Since the federal government began incentivizing municipalities to conduct flood-mitigation projects 25 years ago, more than 1,400 communities in every state have begun participating in the National Flood Insurance Program (NFIP). Only Roseville, Calif., has achieved Class 1 Community Rating System (CRS) status, earning residents a 45% discount on their insurance premiums.
Thanks to a proactive attitude, a municipality on the country’s other coast is moving closer to that goal.
The City of Burlington, N.J., is currently certified as a CRS Class 8 community. Residents get a 10% discount on flood insurance, which saves them at least $250 a year.
The Sewer & Drainage Utility Division is using federal resiliency funding so they can continue to avert catastrophic flooding. The project will help qualify the city for additional CRS points and potentially a Class 7 status after its 2018 review, earning 10,000 residents an additional 5% discount.
Staying a Step Ahead of Development
The division’s been dealing with the unexpected consequences of development for centuries. Quakers settled across the Delaware River from the City of Philadelphia in the late 1600s. After serving as the birthplace of the American revolution, Philadelphia grew into the state’s largest city and Burlington became a suburb of sorts.
Today, stormwater runoff from a 1,200-acre area converges at John F. Kennedy Lake next to the city’s 2.7 mgd wastewater treatment plant. There, treated effluent from the city’s sanitary sewer system is mixed with the stormwater in a common pump sump and the combined flow is pumped under a commuter rail line to the river about a half-mile away.
About 75% of the city is located in the floodplain. During heavy rains the city’s stormwater pumps have increased the plant’s output to 8 mgd. Even a two-year storm brings high volumes to the facility. Thus, when storms are forecast, division employees spring into action to lower the lake’s level to provide 10 million more gallons of runoff storage. Anything they can do to postpone flooding gives emergency responders precious minutes to reach people who need help.
In 1916, twin 25 hp pumps were installed to move the sanitary effluent through a 72-inch pipe under the train tracks to a drainage channel that led to the river. In the 1950s, the channel was converted to a 54-inch discharge pipe and 60 hp and 100 hp pumps were added to handle stormwater runoff. In 2009, a portion of the 72-inch discharge culvert was lined with 54-inch PVC inserts.
During storms, the 60 hp pump is taken to full throttle and, if necessary, the 100 hp backup pump is brought online. This prevents catastrophic flooding between the river and Route 130 and limits flood damage, but hurricanes and high-intensity rains still manage to flood streets and basements.
‘Smart’ System Ensures Reliability
Recognizing the increasing frequency and ferocity of storm events, plus sea level rise projections for the next 80 years, the division asked us to develop a plan to increase the lake’s storage capacity.
Our initial review revealed the lake discharge pipe’s invert elevation was higher than the lake bottom, so dredging to increase depth wouldn’t increase capacity. Enlarging the lake wouldn’t work, either; homes and commercial properties around the lake limit potential expansion to storage for a one-year rain event, which the 60 hp pump was already handling.
So we shifted our attention to the pumps that had been installed more than five decades ago. Parts are no longer available for either pump and must be machined and fabricated when maintenance is necessary. One manufacturer’s no longer in business.
After analyzing the pump pit, we recommended replacing the pumps with two 150 hp pumps equipped with monitoring equipment to track pump current and operation hours.
The monitoring equipment consists of level transducer pump control and float switches in the event of a transducer failure. The new pumps will also be connected to the existing standby generator for backup power. Variable-speed motors will extend lifespan by enabling the pumps to be used alternately and operate at optimum pumping rates.
The two new pumps increase the capacity of the pump station and provide redundancy. The size of the pumps is based on the available electrical capacity. An electrical evaluation showed that the largest motor that could be used with two pumps running was 150 hp. Even with that limitation, one pump running matches the current 31,000 gpm capacity of the pump station. With two pumps running, projected flow rate is 58,000 gpm.
Our estimated cost to replace the old pumps was $780,000. The next step, as always, was to fund the project.
Project (Almost) Pays for Itself
After Hurricane Sandy in 2012, money became available through the Federal Emergency Management Agency’s (FEMA) Hazard Mitigation Grant Program (HMGP). The division asked us to help apply to the New Jersey Office of Emergency Management.
First, we created maps showing the number of residences, commercial/retail properties, schools, and public buildings affected by 50-, 100-, 200-, and 500-year storms. Then, we ran FEMA benefit-cost analyses for each scenario should both pumps fail.
Our damage estimates ranged from $65 million to $81 million. More than 1,000 homes would benefit from the pump upgrades.
It didn’t take long for the state’s Office of Emergency Management to make a decision. The division was awarded a federal government share totaling $166,039, which still left a substantial balance for the city to bridge. Once again the division enlisted our help, this time with applying for a low-interest loan through the New Jersey Environmental Infrastructure Financing Program (NJEIFP) administered by the New Jersey Department of Environmental Protection.
The project is currently in design. The HMGP agreement and NJEIFP loan require improvements to comply with 500-year flood standards, which wasn’t a requirement for our initial cost estimate. Electrical service must be run from the treatment plant’s power distribution center, which was built in the 1990s to meet 100-year flood requirements. That building must be floodproofed to the higher elevation and will be fitted with removable flood barriers at the entry doors and a mechanical ventilation vent. As a result, project costs could increase 10%.
The project is expected to go out for public bid and be constructed and fully operational by the end of 2017.