2021/04/28 Council Agenda Packet

they intend to require exclusive use of the Thornton Sullivan parking lot. Their request also includes closure of "All water access, dock & waterline up to playground area" The race course map shows that the race occupies the vast majority of the lake, preventing much of the public from enjoying other water uses. In recent years the advent of paddleboards has dramatically increased the number of people using the lake on summer weekends. I would ask that (whether one race day or two) that the race course be moved farther away from the Thornton Sullivan swimming beach, and more of the beach be opened to the public where pit space is clearly not needed. Effects on water quality: There has been speculation that the race boats will churn up the water surface and increase the dissolved oxygen in the lake. I am a volunteer for the City/County lake monitoring partnership and I measure and/or sample Silver Lake water 2-3 times each month from May through October, and have found that dissolved oxygen is not problem for Silver Lake. However a great deal of effort and expense has gone into improving the water that drains into the lake, and the upcoming trail improvements will improve it further. Unfortunately, the emissions of the outboards are a cause for concern, and extending the race day(s) will increase those emissions. The outboards are generally two-stroke gasoline race motors, which burn a mixture of gasoline and oil, unlike the four-stroke engines in our cars, motorcycles, and most motor vehicles. These two-stroke motors can have an impact on water quality. The California division of boating and waterways (https://dbw.parks.ca.gov/?page_id=28770) says "A carbureted two-stroke engine can emit up to 25-30 percent of its fuel unburned into the water or atmosphere, which is why high -emission engines are prohibited on some lakes." Discover magazine http://discovermagazine.com/2008/may/21-two-strokes-and-youre-out) notes that "A single two-stroke engine produces pollution equivalent to that of 30 to 50 four-stroke automobiles." A Wisconsin DNR study (https://www.rmbel.info/boat-motors-and-water-quality/) explained that "Boats can affect water quality in a few different aspects. First, they can add metals and chemicals to the water column. A certain amount of the fuel that enters into a motor is discharged unburned and ends up in the water." They also noted that "the boats also mix up sediment from the bottom when operated in shallow water, and this can cause problems." Their report said that a 50 hp boat can churn to depth of 15 ft. This effect will most strongly be felt in the pit area and for some distance out into the lake, as Silver Lake is shallow there.