1

Utilizing Geographic Information Systems in Assessing Unauthorized Waste Disposal Sites In Olmsted County Minnesota Alexander S. Webb1, 2 1Department of Resource Analysis, Saint Mary’s University of Minnesota, Winona, MN 55987 2Solid Waste Division, Olmsted County Public Works Department, Rochester, MN 55904 Keywords: Unauthorized Waste Disposal, Solid Waste, Unauthorized Dumping Inventory, Environmental Hazard Analysis, Geographic Information Systems, Local Government, Olmsted County Abstract The scope of illegal dumping is a broad problem that affects many rural and urban communities economically and environmentally. Economic impacts are felt when income from user fees for legally operated dumping and recycling facilities are lost due to illegal dumping and disposal practices. Consequently, funding dollars must be spent in providing staff technical support in the investigating and mitigating aspects associated with illegal dumping issues. Economics is also of concern to commercial developers who, as suburbia expands, are conducting assessments to determine the existence and impacts of historical dumps on rural properties considered for development. The more prominent threat that evolves with the illegal and improper disposal issue are the negative environmental impacts associated with them. Such impacts can include groundwater and surface water contamination potential, conditions that harbor disease and vector species, and migration of methane and other gases created during decomposition of waste.

In an effort to investigate such sites throughout Olmsted County and work in a direction towards achieving the objectives set forth in the Rochester-Olmsted Planning Department (ROPD) Comprehensive Water Plan for dealing with uncontrolled waste disposal (Anonymous, 1990), a methodology has been developed to aid in inventorying and assessing unauthorized dumping activity. This paper discusses the processes and methodology that was developed in an attempt to gain better understanding and quantification of the relative risks posed by unauthorized dumps and to assist in determining the level of need for funding and abatement considerations. The methods employed serve to locate, map, and inventory both active and inactive unauthorized dumpsites to aid in the development of as complete of a site profile as possible, and to perform environmental risk analysis for establishing priority sites for further investigation and potential remediation. This approach integrates the use of available historic and current file records, field surveys, aerial photographs, and digital data in a Geographic Information Systems (GIS) format.

The gathering and compilation of source information was a cooperative effort made possible through the involvement of public agencies, private companies, Township Board members, and the Unauthorized Dump Work Group (UDWG) volunteers. The UDWG was formed for the purpose of bringing together knowledgeable and interested persons to provide program guidance in dealing with unauthorized dumps, ultimately making policy recommendations to the Olmsted County Environmental Commission and County Board.

2

Introduction

The adverse effects of chemical leachate and landfill gas migration from former waste disposal sites became a major public concern in the late 1970’s. In response, Congress passed the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) or “Superfund.” This law directs procedures, and standards for cleanup and mitigation of waste disposal sites be developed based on relative risk to the public health, welfare, and/or environment. The criteria must take into account the population at risk, hazard potential of the substances, potential for contamination of drinking water supplies, potential for direct human contact, and potential for destruction of sensitive ecosystems. States are required to annually nominate priority sites for remedial action based on the aforementioned factors. Though this is a federal mandate, the majority of superfund site responsibilities have been delegated to the state government level (Adams et. al, 1997). Existing in the environment alongside these “larger scale” superfund sites are the smaller scale and less prominent, but more numerous and wide spread unauthorized dumping and disposal sites that are not being as stringently addressed. For years these types of open dumps have been located in convenient gravel or quarry pits, sinkholes, eroding drainage ways, ravines, floodplains, wetlands, and just about anywhere on the “back 40” that would suffice. Such areas accumulate garbage, tires, white goods, barrels, pesticide containers, anything and everything imaginable (Anonymous, 1988). Much like the designated superfund sites, these dumping areas also harbor potential threats to humans and the environment. Documentation of such past unauthorized dumping activities and even legal waste

disposal activities is at best incomplete, and in most instances non-existent. In recent years, there has been a revitalized environmental awareness and growing concern regarding these types of illegal waste disposal sites. Numerous local governments and their agencies are currently faced with the challenge of identifying and addressing these smaller sites.

It is hoped that the information compiled and processes undertaken in this study will prove to be a useful and an inexpensive tool for aiding in the discovery of detailed site information on the many reported sites about which little is known. If the methodology is found to be viable, it can be used on a larger scale by other local governments, particularly counties and large municipalities to inventory active and inactive sites and to establish priority sites for directing further investigation and cleanup efforts. The results of such inventories and investigations can also be used as an aid to forecast the need for future funding, staffing, and abatement considerations. Historically in Olmsted County, the Health Department and Board of Health were charged with the responsibility for general administration and enforcement duties in dealing with a variety of issues associated with dumping practices. Today, any number of agencies may be involved in waste disposal issues depending on jurisdiction, relevant permit needs, and the rules and ordinances coming into question. The agencies most commonly involved are the Olmsted County Health Department (OCHD), the Olmsted County Public Works (OCPW), the Rochester-Olmsted Planning Department (ROPD), the Minnesota Department of Natural Resources (MDNR), and local Township Boards. The involvement of numerous agencies and the shifting of responsibilities over time has created confusion about which agency is

3

responsibile for enforcement of unauthorized dumping cases. Prior this project, the first large scale and documented dump inventory in Olmsted County occurred in 1967 with the Olmsted County Health Department identifying 40 sites in 8 townships by conducting a windshield survey of dumpsites by traveling all the roads in the County (Anonymous, 1988). These sites included designated city/village dumps, sites which represented water pollution hazards, scattered refuse, sites used for dumping that could be developed into township dumps, junk yards, abandoned or disorderly keeping of cars, and storing of junk cars that could be developed into junk yards.

In 1980, the MPCA submitted a similar report that surveyed and ranked municipal solid waste sites for the purpose of either renovation or closure. Many of these dumpsites surveyed by the MPCA were previously identified in the 1967 OCHD survey as a city or village dump.

In a 1986 survey by the University of Minnesota as part of the development of the County Geological Atlas, 845 sinkholes were surveyed within Olmsted County (Maki, 1988). Of the identified and surveyed sinkholes, 50% contained some type of waste and/or were located in an area where they readily transported contamination from surrounding land directly into the groundwater. Four percent contained pesticide containers, and 30% were rated as having a high potential for groundwater contamination.

From 1967 to present, there have been numerous complaints involving solid waste storage and zoning violations filed with OCHD, OCPW, and ROPD.

It should be noted that under established state regulations, farmers can legally burn and bury their own municipal solid waste if it is done in a non-nuisance manner. However, there is virtually no

inspection of farm dumps to determine if they are in compliance with these regulations. For discussion purposes, one could assume that some fraction of the1300 farmsteads in Olmsted County (1995 data), are not in compliance. If this number were even 10%, an additional 130 dumpsites could exist, adding a significant increase to the total number of dumpsites determined through other methods. No County or State regulatory authority has committed the resources necessary to perform inspections on farmsteads to identify the presence or absence of farm dumps. Since limited information exists on non-compliant farm dumps, they were not addressed in this project unless records for specific sites were already on file.

Study Area

Olmsted County is located in Southeastern Minnesota (Figure 1), covers 656 square miles, and is comprised of 18 townships. The county’s population is approximately 124,000 with the majority of the population (86,000) residing in the center of the county in the city of Rochester.

Figure 1. Location of Olmsted County, MN.

Five watershed areas lay within Olmsted County, Middle Fork Zumbro River, South Fork Zumbro River, Silver Creek, Whitewater River, and North Branch Root River (Anonymous, 1990). No natural

4

lakes occur with Olmsted County, and man-made reservoirs are few, the largest being Lake Zumbro located at the north edge of the county and formed by the damming of the Zumbro River in Wabasha County.

The landscape is relatively flat with the predominant land use being agriculture. The area is rich in Karst terrain, characterized by distinctive surface landforms of closed depressions (sinkholes), and underground drainages. Other landforms include quarries, gravel pits, sandpits, and springs. A review of United States Geological Survey (USGS) 7.5 Minute Series Topographic Quadrangle maps show there to be approximately 75 gravel/sand pit and 36 quarry designated locations within the county. Additional surveys have documented 461 spring locations (Table 1). Geologically, the county is covered by a mantle of pre-Wisconsin drift which is commonly less than 50 feet thick, and underlain by relatively flat lying sediments ranging in age

from Upper Ordovician to Cambrian. Many of these units are carbonates with the majority of municipal drinking water supplies extracted from the Prairie du Chien-Jordan aquifer (Olsen, 1988b).

Due to time, feasibility, and practicality, the larger study area of Olmsted County was subset to the individual township of Cascade (Figure 2). This township served as the pilot study area for testing the devised methodology in the processes of field investigation, verification, and the performance of an environmental ranking system and risk analysis using GIS. Cascade Township was selected because the pertinent data available from Rochester-Olmsted Planning Department was in a current GIS digital format. Additional analyses were performed at a larger countywide level in an attempt to gain insight on dumping patterns and help to identify locations most vulnerable to unauthorized dumping.

Table 1. Summary of Total Individual and Total Aggregate Landforms by Township and Percentage of Cumulative Total Existing Within Each Township. Townships Landforms Sinkholes Springs Quarries Gravel/Sand Pit Total % of Total Cascade 11 6 0 23 40 2.9 Dover 15 29 1 2 47 3.4 Elmira 20 37 3 0 60 4.4 Eyota 97 34 0 6 137 10.0 Farmington 25 3 0 2 30 2.2 Haverhill 6 81 1 2 90 6.6 High Forest 14 9 8 2 33 2.4 Kalmar 19 27 2 12 60 4.4 Marion 5 25 3 2 35 2.7 New Haven 2 7 2 6 17 1.2 Orion 400 57 2 0 459 33.6 Oronoco 41 2 0 5 48 3.5 Pleasant Grove 111 25 4 0 140 10.3 Quincy 6 31 0 1 38 2.8 Rochester 27 10 6 2 45 3.3 Salem 10 11 1 2 24 1.8 Viola 2 59 0 1 62 4.5 Totals 811 453 33 68 1365 100.0

5

Figure 2. Olmsted County Townships: Pilot Study Area-Cascade Township. Methods

File Review

State and local health departments, the Minnesota Pollution Control Agency, the County Public Works Department (Solid Waste Division), the ROPD, as well as individual Cities and Townships all have accumulated some information on disposal sites within Olmsted County. Very little information regarding the environmental impact of these sites exists. The first step taken in addressing the unauthorized dumping issue was to review agency file records, all primarily in hard copy format. Before any major review effort and synthesizing of information could be initiated, review and mass organizing of file records was necessary.

Olmsted County Solid Waste Division possessed a collection of files and folders with historical and current dump complaints, accompanying photos, pertinent literature, and agency related reports. These items were reviewed and categorized by township and agency affiliation so they could be easily assessed to locate information regarding dumpsite complaints, investigations, and previous site reviews. When information was located, all pertinent facts (i.e. date, location, contents, owner, etc.) were transcribed into a master logbook.

A review of ROPD files containing information sheets, notes, and photos of locations cited for solid waste and zoning violations was then conducted, followed by a review of OCHD and MPCA files. Additional information obtained from the MPCA files aided in determining if certain dumpsites, noted to contain demolition materials, were actually approved and permitted demolition dumpsites. The collected and logged information obtained from these four file reviews were entered into an Access database. Initially this database was crude and primarily used to compile a list of all reported dumpsites. Information input into the database consisted of a unique parcel identification number, property owner’s name, year of initial complaint, township, range, section, quarter section location, the address of site if known, and other comments pertaining to dump contents and size. Aerial Photo Review

An aerial photo review was then performed to determine if verification of file information was possible and to expand on site information not already available in the files. At the onset of the aerial photography review it was decided that the objective would to be to survey the photos, attempting to identify known site locations only and not delineating site boundaries. There were several reasons why this level of review was selected. An assessment of available aerial photographic resources at OCPW revealed the availability of photos for the years of 1937, 1971, 1984, and 1996. However, no stereo pairs existed for any flight year, preventing photos to be viewed stereoscopically, greatly hindering interpretation efforts. The majority of reported sites would often be too small to detect or delineate without the availability of

6

stereoscopic photos (Nelson et al., 1983). Time and money were limiting factors that inhibited an intense and extensive air photo review for identifying sites for which no staff knowledge or records exist. Mapping Locations Mapping of reported dumpsites was performed using ESRI ArcView 3.0a software which was the most current version installed at the onset of the project on common users desktops at the County offices. The first step of this task was to acquire digital data coverages. The data sets provided by the Rochester-Olmsted Planning Department GIS staff included city limit boundaries, roads, rivers, Public Land Survey System (PLSS), county digital orthophotos, and 1996 parcel data. Data formats provided were ArcView shapefiles, ArcInfo Coverages, and Computer Aided Drafting (CAD) .dwg format. All data worked with were initially in the State Plane Coordinates System and North American Datum (NAD) 27 projection. After initial data acquisition, the next step was to add current and historic dumpsite locations to the township coverages. First, a township was selected with the roads, parcels, PLSS, and orthophotos being displayed in ArcView. Four new point themes were created with each representing a different dump classification. These preliminary categories were 1) Other Dumps, 2) Industrial Dumps, 3) Demolition Dumps, 4) City/Village Dumps. The first category, Other Dumps represented sites not classified as one of the other type of dumps. Examples of possible contents in these dumps include tires, wood, metal, miscellaneous garbage, white goods, and unpermitted demolition material. The second category was classified as industrial dumps. Designated dumps of this nature are

only located in Cascade and Rochester Townships, based on the MPCA Industrial Landfill permit list. Third, demolition dumps are MPCA recognized and permitted sites that are comprised of demolition debris. The last category, City/Village dumps represent sites that were recognized and used as centralized dumping spots for cities, villages, or townships in the past, as well as facilities currently in operation. Using the information compiled in the Access database and sorted according to township, sites were mapped one by one as a GIS data theme in ArcView. The most practical method in mapping dumpsite locations was to reference detailed air photos (various scales) for the year that the site had been reported. If the sight was not visible on the photo, subtle land features and clues such as quarries, sand pits, ravines in the area, and access points were interpreted for determining likely dumping areas (Barnaba et al., 1991). In mapping more recently reported sites, ortho-rectified digital orthophoto (DOQ) imagery was used in ArcView. In many cases it was also necessary to use current and dated versions of county maps, land atlases, and plat books in conjunction with the aerial photography and DOQs to piece together information making it possible to tie dump records or complaints to land parcels and previous or current ownership. Upon coverage creation, in an effort to make items more manageable and gain the ability to compare features of townships to one another (Table 2), the Xtools extension was used to clip all data down to the level of individual townships. This was accomplished using the PLSS coverage and converting each township into separate shapefiles. The naming convention for these shapefiles consisted of combining the township name with the two-digit code established by the county surveyors. The

7

Table 2. Summary of Total Individual and Total Aggregate Dump Classifications by Township and Percentage of Cumulative Total Existing Within Each Township.

Townships Dumps Other City/Village Industrial Demolition Total % of Total Cascade 16 5 2 4 27 16.3 Dover 3 0 0 0 3 1.8 Elmira 0 1 0 0 1 0.6 Eyota 4 1 0 1 6 3.6 Farmington 0 0 0 0 0 0.0 Haverhill 11 0 0 0 11 6.7 High Forest 3 1 0 1 5 3.1 Kalmar 19 2 0 2 23 13.6 Marion 28 0 0 1 29 17.5 New Haven 6 0 0 0 6 3.6 Orion 4 0 0 0 4 2.4 Oronoco 8 2 0 1 11 6.7 Pleasant Grove 7 0 0 0 7 4.2 Quincy 2 0 0 0 2 1.2 Rochester 8 0 4 4 15 9.6 Rock Dell 4 0 0 0 4 2.4 Salem 9 0 0 1 10 6.1 Viola 1 0 0 0 1 0.6 Totals 133 12 6 15 166 100.0

surveyor code was devised by taking the last number of the township and combining it with the last number of the range. For example, New Haven is Township 108 Range 15, the two-digit code is 85, the new shapefile was named NewHaven85. The shapefiles created in this manner were then used as the clip covers in sub-setting all theme features down to their respective township, with each clipped theme having a name with its respective two–digit code attached. All individual township themes were then brought together in ArcView, symbolized appropriately, layouts created, and hard copy maps produced. This completed the initial file inventory and mapping process. Interview Process With the initial mapping stage completed and a variety of sites identified, the next step was to obtain additional information on known sites and identify new sites through

interviews with individuals thought to have strong knowledge and involvement with the issue. The goals of the interview process were to verify and clarify activity of reported sites, produce more detailed site information on identified sites, discover unreported sites, and to provide information necessary to rank sites and evaluate potential impacts. The first generation dumpsite maps were initially presented to the Public Works Department Solid Waste Division staff for review. Once reviewed, minor cosmetic changes and revisions were made to the overall appearance in creating a more friendly map layout design. The revised maps were then presented to the UDWG for input and suggestions on how and whom to approach with this information. It was then decided to undertake a more detailed pilot study of Cascade Township after an initial presentation to the Cascade Town Board to discuss project area aims, goals, and reported dumpsites within their township. The Cascade Town Board was very receptive and cooperative, providing

8

significant positive input and feedback. Next, a staff member from the local MPCA office in Rochester was interviewed. Information from this interview helped in separating dumps with demolition material contents into authorized and permitted demolition sites and unauthorized non-permitted sites. The MPCA was also helpful in providing insight on locations that had been mapped, as well as helping to refine their mapped locations and in adding sites and information for dumps not appearing on the map. County employees based out of the Kalmar landfill were the next to be interviewed. They offered no new sites, but did provide additional information on mapped sites. Seeking input from the private sector, a representative from a local consulting firm, McGhie and Betts, Inc, in Rochester was contacted. They were provided with the current compiled dump information and asked to compare it with county site information that they had previously collected from consulting work and Phase I audits. No feed back or follow-up occurred. Additional interviews included a Minnesota Department of Natural Resources (MDNR) law enforcement officer and a representative of the Olmsted County Soil and Water Conservation District (SWCD), no new information was provided.

To date of this work, not all dumpsites existing in the county have been reported, nor have all the mapped locations been verified for current status, contents, or mapped location. To complete such will be a continuous process that will require an ongoing cooperative effort between numerous agencies and personnel. As new information is reported, and previously recorded information refined, the GIS database will be updated to reflect current information. Likewise, as mapped sites progress through the verification process and are found to be non-existent or of no

significant threat, they will be removed from the current database. However, information pertaining to such sites will be kept as a part of a historical account record.

Data Acquisition Data themes were obtained from a variety of sources but were ultimately channeled through the Rochester-Olmsted Planning Department GIS Division. All initial data sets were in State Plane Coordinates and NAD27 projection. ROPD has recently developed their own County Project coordinate system and are using it with the NAD83 projection. Since unauthorized dumping presents a potential responsible party liability and because Olmsted County has some enforcement responsibility for solid waste management related to the collected information and subsequent analyses, the Olmsted County GIS staff handled all data requests, data set conversions, quality assurance and quality control on converted data. This presented significant time delays in obtaining compatible and useable digital data sets desired, and limited spatial analyses capabilities within the project due to incompatible data. Very limited data sets existed in the County Coordinate System NAD83 projection at the time of project inception so nearly all requests for data resulted in the need for data conversion. Basic coverages requested and received for the project (County Project NAD83) were city limit boundaries, roads, rivers, lakes, PLSS, land use, soils, wellhead protection areas, parcels (current as of 2/99), and conversion of the dumpsite locations created in State Plane NAD27. UTM coordinates documenting sinkhole and spring locations from a 1986 survey were converted for use with this project. Rochester Public Utilities (RPU) provided their digital County Well Index (CWI) in X-Y coordinate format. The

9

ROPD provided digital coverage of several plates of the Minnesota Geological Survey Geologic Atlas plates. At the time of project inception, only four out of the nine plates were available in a digital format and used in analysis. The plate layers available and used were, Sensitivity Of The Ground-Water System To Pollution, Depth To Bedrock and Bedrock Topography, Geological Resources, and Bedrock Geology. For field use in locating and mapping specific dumpsites, dumpsite locations were overlaid onto DOQ’s (digital orthophoto quadrangles) and/or DRG’s (digital raster graphics). DRG’s were also used in referencing quarry and gravel pit locations in creating new coverages for these features since no existing coverages could be located. The mapped feature locations from the DRG’s were approximate, with final adjustments being made by visually inspecting and locating the quarries and gravel pits on the digital orthophotos. To ensure a complete coverage was created, these locations were cross-referenced with soil and land use coverage classifications. If quarry and pit locations were found to be absent from the newly created coverage, they were added based on soil and land use classifications. Field Verification

For the Cascade Township pilot study area, a best effort field investigation was made, wherever it was legal and feasible to visually locate, inspect, and inventory sites.

Sites owned by the County or other publicly owned sites, were easily located and accessible, allowing for visual inspections and inventories to be made. The majority of private sites were for the most part located, but less accessible. When possible and not prohibited by barriers or trespass signs, on foot assessments were completed. If prohibited, vehicle

assessments from advantageous viewpoints sufficed. A small number of sites were not located and therefore no assessment was possible. Most sites visited had no significant indicators of dumping at the surface, suggesting that their contents were buried or since being reported had been cleaned-up. Analyses Site Ranking Analysis Ranking Design This ranking system has been developed as an attempt to apply a relative ranking scale to all reported or discovered dump locations within the pilot study area of Cascade Township. Conceptually, the objective of creating the ranking system was to aid in investigation in a logical, consistent, and cost-effective manner. It was hypothesized that an evaluation of dumpsites by means of a ranking system could be used to prioritize which sites may be in need of further action by assessing the hazard potential associated with potential for contaminant migration through various pathways to the groundwater. Additionally, this system might be useful for identifying areas that could be likely locations for unauthorized dumps.

The ranking system was devised after consulting with staff from the Olmsted County Solid Waste Division and the Rochester-Olmsted Planning Department (Goslee and Huberty, 1997) about various methodologies of ranking system design and the categorical variables to consider within the ranking analysis. The ranking system developed for this project takes into consideration a large number of interdependent variables. The protocol for ranking was to overlay digital data of dumpsite locations onto several layers of

10

other information such as soil type, land use type, bedrock geology, proximity to surface water, etc. to obtain a site characterization for each dumpsite. Each characterization element of the analysis model was then scored or ranked based on a predetermined set of categorical criteria. Ranking scores were assigned so that a lower value represents the beginning of the hierarchical order (i.e., a value of 1 represents a worse condition for contaminant transport than a value of 2). Once all categorical variables are ranked, values are summed. Those sites having lower cumulative scores are areas suggested to be more vulnerable or sensitive to the impact of unauthorized dumping, suggesting more thorough investigation needs to take place at these locations. An assumption was made for this model that all dumps were equal with respects to their contents and their relative size. These are factors that if actually known and incorporated into the ranking system, would significantly influence and serve to strengthen the model. However, these parameters cannot be concretely determined without intensive and expensive field investigations, samplings, and lab testing, so for all intent and purposes were assumed to be equal for this analysis. Site Ranking Categories Environmental atlases and natural resource inventories contain valuable information on the location and types of important environmental features such as soil characteristics, land use types, subsurface geology, and water features. The use of such information can prove particularly beneficial in assessing the potential impact of unauthorized dumpsites on their surrounding environment when they are used in conjunction with one another. A general geologic analysis of dumpsite locations and their surrounding areas was

done so sites could be evaluated and ranked according to their potential impacts on surface water and ground drinking supplies and ultimately on nearby residents. In general, hydrogeologic analyses examine the important factors that directly influence the production, containment, attenuation, or migration of leachate. These generally involve evaluation of the surface and groundwater systems, soils, bedrock, permeability data, and any structures within the overburden or bedrock that control either the direction of movement, rate of movement, or local concentrations of fluids (Olsen and Hobbs, 1988). Soil Type

This category evaluates the conditions of sediment characteristics and permeability and their influence that either enhances or decreases the infiltration of leachates into groundwater.

The first step in ranking soil type was to determine the general soil classification at each dump location. This information was then referenced to The Soil Survey of Olmsted County Minnesota (Poch, 1980). Found within this literature is information pertaining to different soil classifications and a description of restrictive soil features in relation to certain types of use. One such description is a Sanitary Facilities Table containing a column of Area Sanitary Landfill information. This table contains soil types that have been assigned a classification of Severe, Moderate, or Slight, depending on characteristics and associative factors that the soil types are prone to for the purpose of containing a landfill. Classifications are made based on the depth to bedrock, susceptibility to flooding, wetness, seepage, and slope. Although this information provides guidelines for locating approved sanitary landfills, the principles associated

11

with unauthorized dumps are the same and therefore were used in the evaluation criteria for this project. The only modification employed was to use an associated numerical value for each classification, 1 for Severe, 2 for Moderate, and 3 for Slight.

Land Use

This category serves to examine dumps that are located on land categorized such that the exposure rate or risk potential to humans would be considered to be higher than other land use classifications.

The land use data set referenced contains 37 land use classifications. For the purpose of the ranking system, the homestead and park/playground classifications were kept separate, while all other classes were grouped together. Dumpsites located on lands with the homestead designation were considered to be more critical areas due to greater potential for long-term exposure to groundwater contaminants, therefore they received a ranking score of 1. Parks/playgrounds were considered the second most critical type because of the potential exposure to younger children; they received a score of 2. All other land uses were considered to have less potential for contaminant exposure and were scored a 3.

Geological Sensitivity Level

Sensitivity level refers to the local geologic conditions that affect the rate of water movement below the land surface and therefore the rate surface contamination will enter groundwater resources.

The digital version of Sensitivity of the Ground-Water System to Pollution (Plate 6) of the County Geological Atlas (Olsen and Hobbs, 1988) was referenced to determine the different amounts of geologic protection for local groundwater from dump

contaminants. The sensitivity plate contains six categorical rankings to indicate how sensitive an area is to contamination: very high, high, high moderate, moderate, low moderate, and low. Numeric ranking factors were added to these categories as follows: 1= Very High, 2=High, 3=High Moderate, 4=Moderate, 5=Low Moderate, 6=Low.

Bedrock Geology Type

The solid rock masses that lie at or beneath the land surface are major reservoirs for drinking water supplies in Olmsted County. Additionally, the various types of bedrock formations that lie at or beneath the land surface significantly influence the migration of contaminants from the surface to the underlying aquifers, thereby allowing the migration of contaminants to the water supply aquifers. Where Decorah shale is present, it acts as a confining unit and retards the vertical migration of contaminants into underlying aquifers (Olsen, 1988a). Where a Decorah shale layer is not present, a greater chance exists for a completed pathway to the underlying Prairie du Chien or Jordan aquifers resulting in possible contamination. On this basis, areas where a Decorah shale layer is not present received a 1, and where it is present a 2. Depth to Bedrock

In addition to the previous category of bedrock geology type, the depth to these bedrock layers also significantly influences seepage rates of surface contaminants in reaching bedrock aquifers. In areas of the county where thicker soils are present the soils are typically clay layers, which retard the vertical movement of liquid solutions. Where shallower or more permeable soils exist, there is a higher contamination potential due to reduced travel distance and

12

travel time which reduces treatment and dilution opportunities before the contaminants can reach the aquifers (Olsen, 1988b). Therefore, the ranking applied to the depth of bedrock categories are: less than 50 feet =1, 51-100 feet=2, and 101-150=3. Geological Resources

Geological resources refer to aggregate resources such as crushed rock, sand, and gravel. Where these resources occur, they are classified based on their estimation of quality. Those classed as primary resources are those that are of commercial value, generally being at least 20 feet thick, have a minimum of overlying material (usually less than 10 feet), and contain at least 35% gravel-size material. These characteristics make thicker “pockets” of gravel resources that are more likely to be well connected to underlying aquifers and thus more suitable for contaminant transport. Those classified as secondary resources meet any two of the three criteria listed above and therefore lessen permeability characteristics. Upland sand and gravel resources are thinner than the other resource deposit types and are often rich with clay material, making it the least permeable of the three classification (Kuhns, 1988). Based on each classification’s characteristics, ranking attributes are Primary Resource =1, Secondary Resource =2, Upland Resource =3, and None = 4. Alluvial Soils

This category is for the evaluation of soil materials that are associated with conditions of deposition from running water or from the occurrence of flood events. Here, as in the ranking of soil type category, the general soil type of each dump location was referenced to a table and column in The Soil

Survey of Olmsted County Minnesota (Poch, 1980). The column referenced was the Flooding Frequency from the Soil and Water Features table. Using the information provided here, a ranking score was assigned based on flood frequency as follows, 1=Frequent or Occasional, 2=Rare or None. Hydrological Conditions

This category focuses on the grouping of area soils into one of three classifications, hydric, floodplain, or other. Hydric soils are defined in the Wetland Conservation Act as soils “that are saturated, flooded, or ponded long enough during the growing season to develop anaerobic conditions in the upper part.” In essence, where hydric soils are present, wetlands are potentially present. As such, these areas have a high sensitivity to contaminant impact and disturbance. In contrast, floodplain soils are typically alluvial soils that border a stream or river and were deposited by flowing surface water. Dumps in these areas may be problematic because of their high permeability and because they are periodically exposed to erosional flooding events. The potential for resulting negative impacts depends on the frequency and severity of flooding events and the soil permeability values. Information about hydric soils was obtained from a specially developed ROPD database file (ocsoils.dbf) that was joined to the general soils database file (soils.dbf) derived from the Olmsted County soil survey maps. The three categories of hydric conditions were ranked, Hydric Soils = 1, Floodplain Soils =2, and All Others = 3.

Highly Erodible Lands

13

This category ranks the erosion potential of the different soil types based on erosion factor calculations. These calculations (established by the Soil Conservation Service) are used to predict the erodibility of different soil types and are based on slope, length of slope, and susceptibility to erosion by water (K factor).

This category was also evaluated through referencing the ocsoils. database file. Contained within this file is a value field code containing a unique number that is associated with each soil type. This unique number is then cross-referenced with Highly Erodible Land Cover (HELC) text document that states if that particular soil has been calculated as highly erodible or non-erodible. In ranking, Highly Erodible Lands received a 1, and Non-Erodible a 2.

Water Supply Impact

There are numerous pathways of exposure between contaminants from unauthorized dumps and human receptors. Drinking water containing unacceptably high levels of toxic chemicals has high potential for directly impacting human health if consumed and therefore it is important to identify possible water sources that are in close proximity to potentially hazardous dumpsite locations.

In examining potential risk to water sources there were three different categories focused on, all at a proximity distance of one-quarter mile. Since the methodology and criteria used in ranking all three categories was the same, discussion here will apply to all three, surface water, springs, and wells. The capabilities of the GIS tools employed made it possible with relative ease, to query dumpsite locations and determine which ones were located within the ¼ mile distance criteria. Those that were within this distance to water features were numerically valued at 1, all

others falling outside the distance were valued as 2.

Wellhead Protection Areas

Additional concerns to the protection of water resources within Olmsted County are dumpsites that lie in designated wellhead protection areas. A wellhead protection area is defined as “the surface and subsurface areas surrounding a water well or wellfield, supplying a public water system, through which contaminants are reasonably likely to move toward and reach such water or wellfield” (Adams et. al, 1997). By law, every state is required to protect wellhead areas within their jurisdiction from contaminants that may cause adverse human health effects. 12 wellhead protection areas exist within Cascade pilot study area. Each wellhead protection zone is further categorized by the amount of travel time (5, 10, 20, or 50 years) it takes water to reach the public water system from a certain point within that protection zone. Dumpsites were ranked as either being Within (1) a designated wellhead protection zone, or Outside (2) the protection zone. Proximity to Sinkholes

Sinkholes are a common geologic feature on the landscape within several Olmsted County townships. Once the processes have occurred that form sinkholes, these sinkholes then provide a direct link between activities on the surface and underground aquifers. As discussed earlier, many sinkholes in the past (as well as present) have been used as open dumps, containing many types of materials and discarded chemicals and containers. These actions have created the potential for water flowing through the debris to transport contaminants into the underlying carbonate aquifers that

14

serve as common source of water for both domestic and animal use.

GIS capabilities made it possible to query dumpsite locations to determine which dumpsites are located within a proximity distance of ¼ mile to sinkhole locations. Those that were within this criteria distance were scored a 1, all others outside ¼ mile were scored 2.

Dump Profile Analyses Having compiled known dump information at a countywide level earlier in the study through the use of various GIS spatial methods, further site review and statistical analyses were performed in an attempt to evaluate dumpsite locations, and if possible create a dumpsite profile. Such a profile could then be used as an aid in identifying areas meeting those criteria which could then be targeted for investigation to determine if actual unreported dumping activities are taking place at these locations, or to help in establishing preventative measures to preclude future dumping. The parameters evaluated with respect to dump locations were: landform types, land use classifications, and proximity to primary and secondary roads. The author of this work acknowledges that the occurrence data for dumping activity ranged over a period from 1967 to 1997 and analyses were performed using more current data sets for landforms, land use, and road classifications. This was deemed acceptable since the dump profile analysis is to be used for general understanding at a broad level and to serve as a baseline for future, and more in depth investigations.

Landforms

As mentioned earlier, unauthorized dumps are most often located in convenient areas such as gravel or quarry pits, sinkholes, eroding drainage ways, ravines, floodplains, and wetlands. Statistical analyses were performed to test the correlations and strength of relationships of the landform types of sinkholes, springs, quarries, and gravel pits with dumps. This effort was done in an attempt to determine if certain landform types are more prone or being targeted as dumping locations. Land Use Classification

To obtain a general overview of what land use types dumps most often occurred on within the study sites, a frequency data table was constructed (Table 3).

From this frequency table it can be noted that the 3 land use types of non-farm, ungrazed grass, and deciduous forest account for approximately 50% of all dumpsites. Additionally, the information in the table was used to perform analyses to statistically determine if dumping on these land use types was occurring due to complete randomness or if they are possibly more prone to unauthorized dumping activity due to other factors. Proximity to Roads

The third and final portion of the dumpsite profile was to examine the number of dumps within a particular distance to primary and secondary roads. It is assumed that most people participating in unauthorized dumping activities are circumventing the fee-for-service solid waste management system and have no desire to get caught. Therefore, it is

15

Table 3. Summary of Cascade Township Land Use Types on Which Dumps Occurred, Total Acreages of Those Land Use Types, and the Total Number of Dump Occurrences on Those Land Use Types. *Note: All Other Land Represents the Remaining Land Use Types for Which No Dump Occurrences Were Recorded. Land Use Type Total Acreage % of Total Acreage Total Dumps % of Total Dumps Non-Farm 22805.4 5.5 37 22.4 Parks 2328.7 0.6 1 0.6 Transportation 3951.6 0.9 3 1.8 Landiflls 434.6 0.1 5 3.0 Quarry/Gravel 1050.5 0.3 8 4.9 Contin. Straight Row 81786.2 19.5 16 9.7 Stripped Crop 14725.4 3.5 1 0.6 Ungrazed Grass 42648.0 10.2 22 13.4 Contin. Hayland 4231.0 1.0 2 1.2 Deciduous Forestry 29709.5 7.1 20 12.2 Unmanaged Pasture 31929.0 7.6 13 7.9 Straight Row Crops 81786.2 19.5 15 9.0 Homestead 10800.4 2.6 10 6.1 Managed Pasture 15605.1 3.7 12 7.2 All Other Land 74878.0 17.9 0 0 Totals 418669.6 100.0 165 100.0

hypothesized that people are more likely to engage in unauthorized dumping from secondary roads, where there is less likelihood of being seen and reported. Results/Discussion

Site Ranking Results

To reiterate, the methodology described has been designed to inventory and rank active and inactive sites for which little information is available. This study does not attempt to deal with comparative risks associated with specific chemical substances due to the fact that concretely determining such information would prove tremendously expensive and time consuming. However, it does address some of the hydrogeologic conditions that control and influence the migration of waste decomposition products under typical geological conditions. In the initially devised ranking system as earlier described, no one category (or factor) was considered to be of primary concern or of greater importance so all numerical ranking values were equally

weighted. As an example, Table 4 illustrates the evaluated criteria and respective scoring of categories for one particular dumpsite within the pilot study area. All 27 dumps in Cascade Township have been scored in an identical manner, with the information being organized in an attribute table in ArcView. This dump information can be quickly and easily identified, accessed, or queried in ArcView for comparison purposes.

The results from using this non-weighted ranking methodology proved to be rather inconclusive, as overall scores were rather evenly distributed. This limited dispersion of scores made it difficult to clearly distinguish between the various hazard potentials of dumps as the presence or absence of one or two influencing conditions proved to be inconsequential given the number of factors and the small range of ranking values applied. A total of 27 dumpsites were ranked in Cascade Township, with 1 site having the low score of 22 (high priority sites), 1 site scoring 30 (lowest priority site), and an average dump

16

Table 4. Example Summary of Ranked Attributes for One Unauthorized Dumpsite in Cascade Township, Olmsted County Minnesota.

Township Cascade Parcel_id 56778 Feeowner *****1 Taxpayer *****1 Fdeladr *****1 Soil Type Mt. Carrol Silt Loam Soil Ranking 1 Land Use Type Unmanaged Pasture Land Use Ranking 3 Sensitivity Level High Moderate Sensitivity Ranking 3 Bedrock Geology Type Decorah/Platteville/Glenwood Bedrock Geology Ranking 1 Depth To Bedrock < 50 ft. Depth To Bedrock Ranking 1 Sand/Gravel Resources None Sand/Gravel Ranking 4 Alluvial None Alluvial Ranking 2 Hydric Other Soils Hydric Ranking 2 Proximity To Surface Water Yes Proximity To Surface Water Ranking 1 Proximity To Springs No Proximity To Springs Ranking 2 Proximity To Sinkholes No Proximity To Sinkholes Ranking 2 Proximity To Wells Yes Proximity To Wells Ranking 1 Erosion Prone Yes Erosion Prone Ranking 1 Wellhead In Wellhead Ranking 1 Total Score 25 1 Private Data

score of 26. The lowest score any one site could receive within this system is 14, with a possible high of 39 (Figure 3).

The initial ranking methodology was re-visited for the purpose of creating a modified methodology that would more clearly establish high priority sites for further investigation. The first refining step was to reassess all 14 ranked categories and select the factors thought to have the most significant influence on hazard potential.

From this step, 4 of the 14 categories (proximity to wells, proximity to sinkholes, wellhead protection areas, and bedrock geology) were re-weighted with more emphasis. These 4 categories were emphasized for the following reasons: 1. Proximity to private drinking water wells- higher potential to ingest contaminated groundwater, 2. Proximity to sinkholes – serve as a direct conduit between surface activities and groundwater, 3. Bedrock

17

geology type – affects aquifer vulnerability, and 4. Locations within wellhead protection areas – potential threat to public drinking water sources. Each of these 4 categories were weighed equally to one another using the same ranking criteria or conditions as the original ranking method, however, they were scored a negative 100 (-100) instead of a 1. A large negative number was used to emphasize priority since the lowest accumulated score represented the highest priority sites. The use of such a large negative number for rating critical factors allowed for a quick comparison of scores to determine which sites were most sensitive to the factors considered to be the most critical. Additionally, it reflects how many of the critical factors for each site are present (shown by a higher negative score). All other scoring within the revised system remained identical to that established and used in the first system (Figure 4). In comparison to the results of the first ranking scores, the second methodology

provided a greater range of scores. Scores ranged from –277 (highest priority site) to 28 (lowest priority site) with an average score of –157. The lowest score any one site could receive within this system is -390, with a possible high of 39.

This system resulted in a greater dispersion of scores that made it easier to differentiate the top four sites for which further investigation is needed. Three of the top four sites are classified in the Other Dump category and the fourth is a City/Village Dump. The top two sites have critical factors of being within the proximity distance to wellhead protection areas and wells. The last two are within the proximity distance to wells. A comparison of two scores obtained from both systems for these four sites reveals that two of the four sites are high priority sites by both methods. The other two high priority sites under the revised methodology were rated as average

Ranking System #1

0

1

2

3

4

5

6

7

8

14 22 23 24 25 26 27 28 29 30 39

Ranked Dumpsite Scores

# of

Dum

ps

(High Priority Site) (Low Priority Site)

Figure 3. Score Distribution of 27 Ranked Sites (Original System).

18

Ranking System #2

0

1

2

3

4

5

6

-390 -277 -276 -180 -179 -178 -177 -176 -175 -174 -173 -172 -78 -74 -73 28 39

Ranked Dumpsite Scores

# of

Dum

ps

(High Priority Site) (Low Priority Site)

Figure 4. Score Distribution of 27 Ranked Sites (Revised System).

under the first methodology. Additional analysis of the four

“critical factors” for all 27 ranked dumpsites shows proximity to wells to be most common factor, occurring at 24 sites. Bedrock geology type was the second most common factor, critical at 21 sites. Locations within wellhead protection areas were only critical at three sites, while proximity to sinkholes as a factor at only one site.

Landform Results

In testing the relationships between the sets of numeric data of landforms and dumps (Tables 1 and 2), Pearson’s correlation tests were performed. The first test focused on the interrelationship between aggregated landforms and aggregated dumps. Results from this test showed a Pearson’s correlation coefficient of –0.1715 and a p-value of 0.496, which indicates that the correlation between all landforms and dumps is not significant. Further testing

was performed to compare dumpsite locations to the following specific landform types: sinkholes, springs, quarries, and gravel pits. Results, illustrated in Table 5, suggest that the relationships of sinkholes, springs, and quarries with dumps were not significant. However, the relationship between gravel pits and dumps yielded a Pearson’s correlation coefficient of 0.604, indicating a positive relationship. A regression analysis was then used to assess the contribution of the independent variable of gravel pits to the dependent variable of dumpsites. A resulting p-value of 0.008 suggests that there is a highly significant direct relationship between gravel pits and dumpsites.

As mentioned earlier, results from a field survey of sinkholes conducted by Olmsted County Health Department staff Minnesota showed that 50% of surveyed locations contained some type of waste. Since this field survey was done in confidentiality, those findings could not be

19

Table 5. Correlation Statistics Showing the relationship of Dumpsite Locations to Landforms

LandForm Pearson Correlation Coefficient Regression Analysis (P-Value) All Landforms -0.172 0.496 Sinkholes -0.183 0.468 Springs -0.172 0.495 Quarries 0.059 0.817 Gravel Pits 0.604 0.008

included in this analysis. As a result, the actual number of sinkholes used in statistically testing the relationships to dumpsite locations, are greatly under represented in this test. Therefore, both gravel pits and sinkholes should be considered as the most likely landform types to harbor or receive unauthorized dumping. Land Use Results

In analyzing dumpsite occurrences in relationship to land use classifications, a chi- squared goodness-of-fit test was used. This test was used to compare the observed frequencies of dumpsites occurrences on the 14 land use classifications to the expected number of occurrences. The results of the goodness-of-fit test yielded a chi-square value of 110.775 which, at 13 degrees of freedom, exceeds the chi-squared distribution critical values resulting in a p-value of < 0.001. With such a low p-value, the probability that the distribution of observed dumps on certain land use types with a high number of occurrences is not likely to be due to chance alone. This is also substantiated by the fact that non-farm, ungrazed grass, and deciduous forest land use types account for approximately 50% of all dumpsite locations and comprise less than ¼ of the total acreage for the 14 land use classifications identified (Table 3). For purposes of this study, the focus was only to

establish a dumpsite profile that could be used as a tool in identifying likely dumping areas. Further investigation and a more comprehensive examination of dump characteristics in future projects may help to better identify the attributes and qualities these land use types posses that make them more appealing to unauthorized dumpers. Proximity to Roads

The results of a GIS “select by location” query yielded 112 out of 165 dumpsites within ¼ mile of primary or secondary roads. Further querying of the 112 identified dumpsites was done to distinguish between those sites that are within proximity to primary roads only, and those that are within proximity to secondary roads only. Again, using a “select by location” query, 47 sites were identified as being within ¼ mile of primary roads, and 97 within ¼ mile of secondary roads. With obvious overlap occurring with the proximity to roads analysis, the assumption of people being more likely to dump near secondary roads was used to discount double reporting. Based on this assumption, 15 dumpsites occur within ¼ mile of primary roads and 97 within ¼ mile of secondary roads. Again a chi-squared goodness-of-fit test was used to compare the observed frequencies of dump occurrences within ¼ mile of primary and secondary roads to the expected number of occurrences. The resulting chi-square value

20

of 60.04 which, at 1 degree of freedom exceeds the chi-squared distribution critical values resulting in a p-value of < 0.001. With such a low p-value, the probability that the distribution of observed dumps occurring within ¼ mile proximity distance to primary or secondary roads is not likely to be due to chance alone. Such a high dumping frequency in close proximity to secondary roads suggests that these areas are being targeted. Conclusion

The goals of this project were to use an integrated GIS approach in developing an economically feasible unauthorized dump inventorying methodology. This methodology would then used for the purposes of compiling unauthorized dumpsite data, evaluation of the data, identifying and prioritizing sites for further action, and in creating a dumpsite profile that could be used for identifying likely dumpsite locations. Each of the aforementioned goals were successfully accomplished.

The devised methodology for compiling, evaluating, identifying and prioritizing sites through an environmental ranking system and risk analysis using GIS was completed on 27 dumpsites within the pilot study area of Cascade Township. Each of these 27 dumpsites were clearly identified as to their priority for which further investigation is needed.

In creating a dumpsite profile analysis, information compiled at a countywide level was used. Evaluated were the landform types dumps were occurring in, dominant land use classifications dumps were being found on, and dump proximity to primary or secondary roads. From this analysis, it was found that targeted dumping areas are the landform types classed as gravel pits, land use classifications of non-

farm, ungrazed grass, or deciduous forest, and dumpsites are most frequently within ¼ mile of secondary roads. Using an integrated GIS approach proved useful as it enables the user to process data, analyze and query spatial relationships that exist within and between spatial data, and produce a number of products that can be presented in a readily understood form. Provided that the necessary digital data sets exist, and new data creation is minimal, this can be done in an affordable manner. This study has demonstrated the usefulness of GIS as a tool to record and evaluate a comprehensive site inventory within the office environment in a cost effective manner. This is important since the local, state, and federal agencies that are charged with the responsibility of addressing unauthorized dumpsites are typically under funded. In dealing with the overall issue of unauthorized dumpsites, there is still much to be done. Monitoring of existing dumpsite growth and the recording of new sites needs to take place so evidence may be presented when seeking funding to establish educational, enforcement, and cleanup programs that can be adopted to address the issue. Using GIS databases offers the potential for many more analyses to be carried out and many more questions to be asked and answered, lending itself as a tool for decision support that can continually be built upon. Acknowledgements

This research was funded by the Olmsted County Public Works Department and thanks goes to the numerous individuals employed by OCPW, ROPD, OCHD, MPCA and MDNR who generously provided time and support in locating and providing all necessary information. Special recognition goes to Barb Huberty (former OCPW Environmental Analyst) for all her

21

invaluable input, support, and patience throughout the project. I would also like to thank the faculty and staff at Saint May’s University of Minnesota who provided the working facilities, necessary hardware, software, and technical expertise throughout. A special thanks goes to committee chairperson, Dr. David McConville. References Adams et al. 1997. Environmental Law

Handbook. 14th Edition Government Institutes, Inc, Maryland, 567 pp.

Anonymous. 1990. Olmsted County Comprehensive Water Management Plan 1998-2002. Olmsted County Environmental Commission and Olmsted County Administration, Olmsted, MN, 131 pp.

Anonymous. 1988. Solid Waste Disposal Investigation. . Unpublished, Olmsted County Health Department, Olmsted, MN, 9 pp.

Barnaba, E.M., W.R. Philipson, and A.W. Ingram. 1991. The Use of Aerial Photographs in County Inventories of Waste Disposal Sites. Photogrammetric Engineering & Remote Sensing . 57 (10): 1289-1296.

Goslee,S., and B. Huberty. 1997. Personal Communications. Rochester, MN, April.

Kuhns, M.J. 1988. Geological Atlas Olmsted County Minnesota-Geologic Resources. Minnesota Geological Survey, University of Minnesota, Minneapolis, MN.

Maki, Geri. 1988. Sinkholes. Unpublished, Olmsted County Health Department, Rochester, MN, 15 pp.

Nelson, A.B., L.A. Hartshorn, and R.Y. Young. 1983. A Methodology to Inventory, Classify, and Prioritize Uncontrolled Waste Disposal Sites.

United States Environmental Protection Agency, Las Vegas, NV, 126 pp.

Olsen, B.M. 1988a. Geological Atlas Olmsted County Minnesota-BedrockGeology. Minnesota Geological Survey, University of Minnesota, Minneapolis, MN.

Olsen, B.M. 1988b. Geological Atlas Olmsted County Minnesota-Depth to Bedrock and Bedrock Topography. Minnesota Geological Survey, University of Minnesota, Minneapolis, MN.

Olsen, B.M., and H.C. Hobbs. 1988. Geological Atlas Olmsted County Minnesota-Sensitivity of the Ground-Water System to Pollution. Minnesota Geological Survey, University of Minnesota, Minneapolis, MN.

Poch, G.A. 1980. Soil Survey of Olmsted County, Minessota. United States Department of Agriculture Soil Conservation Service and Minnesota Agricultural Experiment Station, Olmsted, MN.

22