Drainage plan

The Alewife-path construction team has a plan to prevent water spilling down Cottage Ave. from eroding the entrance and puddling on the path.

The new plan would direct rainwater around the path into the swales on either side. (Detail.)

Thanks to Wayne Chouinard, Arlington’s Town Engineer, for sharing the drawing. Wayne has the unenviable task of standing between people like me and the project team. The full drawing is here.

It’s been clear since August of last year that rainwater runoff sluicing down Cottage Ave. can erode the stone dust of the entrance. I wrote about this problem in December. (Notwithstanding that, this blog is really about Mass. Ave. Most of the time.)

Wayne met with me on site back in June (more photos of erosion, also of standing water on the path). He told me the project team knew of the problem and had a plan. This is it.

As I read these drawings (and I am not an architect), the plan is to extend the drainage swales that lie on either side of the entryway, curving NW so that they abut the end of the street. The planners intend curbing and other design changes to direct the water into the swales.

Right now there is an asphalt walkway, the remains of the old entry way, on the southern edge of things, that is slated for removal. Apparently under this plan that area will be kept unobstructed to allow water to reach the southern swale (which will be extended under the old path).

If so, it means that the neighborhood will have an alternative way to get onto the path, for instance when the main entrance is obstructed with snow-plow banks.

This looks promising. I had thought the plan was to direct water to the swales over the stone-dust entry paths, but the idea here (as far as I can tell) is to divert most of the flow around those paths, north and south.

The weak point, if there is one, looks to be the entryway itself, where an ADA-compliant ramp will breach the 6-inch curb that is proposed to keep water off the path.

Possibly the plan is to raise the concrete entrance, slanting down to grade. If so, I think there will be a puddle at the foot of the street, unless the end of Cottage Ave. is also regraded.

(There’s no storm-water drain there.)

But if the entrance is not raised enough to block the water, I do not have much hope that the stone-dust entry paths will last very long, grading or no.

Honesty compels this final observation: My opinion is arguably worth less than that of a landscape architect.

I can’t seem to stop writing about the Alewife paths (previous Alewife post, first Alewife post, next Alewife post, all Alewife posts, all erosion-and-drainage posts for goodness sakes). However, this is a blog about Mass. Ave., and I expect there will be some news on that front soon.

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