Blue Marsh Dam provides some protection from flooding in Berks

Keith Mayer, Reading Eagle, Pa.
·2 min read

Jun. 20—Blue Marsh Dam was built in the years following the flooding from the remnants of Tropical Storm Agnes in 1972, but the plans had been on drawing board since the 1950s, said Steve Rochette, public affairs officer for the U.S. Army Corps of Engineers, Philadelphia District.

The dam in Bern Township regulates the flow of the Tulpehocken Creek, which runs into the Schuylkill River about where eastbound Route 12 crosses from Wyomissing into Reading.

Christine Lewis-Coker, water manager with the Philadelphia District, said the dam operators manage the dam level and prepare when significant rain-making events are forecast by the National Weather Service and on the advice of the hydrologists with the Middle Atlantic River Forecast Center, a division of the weather service.

"We operate as normal and we try to hold back (during a storm) and release after the storm has passed," Lewis-Coker said.

The worst flooding in the dam era was in 2006 when a very wet week culminated in a deluge and the river overflowed in Reading in the second highest crest on record.

But the dam's area of influence decreases with distance. That's the lesson from the flooding downstream during the passage of the remnants of Hurricane Ida in 2021.

Operators did lower the level before Ida.

"Even though we knew a lot of rain was coming ... there was very little Blue Marsh could do to alleviate the flooding," Lewis-Coker said.

Pottstown, Phoenixville and Norristown were particularly hard hit by the flooded Schuylkill.

"We minimized the flow to less than 100 cubic feet per second, almost our minimum, and the flooding still continued," Lewis-Coker said.

The minimum is about 50 cubic feet per second and normal is about 200, she added.

The reason for the flooding downstream was due to the volume and rate of rainfall downstream, which swelled tributaries that join the river south of Reading.

Lewis-Coker estimated the dam controls about 10% of what happens with the Schuylkill by the time it reaches Norristown and Philadelphia.

Recent years have seen more precipitation, but it hasn't affected the dam operators' procedures, Lewis-Coker said.

"With the Idas, we have to work harder," she said.