the actual well recharge areas.  Missing data for certain wells and unseen geologic factors prevent exact delineation of each recharge area without exhaustive data collection and costly study of each well or group of wells.  The source water areas delineated under this project will be used for the purpose of completing source water assessments and as guides for communities interested in source water protection.  The Department makes no claim that these are the actual recharge areas, and may amend any source water area as new data or delineation methods become available.

Source water areas are commonly depicted to immediately surround a well. An example of a remote recharge area could occur in an area where an impermeable geologic formation prevents the downward migration into an aquifer.  In this case, the area directly around the well does not provide natural recharge to the well. Under such a confining layer, water must travel horizontally from other areas, and a remote recharge area may occur beyond the confining layer where water naturally recharges the aquifer. If a remote recharge area occurs beyond the ten-year time-of-travel distance, it will not be identified. If a remote recharge area occurs within the ten-year time-of-travel distance it will be included as part of the source water area, but may not be differentiated from the rest of the source water area.  The entire ten-year time-of-travel area will be declared the source water area. This is more conservative than including only the remote recharge area as the source water area.  While a confining layer may retard natural migration of contaminants into the drinking water aquifer, abandoned or improperly constructed wells could provide pathways for contaminants to quickly bypass a confining layer.

Time-of–travel calculations that are used to delineate recharge areas are based on slow movement of water through uniform rock formations.  These calculations are not always appropriate for karst areas where solutionally enlarged conduits allow rapid movement of water and contaminants from place to place.  Unfortunately, there are no good ways to predict movement through karst, so the Department will rely on the traditional time-of-travel calculations to delineate estimated source water areas and take special note that wells in karst areas are more vulnerable. 

Digital groundwater models and other analytical techniques of various types are typically used to delineate groundwater recharge areas.  The best accuracy can be obtained where detailed, site-specific aquifer and well information are gathered and used so that the groundwater models can be calibrated with data collected at the site.  Unfortunately, depending on the number of wells in use, the hydrogeologic complexity of the aquifer, interference from other wells and other factors.  Such detailed studies may take a minimum of several weeks; more realistically, several months may be required to perform a reasonably complete source water delineation study for a water supply that uses several wells.  The cost of performing detailed studies on all public water supply wells in Missouri would be enormous.

Since it is not feasible to conduct detailed source water assessment studies on all public water supply wells in Missouri, a multiple ranking approach will be used to establish the level of assessment that each public water supply well will receive.  Initially, all of the public water supply wells will be evaluated using a relatively simplistic analytical technique to estimate their source water areas. Some of the data necessary for calculating rudimentary source water assessment areas are already in the Public Drinking Water Program GIS database.  An example of the existing data accompanies Figure 1.  Additional data will be added to further identify the geologic formations yielding water to each well and assign storativity and transmisivity values.  This information will be used to calculate time-of-travel areas around each wellhead in a method commonly referred to as calculated fixed radii. All of Missouri’s public water-supply wells will receive this initial assessment. Unless there are unusual circumstances, it is anticipated that transient noncommunity supplies will not receive further evaluation during this study. 

A ranking system will be applied to the nontransient noncommunity wells and the community wells to determine the level of evaluation each will receive.  How individual wells are ranked will be based on the relative importance of the well as a water-supply source, and its hydrogeologic susceptibility to contamination.  It is proposed that water supplies will be prioritized based on the following criteria:

  1. Type of public water supply system
  2. Geologic and hydrologic characteristics of the aquifer used
  3. Well construction
  4. Water-quality history of the supply
  5. Size of population served by supply
  6. The availability of alternative water sources

Community public water supply wells, since they generally serve the greatest number of people on a continuous basis, will receive a high priority.  Non-transient noncommunity systems, which serve the same group of people daily such as at schools and factories, will have a moderate priority.

A literature search will be made at the onset of the project to locate existing data, publications, and unpublished reports and maps that can be used to delineate source water areas.  Wellhead protection studies and source water delineations have been performed in a few places in Missouri.  Wherever possible, the results of these previous studies will be used.

Understanding the hydrogeology of the aquifers supplying public water supply wells is paramount in assessing the risks to water quality.  Some of Missouri’s many aquifers are so geologically and hydrologically isolated that surface activities, even those in close proximity to properly constructed water wells, present very little risk to them.  Other aquifers are much less isolated and wells producing from them are more susceptible to the effects of surface activities.  Public water supply wells in areas of highest potential susceptibility will receive the greatest degree of analysis.  Wells in low risk areas will receive correspondingly less analysis.  A preliminary analysis shows that the aquifers in the groundwater provinces listed below range from having the greatest (1) to the least (8) susceptibility:


  1. Unconsolidated shallow alluvial and glacial drift aquifers (Mississippi and Missouri River alluvium, Bootheel alluvium, glacial drift excluding drift-filled preglacial valleys)
  2. Springfield Plateau (Springfield Plateau aquifer)
  3. Salem Plateau (Ozark aquifer)
  4. St. Francois Mountains (St. Francois aquifer where unconfined, igneous rock aquifers)
  5. Springfield Plateau (Ozark aquifer, St. Francois aquifer)   
  6. Drift-filled preglacial valleys in northern Missouri
  7. Osage Plains (Springfield Plateau aquifer, Ozark aquifer)
  8. Southeast Lowlands (Wilcox and McNairy aquifers)


The water-quality history of each supply will be examined to help determine if the supply may be under the influence of surface water or if the well may have construction problems.  Public water supplies that appear to be influenced by surface water or have construction deficiencies will receive a higher level of assessment than supplies that do not.  Supplies serving large populations will receive a higher level of assessment than supplies that have small service populations.  Water systems in areas with few possibilities for alternative supplies will receive a higher level of assessment than systems having good alternatives.

Community public water supply systems will receive the most detailed analysis.  The level of detail will depend on the susceptibility of the wells to contamination.  Wells producing from aquifers that are hydrogeologically most secure from contaminants will be assessed using available hydrologic data.  Relatively simple groundwater models or analytical techniques will be used to assess the source water areas for these wells.  If funding allows, well logs may be prepared for the community public water supply wells that have not previously been logged, but for which samples of the well cuttings are available.  Wells that serve community systems in areas where geologic conditions increase the susceptibility for contamination, especially supplies that are suspected of being under the direct influence of surface water, and supplies where there are no reasonable alternative sources of water, will receive the most detailed evaluations.  More complex groundwater models or analytical techniques may be used for these systems.

Nontransient noncommunity public water supplies will receive an intermediate level of analysis.  The level of analysis will be based solely on existing hydrogeologic information.  If existing hydrogeologic, well construction, and water quality data show that a well has a very low susceptibility to contamination from surface activities, it will receive a level of analysis similar to that used for a transient noncommunity public water supply.  Assessments of wells in areas that are geologically more prone to contamination will be based on available hydrogeologic information, past water-quality history, and the availability of alternative water sources.  Greater attention will be given to supplies serving the greatest number of people, supplies that are thought to be under the direct influence of surface water, and supplies where there is no reasonable alternative source of water.

PDWP’s existing GIS system will be expanded and used to store the results of source water delineations. Fields will be added to the GIS data and populated to store the findings of this project such as the identity of the strata that produces water for each well and significant confining layers.  The delineated source water areas will also be added to the GIS.  PDWP will complete preliminary source water delineations using calculated fixed radii by November 1999. The remaining term of this project will be spent doing more extensive analysis on the wells determined to be high priority. PDWP will utilize results from hydrogeologic studies completed by other entities and adopt the most scientifically defensible delineations for the source water assessment.  Source water delineations will be continually updated as better information becomes available.

Surface Water

There are over 150 surface water intakes that supply public drinking water in Missouri.  The watersheds upstream of these intakes range in size from several acres to hundreds of millions of acres. For surface water intakes having small watersheds, the entire watershed will be considered the source water area. An example of a small watershed is shown in Figure 2.  Some public water supplies draw water from large bodies of water such as Mark Twain Lake, Harry S. Truman Reservoir, the Missouri and Mississippi Rivers, and others.  It is not expected that every potential contamination source can be accurately identified in these large watersheds. For this reason, a method will be needed to determine priority areas within such large watersheds. PDWP will use a 5-mile radius upstream of the intake to delineate this priority area for every watershed greater than 40,000 acres. These source water areas will be digitized into GIS. An example priority area bounded by a 5-mile radius is shown in Figure 3. In this example, the priority area is bounded by the topographic watershed, but does not extend beyond 5 miles of the intake. As described in the following section, PDWP will search databases to inventory potential contaminants for the entire watershed, but will only conduct field reconnaissance in the 5-mile priority area.  Field reconnaissance will be employed to verify potential contaminant sites listed in existing databases (see contaminant inventories) and to identify sites that are not in existing databases. Susceptibility determinations and source water assessments will be based on any information available for the entire watershed.  Contaminants found in the priority area will not be weighted more heavily in the susceptibility determination.  PDWP believes activity in the entire watershed is important.  The 5-mile radius was chosen as the largest unit for which complete inventories can be conducted in the time frame allowed by the SDWA. In the future, PDWP may replace these 5-mile radii to delineate these priority areas based on time-of-travel.  For instance, an area would be delineated where surface water and associated contaminants would reach the intake in 1, 5 or 10 days.

Conjunctive Delineations

Conjunctive delineation of source water areas will be considered during the delineation process.  Conjunctive delineation refers to delineating the watershed that may deliver surface water and associated contaminants into a delineated wellhead source water area.  Conjunctive delineation will be used for groundwater sources that are determined to be under the direct influence of surface water. PDWP has already delineated surface water watersheds for infiltration galleries that are suspected to be under the direct influence of surface water.  PDWP uses several criteria to screen for wells under the direct influence of surface water including the effectiveness of the well seal, details of the well construction, proximity to a surface water body, and historical turbidity and bacteriological monitoring results.  If these factors make the well suspect, microparticulate analysis is used to identify potential surface water indicators such as algae.  If surface water indicators are present, the well is determined to be under the direct influence of surface water. 

There may be some wells in Missouri that are indirectly connected to surface water.  Wells that are indirectly connected have no direct pathway to surface water, but surface water may infiltrate through alluvium to reach the well in less than the 10-year time-of-travel established as the source water area. Conjunctive delineation is appropriate any time a surface water body is intersected by the 10-year time-of-travel delineation and local geology does not isolate the producing aquifer from surface water influences. If the surface water watershed is small, it may simply be added to the source water area.  Most surface water bodies that significantly contribute to the groundwater are expected to be large with large watersheds.  For example, several well fields may be indirectly influenced by the Missouri River whose watershed covers millions of square miles. PDWP does not feel it can adequately characterize individual pollutant sources in these large watersheds.  For purposes of assessment, the surface water body will be treated as a single potential source of contamination.

It has been suggested that every potential contaminant source in an adjacent watershed needs to be identified, and that PDWP could treat it as a surface water watershed and inventory contaminants in a 5-mile radius upstream of a well field.  Because it may take as long as ten years for contaminants introduced by the river to reach a well, this makes it different from a surface water intake.  PDWP is not convinced that a short-term release, such as a spill that passes in a matter of days, will leave a lasting impact on the groundwater.  PDWP feels the groundwater quality depends more on the consistent chemical makeup of the river.  The consistent nature of the river is not determined only by nearby contaminant sources, but by the entire watershed.  Rather than extrapolate the effects of contaminants miles from the drinking water source, PDWP chooses to recognize that a river can be a source of many unidentified contaminants. It is analogous to when a highway passes through a wellhead area.  Instead of inventorying all contaminants that may pass over the North American road network, it is recognized that a wide variety of contaminants may be introduced by passing vehicles and possible accidents.


The Public Drinking Water Program seeks to identify the location of any potential contaminant that threatens a public drinking water supply.  Appendix E lists the chemicals that are considered to be potential contaminants if they have ever been manufactured, used, stored, transported, or disposed in a delineated source water area.  The list in Appendix E also includes radiological contaminants, bacteria, pathogens, parasitic organisms, and viruses.  This conservative approach to identifying contaminant sites means that even facilities that properly use a listed chemical and operate in an environmentally sound manner may be identified, because there is always the slight risk of an accident.  Transportation corridors like roads, railways, and rivers also have a risk associated with them.

Even before the final source water areas are delineated, PDWP must begin to inventory potential contaminants in order to complete the assessments in the time allotted by the SDWA.  PDWP has a head start with the Synthetic Organic Chemical (SOC) sites that have been identified as part of the Vulnerability Assessment of Missouri Drinking Water to Chemical Contamination (Vulnerability Assessment)(updated with new URL) As part of the Vulnerability Assessment, over 100 databases (see Appendix D) are routinely searched for any sites where Synthetic Organic Chemicals may have been manufactured, used, stored, transported, or disposed. The results of these searches have been added to GIS in the form of point and polygon coverages for chemical specific sites, suspected chemical sites, and pesticide dealership sites where various common pesticides could be located.  These sites have been identified state-wide.  Over 3,000 SOC sites currently reside in PDWP’s GIS database.  This data is currently being maintained by the Center for Agricultural, Resource and Environmental Systems (CARES) under a cooperative agreement with the Public Drinking Water Program. Figure 1 and its attachments show examples of potential contaminant sites that have already been identified.  Maps like these are currently available for every public water supply in Missouri.  They can be viewed on the Internet at (updated with new URL)

Synthetic Organic Chemicals are man-made and do not occur in nature.  Common SOCs are pesticides and wood treating chemicals.  Many SOCs have special permit or reporting requirements.  These factors combine to make these type of chemicals well suited for the type of searches conducted as part of the Vulnerability Assessment.  Locating the remaining potential contaminants to public drinking water sources poses a more difficult problem.  (See Appendix F for a list of potential contaminants.)  Contaminant sources such as gasoline storage tanks or domestic sewage disposal are seemingly ubiquitous.  PDWP is working with its sister programs in the Department of Natural Resources as they begin to build GIS data for the sites they regulate.  These sites include: hazardous waste sites, underground storage tanks, solid waste landfills, abandoned mines, and sites regulated under the Clean Water Act.  PDWP will also search existing databases (Appendix D) for an expanded list of chemicals just as was done for SOCs. Once these data layers have been completed, keeping them updated will be an ongoing task.  Potential contaminant sites identified through these databases will be maintained on a statewide basis.  In other words, they will be identified whether they are in a source water area or not.

To augment contaminant inventories in source water areas, additional contaminant sources can also be inferred from USGS topographic maps or other available basemaps.  Features appearing on these maps such as highways, railroads, or sewage treatment works can be inventoried as potential threats. The most effective way to inventory contaminants is also the most resource intensive.  Using PDWP staff to field check GIS data and identify additional contaminants could produce highly reliable source water assessments. It is not expected that PDWP will have adequate resources to do this on a statewide basis in the time allotted by the SDWA.  PDWP will continue to obtain information gathered by volunteer organizations and communities that implement source water protection plans.  Currently, PDWP is providing special maps to communities who want to develop source water protection plans.  These maps display all current data on potential contaminant sites.  The local source water teams return additions and correction to these maps to PDWP. All reconnaissance information obtained is stored in GIS and displayed on source water maps for groundwater and surface water systems. Examples of these maps for a groundwater system and a surface water system are shown in Figures 1 and 2.  PDWP has recently begun a cooperative project with CARES for which CARES staff will be verifying and collecting potential contaminant site locations in the field.  They will be identifying sites in the ten-year time-of-travel radius for community wells, in small drinking water watersheds, in priority areas of large watersheds, or other nearby sites that can be collected expediently.  CARES will be verifying locations of sites in existing databases and collecting locations for potential contaminants that are not in current databases.  Sites being located that are not in existing databases include sources that are obvious enough to be seen when driving through a source water area, but too small to be regulated.  These include private fuel storage tanks, small animal feed lots, and private sewage lagoons.  Septic tanks have been identified as a concern for some source water areas, but cannot often be seen by CARES field staff.  To address this problem, PDWP will identify communities that do not have public sewer and extrapolate that each residence has on-site sewage. 

Nonpoint sources of contamination will also be considered.  PDWP has produced accurate land use maps for 23 public drinking water lakes (90,000 acres).  These maps identify areas subject to nonpoint pollution as a result of cropland, pasture land, golf courses, parking lots, etc.  These land use maps were field checked when produced.  Figure 2 includes an example of this land use information.  PDWP will complete an additional 120,000 acres of land use mapping by July 1999.  This additional mapping will be made from existing aerial photographs and will not be field checked in order to accomplish more mapping.  Field checking can be done at a later date by PDWP staff, staff from other agencies, or source water protection volunteers.  PDWP will continue this type of mapping until all watersheds smaller than 25,000 acres have been mapped. Less accurate land use data is available statewide.

Source Water Areas that Cross State Boundaries

The data layers for potential contaminants as described above will be specific to the state of Missouri.  Most of the source water areas that extend beyond the boundaries of Missouri are so large that contaminant inventories are impractical.  Figure 4 shows the extent of Missouri’s largest source water area.  PDWP will attempt to acquire contaminant data for areas of Illinois, Iowa, Nebraska, Kansas, and Arkansas if such data exists in a readily available form.  There are a few small to medium source water areas along the western edge of Missouri that cross into another state.  The portions of these areas that lie in other states are so small that field reconnaissance can be used to identify any potential drinking water contaminants.

PDWP has contacted neighboring states to identify drinking water intakes downstream of Missouri.  These intake locations have been incorporated into our GIS for reference during spills or other emergencies.  Further coordination with other states will be attempted so this effort can be reciprocated.


PDWP will combine all the data assembled for source water assessments and historical monitoring data to determine the susceptibility of each public water source.  Figures 1 and 2 include examples of susceptibility information that has been summarized.  A similar format will be used to present the results of the source water assessments for both groundwater and surface water supplies.  The maps and tabular data will be expanded to include the wide range of potential contaminant sources.  All water supplies are susceptible to a certain degree, and deserve to be protected from contamination.  The purpose of these assessments is to identify factors that make each water system particularly vulnerable to better guide source water protection efforts.

The following sections describe how susceptibility will be determined based on individual factors.  For each factor, a source will be determined to be not susceptible, moderately susceptible, or highly susceptible.  If a source is not susceptible, the source water protection team need only make sure that conditions do not change making the source susceptible.  An example would include maintaining a sanitary seal at the well casing.  If a source is moderately susceptible, the source water protection team should be aware of the potential threat and consider strategies to decrease the likelihood of contamination. Many water sources may be moderately susceptible because certain chemicals are present in the source water area, but drinking water is not imminently threatened as long as those chemicals are handled properly.  If a source is highly susceptible, immediate attention and action is required to ensure a safe drinking water supply.  Examples of required action may include repair to a well, removal of contamination source, or increased chemical monitoring.

Groundwater Sources

A map similar to Figure 1 will be presented for each public water system. The map will show the location of each public well, the delineated source water area, and all identified potential contaminant sources. When their locations are available, neighboring wells will also be shown on the maps.  Neighboring wells are potential conduits for contaminants into the drinking water aquifer, and they may also be additional sources of local groundwater data.  Data sheets describing well construction, hydrogeology details, and potential contaminant details will accompany each map.  Data sheets will consist of tables like those shown in Figure 1, but will be expanded to include all the chemicals that will be inventoried for source water assessments. Data sheets will include the susceptibility determination for each water supply.  Factors determining susceptibility are all recorded in GIS.  The data in GIS will be queried as described below.

A well is highly susceptible if it is not state approved.  If a well was not drilled and constructed to proper standards for a public water supply, the field in GIS for state approval has been marked negative and the well will be considered highly susceptible.  If the field is not marked negative, it is assumed the well is state approved and the well is not susceptible.  A well that was drilled to proper standards, but has since deteriorated to the point of allowing contaminants to enter the well will no longer be considered an approved well.  With the exception of grandfathered wells, unapproved wells are not allowed to be used for public supplies and should be replaced.

If a well is determined to be susceptible because it is not a state approved well, a statement will be added to that system’s source water assessment reading, ”The unapproved well (or wells) operated by this system is highly susceptible to contamination.  This deficiency should be corrected immediately.” 

A well is highly susceptible if it is under the direct influence of surface water.  If the well has tested positive for surface water indicators such as algae or high turbidity the field in GIS called GWUDISW has been marked positive and the well will be considered highly susceptible.  If the GWUDISW field has not been marked positive, the well is not susceptible. 

If a well is highly susceptible because it is under the direct influence of surface water, a statement will be added to that system’s source water assessment reading, “A well (or wells) operated by this system is under the direct influence of surface water and is highly susceptible to contamination.  Because the well in influenced by surface water, the water it produces must comply with the Surface Water Treatment Rule.”

Surface water can intrude if a well casing is not protected from surface drainage.  The casing on public wells is required to extend 18 inches above the ground.  If the value of the GIS field for the elevation of the top of the casing is less than 1.5 feet, the well will be considered highly susceptible.  Likewise, if the value for the surface drainage field is “unsatisfactory”, then the well will be considered highly susceptible.  A value of unsatisfactory in this field indicates the well is not sealed or vented properly, or the well is not protected from flooding.

If a well is highly susceptible because of this type of wellhead deficiency, a statement will be added to that system’s source water assessment reading,” A well (or wells) operated by this system is not adequately protected from contamination because of unsatisfactory seals or surface drainage at the wellhead.  These deficiencies should be corrected immediately.”

A well is considered highly susceptible if it has had previous detections of certain chemicals.  The following will be employed to make these determinations.  If the field in GIS for “VOC Detections” is positive, then the well is highly susceptible.  PDWP’s Volatile Organic Chemical (VOC) monitoring data will also be checked.  Any system showing VOC detects will be investigated to determine which well was the source of the VOCs and that well or wells shall be considered highly susceptible.  The same will be done for PDWP’s Synthetic Organic Chemical (SOC) monitoring data. Any well that has consistently detects SOCs will be considered highly susceptible. If the GIS field for “nitrate detections” is positive, then the well will be considered highly susceptible.  PDWP’s nitrate monitoring data will be checked to find any other systems that detected nitrates at or above one-half the MCL.  Any wells that detected nitrate at or above one-half the MCL will be considered highly susceptible.  PDWP’s Inorganic Chemical (IOC) data will be reviewed to identify wells with IOC above naturally occurring or harmful levels. Wells found to consistently detect IOCs above naturally occurring or harmful levels will be considered highly susceptible.  PDWP’s bacteriological and virus monitoring data will be reviewed to indicate any wells that consistently detect contaminants.  Wells found to consistently detect microbiological contaminants will be considered highly susceptible.  The word consistently, as used in this paragraph is meant to distinguish data believed to indicate actual contamination of drinking water from data that is not repeatable and likely the result of sampling error.  The determination of what data is consistent and what is in error will be done by experienced staff in the Public Drinking Water Program.

If a well is determined to be susceptible because of detection histories, a statement will be added to that systems source water assessment reading, ”This system uses a well (or wells) that shows signs of contamination.  The Department of Natural Resources will monitor the degree of contamination.  The water system should consider replacing and abandoning this well, or treating the water produced by this well to remove contamination.”

A well is highly susceptible to weather, vandalism, and sabotage if the well is not in a locked well house of adequate construction and security measures such as fencing and lighting.  A field to record this data does not yet exist in GIS, except in the instances where the value of the “surface drainage” field has been entered as “inside a building”.  This data is not adequate to make the susceptibility determination. 

A statement will be added to every source water assessment reading, “This system was not assessed to determine if adequate security devices such as padlocks, gates, and lighting are in place to deter vandals and saboteurs.  All water systems should have this type of protection in place.”

There are many geologic factors that can influence the susceptibility of a well. In an effort to consistently evaluate over 3500 public wells across Missouri, PDWP will use the five following factors to summarize hydrogeologic susceptibility.  Databases containing this information are not yet complete, but are being constructed with this as their primary purpose. A well will be considered moderately susceptible if one of its producing aquifers: 1) is a near-surface (<100 feet deep) fractured bedrock aquifer, 2) has conduit-flow conditions due to surficial karst topography, 3) is not overlain by a confining layer, 4) is overlain by a conductive (>5x10e-4 cm/sec) formation (including soil) or, 5) a producing aquifer is confined, but there exist open, abandoned wells penetrating that layer.

If a well is determined to be susceptible because of geologic factors, a statement will be added to that systems source water assessment reading,” A well (or wells) serving this system has been determined to be susceptible due to geologic conditions. The water system and the wellhead protection team should take extra care to ensure that all potential contaminants in the source water area are handled properly to avoid contamination of the drinking water supply.” 

MDNR has attempted to locate a wide range of potential contaminant sites.  All contaminant site information has been assembled in GIS and will appear on wellhead maps.  Only a small percentage of the potential contaminant sites collected have been known sources of contamination.  A well will be considered highly susceptible if one of these known sources of contamination is located in the source water area.  GIS will be used to determine if a known contamination source is located in a source water area.  PDWP will use the source of the information to judge whether a potential contaminant site may indeed be a known contamination site.  Any sites identified in databases of Leaking Underground Storage Tanks, Superfund sites, CERCLA sites, RECRA sites, or similar databases will be considered known contaminant sites.  These are believed to be a greater risk than sites acquired from databases such as Hazardous Waste Generators or Licensed Pesticide Applicators where chemicals are present but handled in an environmentally sound manner.  If there are no known contaminant sites, but there are potential contaminant sites in a source water area, the associated well will be considered moderately susceptible.

If a well is determined to be moderately susceptible because of the presence of potential contaminant sources, a statement will be added to that systems source water assessment reading,” A well (or wells) serving this system has been determined to be susceptible due to the presence of potential contaminant sources. The water system and the wellhead protection team should take extra care to ensure that all potential contaminants in the source water area are handled properly to avoid contamination of the drinking water supply.”

If a well is determined to be highly susceptible because of the presence of potential contaminant sources, a statement will be added to that systems source water assessment reading,” A well (or wells) serving this system has been determined to be susceptible due to the presence of potential contaminant sources. The water system and the wellhead protection team should take extra care to ensure that all potential contaminants in the source water area are handled properly to avoid contamination of the drinking water supply.  Periodic monitoring will be required to track contamination of the well(s).  If possible, contaminant sources should be removed from the source water area.”

Abandoned wells can provide conduits to shorten the path contaminants travel before affecting a drinking water aquifer.  For this reason, wells will be considered moderately susceptible if abandoned wells are located in the source water area.

If a well is determined to be susceptible because of the presence abandoned wells, a statement will be added to that systems source water assessment reading,” A well (or wells) serving this system has been determined to be susceptible due to the presence abandoned wells.  Abandoned wells should be properly plugged to avoid contamination of the drinking water supply.”

Septic tanks are potential threats that were not located in GIS.  Databases do not exist in Missouri for private septic tanks locations, and they are difficult to spot by our field investigators.  To evaluate the threat posed by septic tanks, PDWP will do the following.  By looking at the database for permitted wastewater discharges, it can be assumed which areas are served by community sewer systems.  Therefore, these areas will not have individual septic tanks.  If an area is not served by a community sewer system, every residence is assumed to have a septic system.  Residences can be seen on the topographic maps used to delineate source water areas.  If a source water area can be assumed to contain septic systems by this method, then the associated well will be considered moderately susceptible.

If a well is determined to be susceptible because of the presence of potential contaminant sources, a statement will be added to that systems source water assessment reading,” A well (or wells) serving this system has been determined to be susceptible due to the presence of potential contaminant sources. The water system and the wellhead protection team should take extra care to ensure that all potential contaminants in the source water area are handled properly to avoid contamination of the drinking water supply.”

Another potential contamination source that was not adequately captured in the databases is submersible well pumps that may contain PCBs or other non-food-grade oils. There has been one instance in Missouri where a well pump failed and released PCBs into the well.  PDWP’s GIS data contains the pump type (i.e. submersible, vertical turbine, etc.) and in some cases even the pump manufacturer.  A report published by the Wisconsin Department of Natural Resources (PUBL-DG-025-98) describes some pumps that may contain non-food-grade oils.  PDWP can compare this report with the data in Missouri’s GIS to eliminate a small percentage of wells from consideration.  PDWP feels there are too many unknowns to declare the remainder of the wells susceptible, but will instead recommend the water supplies contact MDNR or the pump manufactures with the type, age and model number of their pumps to determine whether they contain potential drinking water contaminants.

Wells are susceptible to contamination if transportation corridors pass through the source water area.  Trucks, trains, or barges moving along these corridors can have accidents.  Such accidents could result in the release of potential drinking water contaminants.  GIS will be used to determine which source water areas are threatened by transportation corridors.  If an active railroad passes through a source water area, the associated well will be considered moderately susceptible.  Almost all source water areas have roads passing through them.  The minimum length of road needed to access a well is estimated to be one mile.  Based on this, any well whose source water area has more than one mile of road passing through it will be considered moderately susceptible.  Based on these conservative assumptions, almost every public well in the state of Missouri will be considered susceptible.  Nevertheless, MDNR feels it is an appropriate way to address a real threat.   It was previously mentioned that barges carry potential contaminants.  In addition, to barges and all other watercraft, lakes and stream themselves can carry waterborne contaminants into a source water area.  To address this, wells whose source water area adjoins Class P streams or classified lakes will be considered moderately susceptible.  Classified Lakes include all lakes that are waters of the state.  Class P streams are those which maintain permanent flow. These definitions can be found in 10 CSR 20-7.

If a well is determined to be susceptible because of transportation corridors, a statement will be added to that systems source water assessment reading,” A well (or wells) serving this system has been determined to be susceptible due to the presence of transportation corridors. The water system and the wellhead protection team should develop contingency plans to avoid contamination of the drinking water supply if potential contaminants are spilled.”

Surface Water Sources

A topographic map similar to Figure 2 will show the boundaries of each surface water watershed. The delineated priority area will be shown for the large watersheds.  When land use information is available, a map like the one accompanying Figure 2 will also be provided. Each map will be accompanied by data sheets describing potential point and nonpoint sources of contamination. All surface water sources are susceptible. Data sheets will include the susceptibility determination for each water supply based on the following factors.

An intake will be considered highly susceptible based on detection histories if Volatile Organic Chemicals (VOCs), Synthetic Organic Chemicals (SOCs), or Inorganic Chemicals (IOCs) are consistently detected. The word consistently, as used in this paragraph is meant to distinguish data believed to indicate actual contamination of drinking water from data that is not repeatable and likely the result of sampling error or contaminants that quickly passed through the surface water body, are no longer present, and not likely to return.  The determination of what data is consistent and what is in error will be done by experienced staff in the Public Drinking Water Program.

If an intake is determined to be susceptible because of detection histories, a statement will be added to that systems source water assessment reading, ”This system uses a water source that shows signs of contamination.  The Department of Natural Resources will monitor the degree of contamination.  The water system should treat the water accordingly to remove contamination before it enters the distribution system.  The water system and watershed protection team should also make an effort to eliminate contaminants entering the source water.”

MDNR has attempted to locate a wide range of potential contaminant sites.  All contaminant site information has been assembled in GIS and will appear on watershed maps.  An intake will be considered moderately susceptible to contaminants if any contaminants listed in Appendix E are found in the source water area.  Empirical data in Missouri has shown that surface water sources are less sensitive to point sources of contamination and more sensitive to non-point sources of contamination.  To address this, land use maps will be produced for drinking water watersheds.  GIS will be used to calculate land use percentages for determining susceptibility of each intake.  Pesticides from row crop agriculture have proven to be the most troublesome contaminant for Missouri surface water supplies.  If an intake’s watershed is greater than 30% cropland, the intake will be considered highly susceptible to contamination.  All other watersheds will be considered moderately susceptible.

If an intake is determined to be susceptible because of land use, a statement will be added to that systems source water assessment reading, ”The watershed serving this system contains more than 30% crop land.  All watersheds are susceptible to contamination. A significant amount of cropland increases the chances that pesticides, nutrients, and sediments will contaminate the drinking water source.  The water system and the watershed protection team should seek to reduce the risk of contamination.”

Integrity of the intake structure and the pipeline to the treatment plant is to be evaluated.  Missouri currently does not have any open constructed conveyances for raw water.  Each surface water supply has a closed pipeline from the intake to the treatment plant.  If a raw water transmission line were to have a breach near a potential contaminant site, the water supply would be susceptible.  PDWP will identify potential contaminant sources along the pipeline run for raw water transmission lines.

If a water body supplying a drinking water intake receives recharge from a contaminated groundwater source, and that contamination did not attenuate before reaching the intake, the intake would be considered highly susceptible.  No instances of such contamination are known to exist in Missouri. 

Intakes are susceptible to contamination if transportation corridors pass through the source water area.  Trucks, trains, or barges moving along these corridors can have accidents.  Such accidents could result in the release of potential drinking water contaminants.  GIS will be used to determine which source water areas are threatened by transportation corridors.  The intakes associated with these source water areas will be considered susceptible.

If an intake is determined to be susceptible because of transportation corridors, a statement will be added to that systems source water assessment reading, ”The watershed serving this system contains transportation corridors.  All watersheds are susceptible to contamination. Transportation corridors increases the chances of contaminants entering the drinking water source. The water system and the watershed protection team should develop contingency plans to avoid contamination of the drinking water supply if potential contaminants are spilled.”

For both groundwater and surface water supplies, PDWP will draw on databases currently being compiled to address each of the susceptibility factors listed above.  An algorithm, as described above, will be used to query the databases and produce a susceptibility determination like the examples shown on pages 29 and 35 [figure 1].  This algorithm will be applied consistently to all source water areas.


All source water assessment information will be available to the public directly from PDWP and via the Internet.  PDWP ( ) has provided a link from its Internet homepage to CARES ( ). CARES’s Internet homepage will feature some narrative description of vulnerability and source water assessments, interactive maps displaying relevant data chosen by the user, and online maps of each public water system’s source water assessment area.  Figure 1 is an example of the water system maps that are currently available over the Internet. These are currently available for every groundwater system, and will soon be available for every surface water system. CARES and PDWP will also provide links to the Missouri Spatial Data Information Service ( where updated GIS data can be downloaded. 

Much of the public will receive their source water assessment information through Consumer Confidence Reports (CCR). Consumer Confidence Reports will be provided by water suppliers to their customers and are intended to convey information about the quality of the drinking water and compliance with the Safe Drinking Water Act. PDWP will share assessment results with the public water supplies by providing them summary sheets and maps of their source water areas.  These assessment results will provide the water suppliers with all the information necessary for inclusion in their CCR.  Consumer Confidence Reports must include descriptions of the water system’s source, a summary of the system’s susceptibility determination, and information on how a system’s complete source water assessment can be obtained. Public water supplies must provide Consumer Confidence Reports to their customers on an annual basis.  Source Water Assessments will be provided to water supplies only in the year they are completed. 

PDWP has developed several series of maps that display source water assessment information. They include a statewide map, regional maps, county maps, and individual water system maps. The individual water system maps and accompanying data sheets total over 5,000 pages of source water information. All maps produced by PDWP are available by request.  Upon completion of the assessments, PDWP will publicize the availability of these maps for use by local people interested in source water protection.


Implementation of Missouri’s source water assessment plan is the responsibility of the PDWP.  Participation in source water assessments and source water protection by water systems or communities will be voluntary.  Local participation will continue to be encouraged as it has been through our existing Wellhead Protection Program.  It is hoped that the increased activity by PDWP in this area and the increased availability of relevant information will encourage increased local interest in source water protection.

PDWP’s source water assessments will build upon the existing vulnerability assessment project.  Source water assessment activities are well under way as is necessary in order to meet federal deadlines for completing this monumental task.  Advisory committee and public meetings took place during summer and fall of 1998.  The original version of this document was submitted to EPA by February 6, 1999.  EPA may take as long as nine months to approve this plan.  The longer EPA takes to approve this plan, the longer PDWP will have to complete the assessments.  Source water assessments must be complete within two years of EPA approval of this plan.  In accordance with the Safe Drinking Water Act and U. S. EPA guidance the Missouri Department of Natural Resources is requesting the additional eighteen-month extension in order to complete more thorough assessments of Missouri’s public water sources.

The timeline as described below was developed with the eighteen month extension in mind, as was all the planning, funding, and hiring of personnel to complete these assessments.  In order to complete source water assessments without the eighteen-month extension, MDNR must cut short the time allowed to refine wellhead delineations and the time allowed to gather potential contaminant information.  This information is crucial to completing accurate and meaningful source water assessments.  Without complete contaminant inventories and the best wellhead delineations possible, PDWP cannot meet the goal of source water assessments, which is to provide for the protection and benefit of public water systems.

All public drinking water sources and preliminary source water assessment areas are in GIS.  Maps of these areas were provided to each public water system in 1995 and are currently available to any interested parties. Collection, maintenance, and dissemination of source water data in GIS is an ongoing process.  This has been underway for over a year and will continue indefinitely.  This source water data includes locations of water sources, source water areas, and potential contaminant sources.  In April 1999 maps of source water areas became available over the Internet.  These maps will eventually evolve into the format for source water assessment results.  In May 1999 field reconnaissance will begin in order to collect potential contaminant information.  Field reconnaissance is scheduled to continue until July 2000.  Reconnaissance will not likely be complete for every source water area by that date.  This activity may continue beyond that date.  In November 1999 preliminary wellhead area delineations will begin. Delineations for all wells will be complete by November 2001, however further refinement of wellhead areas will continue until December 2002. Susceptibility determinations will begin in August 2000.  Those determinations and the format for the assessment results will be refined until December 2002 when they will be complete.  Assessment results will have been presented to the public by May 2003.

MDNR will report progress on source water assessments to EPA through the Wellhead Protection Program Biennial Report.  The report will include the number of public water supplies categorized as ground water, surface water, or combined.  The report will include the number of public water supplies with completed delineations, potential contaminant source inventories, susceptibility determinations, and the population served by these systems.  The report will also explain how completed assessments have been made available to the public.

Beyond the date by which Missouri is required to complete source water assessments, work will focus primarily on maintaining the data assembled for these assessments.  New wells and potential contaminant sites will constantly need to be added to the GIS.  Other GIS data such as geology and land use is constantly being improved.  That data will be assimilated for use in source water assessments. Delineation of source water areas for new wells will follow the same methods employed for this project or better methods as they become available.  Updated susceptibility determinations can be completed when deemed necessary.  Methods for determining susceptibility may be varied as the particular need dictates.

Missouri is taking advantage of the 10% set aside from the Drinking Water State Revolving Loan Fund.  This allows $2,185,760 to be spent on Source Water Assessments.  This set aside is funding three geologists to delineate groundwater recharge areas and assemble geologic susceptibility information.  It will also fund one Environmental Specialist to conduct Total Maximum Daily Load Determinations for drinking water watersheds.  In addition to funding these four employees and all associated benefits and equipment, $577,513 is available for contract work.  $214,473 of these contact dollars have already been committed to CARES for some of the GIS and Internet work described in this plan.


Wellhead protection and watershed protection programs are voluntary on behalf of local authorities or other interested parties.  The elements that go into source water assessments: delineation of source water areas, contaminant inventories, public involvement, and susceptibility determinations are all elements of a source water protection program.  Source water protection also includes contingency plans and plans to manage source water areas.

The Missouri Department of Natural Resources has had a Wellhead Protection Program since 1994.  The Wellhead Protection Program consists of giving guidance and encouragement to local entities developing their individual wellhead protection programs. This program will continue in conjunction with source water assessments. The Department will increase its efforts in both wellhead and watershed protection by promoting the cost and health benefits of protecting sources of drinking water. PDWP will have two new staff persons dedicated to source water protection.  The Department has seen an increase in the number of communities interested in source water protection and expects this trend to continue.

It is hoped that source water assessment activities by the state will encourage the establishment of source water protection programs.  The source water area delineations and contaminant inventories should provide a good head start for anyone interested in developing a source water protection program.  Source water assessment results will be made easily available to the public in order to serve this purpose.

Figure 1 - Ground Water Example

Figure 2 - Surface Water Example

Figure 3 - Example Priority Area

Figure 4 - Example Interstate Source Water Area

No image available
Appendix A - Advisory Committee Members

Representatives of these organizations were invited participate on the source water assessment advisory committees

Technical Advisory Committee

* Center for Agricultural, Resource and Environmental Systems
* U. S. Geological Survey
* Missouri Department of Agriculture
* ALPD Hazardous Waste Program (updated name and URL)
* WPSCD Soil & Water Conservation Program (updated name and URL)
* ALPD Solid Waste Management Program (updated name and URL)
WPSCD Water Pollution Control Program (updated name and URL)
* Missouri Department of Health
* Consulting Engineers Council of Missouri
* Natural Resources Conservation Service
* Division of Geology and Land Survey (now Geological Survey and Resource Assessment Division)
* Missouri River Public Water Supplies Association
* Mark Twain Water Quality Initiative
* Missouri Rural Water Association
   Missouri Society of Professional Engineers
* Missouri Groundwater Association
* EPA Region VII
* University of Missouri Outreach & Extension
* State Emergency Management Agency

Public Advisory Committee

   Missouri Adult Day Care Association
* Missouri Dairy Association
   Missouri Association for Community Action
   Missouri Association of Soil & Water
* Missouri Farm Bureau
   Missouri Municipal League
   Missouri Public Health Association
   Missouri River Communities Network
* Missouri Corn Growers Association
* Missouri Ag industries Council
   Conservation Federation of Missouri
   Missouri Association of Homes for the Aging
   Missouri Beef Industry Council
   Missouri Forest Products Association
   Missouri Industrial Development Council
   Missouri Poultry Federation
   Missouri Residential Care Association
* Dairy Farmers of America
* Monsanto Co.
   Today’s Farmer Magazine
   Missouri Soybean Association
   Missouri State Medical Association
* Sierra Club
   DuPont Agricultural Products
* Farmland Industries
* Missouri Pork Producers Association
* City of Kansas City Water Services
   Missouri Rural Services Council
   Missouri Soybean Programs
* League of Women Voters
* The Healthy Planet
* Novartis Crop Protection
* Watershed Committee of the Ozarks
   Missouri Association of Municipal Utilities

* groups that accepted the invitation to participate.

Appendix B - Public Comments

These are the comments (C) made by the DWSWA advisory committee members during the committee meeting on August 11 and August 18, 1998.  Each comment is followed by PDWP's responses (R).

1. C    The topographic maps that PDWP intends to use as base maps on which to present the results of the assessments may not have been revised in recent years.  Some features on the maps may no longer exist, or some existing features, including public drinking water lakes, may not be shown on the maps.

R    The maps in question are 1:24,000 scale topographic maps produced by the U.S. Geological Survey.  The revision dates of these maps vary from 1996 to 1952. These are the best maps available, and PDWP feels they will serve the project well.  The assessments may also benefit from old maps that show features such as treatment plants, railroads, or lagoons that are no longer present, but may have left contamination behind. All public drinking water sources will appear on the maps.

3. C    Many local communities are already working on Source Water Protection (SWP) projects.  How does PDWP intend to link DWSWA with the work that is already being done locally?

R   PDWP has had contact with some of the local SWP projects, but not extensively enough. PDWP will seek a more formal link to those projects.   Local SWP efforts are expected to be more detailed than the assessments completed by the state.  PDWP intends to share its information with local teams.

4. C    There may be some confusion between the Unified Watershed Assessment and the Drinking Water Source Water Assessment.  Do they need to be coordinated or tied together somehow?

R    As a result of these comments, there are now committee members common to both assessment projects.  This will help to keep the assessments coordinated.  The following fact sheet has also been developed to explain the differences between the two projects.

Drinking Water Source Assessments
The Unified Watershed Assessment

The purpose of this fact sheet is to clarify the differences between the Unified Watershed Assessment (UWA) and Drinking Water Source Water Assessments (DWSWA).  Both assessments are currently being done at the state level to satisfy nation-wide directives.

DWSWA are required by the 1996 amendments to the Safe Drinking Water Act.  Each state must prepare an assessment plan for EPA's approval by February 1999.  Each state will have two years after the plan is approved by EPA to complete the assessments. DWSWA must delineate source water areas for public drinking water sources.  Source water areas are areas around a well or upstream of a drinking water intake in a lake or river.  DWSWA will seek to identify each potential contaminant source within the source water areas and assess the water sources susceptibility to contamination.  The results of the DWSWA will be distributed to the public to encourage local groups to do what they can to minimize the risk to their water supply.

UWA is a component of the Clean Water Action Plan announced by President Clinton.   The Clean Water Action Plan brings environmental agencies together with federal conservation agencies to merge their respective assessments of water quality and natural resources into a single unified assessment.  The UWA will result in the classification of every 8-digit watershed into one of four categories; I) in need of restoration, II) in need of protection, III) public lands with pristine or sensitive aquatic conditions, IV) watersheds with insufficient data to classify.  Category I watersheds are prime candidates for restoration funding under the Clean Water Action Plan. Following the finalized Missouri Unified Watershed Assessment, the next step in the Clean Water Action Plan will be to develop comprehensive watershed restoration action strategies to restore the health of those watersheds in need of attention based on the Category I assessments.

DWSWA will focus only on drinking water source water areas and identify risks specific to each drinking water source.  UWA will place every 8-digit hydrological unit, which are typically much larger than a source water area, into one of four categories for restoration funding.

5. C    What kind of staffing effort does PDWP plan to devote to DWSWA?

R    Plans call for three geologists in DGLS to delineate source water areas for public wells, one environmental specialist in our northeast region to work on source water protection for surface water systems, and one in the central office to coordinate DWSWA and SWP activities. Some work may also be done by contracted entities.  There will also be one person funded in the Water Pollution Control Program to develop Total Maximum Daily Loads (TMDLs) for drinking water watersheds.

6. C    What kind of funding is available to public water supplies as part of DWSWA?

R    Through the Drinking Water State Revolving Loan Fund (DWSRF), loans could be given to community water supplies to implement source water protection.  However, the procedures for distributing such loans have not yet been set up by PDWP.

7. C    How many people does PDWP have in the field to verify source water assessments?

R    Current PDWP field staff are assigned to other duties.  It is rare that they have time to verify assessments, but it can be done if there is a priority situation or if the work coincides with their routine duties.

8. C    PDWP should consider defining priority areas within large watersheds.  How will PDWP determine source water areas for large watersheds?

R    Initially, the area within five miles of an intake will be considered a priority area. PDWP would prefer to base priority areas on a time-of-travel analysis, and will do so when a convenient method is available.

9. C    What contaminants have been found in public water systems?  Communities would be more receptive to implement SWP if we could point out known contaminant problems and recommend SWP as a means to address those problems.

R    This is what DWSWA is attempting to accomplish. TCE has been found in some community wells and atrazine is a problem for many surface water supplies.  One function of DWSWA should be to identify the particular contaminants that threaten each water source so communities will be better prepared to prevent contamination.  Microbiological contamination is a priority concern for PDWP, because there is a lot that is unknown about it.  It is hoped that DWSWA will help with the identification and resolution of microbiological problems, and better prepare PDWP when it comes time to implement the Groundwater Rule.  The Groundwater Rule, formerly known as the Groundwater Disinfection Rule, is expected to be more stringent than current regulations in order to guard against microbial contamination. The 1996 SDWA amendments also require Consumer Confidence Reports (CCRs). CCRs will be distributed to water system customers annually beginning in 1999. CCRs will inform customers of the quality of their drinking water and provide brief information about the source water assessment and how more information can be obtained.

10. C    What else could be done to convince communities to do SWP?  Possibilities may include lower insurance rates, reduced testing frequency, or priority points toward DWSRF awards.

R    The DWSWA plan is being developed with source water protection in mind, but does not go as far as developing incentives for SWP. The best way to foster effective source water protection plans is to educate the public about potential risks and the costs that can be saved through prevention. Extra incentives get the attention of some communities, but the best source water protection plans come from communities that understand the true value of the plan itself. Systems with source water protection plans will receive an extra 10 points on their application for low interest loans through the Drinking Water State Revolving Loan Fund. Reduced chemical monitoring may also be possible through source water assessments and protection plans. This is not as much of an incentive in Missouri, because water systems do not pay for required monitoring directly. Insurance rates in other states have also been reduced in certain communities that completed source water protection programs.

11. C    Known contamination sites that have been extensively studied could be a source of additional information.

R    PDWP intends to take advantage of all information sources available.  Some information will be obtained by coordinating with other DEQ programs.  Information can be gained about potential contamination sources, and any available groundwater studies will be used to aid source water delineation.

12. C    What kinds of enforcement actions are required or can be used in conjunction with SWP?

R    There is no new enforcement authority provided for source water protection.  EPA has recently proposed a rule that would regulate large capacity cesspools, industrial and automotive waste disposal underground injection wells in source water areas.  If the state does not define these source water areas, the regulations will apply state-wide. Any enforcement authority granted through existing rules can be enacted to ensure environmental compliance within source water areas.

13. C    The list of contaminants in Appendix F (Appendix D in 7/1/98 draft) should be expanded to include the chemicals listed in DEQ's Cleanup Levels for Missouri (CALM).

R    The CALM will be reviewed, and any appropriate chemicals will be added to the list in Appendix F.

14. C    There may be some contamination problems such as Trihalomethanes (THMs) that may not be addressed by the current SWDWA plan.

R    Subsequent drafts will be a comprehensive as possible.  THMs will be addressed by looking at nonpoint sources of organic loading in surface water watersheds.

15. C    A list of types of facilities that commonly have potential contaminants of concern should be included in the plan.

R    Such a list is included Appendix F of this draft plan.  This list was borrowed directly from the existing Missouri Wellhead Protection Program.

16. C    The Hazardous Waste Program (HWP) has a great deal of information.  HWP needs to know what kind of information PDWP would like to incorporate into the SWDWA so they can coordinate within the program.

R    PDWP, HWP, and CARES staff will meet and work together to bring HWP data into GIS and the DWSWA.

17. C    There may be other sources of information that have not yet been considered, such as those generated by the Farm*A*Syst program.  Although, most Farm*A*Syst information may be confidential.

R    PDWP and CARES are always looking for additional sources of information.  Any contaminant information that must be held confidential is of no use to DWSWA. However, communities developing source water protection plans could look to those programs as models for their own plan. Information on Farm*A*Syst and Home*A*Syst can be accessed online at

18. C    Does PDWP see a need for formal agreements with other states?

R    PDWP will contact neighboring states to attempt to acquire contaminant information for watersheds which cross into other states.  PDWP has already received drinking water intake locations for state downstream of Missouri. EPA Region VII has agreed to assist in obtaining interstate information.

19. C    Perhaps DWSWA results should be included in the Consumer Confidence Reports (CCRs).

R    This is required by the final CCR rule.

20. C    PDWP should be cognizant of the possibility of abuse of the DWSWA information by special interest groups. PDWP should spend time with the news media to explain the program, and make the meaning of potential contaminant sources clear. The media needs to be educated so they understand the levels of risk. This shall be a challenging, but important task for PDWP and other DNR programs that face similar issues.

R    This shall be a challenging, but important task for PDWP and other DNR programs that face similar issues. PDWP is very concerned that DWSWA information be presented clearly and correctly. The difference between potential contaminants and the relatively rare instances of actual contamination is an example of a point that needs to be made very clearly.

21. C    The Solid Waste Program may have landfill locations that would benefit DWSWA.  The USGS has published groundwater studies for some local areas.  The Missouri Rural Water Association my be able to help locate potential contaminant sites and help publicize the DWSWA plan.  NRCS may have information regarding local watershed plans.  University Extension may have pertinent information about surface water supplies.  The Missouri Department of Agriculture has information on pesticide applicators and wood treaters.  The Soil and Water Conservation Program may have helpful information about soil and hydrology.

R    All these sources of information will be helpful.

22. C    By putting the location of drinking water facilities on the Internet, are we not providing a guide for the local, national and international terrorist?  Should this information be so easily available?  Has anyone pointed this out to EPA?

R    This is a risk PDWP has to take in order to educate people about their source of drinking water.  It would be impossible to make these locations top secret, so PDWP will seek to make the general public aware of the threats facing their drinking water.  We have always encouraged water systems to secure their facilities with locked gates, well houses, etc.  Threats of sabotage will be included in the source water assessments.  Adequate security for drinking water facilities may be the most important source water protection activities a system can do.

23. C    Will DWSWA address only public water systems?

R    DWSWA will only address public water systems.

24. C    Is DWSWA aimed at protecting the aquifer or only the wellhead?

R    DWSWA are aimed at protecting the wells, but you can't do that without protecting the aquifer.  Delineations and contaminant inventories will pertain to the portions of the aquifer that contribute to public wells.

25. C    When contaminants are found during assessments, will information be provided on the date they were found?

R    Most of the contaminants DWSWA will identify are merely potential contaminants.  Relatively few will have a date of discovery or date of laboratory analysis to associate with them.  For those sites that do, parties interested in contaminant site details and histories can be referred to the agency from which PDWP obtained the data.

26. C    How does PDWP plan to select contaminants for the list of those to be tested or looked for under DWSWA?

R    PDWP will seek to identify any potential contaminant with adverse health effects in drinking water. The list began with chemicals listed as drinking water concerns by EPA, and any additional contaminants of concern were added. The preliminary list is included in Appendix F. PDWP is soliciting suggestions to be added to the list. A limited amount of testing may be done to aid in the susceptibility determinations. Most testing will be dictated by our regular monitoring procedure.

27. C    One map in the plan indicates it was developed in 1982.  Has that or will that be updated? Different maps utilize different sources of data or databases. Does PDWP plan to use the best available data?

R    The map in question is shown in Figure 2.  The 1982 county assessor's map was field checked and updated in 1997 to produce the map shown in Figure 2.  All PDWP maps can be updated as needed.  PDWP uses the best maps available.

28. C    Is the term "potential contaminant source" defined by law or is that definition up to the state.

R    It is up to the state to determine what a potential contaminant source is.

29. C    What is the process after the draft is finalized?   Will this committee be involved in responding to comments by EPA?

R    The plan must be submitted to EPA by February 6, 1999 for review and approval.  EPA has nine months to approve the plan.  During that time, revisions will probably have to be made to gain EPA approval.  If time allows, the advisory committees may be called upon to review EPA's comments, but this is not required as part of the approval process.

30. C    What resources does the state have to implement the program?

R    The full 10% set-aside provided in the DWSRF will be used to develop and implement the DWSWA.

40. C    Have groundwater models been developed in conjunction with WHP projects, such as Cuba and Hollister, which could be used in the SWAP process?  Are simplified models available?

R    Techniques are there, but it is difficult to apply them to a large number of wells and there is inadequate basic data to use, such as well production records, to use with those models.  Broad assumptions have to be made to apply those models.

41. C    Some chemicals listed in Appendix F are not labeled for use in Missouri and could possibly be removed from the list, while some new agricultural chemicals are missing from the list.

R    PDWP may choose to leave the unlabelled chemicals on the list, because thy could still be harmful in drinking water even if their probability of occurrence is low.  PDWP would also appreciate suggestions for chemicals that need to be added to the list.

42. C    Nutrients that can cause taste and odor and other problems in drinking water should be considered.

R    Land use mapping will likely be used to assess lake's susceptibility to nonpoint source contamination. Total Maximum Daily Load determinations will also address this.

43. C    Taking the source water protection message to the schools and teaching school children could be an effective way of educating the public as a whole and inspiring local source water protection efforts.

R    PDWP agrees this could be a effective way of delivering an important message.  PDWP will probably not pursue this action as part of the development of the DWSWA plan.

44. C    The State Emergency Management Agency (SEMA) and Local Emergency Planning Committees (LEPCs) should be involved in the DWSWA process.

R    PDWP invites everyone to comment on the DWSWA plan.  An invitation has been extended to SEMA. Some LEPCs have already received word of our plan and have attended our public meetings and provided comments. PDWP will work on invitations to additional LEPCs.

The following comments were made at the 6 public meetings held around the state:

45. C    In terms of potential contaminants, how will PDWP address submersible well pumps containing oils with PCBs, Polyaromatic Hydrocarbons, or other potentially harmful additives?

R    A literature review will be conducted to identify which pumps may be subject to these hazards. These pumps should certainly be identified as potential contaminant sources. PDWP may determine what corrective actions need to be taken once the problem has been assessed.

46. C    Are the ½ mile radius buffers meant to represent the recharge areas for the wells? Recharge areas will vary more than that. I am concerned about the 1/2 mile buffer.  I don't feed this is adequate.   Maybe there needs to be a second round of assessments to go back for more thorough delineations.

R    Comparison with hydrogeologic studies of alluvial wells and PDWP’s chemical monitoring records indicate that ½ mile radii do approximate the recharge area for many wells. However, varying geology is bound to produce some recharge areas that differ greatly from a one-mile circle. This source water assessment plan will include examination of geologic and hydrogeologic information to delineate wellhead recharge areas with greater accuracy that one-mile circles. The first year of source water assessments will provide delineations to replace the ½ mile buffers with estimated source water areas based on regional geology and pumping capacity. The following years will produce a second round of delineations based on local geology for community wells.

47. C    How does PDWP address contaminants in flood plains? Has PDWP assessed the public wells that were flooded in 1993? Have all those wells been raised above the flood level?

R    Contaminants located in flood plains will be inventoried no different that other contaminants. Flood plains may affect the shape or size of some delineated source water areas. The susceptibility determinations will consider how flooding may threaten a drinking water source and identify contaminants that may be a greater risk because of flooding. PDWP conducted engineering studies and microbiological testing of public wells that were affected by the 1993 flood. Many facility improvements were made, but any facility in a flood plain is at risk, and this will be included in the upcoming source water assessments.

48. C   Will new water systems or systems with new wells have to prepare source water assessments?

R   New wells will be subject to the existing siting requirements. Source water assessments for new public wells will be completed by the state. Water systems will be asked to contribute as much information as possible on well construction and nearby contaminant sources.

49. C    Are reconnaissance maps supplied to the water systems?

R    Reconnaissance maps were mailed out to the water systems in 1995. Reconnaissance maps are always available by request. Reconnaissance maps and susceptibility determinations will be sent to the systems when the assessments are completed.

50. C    Is the chemical site data maintained by PDWP cross referenced to the community right to know databases.

R    The chemical sites currently PDWP’s GIS database were extracted from over 100 other databases. The source database for each site can be identified, many of which owe their existence to the community right to know laws.

51. C   PDWP should take advantage of dye tracing studies that indicate groundwater travels long distances.

R   Much of the dye tracing done is Missouri is conducted by the Division of Geology and Land Survey (DGLS). DGLS also maintains the most comprehensive geologic information for the state. PDWP is pleased to have three geologists from DGLS working on the wellhead delineations for the source water assessments. The large number of wells and short time constraints for the assessments may not allow in depth investigation for each well.

52. C    Has PDWP looked at sanitary landfills and Confined Animal Feeding Operations (CAFOs)?

R    Some location information for landfills and CAFOs is currently in GIS. Better location information will be acquired so these sites can be included in the assessments.

53. C    If CAFO locations were available, would they appear on source water assessment maps?

R    CAFOs that are regulated by DNR will appear on source water assessment maps. If locations of smaller operations are provided from other sources, they will also be placed on source water assessment maps.

54. C   Will private wells appear on source water assessment maps?

R   Where private well locations are available, they will be identified as potential pathways for contaminants to enter groundwater. Locations are not available for many private wells. In some instances where private wells have been tested positive for chemical contamination, they already appear on PDWP’s source water maps.

55. C    Will source water assessments include potential problems related to the year 2000. Will there be any year 2000 problems?

R    Water systems relying on computers to manage their facilities should take precautions to avoid year 2000 problems. Most year 2000 problems are more likely to affect the pumping, treatment, or distribution system; and should not have an effect on the water source. Therefore, year 2000 problems will not be addressed by source water assessments.

56. C    Has PDWP considered a three-dimensional determination of recharge areas?

R    PDWP intends to use the limited three-dimensional information that is available to project an area on the land surface that represents the recharge area for a well.

57. C    Is well log data good enough to know if caves are present and if openings are cased out?

R    Some well logs indicate where voids were encountered during drilling, and some records exist to describe how these voids were cased or grouted.

58. C   When susceptibility determinations are being made, is there a trigger to raise a red flag to DNR or EPA to declare a serious potential danger, and a mechanism for the agency to follow up to mitigate the problem? Smaller supplies often need problems brought to their attention. Such a mechanism should be part of this process. Can this be done through DNR’s Technical Assistance Program (TAP)?

R This type of mechanism has not been designed for source water assessments. PDWP will consider devising something like this as part of the susceptibility determinations. It is most likely that this will be carried out by PDWP staff in conjunction with routine inspections and sanitary surveys.

59. C    How could someone use PDWP’s maps electronically?

R    PDWP can provide electronic graphics files for each map. These graphics files can be used to reproduce the maps, but are not suited for customizing. Custom maps can be created by users at Data can also be downloaded from and to be used in GIS software.

60. C   How will Confined Animal Feeding Operations (CAFOs) be addressed?

R   CAFOs will be identified as potential contamination sources. PDWP will capture the locations of all CAFOs large enough to be regulated by DNR. If a source of information is available to identify smaller CAFOs, they will also be captured.

61. C   What urban non-point sources of contamination is PDWP looking for? Will golf courses, parking lots, etc. be identified?

R   PDWP will identify urban areas in general as having increased non-point sources of contamination. Non-point sources such as golf courses, parking lots, etc. will be identified on land use maps for small (<25,000 acres) drinking water watersheds, however these watersheds are generally in rural areas.

62. C    What can de done for communities that do not have jurisdiction over their entire source water area?

R    Voluntary agreements will need to be made between jurisdictions.

63. C    Will source water assessments reduce required monitoring?

R    PDWP has already reduced monitoring for Synthetic Organic Chemicals (SOCs). The information gathered for source water assessments may justify further reduced monitoring, and PDWP may do so in the future, but not immediately.

64. C    Farmers are willing to work with agencies to improve their methods, but they respond adversely to being regulated.

R    It is because of this trend that source water assessments are being prepared for the public, and source water protection will remain voluntary.

65. C    How will operators of public water supplies be affected by source water assessments?

R    Source water assessments will be completed by PDWP. Operators are encouraged to contribute information that might improve each assessment, but they are not required to do so. Assessment results will be provided to each water system for their use. Water systems are required to summarize assessment results in the Consumer Confidence Reports (CCR) and include information on how to obtain detailed assessment results. Consumer Confidence Reports must be provided to water system customers annually.

66. C    Please explain the time-of-travel concept.

R    If a well recharge area is delineated as a ten-year time-of-travel, that means it will take approximately ten years for water or contaminants at the perimeter of that area to be pumped into the water system.

67. C    How is the depth of a well factored in to its assessment?

R    The depth of a well determines the geologic layer from which it draws water. The susceptibility of a well is a factor of its construction and the susceptibility of the geologic layer from which it draws water.

68. C    Are there indicator contaminants that are used to predict the likelihood of future contamination?

R    The presence of any contaminant is an indication that the well would be susceptible to further contamination and would often trigger increased monitoring of the well.

69. C    What information on Superfund sites will be presented in the assessments?

R    Information on all potential contaminant sites will include the name and location of the facility, potential chemicals present, and source of the information. Facility details can then be acquired from the original information source.

70. C    What data is available on natural contaminants, and will they be part of the assessments?

R    Information is available on areas with naturally high chlorides and dissolved solids in groundwater. Radionuclides, fluoride, and lead have also been found to occur naturally in certain areas. PDWP will attempt to address naturally occuring contaminants where applicable.

71. C    Is monitoring data available over the Internet?

R    Monitoring data is not available over the Internet, but this is something PDWP is considering.

72. C    Would the state include contaminants identified by the public in the assessments?

R    PDWP welcomes contaminant information from all available sources. The source of information will be recorded for future reference.

73. C    What mapping will be done for the Missouri River?

R    PDWP has mapped the Missouri River watershed to the Canada border. The contaminant data collected from existing databases will be collected statewide. PDWP will likely define a priority area just upstream of any drinking water intake that can be clearly mapped.

74. C    Is water quantity part of the assessment?

R    Source water assessments focus primarily on water quantity. However, PDWP does consider water quantity an important factor and will continue to address these issues in conjunction with source water assessments.

Appendix C - Public Meeting Announcements

(flyers not included)

(new releases not included)

Appendix D - Sources of Contaminant Information

Appendix E - List of Potential Contaminants and Contaminant Sources

Appendix F - List of Acronyms


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Revised on May 05, 2008