Rising Waters, Brooklyn Battles: Fixing Floods in the Heart of NYC

Rainwater is becoming more intense and groundwater tables are rising throughout New York City. 10 Plaza Street East, a Brooklyn co-op, felt this full force during 2021's Hurricane Ida when its entire subcellar floor flooded, including the storage room, the laundry room and the bike room. It happened again in 2022, and the board took matters in hand by bringing in Cowley Engineering. Habitat’s Emily Myers interviews Michael Monteiro, senior project manager at the engineering firm to find out why the subcellar continued to flood and what the fix was.

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Transcript

Emily Myers: Welcome to Problem Solved, a conversation about challenges facing New York Co-op and condo board directors. I'm Emily Myers with Habitat Magazine and I'm joined by Michael Monteiro, senior project engineer at Cowley Engineering. Flooding is a major problem for many New York City buildings and putting off the repairs can be dangerous.

Water damage can cause structural problems, and even building collapse. And as storm intensity increases, it's even more important to identify and address leaks quickly. Michael, you are working with a co-op at 10 Plaza Street East in Brooklyn to address years of leaks. Can you explain what's happened?

Michael Monteiro: Certainly. Thank you for having me, Emily. So at 10 Plaza Street East, this all started back in September 1st, 2021 when Hurricane Ida hit New York, and as per the building superintendent who's been there for 15 years, this was the first flooding event that occurred at the sub cellar level of the building. The entire sub cellar flooded, which includes the storage room, the laundry room, the bike room. It even led out into the parking garage. All along Flatbush Avenue, all the spaces there were affected by this rain event. 

Emily Myers: Do you have any idea why the water started leaking into the sub cellar at that moment? Ida was of course extremely intense rain, but was there something else that had happened?

Michael Monteiro: So there are several factors at play here. 10 Plaza Street East is located right at the corner of Grand Army Plaza, so you have the subway station there. So due to years of vibration from the subway station, from vehicular traffic, cracks have developed in the foundation wall. Now this is normal .

The second factor is the rise of the groundwater table. Due to the intensity and volume increases after major rain events, the groundwater gets saturated, causing the groundwater table to rise and once the water table rises surrounding the foundation walls, the water's infiltrating through these cracks that have developed over the years.

So it's a combination of those factors.

Emily Myers: Okay. So the major flooding happened three years ago in 2021. At what point were you brought in to deal with the problem? 

Michael Monteiro: During the local law repair cycle. The building is a Cycle A Local Law 11 building. We were brought in February of 2021 to do an initial investigation of the exterior envelope problems. Then we left off. We didn't hear back until we were ready to get the project started, which was in March of 2022.

At this point is when during our initial kickoff meeting, the building superintendent notified myself of, Hey, we had this flood after ida, and he showed me videos, all of that. So I wasn't called in immediately after Ida to investigate. So once we were on in 2022, during the repair project, on September 13th, another major rain event happened where the same situation occurred.

The entire sub cellar was flooded. At this point, the board and the property manager requested for Cowley Engineering to investigate what was the issue and how to solve it. So that's where we were initially engaged to investigate the subcellar flooding. 

Emily Myers: And so what were the solutions here? 

Michael Monteiro: So the first step was to find a way to essentially pump out the groundwater. Find a way to reduce the groundwater table from rising.

 Our first approach was to install a footing drain along the laundry room. That's where the source of the flooding always commences. So we chopped out two feet away from the footing. And we installed a footing drain, which would collect the groundwater as it rises, and then that would discharge into an existing sump pit with two existing sump pumps in the laundry room.

That was step one. 

Emily Myers: Was there anything in place at the building already to alleviate flood risk? 

Michael Monteiro: No, not at all. The sump pit that was currently in place was only collecting discharge from the laundry machines and from the drainage in the parking garage, but there was nothing to collect groundwater.

Emily Myers: Okay, so you put in the footing drain. Were there other solutions needed? 

Michael Monteiro: Again, this was the first step approach. Another solution was to drill, weep holes around the sump pit to help create capillary action and collect additional groundwater. But because we were in the middle of a $1 million plus facade project, the board wanted to try this as a phase one approach, which I was, it was my plan as well.

We did this repair work, this phase one project. The price value for this was $45,500. This repair was done and no leaks, no infiltration, nothing until September, again, third September in a row, September 29th, which was a major rain event. The flooding occurred again. Now what happened this instance is the footing drain was working, per the building superintendent, but sand was coming in through the cracks in the foundation wall.

The sand got into the footing drain and it clogged it. So the water was unable to be discharged into the sump pit so another flooding of the subcellar occurred. At this point, we put together a more comprehensive scope of work, which included the full removal of all plaster along the foundation walls on Flatbush Avenue into four different rooms, and on Plaza Street East in the bike room, where due to the hydrostatic pressure buildup underneath the slab in a bike room, the slab broke. The slab was original to the structure. There was no reinforcement in the slab. It was a three inch slab. That created a very hazardous condition. So we had to immediately cordon off the area, cordon off the space. Residents were not allowed to go into the bike room and the board had to act immediately. 

Emily Myers: And had your footing drain work done anything to help or because of the sand coming in and blocking, was the flooding back to its Ida levels? 

Michael Monteiro: No, it was back to its Ida levels. It slowed down, and once the rainstorm commenced, the footing drain was working. But once the sand built up in it, then it was no longer working. 

Emily Myers: You came up with a new plan. What did that involve?

Michael Monteiro: Okay, so the new plan involved the exposure of all the foundation walls along Flatbush and the one space on Plaza Street East. We were going to repair all of the cracks that were visible along the foundation walls to essentially eliminate any paths for groundwater to get in through. So we did gel injections and we did concrete patching.

Once the foundation wall was sound and repairs were complete, we had the contractor apply a negative side waterproof coating that resists hydrostatic pressure called AQUAFIN-1K. This was done. In addition to that, were able to have the weep holes drilled in the sump pit in the laundry room to now collect all of that groundwater below grade.

And the sump pumps, which were originally one horsepower, there were two, they were replaced to five horsepower sump pumps to help account for the introduction of new discharge that the sump pit would be taking on. In addition to that, we replaced the bike room slab with the new slab with proper reinforcement, and that's the repair that's been done.

Emily Myers: Okay, so your initial cost was 45,000 for the footing drain. What was the cost of the total repair? 

Michael Monteiro: $200,000 all in. 

Emily Myers: And has it been put to the test yet? 

Michael Monteiro: They're actually finishing up the project now, so let's see. September seems to be the date where all this magic happens, so we'll see.

Emily Myers: Okay. And just broadly if flooding like this is left unresolved, obviously the board it sounded like delayed their work somewhat, partly because they were doing other work. But if it is left unresolved, what's at stake for the building? 

Michael Monteiro: What happens when these conditions do go without being examined by a licensed professional engineer or design professional, the concrete will begin to spall due to rust that develops in the reinforcement.

Once rust begins to build up in the structural steel, it weakens the structural integrity of the building, which can lead to major problems. 

Emily Myers: This leak or this flooding didn't affect the parking garage at the building, if I understand correctly. 

Michael Monteiro: No, it did not. So immediately, once we were brought on and the superintendent notified us, I did an examination of the entire sub cellar and parking structure, which included hammer sounding of structural support columns and foundation walls.

Everything was structurally sound and stable. This allowed the board time to properly plan and budget to do this repair work. 

Emily Myers: So what lessons then can be learned from this experience? What steps can other co-op and condo boards take to prevent or address similar issues?

Michael Monteiro: Rainwater intensity is on the rise and groundwater tables rising throughout New York, so it's important for the building's resident manager or even residents who go to use the laundry room or making their way to their vehicles in the parking garage to pay attention and see for any signs of infiltration or leaks, and to bring it to their property manager's attention so that they can immediately contact the design professional to come out and investigate.

A lot of times sub cellars, basements, they're ignored. Nobody sees them. That's where the issue lies. So it's important to, if you see something, let your property manager know. 

Emily Myers: And when you say see something, it's leaks or, is it even cracks? 

Michael Monteiro: Excellent question. So not only if you see any signs of water filtration, but if you see any cracks on the foundation wall, anything that appears hazardous, it should be brought up to the property manager.

Emily Myers: That's great. Thank you so much. Michael Monteiro, senior project engineer at Cowley Engineering.