Spots of flood mitigation

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Spots of flood mitigation
City engineers are working on inlet expansion on East and West Del Ray Avenue through next week. (Photo/City of Alexandria)
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By Olivia Anderson | [email protected]

Following years of damaging summer storms that have resulted in dangerous and destructive flash flooding, Alexandria is undertaking flood mitigation efforts. There are several facets to the city’s attempt to prevent recurrences, one of which is a spot improvement flood mitigation project that involves expanding inlets in Del Ray.

The project underway on Del Ray Avenue consists of increasing the dimensions of the current inlets located on either side of Commonwealth Avenue. For West Del Ray, inlets will increase from a three-foot opening width to 12 feet on the north and 20 feet on the south. For East Del Ray, the inlets will increase from four feet to 16 feet. These inlets, which are the curb cuts that funnel water to underground pipes, serve a fairly large area and quickly fill up during heavy rainfall due to their smaller size.

Although the underground pipes have enough capacity for a standard design, the inlets that lead to those pipes are undersized. Therefore, the inlet expansion will provide a larger opening along the curb line for the water to enter and hopefully prevent flooding across Commonwealth Avenue during heavy rainfall.

An inlet on West Del Ray Avenue before the expansion. (Photo/City of Alexandria)

“There’s enough room for water in the pipes underground. It’s the opening in the curb, that inlet, that’s not big enough,” Amanda Dolasinski, communications specialist for the Department of Transportation and Environmental Services, explained. “So, the engineers are making that opening bigger, but the pipes themselves have enough room to hold that water underground.”

The city has been analyzing its storm sewer capacity over the past decade. A citywide examination, called the City of Alexandria Storm Sewer Capacity Analysis, was completed back in 2016. The report highlighted several vulnerable areas that didn’t meet the city’s standard for capacity.

Flooding in these areas, which had previously been sporadic, became much more frequent starting in 2019, and over the last couple of years the city has, using the 2016 analysis coupled with reports of flooding, nailed down certain areas that are priorities for mitigation efforts.

The citywide analysis revealed that most of the capacity issues originate at street level, according to Brian Rahal, a civil engineer with the city’s stormwater management division.

“So, with three pieces of information: the analysis study from 2016, reports of flooding and knowing that a severe pinch point of a lot of these locations is the actual input at the curb, we’ve decided to tackle these big flooding areas in sort of a two-pronged approach,” Rahal said.

The first approach includes the big capital project that will increase the capacity of the large storm sewers. The other is to determine opportunities for quick spot improvements that require significantly less time than the full capacity projects, which could take up to three years just to design.

The bigger storms that have occurred during the past few years – and are expected to continue due to climate change – require major upgrades to the storm sewer that Dolasinski said are currently in progress.

However, Rahal also noted that the spot improvements are incremental steps that will significantly decrease flooding when it comes to small to medium-sized storms.

“We kind of view these inlet expansion projects as some low-hanging fruit that we can get to really quickly and give us a quick win and really make a difference at the street level. It’s going to make a big improvement,” Rahal said.

Del Ray resident Katie Waynick is familiar with sewage flooding. Her home received major damage from two rainstorms in July 2019 and July 2020 – even after installing a backflow preventer – and she’s been urging the city to prioritize its flood mitigation efforts ever since.

An inlet on West Del Ray Avenue after the expansion. (Photo/City of Alexandria)

Waynick now monitors the @DrainALX Twitter account, which advocates for addressing and educating residents about major infrastructure issues. She said that although Alexandria’s flooding issues are nowhere near over, credit should be given to city officials for listening to residents and taking tangible steps to address the problem.

“Looking ahead, we still have a ways to go but it has been incredible to see how far we have come in just two years,” Waynick said. “Each of these projects represents a significant investment in our infrastructure that should begin to improve the quality of life for impacted residents – and that is exciting to see.”

According to Rahal, the city finished expanding the W. Del Ray Avenue inlets last week. Contractors are currently working on expanding inlets at E. Del Ray Avenue. Rahal said the process has been moving along smoothly and anticipates that the entire project will be completed by next week.

During the implementation, residents have been experiencing some blocked roads for certain periods throughout the day.

“To get a bunch of equipment out there, trucks and backhoes, it takes up some space so there is some traffic disruption throughout the day, but they clean up the site and make it available to traffic in the evening,” Rahal said.

Spot improvement projects are supported through the city’s Capital Improvement Program and Stormwater Utility Fee, the latter of which was doubled from an average fee of $140 to $280 in February 2021. According to the city, the fee increase, which varies based on each home’s size and structure, will add approximately $150 million to funding for capacity projects and flood mitigation during the next 10 years.

As part of the Flood Action Alexandria program, the spot improvement projects work to increase the functionality of the city’s sewer system, which includes hundreds of miles of underground pipes, inlets and manholes. The process includes four phases: investigation, planning, design and implementation.

Spot improvement projects are supported through the city’s Capital
Improvement Program and Stormwater Utility Fee. (Photo/City of Alexandria)

Improvements to Mount Vernon Avenue are next on the agenda. Inlets will also be replaced there to improve drainage and prevent the recurrent flooding in alleys that the area has experienced in recent years. Additionally, the city is looking at stabilizing degrading and eroding banks and protecting the sanitary sewer line at Oakland Terrace and Timber Branch banks.

Several potential spot improvement project areas are currently under investigation, such as Hume Avenue, South Jordan Street, East Monroe Avenue and Wayne Street, North Overlook, North Columbus Street, Carlisle Drive Alley and Walleston Court.

Rahal emphasized that although these smaller-scale projects will not immediately fix the longstanding flooding problems residents have been facing for years, they are a surefire way to address localized flooding issues while simultaneously chipping away at the bigger ones.

“We’re working hard every day, and our spot projects are all part of our bigger plan to mitigate flooding in the city. These are localized projects that we can do quickly, while we’re working on the large infrastructure projects,” Rahal said.

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