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Yardley Borough is prone to
flooding and local government officials have been taking steps to reduce
the severity of the problem. Remediation is needed within the Borough
because new area construction has created increased runoff during storm
events, flooding out homes and businesses. In a healthy ecosystem,
trees soften the blow of heavy showers, leaves and native vegetation
absorb rain water, and water is naturally recharged to underground
aquifers to replenish reserves. After considerable development in the
region, high velocity runoff amasses from hard surfaces during
downpours, resulting in habitual flooding. This project is one attempt
to mitigate the hazardous floodwaters endured by this community.
In conjunction with site improvements at Buttonwood Park including a
plaza, sidewalks, and parking, stormwater Best Management Practices (BMPs)
were incorporated into the new design of the Park. Phases II and III of
the redevelopment were completed in the fall of 2003 and the spring of
2004. The goal of this stormwater management system was to
encourage the percolation of runoff instead of letting it contribute to
the overburdened municipal rainwater conveyance facilities, which flood
during peak flow storm events. The system detains surface water and
eliminates pollution loading into nearby waterways.
Initially, porous
pavement was planned to be installed, but percolation tests found that
parking area soils were not suitable for pervious asphalt, though the
roadway soils were. The plans for porous pavement were scrapped, and a
subsurface stormwater collection system was instead installed.
This system is comprised
of two excavated percolation pits installed with concrete vessels known
as infiltration chambers, an infiltration trench, and a new conveyance
system to pipe the water to these percolation pits. Surface water is
directed towards inlets, where solid piping leads stormwater beneath the
pavement into the infiltration chambers to effectively clean water
before it is returned to the ground. The black drainage piping is
hooked into the vessels, and the pits are backfilled with rock. The
rock allows enough air to enter the infiltration pits for indigenous
organisms to survive and perform bioremediation before the runoff
recharges.
Native plants were
installed on the site to provide additional cleansing and water
retention performance, while also beautifying the site. The native
plant list is available
here,
and a planting diagram
can be found
here. Bowman’s Hill
Wildlife Preserve helped the Borough pick out native shrub and tree
species for the park.
The
infiltration chambers can be periodically pumped out to be cleared of
sediment and debris. Inspection of the chambers is required on an
annual basis.
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