The Monterey Bay Aquarium behaves like an architectural appendage of the Pacific Ocean, drawing in and then relinquishing every drop of its 2 million–gallon capacity from the bay that pummels its structural foundation. The rapid exchange of seawater, at a rate of up to 2,000 gallons per minute, sustains impressive exhibits, such as a 28-foot-tall kelp forest ecosystem populated by the likes of leopard sharks, rockfish, and color-changing octopuses native to Monterey Bay, Calif. Open-air decks and a tide pool allow for sweeping views of the coastal landscape, the occasional harbor seal or humpback whale, and even the birth of a wild sea otter on the rockwork earlier this spring.
This physical connection to the sea helps the aquarium attract 2 million visitors per year. But it also represents its greatest vulnerability. “The sea has never been friendly to man,” Joseph Conrad wrote in his 1880 essay “Initiation,” while working as a sailor. Nor is the sea kind to buildings. Salt, if unchecked, could corrode the aquarium’s reinforced concrete structure and exhibit tanks, while the countless microscopic organisms inhabiting the water could clog its pipes and foul its reservoirs.
These challenges were not lost upon Chuck Davis, FAIA, founding principal of EHDD, the San Francisco–based firm that designed the aquarium back in the early 1980s. “We were talking about not only building over the water, but also running seawater all through the building,” he recalls. Though he had seen the deteriorating conditions of older, existing aquariums, he and his team embraced the target life span set forth by project benefactor David Packard and the David and Lucile Packard Foundation: 50 years.
Now 32 years old, the Monterey Bay Aquarium has won the AIA Twenty-Five Year Award, an affirmation of its lasting success. It is on track to reach the half-century mark handily, with help from several expansions, renovations, and systems upgrades along the way, mostly overseen by EHDD. The design highlights both regional ecology and the no-frills architecture of Monterey’s Cannery Row. It was “not conceived to be a look-at-me building,” Davis says, but rather “a building that would fit and support its context.”
A series of specialized construction techniques and building systems supports the aquarium’s close communion with the sea. These include a corrosion-resistant, reinforced-concrete structure; a sophisticated water-circulation, or “life-support,” system; and a heat-exchange system that leverages the abundance of seawater. All of this technology, much of it groundbreaking at the time, is a testament to the project’s strong and collaborative team of consultants, Davis says.
The first challenge was installing the concrete foundation in an intertidal zone. Structural engineer Hal Davis (Chuck’s older brother, who worked with San Francisco–based firm Rutherford + Chekene) says, “As soon as the tide went out, the contractor had to mobilize their equipment and personnel, pour the foundations, and then retreat before the tide came back in.”
During low tide, workers would place hollow precast box “coffers,” one for each pier, to provide watertight shafts in which to pour a 28-foot-square column grid. They sealed each box to the rocky, uneven sea floor with a concrete slurry, excavated the inside of each box with jackhammers, and then placed rebar and concrete inside the shafts. “We were putting in reinforcing and pouring concrete at 2 and 3 o’clock in the morning,” Hal Davis says. Corrosion-resistant, fiber-reinforced polymer forms were used for the columns above the sea floor and left permanently in place to help protect the concrete. Precast girders and tees form the main deck (the aquarium’s first floor) over the water. The second floor has a cast-in-place waffle slab.
The next challenge: fighting corrosion. Anything made of concrete—columns, decks, walls, exhibit tanks—could fail if salt reached its steel reinforcing. Hal Davis’ strategy was straightforward: protect the rebar, use a low-porosity concrete, and “build it extremely well.” EHDD also specified epoxy-coated steel rebar, a product that was then just a decade or so old. The impermeable green polymer sheath shields the ferrous metal from marine salts, just as it shields the rebar in highways from ice-melting salts. Construction workers also used PVC-coated tie wire, clipping and hammering the pigtails, or ends, to maintain the concrete’s consistency. Furthermore, EHDD specified a more impermeable concrete mix, substituting flyash for 20 percent of the cement, and increased the clearance between the encapsulated rebar and the concrete surface by a few extra inches.
The contractor Rudolph and Sletten, based in Redwood City, Calif., water-tested all seven of the aquarium’s original concrete tanks and two reservoirs using more than half a million gallons of fresh water to avoid the risk of saltwater infiltration through potential defects. Once the identified defects were remedied, the tanks were allowed to cure over several months to permit moisture vapor emission, and then were coated with Vandex, an impermeable mortar, for an extra layer of protection.
Post-occupancy testing has confirmed the effectiveness of the team’s multipronged efforts, says EHDD director of quality control and construction administration John Christiansen. When concrete core samples taken from the 55,000-gallon sea otter tank were tested in the 1990s, “We found that the amount of chlorides in the concrete at the depth of the rebar would not reach a high enough level for about 85 years to even start corrosion of uncoated reinforcing,” he says. Subsequent cores from the newer portion of the aquarium (also by EHDD) taken in 2010 suggest that it may take 500 years for salt to reach the depth of the rebar. At that point, finally, the epoxy rebar coating would serve as a last line of defense.
The building’s plumbing system is as important as its structure. Monterey Bay was not the first aquarium to draw seawater from its doorstep, but even now, it remains among the largest and most technically advanced. Two 14-inch-diameter intake pipes extend approximately 980 feet from the bay to the pump house, at a depth of 55 feet. The pipes alternate in service every few months: one draws water while the other is left stagnant to reduce the oxygen and kill off the barnacles that have attached themselves to the inside of the pipe. Most intake water is then clarified by filtering it through a bed of sand, which also contains bacteria that convert ammonia (NH3) from animal excretion, a toxin, into nitrate (NO3), which is less toxic. However, the pumps driving water through the filters can inadvertently cause the super-saturation of nitrogen levels in the water, with the disastrous and deadly effect of giving animals the bends. So the next step is critical: sending the water through aeration, or de-embolization, towers to re-balance its dissolved gases.
Not all of the aquarium’s water is treated, however, and this is part of what makes Monterey Bay special. A portion of the intake seawater is pulled, unfiltered, into a secondary system. This nutrient-rich seawater provides food, such as plankton, for filter-feeding organisms like sponges, and introduces biodiversity to the exhibits in the form of algae spores and invertebrate larvae. The aquarium uses more unfiltered water at night, when visual clarity is not necessary.
The seawater makes one final stop before the aquarium expels it back into the tide pool: the heat exchangers. Conceived by the mechanical engineers at the Syska Hennessy Group, the heat-recovery system allows the human- and marine-climate environments to operate more efficiently by addressing their complementary conditioning needs. For example, the Open Sea exhibit, stocked with tuna and sharks and sea turtles, usually requires heating, while the human-occupied rooms and corridors, warmed by lamps, sunlight, and bodies, often require cooling.
Water, Christiansen notes, is more efficient than air at transferring thermal energy, and the aquarium has no shortage of it. Outgoing seawater from the aquarium is pumped through heat exchangers in the basement. These add or subtract energy from the water in the building’s four chillers—three 150-ton rotary electric models by Multistack (which replaced three older units in 2005) and a 200-ton Tecogen Tecochill natural gas engine-driven model from 1996. “Like a geothermal heat pump system, the system at Monterey uses both the hot and cold water from the chillers to heat and cool the building, and the seawater is basically how everything is balanced out,” Christiansen says.
The heat exchange system offers a pleasing metaphor of interspecies harmony as well as energy savings. “To be able to have the human and animal support systems work together in a symbiotic relationship is a big thing for aquariums because, inherently, they’re not energy-efficient buildings,” says EHDD principal Marc L’Italien, who helped design Monterey Bay’s 1996 addition. “The innovative nature of bringing these systems together to consume less energy was really forward-thinking in its day, and it’s still forward-thinking today.”
Project: Monterey Bay Aquarium, Monterey, Calif.
Architect: EHDD, San Francisco
Acoustic Consultant: Charles M. Salter Associates
Construction Manager: Rudolph and Sletten
Civil/Geotechnical/Structural/Life Support Systems Engineer: Rutherford + Chekene
M/E/P Engineer: Syska Hennessy Group
Exhibit Design: MBA Exhibit Design
Project Management: Rhodes/Dahl
Size: 205,669 square feet (original project)
Cost: $55 million (1984 dollars)