The following are examples of additional types of local information that can be used to screen for existing and potential contaminant sources within the WHPA, and are recommended for use in completing 'Source Identification' forms and developing the 'Source Inventory' list (described below):

• Zoning, fire insurance and other maps
• City/county permits, licenses, registrations
• Aerial photographs
• Chamber of Commerce membership lists
• Telephone and business directories
• Community planning, public works, engineering and health departments
• Police and Fire Departments
• Long-time residents of the community
• Local Emergency Planning Committees

2. Identify ‘potential’ sources for further study:

A good map to consult when investigating potential sources is the town's map of the community sewer service network. The intent of the sewer network is to collect and transport raw waste to the sewage treatment plant where it can be treated prior to disposal. When a map of potential contaminant sources is compared to a utility map indicating where the sewers are, it will become obvious where to look for existing and/or potential discharges to groundwater - at those sources not served by the sewer network. City/town engineers also should be consulted to identify portions of the sewer system network that are known or suspected to have failed or are in need of repair.

Current zoning maps and aerial photos assist in identifying the various types of activities which may be occurring within the wellfield area. Comparison of current maps and photos with older versions often illustrates historical practices or sources which may have impacted groundwater or warrant closer study. Aerial photos usually are available through the local NRCS, survey firms, or historical archives in community libraries.

Additional sources of information documenting past and present land uses include 1) local registries of commercial and industrial activities; 2) property transfer records, titles and deeds; and 3) senior citizen interviews regarding locations and practices of historic sources which are no longer in existence.

The following steps discuss procedures which should be implemented to further refine and develop the Source Inventory list: 3. Access Unknown Sources:

'Known' sources are those that already are included in files or data bases, while 'unknown' sources generally are not subject to regulatory controls or have not been brought to the attention of authorities due to oversight or lack of concern. Collecting information on unknown sources generally requires some type of survey to collect information of concern for WHP. This step also provides an opportunity to check information obtained from other sources and to obtain information about previously identified sources that warranted further study. The most thorough and effective way to obtain additional and new information on potential sources usually is through one or more of the following survey types:

• Mail surveys
• Field searches ("Walking Tours")
• Telephone surveys
• Windshield surveys
• Door-to-Door surveys
• Personal interviews

One, or a combination of the survey types listed above must be used to refine and develop the Source Inventory list. WHP plans must identify the type of survey(s) implemented and discuss the measures which were taken to ensure thorough and complete survey coverage within the WHPA.

4. Verify accuracy and reliability of the information gathered on 'Known' and 'Unknown' Sources:

One of the best ways to ensure accuracy of information gathered during source identification is through field checking via "walking tours" or windshield surveys. Information collected through personal interviews can be verified by actual site visits. Telephone confirmation can be useful where a source facility is unmanned (e.g. oil wells). Cross-checking existing databases with any of the survey approaches described above is an acceptable way to verify information on existing and potential sources.

III. Describe sources within the WHPA:

1. Complete Source Identification forms (See Model Form III-1: Appendix H) for each existing and potential source of contamination identified within the WHPA:

Form III-1 (Source Identification Form) is a model form recommended for use by communities performing source inventories.

At a minimum, a form containing the following information must be completed and maintained for each source identified:

• Source owner/operator name and location (by address or latitude/longitude).
• Source type (from Table III-1) and WHPA Zone in which it is located.
• Source Priority Method and Rank (described below).

Completed Source Identification forms must be included in the WHP plan.

IV. Develop the Source Inventory list from completed Source Identification forms:

Using information from the completed Source Identification forms, the Source Inventory list is developed.

The Source Inventory list must contain:

• The same minimum of information as that required on the Source identification forms (above), including each source's priority rank as determined from one of the methods described below. Sources must be grouped by the WHPA Zones in which they are located.
• A description of the WHPA or WHPAs to which the inventory applies;
• The date of completion of Source Identification data collection and survey(s):
• A statement describing the timing of completion of the Source Identification forms with respect to the date of completion of the WHPA delineation and identification of the Source Inventory as either 'Preliminary' or 'Final'*.

* Source Inventory lists developed from Source Identifications based upon an estimated WHPA, or which are developed from Source Identifications completed prior to delineation of the WHPA are 'Preliminary' Source Inventory lists; a statement must be included that describes when and how the 'Preliminary' list will be updated (to a 'Final' Source Inventory) upon delineation of the WHPA (as described in Section II) to ensure that the entire area within the delineated WHPA has been inventoried.

A 'Final' Source Inventory list can be completed within one (1) year of completion of the WHPA delineation for which it was developed and still be considered valid by WDEQ/WQD.

Upon completion, information from the Source Inventory list should be used to complete Parts V and VII of the "Susceptibility Assessment Form" (Appendix F).

In order to evaluate the relative degree of risk that individual sources identified on the Source Inventory list pose to PWS wells, each source must be ranked (prioritized) according to one of the following methods:

• Distance or TOT to nearest public drinking water supply well;
• The 'sensitivity' of the uppermost aquifer underlying the source (as determined from 'Aquifer Sensitivity' maps).
• The number of residents served by the nearest public drinking water supply well that could be impacted;
• The susceptibility of the well, as determined from the 'Susceptibility Assessment Form' (Appendix F);
• Ranking as determined from source prioritization worksheets available in EPA's "Managing Ground Water Contamination Sources in Wellhead Protection Areas: A Priority Setting Approach".

Prioritization of sources is intended to provide the WHP Management Committee an efficient and effective guide in developing and implementing source management approaches (e.g. site inspections, monitoring, data collection, education, etc.) to protect the well or wellfield from contamination.

Once all potential sources have been identified, each source must be plotted on a 'Source Overlay' map of the WHPA delineation map (see Section II). The map must distinguish between 'existing' and 'potential' sources as defined at the beginning of this section. Each source must be identified by a number that links the map location to the information on the Source Inventory list. Different symbols or colors should be used to differentiate between source types, both existing and potential. The Source Overlay must be identified as either 'Preliminary' or 'Final', according to the definitions used above.

Reasons to expand the Source Inventory include: 1) new categories (Table III-1) are identified; 2) new sources (Form III-1; Appendix H) are identified, and; 3) new information is obtained on inventoried sources.

Methods to update the Source Inventory list include: 1) periodic review of existing inventory database material and other information on existing and potential sources of contamination available from local, state and federal agencies, and other public information, and; 2) periodic performance of surveys. The Source Inventory list must be updated at least every two years (see Section VIII of this document), using any combination of the methods described earlier in this Section.

Communities are encouraged to convert Source Inventory data to more useable forms. Methods to accomplish this objective include: 1) standardize data collection methods; 2) organize data by source priority ranking, contaminant of concern, contaminant TOT to the well, etc., and; 3) development of computer databases for efficiency in tracking, organizing and querying source information (data) sets.

Development of a computerized data base on potential sources of contamination within each WHPA is strongly recommended in preference to a manual data base. The types and qualities of data that are to be incorporated into the data base should be specified and evaluated. Data base design involves the formation of a conceptual model of the data (i.e., relationships between different data fields) taking into account all the basic facts and constraints under which the data base will have to operate. Once a data base design is selected, detailed decisions are made on the logistic and physical organization and the layout of data records to facilitate the entering of data to create the data base. Finally, through the data base monitoring phase, the data management system can be fine tuned and modified to increase the effectiveness and efficiency of the system for data retrieval and analysis.

The primary objective of developing a data base is to enable the analysis and processing of data to reveal relationships among various facts and situations. The data base should contain and be organized using information on: (1) types of land-use activities; (2) the spatial location of the identified sources; (3) chemical composition of the material stored or processed at the identified sites; (4) the name of the facility and the owner or operator, and; (5) other information that may be collected as part of the survey.

Ideally, information on potential sources of contamination should be analyzed in conjunction with hydrogeological data and water supply information to provide a basis for decision making on source reduction, aquifer protection, and water quality monitoring. A data base on the spatial distribution of chemical use and disposal is essential for evaluating the need for, type, and location of monitoring activities for potential contaminants. If a contamination event is detected, a data base on the distribution and use of chemicals would allow for a timely and efficient allocation of resources to determine the source or sources of contamination.

POTENTIAL CONTAMINATION SOURCE INVENTORY - A CASE STUDY

As an illustrative example, a basic inventory of potential contamination sources is presented in this section for the Town of Guernsey. Figure III-2 is the base map showing locations of the three municipal water supply wells. Municipal wells produce groundwater from the North Platte alluvium (CF p. 31 Section III; GW/SW Interaction Areas) located within and around the Town of Guernsey. Figure III-3 superimposes WHPAs on the base map. WHPA boundaries were delineated using the arbitrary fixed radius method at a 1000-ft radius around each water supply well. The fixed radius method for WHPA delineation was selected for illustrative purposes to step through the process of inventorying potential contamination sources. Figure III-4 shows potential contamination sources in relation to WHPAs, as discovered by a windshield survey.

Results of this delineation and inventorying process indicate of large amount of overlap of WHPAs for Well Nos. 1 and 2 within the Town, while Well No. 3 is more remotely located. For this example, it may be simpler for management purposes to combine WHPAs for Well Nos. 1 and 2, and treat as a single WHPA (refer to Figure III-3).

Although this preliminary inventory is based on a cursory, windshield survey, it is interesting to note the density of potential contamination sources is roughly similar for all wells, whether they are within the Town’s boundary or located in an outlying, rural area.

Sections
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8
Appendices
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R
Wellhead Protection Program Guidance Document Contents
Wyoming Department of Environmental Quality