Oct 14, 2012

I-35E MnPASS Noise Wall

This is a copy of the letter I sent regarding the noise wall plan and the meeting the city will be having regarding this proposal on October 23 at the Little Canada City Center:

From:     T.W. Day [mailto:twday60@comcast.net]
Sent:    Sunday, October 14, 2012 12:39 PM
To:    'kevin.walker@state.mn.us'
Cc:    joel.hanson@ci.little-canada.mn.us'
Subject:    Little Canada I-35E MnPass Noise Wall

I am a property owner on the west side of Savage Lake, directly across from I35E and north of where the noise barrier on the east side ends.

Thomas Day
2660 Lakeshore Avenue
Little Canada, MN 55117-1320

I want the noise barrier.

The noise barrier will, as I suspect the state knows, will be of limited value in regard to the unhealthy noise levels the freeway expansion has created for our property. When the freeway was expanded and the barrier installed on the east side of the freeway, the noise level in our backyard and inside our home rose significantly (approximately 5-10dB, depending on the time of year and day). The state's "acoustician" made some wild and unsubstantiated claims that we would not see more than 3dB of noise increase after the freeway redesign and none of those assumptions made much sense, even based on the information that you'd hope anyone involved in freeway design would have available (http://www.fhwa.dot.gov/environment/noise/noise_barriers/design_construction/keepdown.cfm).

I have measured the noise level in my backyard at various times of the day, week, year, and since we moved here in 1997 and found that the noise levels have regularly exceeded OSHA safety guidelines for industrial work spaces. Before the freeway expansion and construction of the east side noise wall, my spring measurements (typically worst case in my measurements) were around 80dBA and 86dB unweighted. After the freeway expansion those measurements increased to 87dBA and 93dB unweighted. Doing an extended noise study during those worst case periods found peaks of 98dBA from the middle of our back yard.

Even more disturbing is the fact that the general noise from the freeway was more-or-less unfocused before the east side noise barrier. After that barrier was constructed, the noise levels clearly increased as vehicles approach and pass that reflection source. The fact that noise generators can easily be localized when the are near the barrier proves that the reflection from the east side barrier has increased the noise level on our property. Something the previous "engineer" claimed would not happen and something that any competent acoustician would expect to be a problem.

For people who live within the first 100 feet of the barrier, I would expect a dramatic improvement in noise levels after the proposed barrier is constructed. For those of us who live considerably further from the freeway, I doubt that we'll see significant improvement. An improvement on this plan would be to add absorption to the barrier design. The easiest and cheapest way to do that would be to include a budget for enough evergreen trees to provide year-around full coverage of the noise-generating area. That was part of an earlier noise abatement plan and should be included in this plan. Even if the trees do not provide much effect early on, the larger they grow the more effective they will become and they will not require maintenance if they are planted on the lake-side of the barrier. This can only be good visually and sonically for the embattled residents around our lake.