Rainwater harvesting system greets James R. Herman cruise terminal
Set sail from Pier 27.
Alizabeth Cherian had quite the compressed schedule before the ships came into port. And not just any ships, these were yachts manned by the best crews in the world.
Cherian, P.E., LEED AP BD+C, with the San Francisco Department of Public Works, had less than one year to see her plumbing design and rainwater harvesting system be constructed at the city’s Pier 27 — part of the historic San Francisco waterfront. The first phase of Cherian’s design had to be completed in time for the launch of the 2013 America’s Cup held at San Francisco Bay last September.
“Everyone on the team pulled together with the very tight schedule and coordination,” Cherian says.
As the defending America’s Cup champion, the United States (which won the 2010 title) got to host the 2013 event. Oracle Team USA, the nation’s yacht-racing syndicate said that San Francisco was the only venue to be considered to host in part because the consistent wind and weather patterns wouldn’t hurt set television schedules. The city was awarded the event on Dec. 31, 2010.
San Francisco began commissioning projects to revitalize the waterfront and replace the old warehouse with a new seismically designed facility. Pier 27 conjoins with Pier 29 to form a 10-acre triangular area. The sheet-metal structures were moved to create viewing space for the 17-race event where the U.S. repeated as champions.
A steady tail wind
Getting the core and shell of Pier 27 ready for the America’s Cup was just the beginning. The second phase was the construction and tenant improvement of the James R. Herman cruise terminal, an 88,000-sq.-ft. facility that handles between 40 to 80 cruise ships in the port per year. Ships up to 1,200 ft. long can dock in port. The Herman terminal can easily accommodate 2,600 cruise travelers without an issue and up to 4,000 if needed. The building also is used for events when ships aren’t in port.
As with any new commercial construction in San Francisco, the building had to be designed at a minimum to the United States Green Building Council’s LEED Gold standards.
One major element in Cherian’s design that accumulated LEED points was a rainwater harvesting system. It was necessary to install a harvesting system after the Rainwater Capture Act of 2012 was signed into law by California Gov. Jerry Brown. On top of that, the California Building Standards Commission recently approved Chapter 17 of the California Plumbing Code — a chapter dedicated to rainwater harvesting in the state.
Overall the Herman terminal system — a high-profile application utilizing rainwater harvesting in San Francisco — is a five-tank, 41,000-gal. operation split into two zones. The first zone consists of three, 12,800-gal. tanks that handle the Herman cruise terminal’s nonpotable water needs. It also dramatically lowers the amount of water runoff from Pier 27 that spills into the San Francisco Bay.
To begin the design of the harvesting system, which is expected to save thousands of gallons of fresh water per year, Cherian took a look at the architectural plans and started from the top. She looked at the layout of the roof — that exceeds an acre in size — and began carving out pieces like a pie.
“We divided it into different sections that would make the most sense,” Cherian says.
Each area has different pipe sizes based on the amount of water that will accumulate and how much flow there is to the tanks. In actuality there are two different drain systems working on the roof.
First, there is a conventional system for roof areas smaller than 5,000 sq. ft., wherein the flow rate is determined by the depth of water in the gutter or on the roof. Secondly, there is a siphonic system that utilizes smaller pipe sizes because it is able to achieve higher flow rates by making full use of the head space available between the roof and the discharge point at ground level. Pipe sizes range from 3 in. to 12 in.
“The reason why we used the siphonic system for the majority of the roof area is because of the layout and dimensions of the building,” Cherian states. “If we only used a conventional system, the pipe sizes would be larger and the slope would require too much space.
“We had two headers coming from the opposite ends of the building. One came from the north, the other from the south side. They come together near the middle and go off to the primary filtration system.”
The building utilized Watts backflow preventers which are located on the southwest side of the terminal. The main aspect of the backflow preventers is to protect the city’s potable water supply, but at Pier 27 Cherian says they can be used in the rainwater harvesting unit.
“Every building’s water supply system (potable) is to be provided with backflow preventers to prevent backflow into the city’s potable water system,” Cherian says. “As the last resort, when the rainwater in the large set of tanks reaches below set point and there is no rain, it is set up to draw from the building’s main potable water system.”
Cherian worked alongside Oakland, Calif.-based plumbing contractor Broadway Mechanical. Michael Hohl, the project manager on the Pier 27 job, says that installing a harvesting system such as the one at the Herman terminal allows Port Authority a chance to lead by example.
“Technically, this qualifies the water as having potable quality, but that’s not the intent at all,” he says. “Local code and water board officials and other authorities can all take divergent views about water quality and what constitutes water that is of sufficient quality to drink.”
The pier’s structure also provided a difficult challenge for Cherian’s design. “Since it is being built on an existing pier we had to be very careful about how much weight we could load onto the pier,” she says. “That was a huge consideration. The structural engineer calculated that we could place a load of 400 lb. per sq.-ft.”
Because of the rigorous California and San Francisco plumbing codes, and the region’s desire to lead the nation in being sustainable, a water filtration system had to be designed and installed.
Water from the terminal’s roof is sent to a pre-filtration system where the larger debris is removed before it is collected into a series of above-grade storage tanks.
When there is a call for water, the fluid is pumped through the water treatment system that uses a powerful ozone recirculation system to remove any contaminants. It also disinfects and deodorizes the rainwater before entering the lines devoted to the terminal’s flush fixtures. Ozone kills microbes, enzymes and bacteria so there will be no buildup of organic growth or odor-forming bacteria.
TOTO toilets and urinals, and a JR Smith siphonic roof drain were some of the products specified in the design. On the conventional system, Cherian specified in-line, downspout filters that become part of the pipe.
“We could not just collect rain and let it spill into the bay. We were required to provide a filtration system,” Cherian explains in reference to the Regional Water Quality Control Board requirement. The water becomes non-soluble solids-free after going through the filtration process.
Tying it all together
The second zone features two 1,300-gal. tanks for irrigating a small portion of the pier’s sprawling landscaped area. The latter is designed to have the ability to draw water from the large set of tanks when it reaches below set-point level.
Cherian explains there is an engineer’s rule of thumb where because the area has such a long dry season (May through October) that there isn’t enough water to store to meet demand. According to http://www.weather.com data, there only is on average 2.25 in. of rainfall during that period. From November through April, San Francisco, on average, receives nearly 22 in. of rain for the harvesting system to use.
The irrigation tanks are located on the south side of the terminal. The first zone also handles the fixture flushing demands. Cherian said the LEED consultant told her the Herman terminal would need 15,000 gal. per month dedicated to flushing needs.
“That information was very initial at the beginning of the design process,” she says. “Later on in the design we decided to tie the larger tanks to the smaller collection tanks instead of just wasting the captured rainwater and having it overflow into the bay when the larger tanks reached their capacity.”
Before the Pier 27 cruise terminal project came about, Cherian spent time designing a rainwater harvesting system for another facility.
But today having her work on display and having designed an integral aspect of the James R. Herman cruise terminal is something Cherian looks at with fondness.
“When you think about it, when is the next time the city will build a cruise terminal?” Cherian says. “Being a part of this project was a once-in-a-lifetime opportunity.”