Movement from one access point to another on the same lake during the same day would not require drainage. The rule also includes exemptions for emergencies and governmental activities involving collection of water. Marine sanitary systems are exempt from the new regulation. The rule will take effect in late December 2013 or January 2014. The nine-member commission also voted to publish a proposed rule in the Texas Register for public comment that would add 28 other Central and North Texas counties in the boat-draining mandate, including Bell and Coryell counties where zebra mussel adults were recently found in Lake Belton. That rule could be considered by the commission at its next regular meeting in January. The zebra mussel is a small, non-native mussel originally found in Eurasia. It has spread throughout Europe, where it is considered to be a major environmental and industrial menace. The animal appeared in North America in the late 1980s and within 10 years had colonized all five Great Lakes and the Mississippi, Tennessee, Hudson and Ohio River basins. Since then, they have spread to additional lakes and river systems, including some in Texas. "Unfortunately, zebra mussel larvae, called veligers, are not visible to the naked eye," said Brian Van Zee, TPWD Inland Fisheries regional director based in Waco. "You could be transporting them on your boat and not even know it. This is why it's particularly important to always clean, drain and dry your boat and gear before heading to another water body." For more information on zebra mussels and how to clean, drain and dry a boat, visit www.texasinvasives.org. Additional counties being considered for boat draining requirements include Archer, Bell, Bosque, Burnet, Clay, Comal, Comanche, Coryell, Eastland, Ellis, Erath, Falls, Freestone, Hamilton, Hays, Henderson (west of Highway 19), Hill, Johnson, Leon, Limestone, Llano, McLennan, Navarro, Robertson, Somervell, Travis, Wichita and Williamson.