How would the new Venice Island water basin have fared in Hurricane Irene?

While much of the neighborhood around it was left underwater by Irene’s floods, the old rec center building on Manayunk’s Venice Island was spared — if only momentarily.

The water that deluged the area near Main Street and Shurs Lane covered about 80-percent of the Venice Island rec site and adjacent parking lot, but never made it into the building, said Don Bitterlich, senior project manager for the Daniel J. Keating Company.

Some of the chain-link fencing around the site ended up under water, but a construction trailer and some heavy equipment were moved off-site on Saturday morning, before the storm hit, but the building stayed dry.

It’s a small victory, as the 1960s-era rec center is scheduled for demolition Tuesday morning, part of a $46 million, two-year project to create a performing arts center and install a four million-gallon underground stormwater retention basin meant to alleviate flooding.

The tank, a first of its kind for the Philadelphia Water Department, will be dug out and installed under the current parking lot area.

As explained at a recent meeting by PWD spokeswoman Joanne Dahme, a sanitary sewer runs along the Manayunk Canal, crossing it at Lock Street. It’s only supposed to take in sewer waste, but there is rainwater infiltration during storms. Also, about a century ago, under Shurs Lane, a hole was cut in the storm sewer to divert some rain water to the Schuylkill River, causing an overflow point just south of the intersection, she said.

At 400 feet long, 75 feet wide and 25 feet deep, the new basin will catch and temporarily store diverted storm flow from the sanitary sewer running along the Manayunk Canal. But would the new tank have prevented or lessened the hurricane-level flooding that doused part of Main Street over the weekend?

The short answer, officials say: Probably.

“This is a big tank but this was also a pretty good storm — about 5 ½ inches over a 24-hour period,” Dahme said in an email Monday. “Without the modeling to confirm, we believe it would have worked well in this storm as rainfall was fairly steady, dispersed over a long period of time.”

As for the new performing arts center, Bitterlich said it would have fared well if faced with a storm like Irene. The ampitheater-style building is set at 35 feet above ground level, and flood waters rose to about 28 feet, he said.

“The new project would not have flooded,” he said.

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Contact Amy Z. Quinn at azquinn@planphilly.com