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Park would include moving stream to improve water quality, natural play area for kids

PMG PHOTO: CLARA HOWELL  - Bruce Powers with the parks department helps explain the construction documents of the proposed park plans to community members.Five years later, the site at Iron Mountain Park that was slated for development back in 2015 is now making strides after experiencing geological challenges during the engineering and planning process.

Members of the Lake Oswego City Council, the Parks, Recreation and Natural Resources Advisory Board, and community members visited the site of the proposed Iron Mountain Park improvement project Feb. 27 to ask questions and talk with design consultants about elements of the proposed plan. The engineering cost estimate for the project is $3.4 million.

There is about 6.5 acres of land at the toe of the slope at Iron Mountain Park that would be developed into a park. Major elements of the proposed park plan include a new stream to help improve water quality, a two-stall restroom, a picnic shelter area, a parking lot and a natural play area for children.

The public design process for this site began in 2015 and the master planning process was completed in 2017. The last three years consisted of heavy engineering work.

"We found contaminated soil," said Lake Oswego Parks and Recreation Director Ivan Anderholm. "We found that we have a lot of water that moves through the site and instead of just moving forward with the plan and saying, 'We're just going to assume the liability if anything goes downstream,' we decided to actually come up with an engineer mitigation plan of how we're going to do that and also how to ensure that when people come to this site, they know that we have a cap of soil and that we've mitigated the contamination."

During the engineering process, contaminates like lead and arsenic were found in certain patches of soil.

"Historically, this was a swamp. About 20 feet deep is some very swampy soils, some very wet soils, and then layered on top of that is a whole series of history over time with a little bit of rubble and debris that was dumped long ago over on this end of the park and then some other soil fill on top," said Steve Roelof, landscape architect with Environmental Science Associates (ESA). "There's essentially light contamination in certain areas of the upper soil here where there's a little bit of arsenic, a little bit of lead."

Figuring out how to plan around the geotechnical and contamination challenges took time and after researching and talking to experts and other municipalities about how they manage these challenges, it was determined that a two-foot cap of soil — one foot sourced from soil stockpiled at Lusher Farms and another foot of imported topsoil — will help mitigate contamination.

A base rock layer will be placed underneath where structures or pavement are being built to help prevent future warping or cracking in the pavement.

PMG PHOTO: CLARA HOWELL  - Landscape architect Steve Roelof, center, takes the lead on explaining the proposed Iron Mountain Park plans to community members.One of the key features of the site will be the new stream. Currently the old stream channels through a series of culverts parallel with the Iron Mountain Boulevard and is an old degraded channel with very little flow that discharges into the pond.

The relocated stream will meander toward the toe of the slope and will create an improved aquatic and riparian habitat.

"It's going to be planted very heavily with native trees and shrubs," said Roelof, adding that the stream will have a slow flow, which will be good for amphibians and reptiles.

The upstream connection is blocked by perched culverts so there won't be much fish, if any.

A 10-foot-wide wood bridge will be built so people can cross the stream along with a "subtle" viewpoint near the pond area.

"So we're regrading the banks a bit on the pond and there will be a little gathering area — an overlook out there with some basalt benches, basalt columns, so (a) very natural look and just a little bit of a wood barrier," said Roelof. A low wood guardrail will be placed to keep people and dogs from heading downslope toward the pond.

The natural play area for children will include a large soil mound with a wide slide that follows the hill down.The slide will be ADA accessible.

There will also be boulders, logs and a sand pit in the play area.

The proposal also includes a parking space with about 28 diagonal spaces, a school bus parking space, and a one-way lane with one exit and one entrance.

Community members asked if the restrooms would be locked at night and staff said they would be only open from dawn to dusk.

Other community members asked about trails and what the paths would be made of.

The soft surface trails will be made of decomposed granite — which is ADA accessible — and would connect to existing Iron Mountain trails. Though the proposed trails are not part of this specific project, it is connected.

PMG PHOTO: CLARA HOWELL  - More than 200 trees will be removed for park improvements, but even more will be planted — including native schrubs.Anderholm said the parks department is putting out a Request for Proposal for design and construction for trails soon and they would essentially provide access to the park by way of a big loop that links to existing trails. The rough cost estimate for the proposed trails is $150,000.

"We do have funding that we actually put in our budget so we do have capital money that's dedicated to our trails here," said Anderholm, adding that he's not sure how much funding will be allocated to the trails yet. "When we build soft surface trails, the regulation for building soft surface trails in areas that have sensitive lands is that we do not remove any trees."

Trees, though, will be removed, particularly in the area where the old stream and ditch is, because it will need to be filled.

Overall more than 200 trees will be removed, but Anderholm said roughly 380 trees will be planted.

Representatives from Lake Oswego Hunt, adjacent to the proposed project site, were concerned that with development, people or dogs would wander onto their property during horse shows.

Roelof said the contractor would propose multiple trail routes and then representatives could see the proposed trails and ask questions prior to putting shovel to ground.

Next steps are to go out to bid on the completed construction documents and in April, the parks board will present a construction contact to the City Council for approval.

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