Municipal storage tank solutions
Holding back floodwaters
Because of its coastal proximity and hydrology, much of Elizabeth, N.J., is prone to flooding.
The city is situated next to Newark Bay and, to the south of that, Arthur Kill. From the strait that comprises Arthur Kill, the Elizabeth River branches off and runs through the town. Storms have a habit of pushing water from the bay down the kill, into coastal areas of the town and into the Elizabeth. The lowest drainage area, and the one most affected during floods, has traditionally been the basin draining to Trumble and Sixth Streets.
During the severe wind event of Hurricane Sandy, for example, a massive storm surge hit the coastline and the Elizabeth, causing extensive flooding as well as damage to waterfront facilities; but rain-induced flooding, which is a more regular occurrence, is of even greater concern.
Over the years, the city has spent much time dealing with the situation. Several responses to this flooding have been considered; recently, those conversations have included replacing current sewage lines with larger structures, and building a pump station near the bay. Both options turned out to be exceedingly expensive.
The city also examined the possibility of building a million-gallon underground storage tank at one of several other locations. Dan Loomis, city engineer, said putting such a tank at the current location got to the heart of the problem; so development of a current project that includes it began in late 2013.
“Similar projects have been done elsewhere in other cities like New York City, and some places the tanks may be over ground,” he noted. For Elizabeth, “the current project is most cost effective and appropriate.” Still in the development stages, the city block needed to begin construction on the project was purchased by the city in November.
The plan calls for one drainage station, draining into the underground storage tank; but it will have an impact on other flooding areas in town as well, since the lowest area is at this location.
John Papetti, director of public works, said Elizabeth expects to get a lot out of the process by storing up to a million gallons of water under the ground. “The tank holds the water back until after the storm passes,” he explained.
Sewer lines are mechanically monitored to measure when the water levels are low enough for the tank water to be released into the sewer system; then all the water is treated before delivery into Arthur Kill. Besides alleviating flooding, this solution protects the environment by treating 1 million gallons of water that would otherwise flow into the local watershed untreated.
Another major aspect of the project, Loomis noted, is the rain garden that will be built above-ground, over the tank. The triangularly-shaped area, situated between city streets, measures 7,500 square feet. The tank’s shape will follow the same footprint.
The rain garden will deal with a lot of the initial runoff from a storm. Engineered soils and greens will allow the water to percolate through efficiently so the surface doesn’t get clogged up. Paths and information about the environmental impact of the tank and green space will add to the surface rain garden. Inlets in the streets connected to the tank will be higher than the gutter, so the flow will go into the garden. When the gutter is full, water will spill over into the underground tank and be stored there until the sewer is able to take the flow, with the water passing on to the treatment plant.
Part of the cost for the tank will be covered through low-interest loans from New Jersey’s Department of Environmental Protection Environmental Infrastructure Trust Fund.
“The funding is all on Elizabeth’s dime but is essential and made more affordable by the low-interest loan,” said Papetti. The city bonded the loan and got a much lower interest rate from the Department of Environmental Protection. However, the project would have had to go on even without it.
Several city departments were involved in the project, including public works, which includes the engineering department; finance; and the law department, which helped in purchasing the properties.
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