For example it colors my county, Alameda County, CA in red because there is some system, somewhere in the county where one of these compounds was detected. But the populous areas of the county are served by East Bay MUD, where the data indicates no detection. The actual data lies in a gigantic text file in a zip archive at https://www.epa.gov/sites/production/files/2015-09/ucmr-3-oc...
