By mid-June it should be safe to go back into Clear and Fairview lakes, the dirtiest duo among 87 lakes monitored for water quality by Orlando and Orange County. Since December both lakes have been posted with warnings about potentially hazardous levels of "fecal bacteria." Excrement, in other words. "It is recommended that water-contact activities, such as skiing and swimming, be avoided until further notice," explain notices mailed to residents of homes ringing the lakes. Clear and Fairview are the only lakes in the county so afflicted at this time, and this dubious distinction is historical. For the past five years, owners of the homes around them have been treated to similar warnings. "It's almost like clockwork," says Kevin McCann, the city's lake enhancement coordinator. Just how unhealthy is the water? Those who swallow a mouthful could wind up with diarrhea or other digestive tract problems. Ear and eye problems could develop. Ultimately, though, most emerge with not so much as an upset stomach. Based on recent testing, McCann predicts the lakes will again be deemed user-friendly within two weeks -- once city and county officials have had the opportunity to pow wow over the latest results. So what's with the excessive excrement? "Both lakes have septic systems around them. When the water level is low, it pulls more into the lake," McCann says. Storm runoff may be another factor. To stem the nastiness, the county plans to extend sewers to homes around the lake by 2000. The decision followed a study of Clear Lake that confirmed theories about the septic systems. (A similar study is in the works for Lake Fairview.) Part of Clear Lake is in Orlando, where homes that ring the lake already are connected to sewers. Sewers will be extended to connect those on the county side in the lower-income Holden Heights neighborhood. The price tag -- and there will be no choice -- is estimated at $5,000 a residence. While those living around Lake Fairview, which is located entirely in the city, may be able to tap funds set aside in the city's septic tank-abandonment program, Holden Heights residents apparently will be left to their own devices.