Q.: A considerable area of our parking lot has been messed up with roofing tar--some of it windblown from the roofing operations and some of it dribbled from buckets and kettles. Cleaning with dry ice and scraper would probably be slow and tedious. Is there a faster way?

A.: Investigate water blasting. Manufacturers of water blast equipment can tell you whether it will produce a satisfactory appearance, how fast it will work, and perhaps give tips on technique. Names of seven manufacturers are listed in the December 1983 issue of Concrete Construction on page 904, and their addresses are given in the directory that begins on page 905.