Manmade accelerated soil erosion and the resulting suspension of soil particles in water or air can have detrimental environmental and societal results. Sediment has been identified as the single most common water pollutant, and increased dust is a major contributor to air pollution. Consequently, processes, procedures, practices, and products have been developed, promulgated, studied, and implemented to minimize erosion and resulting sedimentation and dust.
Figure 1. Survey FormTo begin articulating the financial costs and benefits associated with reducing accelerated soil erosion, the International Erosion Control Association (IECA) held an economic summit in 2000. One of the objectives that resulted from that summit was to obtain data on the costs of minimizing erosion and sedimentation for one market segment. Once cost data were obtained, the plan was to address the economic benefits of erosion and sediment control (ESC) for that sector. Based on availability of their data and similarity of agencies, United States departments of transportation (DOTs) were selected as the first sector to study regarding the costs of ESC for highway projects. The main objective was to ascertain annual highway project ESC expenditures.The survey form, shown in Figure 1, and a cover letter were sent to personnel in the 50 state DOTs and in three federal land divisions. Follow-up via telephone and mailing (electronic and postal) was done to increase response. After data were received, respondents were called upon to clarify data and information. Data were standardized into comparable units and entered into spreadsheets. From the data provided by the DOTs, annual total costs for ESC were determined for each responding state, and statistical data were obtained to compare the responses. The majority of states provided data for 2000; some also reported on 1998-2001, which allowed comparisons over time. In addition, ESC total costs were evaluated by categories, including riprap, seeding and mulching, erosion control mats, silt fence, sodding, and hard armor. The total costs for ESC for each state were compared to land area, total lane-miles, and population.Thirty-eight states (or 76%) and two federal land highway divisions responded to the survey. Table 1 provides a summary of the response.Table 1 . Summary of Data Submission for 1998-2001Number of States Providing DataYear62001(6-9 months)302000181999171998Annual Erosion and Sediment CostsFigure 2 presents the annual costs for ESCs applied to highway projects for 30 DOTs and the eastern federal land division. States with the highest reported total erosion and sediment costs in 2000 were Georgia, Texas, and Florida. Rhode Island reported the smallest expenditure. Statistical data on the total annual costs for ESC are given in Table 2.Table 2 . Statistical Annual Erosion and Sediment Costs for DOT Projects in 2000Average$9.01 millionMedian$5.13 millionHighest$38.75 millionLowest$49,136A comparison of erosion and sediment costs as a function of state land area is shown in Table 3.Table 3. DOT Expenditures for ESC per State Land Area in 2000Average$252.6/mi.2Median$118.71/mi.2High$1,492.78/mi.2Low$3.52/mi.2The states with the three highest expenditures per state land area were New Mexico ($1,493/mi.2), Connecticut ($1,139/mi.2), and Georgia ($652/mi.2). Data for per-capita ESC for 2000 are given in Table 4. The average was $2.20/person. Wyoming reported the highest expenditure per capita ($10.1), and Rhode Island the lowest ($0.05).Table 4. DOT Expenditures for ESC Based on PopulationAverage$2.20/personMedian$1.76/personHigh$10.10/personLow$0.05/personOther states with expenditures per capita in the upper range were New Mexico ($7.16), Georgia ($4.73), and Arkansas ($4.66). Figure 3 depicts the total ESC costs per state lane-miles. Three states that spent the most on total erosion and sediment costs (Texas, Georgia, and Florida in 2000) also had the most lane-miles among the reporting states and the highest costs per lane-mile. Table 5 provides statistics as a function of state total lane-miles. Rhode Island, which has the second shortest lane-mile, had both the lowest total annual erosion and sediment expenditures and cost per lane-mile.Table 5. Comparison of DOT Expenditures for ESC Based on Total Lane-MilesAverage$60.12/lane-mileMedian$38.04/lane-mileHigh$310.89/lane-mileLow$3.84 /lane-mileComparison of Annual Expenditures for 1998, 1999, and 2000Of the 19 states and one region reporting total cost data for more than one year, 12 (63.15%) reported increases in ESC annual costs. A representative example is presented for Arkansas in Figure 4. The increase in expenditures from 1998 to 2000 ranged from 2% to 187%, with an average of 67%.Figure 4. Total Annual ESC Costs for Arkansas DOT, 1998-2000
Ting Guo and Nida Igiz are graduate students at Ohio University.