Appendix D: Map Specifications For The HRS Documentation Record
Clarity: The purpose of each map should be specified. Any data contained upon the map should be referenced (e.g., areas of karst noted on a topo map should be referenced to a primary source of the information). The site should be clearly marked on all maps (for large scale maps, it may be clearer to mark the one- or four-mile radius to identify the site), and enough landmarks or key features identified on site sketches to relate the sketch back to the topo map. The reference number should be displayed on the map because often the maps are pulled out of the reference packages to be used. Also note on the maps if any other references were used to compile the information found on the map.
Legibility: Original maps are preferred. (This is especially true of topo maps, which are inexpensive, easy to obtain, and a source of a great deal of information). However, good copies are acceptable if information has been keyed so that color copying is not required to decipher the data. Maps that are difficult to obtain or copy (such as certain geologic maps or water distribution maps, for example) can be send as originals -- the QA reviewers can copy them and return the original. If the Region itself wishes to copy large maps, use a map copier, rather than reducing the copy or piecing together several smaller sheets of paper.
Scale: Maps and diagrams should indicate a scale and a north arrow; if not drawn to scale, that should be stated. The scale should be appropriate to the data depicted. For example, the use of a topo map is probably inadequate to determine area of contaminated soil for all but the largest of areas. Ensure that when copying larger maps, a) the scale is included with the copy, and b) reductions or enlargements are accounted for.
Base Maps: Although information for various pathways or data points within a pathway can be consolidated onto a single map, the use of several maps is preferred to prevent "overloading" any one map. However, when time and resources permit, it is useful to plot well locations, concentration data and geologic formations on a single base map.
Specific maps which can be incorporated into particular areas of the documentation record are indicated below:
Topographic Maps: Usually the most useful maps included in the HRS documentation record are USGS topographic maps, particularly the 7.5 minute quadrangle map. These maps provide many helpful details on the area surrounding the site, and provide an accurate picture of spatial relationships. Among the types of data which can be portrayed on these maps are:
- Target distance limit(s)
- Wells, including nearest well
- Surface water intakes, including nearest intake
- Fisheries and wetlands
- Distance to surface water, including probable point of entry and migration pathway
- Watershed boundaries
- Location of background and hit samples
- Population within one mile for soil exposure pathway.
Note that for reasons of scale, location of soil samples cannot be put on the topo map(s).
Geologic maps. A variety of specialized maps are often available to aid in evaluating of the site. Their use, particularly when trying to define an area of karst or when evaluating aquifer interconnection, is invaluable. Types of maps which might prove useful include:
- Hydrologic unit maps. These identify surface water management areas, and could aid in determining watershed.
- Geologic Quadrangle maps. Keyed to the 7.5-minute series of topo maps, these can be used to generate geologic cross-sections to better characterize the are around the site. A complete set of these maps is currently not available.
- Hydrologic Atlas sheets. These provide information on hydrologic investigations of specific areas. The accompanying explanatory text is also a valuable aid in evaluating the site.
Other maps. Several other sources for maps are available. Municipal water districts, for example, frequently have water distribution maps. The Corps of Engineers or the local development or flood insurance agency has flood control maps. Maps of wetland or other sensitive environments can be obtained from local conservation agencies of the U.S. Fish and Wildlife Service.
Within pathways, maps have different uses and may require different treatment. The following describes the types of information required within each pathway and how to display it.
Always include the following two maps in this section of the HRS record:
- A Site Location map, which can be a copy of a small portion of either the topo or other general use map, to show the general location of the site with respect to county boundaries, nearby towns or communities, and the setting in general.
- A Site Sketch or Map of sufficient scale to show the more detailed setting, including the following: the location of the sources with their name and number are clearly marked; any nearby structures - for example, buildings (identify what they are), roads, railroads, fences and other barriers; paved areas; nearby surface water bodies; and ditches. (USGS topo maps are often too small in scale to show some of the features which affect migration of contamination via drainage in the immediate vicinity of the site.) In some cases, it may be appropriate to show the location of monitoring wells and/or other investigation reports often include these types of sketches and maps and require minor, if any, modification for use in the HRS record. Aerial photographs can also provide valuable information on the layout of the site.
- For any area measurements (and some volume waste quantity calculations), include a scale map, sketch or serial photo that shows the appropriate linear measurements of each area evaluated.
Ground Water Pathway
- A bedrock map is often crucial for describing the aquifer(s) evaluated, especially for sites where geology is complex. Show the four-mile radius (which will pinpoint the site). It is useful to indicate graphically the boundaries between karst and non-karst. If appropriate, show location of nearest well and public supply wells, so that the location of its surficial bedrock area is clearly documented. The USGS and similar publications from which bedrock maps are taken often have cross-section as well. This diagram can be extremely useful in gaining an understanding of the aquifer systems at a site. When time and sufficient reliable data, such as well logs. Include multiple cross-sections, if possible. They should intersect each other at right angles to show the greatest amount of detail. Show both topography and geology of the area.
- Either a scale map or sketch should show the exact location and depth of all Level I and Level II wells, as well as the name of the aquifer being tapped.
- A clear, legible topo map should show the location of the site, the target distance rings (appropriately drawn; not just circles around the midpoint of the site), the nearest well, Level I and II wells, distribution boundaries of municipal supply systems, boundaries of karst vs. non-karst, etc.
- Whenever possible, include the latitude/longitude marks and the key for the scale.
Surface Water Pathway
- A topo or similarly appropriate map is required to show the migration pathway throughout the target distance limit. Include the following features: the location of each source evaluated for this pathway; drainage patterns and probable point of entry for each source; all affected surface water bodies; any structures or barriers that would inhibit overland flow (for example, railroad embankments); and location of drinking water or resource use intakes. Wetlands are best shown on separate wetlands maps. For smaller sites with several sources, it may be difficult to include all this information in an additional map. The reader should be able to use the map to follow the written description in the HRS record of each segment in the target distance limit, as the pathway changes from one surface water body to another, and from fresh to salt water (or vice versa).
- For any observed release to surface water, include a scale sketch or map showing exact locations of all samples discussed in the HRS record for this factor. Location of drinking water intakes or resource use (e.g., irrigation) can be shown.
- Topos or other maps as appropriate should show what areas are evaluated for fish production in the food chain threat. Indicate the linear distance and/or area within an arc that is included in the evaluation. (Unless Level I or II targets are identified, topos showing the full 15 target distance limit are unnecessary.)
- For the environmental threat, a map should clearly indicate the linear distance of wetland frontage and the precise location of sensitive environments, unless security reasons preclude this.
Soil Exposure Pathway
- If not already provided as described above under "Waste Quantity," include a map clearly showing all areas of observed contamination, with all sample locations noted. For targets, show where targets are located within 200 feet of these areas. Indicate where there area are targets (resident population) living on property with observed contamination. Show location of any terrestrial sensitive environments evaluated. Show one-mile radius, and indicate where nearby individual and population targets are located.
- Clearly indicate sources and locations of sampling points if an observed release has been scored. Meteorological data, such as prevailing wind direction should be indicated on the map. If possible, the map or diagram should include any areas which might be considered alternate sources of the release, so that their potential impact can be evaluated.
- Draw distance rings on the map at the required intervals, based on distances from source boundaries or sample locations, as appropriate.