Assistance Packet
(Susceptibility Assessment Form)

This form has been developed in order to help assess the susceptibility of your groundwater source(s) to potential sources of contamination. The Wyoming Department of Environmental Quality, Water Quality Division (WDEQ/WQD) will use the information on this form to evaluate geologic and hydrologic factors associated with each of your Public Water System (PWS) sources (i.e. well, spring or tunnel) in order to estimate the source's potential vulnerability to contaminants that are regulated under the Safe Drinking Water Act (SDWA).

IMPORTANT! When submitted by a 'Non-community' Public Water System (See Glossary) and approved by WDEQ, this form and its accompanying map illustrating the delineated Wellhead Protection Area (WHPA) may serve as that PWS's Wellhead Protection Plan. This form (and accompanying map) may not serve as a complete Wellhead Protection Plan for a 'Community' Public Water System; 'Community' systems must meet the requirements (i.e WHPA Delineation Report, etc.) identified in Wyoming's Wellhead Protection Guidance Document, including completion of this form, in order to obtain WDEQ approval of their Wellhead Protection Plan.

Regardless of the type of Public Water System (Community, Transient Non-community, or Non-transient Non-community) the Susceptibility Assessment Form (Appendix F) must be completed and included as part of any Wellhead Protection Plan submitted to WDEQ for approval.

The information requested on this form may be gathered from a variety of records. Some information can be found on your Statement of Completion and Description of Well or Spring (Form UW 6) filed with the State Engineer's Office (SEO). Please take the time to verify this information. If this information is not current, please note any needed changes. Other useful records include your source and system monitoring records as well as system design plans, water right records, engineering and geologic reports, and water quality monitoring records. If your records are not complete, you may be able to obtain some of this information from the SEO, WDEQ/WQD, or the Wyoming Water Development Commission.

Many of the questions request information about the construction of your well. If your water system utilizes only springs or tunnels, you should still complete the Susceptibility Assessment Form; simply leave blank those questions which do not apply.

Incorrect information or incomplete forms may raise your susceptibility risk evaluation. For these reasons it is important that you take some time to complete the form to the best of your ability. You may not have all of the information that is requested on the form. You may indicate "information unavailable/unknown" in response to certain queries if this is the case.

EPA and Vulnerability:

In 1986 Congress passed amendments to the Safe Drinking Water Act (SDWA). These amendments have been implemented in phases. The most recent phases to be implemented are Phase II and Phase V monitoring requirements which went into effect between 1993 and 1995. Phase II and V deal mainly with monitoring for volatile organic and synthetic organic compounds (VOCs and SOCs). Under Phase II & V the monitoring requirements for these compounds are significantly increased for Public Water Systems (PWS). Realizing that the increased monitoring requirements can be very costly to water systems, EPA has allowed PWSs to reduce or waive monitoring requirements depending upon how vulnerable the water system's sources are to contamination. That is, those sources which are vulnerable to contamination may have more monitoring requirements while those sources that are less vulnerable may have reduced or no monitoring required for many chemicals.

What is Vulnerability?

Vulnerability can be thought of as a water source's (e.g. well, spring or tunnel) potential for contamination. Vulnerability is composed of two factors: the physical susceptibility to the infiltration of contaminants; and the source's risk of exposure to contaminants. Susceptibility is determined by conditions that affect the movement of contaminants from the land surface into a water supply. This would include the depth of the well, its construction, the geology of the area, the pumping rate, the source(s) of groundwater recharge, and the aquifer material. The risk of exposure to contaminants is determined by whether or not contaminants were used in the area of a water supply.

Susceptibility Assessments:

In order to determine a drinking water source's vulnerability to contamination WDEQ/WQD has developed the Susceptibility Assessment Survey Form. This survey form catalogs key susceptibility factors for each source in order to evaluate overall susceptibility. The following information is needed to evaluate hydrologic susceptibility:

  1. Well logs, or other indicators of aquifer characteristics,
  2. Depth and length of open interval,
  3. Date and description of construction,
  4. Record of past monitoring results (nitrates, VOCs, SOCs, metals, and bacteria),
  5. A specific (and accurate) location of the source,
  6. Water level information,
  7. Estimate of wellhead elevation,
  8. A general evaluation of land-use surrounding the wellhead,
  9. Size of the water system, and
  10. Contingency planning.

Monitoring Waivers:

Depending on the results of the susceptibility assessment, EPA may allow that some or all of the monitoring requirements (number and type of paramters, frequency of monitoring) for certain chemicals be waived. This type of waiver is considered to be a "susceptibility waiver". If source information does not allow a system to qualify for a susceptibility waiver, the system can pursue other types of waivers. One option, the Contaminant Use Waiver, involves a more intense inventory of the contaminants that may be found within the source's recharge area. "State-wide waivers" may also offer some monitoring relief. These are blanket waivers granted for chemicals not commonly detected in the state.

PART I: System Information

With a few exceptions, all of the information in this section can be taken from your State Engineer's Office (SEO) Statement of Completion (Form UW 6). The SEO should have a copy on file if your copy has been misplaced. Of particular concern is the information concerning source location and quarter/quarter section, and well depth. You should also note the population served and number of connections in this section; this information should be available from the water system records. Please use this opportunity to review your system records and make sure they are up-to-date.

There are optional items in this section. These include the State Engineer's Office permit number and a latitude and longitude location. If this information is not readily available, these areas can be left blank.

PART II: Well Construction and Aquifer Characteristics Information

Most of the well information can be obtained from the Statement of Completion (Form UW 6 filed with the State Engineer's Office) and design plans that were prepared for the water system. In some cases the information may be found in other system records. Estimates can be made for some factors but these responses must be identified as estimates.

1) Date Well Constructed/Reconstructed:

This information may be found in Item 8 on the SEO Statement of Completion. If you have multiple records representing reconstruction or redevelopment of the well, use the most recent one. Please include a copy of the well log (Statement of Completion - Item 13) with this form.

2) Well Driller:

This can be found in Item 7 on the SEO Statement of Completion. Please enter the name and address if possible.

3) Well Type:

Mark the type of well construction. It can often be found in Item 5 of the SEO Statement of Completion. If this area has not been filled in, please check system records.

4) Well Report (Well Log):

This would include a driller's log, well log, or a detailed design that includes an engineer's "as built" along with a geologic log. The Statement of Completion items 6 and 13 should include a information regarding well construction and the well log(s) for your system if you cannot locate this information in your files. Please attach a copy to your response form.

5) Average Pumping Rate:

This may be available from the system plan or from Item 9 of the SEO Statement of Completion. It is an estimate of the pumping rate in gallons per minute (gpm). If the current pumping rate is different than that listed on the Statement of Completion, or if documentation is absent, please explain how the pumping rate was determined.

6) Source Treatment:

If your water source is treated in any way prior to delivery to your customers, please record that information here. Many water sources are not treated. Of those that are, chlorination (for disinfection) is the most common. Some other common types of water treatment include: other type of disinfection, filtration, fluoridation, or softening (to remove unwanted minerals or chemicals).

It is possible that your system has more than one source that is combined prior to treatment. If that is the case, please record this information in the comment section.

7) Chlorine Residuals:

To be completed only for those sources that are chlorinated. If your system is chlorinated, please record the average chlorine residual for that source (within the distribution system). If more than one source is combined before treatment be sure to record the same information on both susceptibility assessments.

8) Depth to Top of Open Interval:

This is the depth to the top of the screen/perforated area of the well. If there is more than one screened interval, use the depth to the top of uppermost one. If the well is not fully cased use the depth to the bottom of the casing. This information is generally found on the SEO Statement of Completion, Item 6 or in an engineer's "as built" design report. If the well is cased but there is no screen(s) simply mark the depth to the bottom of the casing.

9) Depth to Groundwater:

On the SEO Statement of Completion this would be listed in Item 6. It is the static level of water in the well measured as the depth from the top of the well. It may be significantly different from either the depth of the well or the top of the open interval. If this information is not available on the well log, a current water level measurement can be used as an estimate. If the well is under pressure, or is a flowing well or spring, please mark the form accordingly.
10) Flowing Wells and Springs:
If this source is a flowing well (artesian or free flowing well) or is spring, is there a measure of the flowing or confining pressure? This is an alternative way to measure the aquifer pressure associated with a source. Some artesian wells and springs are under pressure and flow freely at the land surface without the aid of a pump.

This information may be listed in pounds per square inch (psi) or as a flow rate in gallons per minute (gpm). If the information is listed as a flow rate be sure it is not a pumping rate.

11) Surface Impoundments and Reservoirs:

If your source is a flowing well or spring, does it include a surface impoundment, reservoir, pond, catchment basin, or lake as part of its collection system? For this question, "surface impoundments" do not include dosed or covered spring boxes, but refer to impoundments that are open to the atmosphere.

12) Wellhead Elevation:

This is the elevation above sea level of the top of the well casing (that extends above the ground). Sometimes this information can be found on the well log in part 8. An estimate can be made by altimeter or by using a topographic map and estimating the approximate elevation of the wellhead. Elevation can also be estimated relative to a nearby reference point. If an alternative method is used please explain how the estimate was made.

13) Confining Layers:

This section can only be completed with the use of a drilling log, well log, or geologic/engineering report. The log will show the depth, thickness and type of material that was encountered during drilling. These materials may be described in the log as cobbles, gravel, sand, rock, fractured rock, basalt, shale, till, hardpan, or clay. The log should also identify the strata that yielded water. They may be clearly identified or simply noted as "wet" or "seepage". Generally the most productive water bearing zone is where the well has been screened.

14) 'Accident Prevention Zone' (Zone 1 of the WHPA):

Public Water Systems should establish a control zone (i.e. WHPA Zone 1) around the well that excludes major potential contaminant sources. Zone 1 is either a 50 foot or 100 foot radius around the well (See Section II, Wyoming's Wellhead Protection Guidance Document) but can be larger in some cases. This area should exclude buildings, roads, driveways, storage facilities, drainfields and other possible contaminant sources.

15) Wellhead Control and Access:

Note if there is a well-house constructed around the pump and wellhead built specifically to protect the wellhead. Is there controlled access to the wellhead (fenced area, locking cap or access port)? If the wellhead is housed in a building used for other purposes (storage of treatment materials, etc.), please describe.

16) Surface (or Inner) Casing and Annular Seal:

Surface casing and the annular seal of a well commonly extend some distance down the annular space (the space between the well casing and the borehole wall) to protect the well from direct infiltration of surface contaminants. Indicate the type and depth of the surface (or inner) casing and the annular seal.

17) Surface (Protective) Casing, Seal and Well Cap:

A protective casing installed above ground over the well helps to prevent infiltration of surface water into the wellbore during periods of flooding of high runoff; a protective concrete seal set at the surface, sloping away from the well is further protection against the introduction of surface contaminants into the well. A locking well cap helps prevent unauthorized entry or tampering with the source.

PART III: Assessment of Water Quality

The purpose of this section is to evaluate existing evidence of water quality problems in your specific water supply source(s) and to inventory possible threats to future water quality in order to minimize the risk of future contamination.

1) Regional Sources of Risk to Groundwater:

Please indicate if any of the following potential contaminant sources listed on the Table are present within Zones 1, 2 or 3 of your Wellhead Protection Area (WHPA).

'Non-Community' PWSs: Mark and identify the potential sources on the WHPA map, together with other potential sources (see Table III-1,Wyoming's Wellhead Protection Guidance Document) within your WHPA.

'Community' PWSs: Mark and identify the potential sources on the WHPA map, together with other potential sources in your Contaminant Source Inventory' (see Section III, Wyoming's Wellhead Protection Guidance Document).

"Pesticide application" refers to those areas, excluding residential areas, where pesticides, hebicides, insecticides, etc. are commonly applied. Examples include agricultural land, managed forest land, nurseries, and recreational areas (golf courses, parks), all with areas greater than about 2 acres. Also consider right-of-ways (state/county highways, railroads, electric/telephone lines) where herbicides are applied and mosquito/vermin control areas. State and County Public Works Departments, County Weed and Pest Control Offices, and County Agricultural Extension Offices can often supply much of this information.

"Other injection wells" can include French drains (stone-lined pits or trenches) into which liquid waste is poured and allowed to percolate into the ground.

Local governments and health departments may also be able to provide information concerning known contaminant sources such as landfills, clean-up sites, permitted waste discharge sites and businesses or industries that store or dispose of significant quantities of hazardous waste materials in the immediate vicinity of your water supplies (service stations, auto shops, dry cleaners, chemical manufacturing/processing, etc.). This information may also be obtained by contacting WDEQ-Division of Solid and Hazardous Waste. Telephone numbers of municipal and county agencies can be found in the government listings in the White Pages of your telephone directory; state agency contacts are provided in Table III-2 of Wyoming's Wellhead Protection Guidance Document.

If you are unable to obtain sufficient information from public agencies to respond to this question, a simple alternative is to identify the area on a local map and complete either a walking or driving survey of the area, noting potential sources of contamination as discussed in Section III of Wyoming's Wellhead Protection Guidance Document.

2) Source Specific Water Quality Records:

The following four sections will require the review of your water quality testing records. Of primary interest are any records indicating past water quality problems for your source(s) since 1986.

A) Nitrate Monitoring History - The U.S. EPA Maximum Contaminant Level (MCL) for nitrates plus nitrites (as Nitrogen) is 10 mg/l. Levels between 5 and 10 mg/l may indicate some nitrate leaching from surface sources. Note in the appropriate boxes whether you have had nitrate detections below the MCL.

B) Volatile Organic Compounds (VOCs) - MCLs vary for each VOC. Use EPA or lab notification of MCL violations. Total Trihalomethane (TTHM) data should not be considered here.

C) Synthetic Organic Compounds (SOCs) - If you have completed any pesticide monitoring the results should be recorded in this section.

D) Bacterial Contamination - Use coliform monitoring records to respond. IMPORTANT: The main emphasis in this set of questions is to identify those water sources that have a history of source related bacterial contamination. Most of the current bacterial testing is done within a system's distribution system and not at the source. Bacterial contamination in the water system does not necessarily indicate contamination of the groundwater source.

PART IV: Geographic or Hydrologic Factors Contributing to a Non-Circular Zone of Contribution

The Calculated Fixed Radius (CFR) delineation method is simple and relatively easy to apply (see Appendix D); however, it is based on a number of assumptions concerning the aquifer and underground conditions. Very rarely are all of these assumptions true.

The following questions will help identify aquifer conditions which may not be accurately represented by the Calculated Fixed Radius (CFR) method; answer these questions only if you are a 'Non-Community' PWS, or a 'Community' PWS using the Calculated Fixed Radius (CFR) method to delineate the WHPA. If you answer Yes' to questions #1, 2(B), 3 or 4 you must either modify the WHPA accordingly or apply one or more alternative delineation methods (see Appendix D, Wyoming's Wellhead Protection Guidance Document) in order to obtain WDEQ approval.

1) Hydrologic Boundaries:

Hydrologic boundaries are natural features in the earth which shape groundwater flow patterns. Examples include surface streams, lakes, reservoirs, mountains, ridges and other steep changes in elevations. A topographic (topo) map is useful in determining whether such features are present within the circular area around your source(s) having a 5-year travel time radius. If possible, simply attach to this form a copy of such a map with your water source(s) marked and labeled.

Topo maps can be purchased locally throughout the state at map stores, camping stores, etc. You may need more than one map to include your WHPA. If you use a U.S. Geological Survey topographic map please use one that is based on a 7 1/2 minute scale.

2) Aquifer Material:

These questions help identify those sources that may be found in geologic conditions that may affect the source's overall susceptibility. An important consideration can be the nature of the material that makes up the underground environment and forms the aquifer. The information needed to answer these questions might be found in drilling logs, well logs, aerial photos, geologic maps or reports, or engineering reports of aquifer/pump test data and interpretations.

A) The Calculated Fixed Radius best applies to groundwater exhibiting 'porous' or 'diffuse' flow behavior, as opposed to 'conduit' flow behavior. The presence of faulting, fracturing and karst conditions are often indicators that conduit flow exists. Have any of the above mentioned sources of information been reviewed and analyzed for the presence of faulting, fracturing and karst conditions, both within the aquifer as well as within any overlying strata or sediments?

B) Do any of the above mentioned sources of information reveal or indicate that the well is located in an area where the underground conditions are fractured, faulted or karst?

3) Groundwater Flow Type and High Horizontal Flow Rate:

This question will help identify those wells that are located in settings that produce very high natural groundwater flow rates, such as those which often occur in areas where underground conditions include multiple or extensive stratification of coarse sand or gravel. These may be identified in the drilling logs as: gravelly sands, sands and gravel, cobbles, gravel, boulders, or pebbles and are often associated with alluvial fans and outwash deposits, fluvial flood plains and glacial outwash deposits. In these settings, it is possible that the area of contribution around the well is influenced more by the aquifer flow conditions than by the pumping rate of the well, and the WHPA may be highly elongated and not circular. Do any of the above mentioned sources of information reveal or indicate that the well is located in an area where these highly porous and transmissive conditions exist?

4) High-Volume Wells:

These types of activities can have a tremendous effect on the shape of the flow system providing groundwater to your source. Wells located near these types of activities may be influenced by them. Indicate if you are aware of other high-capacity groundwater wells (> 500 gal/min) located within the WHPA. Indicate if there are any large recharge wells (e.g.stormwater run-off, drainage wells, etc.) or large-scale irrigation wells within the WHPA.

PART V: Potential Source Hazards, Controls, Assessment and Management

Only 'Non-Community' Public Water Systems need to complete this part; 'Community' PWSs must follow the guidelines set forth in Section IV of Wyoming's Wellhead Protection Guidance Document.

The ultimate objective of Wellhead Protection is to prevent groundwater contamination within the Wellhead Protection Area (WHPA). Therefore, management of potential contaminant sources (within the WHPA) is an essential component of Wellhead Protection. Non-community PWSs that submit this form (as their WHP plan) to WDEQ/WQD must describe the techniques that will be employed to manage and minimize the threats posed by the potential contamination sources identified

1) Management of Existing and Future Contaminant Sources:

As described below, varying levels of source management approaches are suggested based upon the potential of contaminant sources to impact the drining water supply (i.e. aquifer) or source (i.e. well, spring or tunnel). Public Water Systems should appropriately identify existing controls, assess the adequacy of existing controls, and propose management strategies for potential contaminant sources; on the form, indicate the strategies to be implemented and related information.

Regulatory Management Strategies:

Non-Regulatory Management Strategies:

Regulatory management strategies generally can afford a greater degree of protection, as compared to non-regulatory methods. A more complete description of the applicability, including examples of these strategies is provided in Section IV and Appendices I and L of Wyoming's Wellhead Protection Guidance Document.

PART VI: Contingency Planning (Non-Community PWSs Only)

Only 'Non-Community' Public Water Systems need to complete this part; 'Community' PWSs must follow the guidelines set forth in Section V of Wyoming's Wellhead Protection Guidance Document.

The purpose of this section is to address problems that Non-community Public Water Systems need to overcome in the event of water supply shortages or contamination incidents that may impact the system's ability to supply an adequate quantity of safe drinking water to the public. Contingency plans should focus on the identification of, and solutions for, problems that may arise if protective and preventative measures fail. Potential emergencies such as well, wellfield, or spring contamination, water shortages due to droughts, and interruption of water supply due to power outages or infrastructure failure should be identified and addressed in a contingency plan.

1) Contingency Plan Organization:

The formulation of the contingency plan can be substantially completed and implemented by the public water system. Broader contingency planning has been required since 1986 under the Federal Emergency Planning and Community Right-to-Know Act (SARA Title III). Title III establishes a network of State Emergency Response Commissions and Local Emergency Planning Committees charged with planning response to emergency releases of hazardous chemicals; local emergency response plans may provide a starting point for WHP contingency planning.

In formulating a contingency plan, the Non-Community PWS must address the following considerations: (1) existing system condition and the possible water system failure modes; (2) responsibilities during an emergency; (3) emergency response procedures and contacts; (4) development of new ground and surface water sources in case of long-term shortages or abandonment of contaminated supplies; and (5) sources of emergency funds and procedures for requesting and dispersing such funds. Chapter V of Wyoming's Wellhead Protection Guidance Document (Planning for the Future) can be referenced for more specific contingency planning, additional guidance and information.

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Wellhead Protection Program Guidance Document Contents
Wyoming Department of Environmental Quality