Stormwater Forum and Discussion - Oct 7th, 2018

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Lyons hearing room. Eight attending. Assistant town engineer Bill Copithorne presiding. MS-4 permits are tonight's main topic.

Among other things, MS-4 requires municipalities to develop plans to regulate stormwater runoff from construction projects. We'd like to discuss what qualifies as a construction project, and what kind of oversight is needed.

The town has a stormwater bylaw, which applies to the addition of 350 or more square feet of impervious surface on an existing lot, or 500 or more square feet on a vacant lot. The engineering department currently administers this bylaw, and reviews are generally triggered via building permits. The engineering department review plans, and must sign off before the certificate of occupancy is issued.

The town needs to solidify its process for handling impervious surface changes on newly subdivided lots. For example, the 350 square foot threshold might apply to one side of the subdivision, and the 500 square foot threshold might apply to the other.

What if someone adds a residential walkway? That can increase impervious surface. The state building code exempts residential walkways from building permit requirements, so there's nothing to trigger a review.

Some municipalities exempt single-family homes from stormwater requirements, or lots below a certain size. Applying this convention to Arlington would require some care. Much of our land area is dedicated to single-family homes, and our lots are generally on the small side. Burlington exempts lots under 1 acre, but many of Arlington's lots are much smaller.

The town's water and sewer bylaws were written in 1982, and they'll likely be impacted by MS-4.

MS-4 requires towns to adopt bylaws regulating construction runoff. Inspectional services might need a certified stormwater control inspector to do the inspections.

What about erosion that takes place outside of a construction project? For example, a homeowner that tears up and replants their lawn.

What about long-term maintenance requirements for infiltration systems? The general goal is to require property owners to submit maintenance records, to demonstrate that systems are being maintained. What's the threshold for imposing a reporting requirement. For example, would a small swale need annual inspection reports? And what about new property owners, who might not be aware that these systems exist (or don't understand what they do)?

It may be worthwhile to review conditions that the ARB and Conservation Commission placed on commercial projects, to see where stormwater requirements were imposed. It would also be useful to look at what other towns have done in terms of stormwater bylaws.