The celebrated Alley Theatre, located in downtown Houston, is a 61,000-square foot structure that opened in 1968 and is home to a cutting-edge artistic production company. Since the company’s founding in 1949, it has grown into one of the most prestigious non-profit theaters in the United States and serves as a cornerstone of the Houston arts scene.
During the mid-2010s, the Alley was completely renovated. However, disaster struck in 2017 when Hurricane Harvey dumped the greatest rainfall event in recorded U.S. history on the Greater Houston area. The storm inundated the theater with 17 feet of floodwater. The floodwaters settled in the theater’s stage area as well as the basement level, ruining nearly 100,000 prop pieces—many of which dated back to the company’s founding—causing nearly $18 million in damages. Furthermore, the theater’s electrical room, which sources and controls power for the entire building, was completely destroyed.
“At the time of Hurricane Harvey, the theater was protected against water infiltration pathways that had devastated the basement with 14 feet of water during Tropical Storm Allison in 2001,” says Benjamin Dow, project engineer and senior associate in Walter P Moore’s Diagnostics Group. “The flood protection system mainly secured the connection tunnels to a nearby underground parking structure.”
However when the theater’s staff realized this flood protection system had not been breached, they could not determine how 17 feet of water from Hurricane Harvey had filled the basement. As a result, Walter P Moore was asked by the theater to deploy an emergency assessment team to identify the flood vulnerabilities within the theater.
The assessment revealed the failures that led to the basement flooding as well as other flood vulnerabilities that were discovered did not contribute to damage related to Hurricane Harvey. It was determined that up to six feet of floodwater entered the theater through the pedestrian doors and emergency stairwells at the ground level. However, the largest contributing factor to the basement flooding from Hurricane Harvey was due to an existing electrical vault, which shares a portion of wall that separates the vault from the theater’s electrical room and prop/set storage area. The electrical vault had several vents that opened directly to the sidewalk at the ground level above.
When Harvey spilled massive amounts of rain onto downtown Houston, the streets started to back up with water and any open drain was completely inundated. As the electrical vault filled with water, the wall separating Alley’s basement buckled under rain load, freeing the floodwater to rush in. This led to the theater quickly flooding to a depth of 17 feet.
“Essentially, the basement level of our building that includes a 300-seat theatre, dressing rooms, laundry, storage, and electrical was inundated with water,” says Brandon Kahn, general manager of the Alley Theatre. “There was approximately $15 million worth of damage caused by the flooding. The biggest deficiency was the utility access holes in the driveway at the front of our building and the CenterPoint hatch. We did not have any protection against water filling in the CenterPoint vault.”
The assessment was important for the theater staff to understand the flood-related deficiencies and how they could be prevented. The assessment would eventually grow to include designs and installation of several additional layers of floodproofing that now protects the structure for a 500-year flood plain, plus two feet.
Flood Protection System
The flood mitigation project was challenging because of the building’s constraints—both on the interior and exterior. The latter being the location of the theater in Houston’s densely packed downtown area. Relying on creativity and technical skill, Walter P Moore’s engineers developed multiple flood protection solutions to protect the theater. These solutions did not compromise the building’s architectural significance, interior floor plan and storage capacity, or its structural relationship with adjacent towers and parking garages.
“To meet the client’s vision for the flood protection system, the existing structure was retrofitted with a new flood protection scheme,” Dow says. “Notably, creative uses for existing technologies—for example, employing fiber-reinforced polymer (FRP) strengthening to resist potential floodwaters in lieu of constructing new reinforced concrete walls in the basement’s electrical room and prop storage areas—were installed.”
FRP strengthening did not impact the building’s architecture or useable area—layout and square footage—which could not be structurally altered.
Additionally, the plain glass panels in the lobby atrium were replaced with flood-grade alternatives. These flood protection innovations were implemented to achieve the goal of “barely-there” flood barriers that will protect the building well beyond the devasting power and pathways of future hurricanes.
"We were able to hide everything so most patrons would not even notice there was a flood protection system,” says Jared Wood, partner, Studio RED Architects. “We changed out the glass, which did not change the look, to new glass that could handle water loads, we hid gates in the sidewalk, and built walk off matts into the surface to hide them. We also changed the regular people doors to flood doors. Where FRP had to be added to strengthen walls we found ways to hide it behind finishes.”
Furthermore, the team reviewed other technologies that could also be retrofit into the building’s makeup. They identified several different systems in addition to those previously mentioned that could be employed at various places within the theater. These included:
- Flood doors that look like ordinary doors at the emergency stairwells and exits
- Steel panel flood gates at the stage door, loading docks, and to the tunnelway at both ends of the property
- Flip-up flood gates at the glass lobby entrance that look like floor plates
- A tracked, vertical lift door at the loading dock
- An awning-like flood door between the basement electrical room and the electrical vault that allowed for emergency egress from the electrical vault during normal operating conditions
- A redesigned, subgrade venting system with flood louvers for the electrical vault
- A new steel support structure along the reconstructed basement electrical vault wall that failed during Hurricane Harvey
“All of the solutions that were being made had to be custom made for the Alley,” Kahn says. “We were also on an accelerated timeline because it was the beginning of COVID-19, and we didn’t know how long we would not be doing shows, so we were working to get the construction done as quickly as possible.”
In concert with Studio RED, the Walter P Moore team led the design phase and construction administration for all flood protection enhancements.
“Walter P Moore knew aesthetics and ease of operation were very important to Studio RED and the owner,” Wood says. “We basically didn’t want to change the look of anything, so we had to spend a lot of time together figuring out how to accomplish that.”
W.S. Bellows Construction served as the general contractor on the project installing the flood protection system.
“We installed flood barriers at multiple locations both underground in the Alley’s tunnel system and at street level,” says Johanna McCoy, senior project manager at W.S. Bellows Construction. “Any retrofit in a building like the Alley Theatre is challenging. The majority of the doors we worked on were in tight, enclosed spaces.”
Not only was W.S. Bellows Construction trying to do things like chip concrete safely in these areas to properly install the flood protection system, but they were also dealing with pandemic-related restrictions and the challenges of having workers close together in a safe manner.
“In one sense, COVID was helpful because the Alley was not holding shows and many downtown workers who utilized the tunnels were now working from home, which allowed us to do the installations more expeditiously in some areas that we originally expected to be constrained by available time openings,” McCoy says.
Upon completion of the project in January 2021, an owner’s operating manual was created. The manual outlines flood protection locations, usage, maintenance and manufacturer information to ensure the theater’s current and future maintenance staff understood how to protect the Alley Theatre safely and successfully from flooding that may occur in the future.
Additionally, the flood protection system provides a sense of comfort and assurance to the Alley Theatre’s owners in case of the next major flood.
“The flood protection system definitely gives us a great piece of mind,” Kahn says. “We have also toured around many insurance companies that were blown away with the level of detail and thought that went behind the solutions. We are so grateful for the work Walter P Moore did to make the building feel secure should there be another flood or weather-related event.”
Ray Drexler, PE is a principal and senior project manager in Walter P Moore’s Diagnostics Group. He can be reached at [email protected].
