1. Minnesota Department of Agriculture
  2. Pesticide, Fertilizer
  3. Safety & Cleanup
  4. Guidance Document 9 - Attachment 2

Attachment 2 - Contamination Impacts Survey

A Contamination Impacts Survey should be conducted for each incident site as part of the STEP II remedial investigation (RI). The four exposure pathways are:

  • human health
  • surface water
  • ground water
  • other potential receptors

The human exposure to contaminated soil pathway is evaluated for each site. The other three pathways should be evaluated if the conditions described at the beginning of each pathway section are applicable to the site. For instance, if it is known or strongly suspected that ground water is contaminated, then complete the ground water section of the contamination impacts survey. The results of the impacts survey should be included and discussed in the RI report.

I. Human Exposure to Contaminated Soil

Identify the relative risk to humans, and particularly to children, who may come into direct and sustained contact with contaminated soil.

  1. Does anyone live on the contaminated property?
  2. Are there any residences, schools, daycare centers, parks or recreational areas on property adjacent to the site, or, within 1000 feet of the site. If so, estimate the number of each and how many people may be affected.
  3. How accessible is the site? Is there a maintained and effective fence surrounding the property with a gate which is locked at night? Is the site isolated or guarded?

II. Ground Water

Complete the following activities if ground water analytical data indicates that ground water has been affected or if contamination in the soil and a hydrogeologic assessment indicate that ground water likely has been affected:

  1. Determine whether a municipal water supply is in the site vicinity. Identify any present or potential municipal water supply located within a one-mile radius.
  2. Obtain copies of all well logs within a one mile radius of the site that are on file with the Minnesota Geological Survey. If more than 25 well logs are present, select the logs for any public water supply wells, from unusually deep wells and for wells which are nearest to the site. If the affected water source is a regional aquifer, obtain all well logs from wells constructed in the affected and connected aquifers within a two mile radius of the site.
  3. Contact appropriate local authorities, county water planning officials and local well drillers to determine whether any unregistered or abandoned wells are located within a one mile radius of the site. Report the location, construction, depth and use of any identified wells if the information is available.
  4. Contact the site owner and owners of all property that adjoins the site to determine whether existing or abandoned wells are located on their properties. Report the location, construction, depth and use of any identified wells if the information is available.
  5. Summarize the data on all identified wells in a table, including the following information: Minnesota unique well number or other identifier; the ground surface elevation; the well base elevation; the casing base elevation; water level elevation; and aquifer use. Elevations should be referenced to the National Geodetic Vertical Datum, if possible. Produce a map showing the location of all wells with the map labels corresponding to the information on the tables.
  6. Contact appropriate local authorities and property owners to determine whether any ground water development is scheduled up to one mile down-gradient of the site.

III. Surface Water

Complete the following activities if any surface water body is: a) within 200 feet of the site; and receiving or likely will receive discharge of ground water which is contaminated from the site, or, b) known or suspected of being contaminated from surface water runoff from the site. A surface water body includes wetlands, ponds, lakes, rivers, streams and intermittent.

  1. Identify the water use and classification of each affected or potentially affected surface water body as classified in MN Rules Ch. 7050.0400 through 7050.0470.
  2. For ground water discharges, calculate the potential mass loading from the ground water to the surface water body as shown in below.

MASS LOADING TO SURFACE WATER BODY

  • Characteristics of ground water contaminant plume
Plume width, W, (ft):
Plume thickness, H, (ft):
Hydraulic conductivity, K, (ft/day):
Hydraulic gradient, I, (ft/ft):
Discharge (Q) of ground water plume to surface water body.
Q = W * H * K * I, (ft3/day):
Conversion to liter/day, Q * 28.32 liter/ft3, (liter/day):

 

  • Calculation of contaminant mass in plume entering surface water body
Maximum observed concentration of a single pesticide in ground water as measured in the monitoring well closest to the down gradient surface water body, C1, (ug/liter):
Contaminant mass entering river, M = C1 * Q, (ug/day):

IV. Other Potential Receptors

Consider any impacts from the site which are not previously accounted for. These include areas contaminated by surface water runoff or erosion and area with unusual wildlife mortality, stressed vegetation or visible erosion features.

  1. Are terrestrial sensitive or unique environments, areas of heavy wildlife use or hunting activity, endangered species, or animal feedlots adjacent to or potentially contaminated from the site?
  2. Are there any other potential impacts not previously accounted for?
  3. Identify all other receptors potentially impacted by the agricultural chemical incident (e.g., tile lines, utilities, storm and sewer drainage system, air quality).