Note: the information presented below was prepared with the help of SRA’s professional wetland biologist, Suzanne Tomassi of The Watershed Company.
What’s going on at the Sammamish Rowing Association facility?
SRA has built a new boathouse in Marymoor Park. It replaces the previous boathouse, which was used by rowers for three decades. It is located just behind the site of the old boathouse, but on higher ground. Utilities for the new boathouse were routed underneath the gravel path leading to the building, whose footprint is slightly more than 17,000 square feet.
The new boathouse does not disturb any of the wetlands on the property, as it was built completely within the wetland buffer. A significant amount of mitigation was done as part of this project. The mitigation includes more than 88,000 square feet of wetland buffer improvement, nearly 74,700 square feet of wetland restoration and improvement, and almost 5,000 square feet of wetland reestablishment. That’s more than three acres of mitigation!
What is mitigation and what can I expect to see after it’s complete?
Mitigation is compensation for unavoidable impacts to critical areas and their buffers.
What’s the extent of the mitigation?
Mitigation measures involve removing invasive species from the property and replacing them with native trees and shrubs. This restores areas disturbed by previous land uses to wetland or functional wetland buffer.
For example, a raised berm that was part of a sewage treatment plant that used to be on this site artificially separated two wetlands. This berm was removed as part of the mitigation effort, restoring the hydrologic connection between the two wetlands. The berm area was planted with native wetland trees and shrubs.
Before construction of the new boathouse, the wetland north of the berm and its buffer were almost entirely infested with the invasive species reed canarygrass and Himalayan blackberry. Once these were removed, the whole area, all the way to the property boundary and west to the pond, was densely planted with western red cedar, Sitka spruce, black cottonwood, Oregon ash, red alder, twinberry, Pacific ninebark, and other native species as appropriate for the wetland and buffer conditions. No native vegetation was destroyed in these areas.
To ensure maximum survival rates, SRA committed to irrigating the whole area until the plants were established, and monitoring was to occur for at least 5 years (longer if the site has any trouble meeting the stringent performance standards). By that time, a dense thicket of wetland and buffer should cover about 1.5 acres in this part of the site. A few years after that, young forest will blanket the area where presently there’s very little cover or forage for wildlife. The whole area will be contiguous with the Sammamish River, and birds and other wildlife will be able to travel through it unhindered and undisturbed.
In addition to this completely reclaimed area, another approximately 2 acres of wetland and buffer were improved on the property. All invasive species were removed and replaced with native trees and shrubs. The enhanced areas include the wetland and buffer area along the Sammamish River, as well as other small wetlands that are separate from the large Sammamish River wetland. Debris placed behind the existing boathouse many years ago was removed and the area was restored. The road has been lined on both sides with very dense native vegetation. The restored and improved areas are now bordered with split-rail fencing and “Native Growth Protection Area” signage.
What will the area look like when the mitigation is finished?
The Sammamish River wetland and buffer will be expanded so that the property becomes home to a large, high-quality wetland and forested buffer, contiguous with the river across to south Marymoor Park and to Lake Sammamish. The most noticeable difference from the present state will be the conversion of a great expanse of blackberry and invasive grass to a young stand of native trees and shrubs. This is the area north of the access road. What might be less noticeable to people, but certainly not to wildlife, are improvements to the areas that are already forested, primarily the wetlands and buffers south and east of the road. All invasive species were removed from these areas and replaced with native trees and shrubs. Large woody debris was scattered throughout to provide additional habitat value.
The open water ponds were unchanged except for the addition of some large woody debris. The pond edges were enhanced with native species where appropriate.
In the end, wetland buffer vegetation will be improved so that natural protection of the wetlands is greater than what is there today. In additional to improving the buffers as storm water control and water treatment features, the additional vegetative diversity and complexity will improve habitat. The overall area of available native habitat will be much greater than what is there today.
How many trees are being cut down? Will they be replaced?
Of approximately 590 trees originally on the site, 116 or 20 percent have been removed. Redmond allows the removal of up to 65 percent of significant trees, and more in some cases. Redmond regulations originally required removal of many more trees, but SRA hired an arborist who examined every tree and recommended the removal of only those trees which would actually be damaged by construction. Cut trees were replaced at a replacement-to-removal ratio of nine new trees for every removed tree. This is well above Redmond’s requirement of a one-for-one replacement.
What happened to the cut trees?
The trees remained on-site for wildlife use. A few large trees were placed in the pond and quickly became popular with wildlife – the green herons began hunting frogs from them almost immediately! All of the other large trees were used as habitat features in the mitigation areas. Small trees and some branches were chipped and used as mulch in the planting areas.
How and why was the building site selected? Why wasn’t the new boathouse located elsewhere?
The original site for the new boathouse was going to be just to the southeast of the existing boathouse. However, it turned out that SRA would have intruded on the wetlands on this location. There were three other possible locations:
- Across the path, to the northwest of the existing boathouse. There was a relatively clear meadow on this location. However, rowers would have had to somehow carry boats across a Category I wetland in order to reach the dock. This would have required building a large and unsightly footbridge that was wide enough to handle carrying down an eight-person boat. SRA also would have had to build an entirely new road from the boathouse to the parking lot; a significant additional disturbance given that a road already existed.
- Near the parking lot. There is land outside of the wetland buffer between the pond and the parking lot. However, this location is simply too far from the river; it isn’t practical to carry boats that distance.
- Behind the existing boathouse, just up the path. This turned out to be the best location. The existing road can be used, there is plenty of space to build the boathouse and not intrude on the wetlands, and it is close enough to the river to be viable as a boathouse.
Isn’t the entire area by the river a wetland? It gets pretty wet in winter…
The largest wetland is contiguous with the Sammamish River, but not all of the area is wetland. Wetlands must meet specific scientific criteria in the areas of hydrology, soils and vegetation. Areas not meeting these criteria are not wetlands and do not perform the same functions as wetlands. On the project site, they do serve to protect wetlands, and this is why SRA implemented so many improvements to these “buffer” areas.
Sometimes non-wetland areas have standing water. This can be due to any of a number of conditions, including excessive rains, compacted soils, and past disturbance. Standing water alone does not signify a wetland.
What else did you do to avoid and minimize impacts, and what are you doing during construction to protect habitat?
After selecting the building location, SRA made certain that all wetlands, whether regulated by Redmond or not, were completely avoided. The building is designed with two stories to minimize the footprint and is placed as close to the road as possible to minimize buffer intrusion. Required fire safety features and utilities were placed within the existing road footprint and minimized to the greatest extent legally permissible. All construction materials are inert and non-leaching.
No wetlands were directly impacted by the construction, apart from the enhancement and reestablishment that occurred. Wetlands were carefully delineated by a team of qualified professionals, and the delineation was reviewed and approved. Wetland boundaries were marked by a surveyor, and clearing limits were tightly protected with storm water protection features. An approved back-up plan was in place, just in case an unseasonal storm event provided more water than expected. In addition, a biologist and a building inspector was on-site during site preparation, construction, and mitigation implementation to make sure that all work was properly conducted.