Figure 17.8: Using the map in Figure 17.7, a risk map can be created. In areas showing low combined contaminant and error, risk of contamination is low. Likewise, in areas of high concentration (> 100 ppm), these zones will be remediated, and the risk of leaving untreated water is low. Areas near the cutoff (EPA standard = 10 ppm) pose the greatest risk and need further investigation, because remediation would be a failure if zones over 10 ppm remain, but remediation costs will be excessive if large areas are remediated that already meet the standard.