This is a perfect warm-up swim, and the shortest of the stages. The lake is located on the North side of Mount St Helens on the Cowlitz River. The lake was created by the Mayfield Dam, a 250-ft high concrete arch and gravity dam constructed in 1963 which generates electricity for the city of Tacoma, WA. With fish hatcheries and a few rustic resorts on its shores, it is still a largely unpopulated lake. But does it have a lighthouse? Of course it does. Why? Unclear. 

The swim starts on a small beach on the north side of the lake and proceeds east for about a ¾ of a mile before crossing the lake and heading west then south down the lake. There are two course buoys which must be passed on each swimmer’s right shoulder. The finish is on the beach at the Mayfield Lake Resort. Water temperature on a test swim in mid-July 2024 was 72-75F.

The most remote of all the lakes, it is also the longest of the swims. This lake is also on the Cowlitz River, upstream from Mayfield Lake and is located behind Mossyrock Dam, which was constructed between 1965 and 1968 and is the tallest in Washington state at 606-ft. In 2017, the water levels were lowered 30 feet due to seismic safety concerns. The lower water levels have significantly reduced boat traffic at the east end of the lake due to the closure of the Taidnapam Boat launch. Other than Mossyrock Park at the west end of the lake there is almost no development on the lake.

Swimmers will have a dry start adjacent to the swimming area near the boat launch at Mossyrock Park and proceed along the southeast to the finish at the Dog Mountain Landing Zone. There will be 3 course buoys roughly 4 miles apart that swimmers must pass on their left shoulder. Water temperature on a test swim in mid-July 2024 was 74-77F.

South of Mount Saint Helens on the Lewis River sits our third lake. Lake Merwin was created by the construction of the 313-foot tall Merwin Dam between 1929 and 1931. The dam sits in the town of Ariel, and may have been the area in which DB Cooper jumped from a hijacked airplane with $200k of ransom money in 1971.

The Lake Merwin swim will be a buoy course starting at Speelyai Bay Park swim area. The swim will proceed south out into the main body of water and turn west for roughly 3 miles staying to the right of 2 course buoys. After passing the second course buoy, swimmers will cross the lake to a 3rd course buoy – again staying to the right before turning east. There are two additional course buoys along the south shore that each swimmer must stay to the right of as well. The finish line is immediately after passing under the Yale Bridge at the foot of metal staircase that goes up the right (south) shore to the bridge level. This swim is expected to have the most boat traffic.

In our opinion, the most scenic of the lakes is Yale Lake. The view of Mount Saint Helens from the water is magnificent. Yale lake sits just upstream of Lake Merwin on the Lewis River, and was formed in 1953 with the construction of Yale Dam for hydroelectric power. Since 2020, the lake levels have been kept at least 10-ft below maximum due to seismic concerns.

The start of the swim will be from the beach adjacent to the boat ramp at Saddle Dam Park. From there it will proceed along the western shore. There will be two course buoys that will require swimmers to pass them on the left, the first at about 3.5 miles and the second at about 5.5 miles. As swimmers approach Yale Park, depending on water levels they will need to move further out from shore to avoid large, submerged stumps. Swimmers may observe these before their kayakers do. Further north, by the Cougar Park & Campground there are more stumps that will force swimmers out away from the shoreline, but these should be visible to kayakers. The finish line will be at the Beaver Bay Park boat ramp. Water temperature on a test swim in mid-July 2024 was 72-75F.