Lowering East Ave. under bridge would create major drainage issues

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Peter Libre is co-chairman of the Mayor’s Bike/Walk Task Force, but the letter is not meant to represent that group.

To the Editor:

Surveyor Walter Skidd measured the elevation of the drains under the East Ave railroad bridge to be 18.5 feet (NAVD88 or North American Vertical Datum of 1988, the present sea level reference).

DOT wants to lower the roadway three feet to prevent trucks from striking the bridge, even though bar hung chains or laser warning signals could cheaply accomplish that goal. Lowering the roadway three feet would drop the drains to 15.5 feet. An East Norwalk FEMA flood map shows high risk zone A as 12 to 14 feet NAVD. If sea level rises to 15.5 feet, it will backflood the street; long before that happens, rainwater will back up in the drain due to insufficient height above sea level. Perhaps DOT can show that I am misinterpreting the FEMA maps, but it appears that the proposed lowering of the roadway will cause serious problems for resilience and disaster preparedness.

An engineer at the Public Works meeting last week suggested pumps. But pumps require electricity – often unavailable during a severe storm. If the Osborne and Strawberry Hill bridges became blocked by downed trees or power lines, residents could be unable to flee and emergency personnel unable to enter East Norwalk.

There is considerable uncertainty about how much sea level will rise in the 21st century, but most informed estimates are in the range of two to six feet (https://en.wikipedia.org/wiki/Sea_level_rise), which will put the drains into the flood zone.

A lesser concern is that the grade for the driveway to the East Norwalk train station will steepen to 17 percent, and that of East Ave itself to 5 percent to 6 percent (steeper than arterial standards). In icy or snowy conditions, stuck cars may block East Ave and the train station.

We need our local representatives and mayor to persuade DOT that the bridge reconstruction should not include lowering the roadway three feet.

Peter Libre

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