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Stormwater Filtration System Highlights 'Silver' Santa Monica Library Project
November 01, 2005

By Staff
Appeared in California Construction

A sophisticated storm water collection that will divert pollutants before they can head into Santa Monica Bay is a key sustainable feature in the $40-million Santa Monica Library scheduled for completion last month, according to the principal-in-charge of the project's MEP engineering design firm.

The city of Santa Monica has an aggressive storm water policy that requires building owners to retain, filter and release the first .75 in. of rain from each storm.

"During schematic design, we went through an exercise where we looked at the annual amount of rainfall throughout the year and decided to substantially build upon that .75-in.-capture-and-filter policy," said Rob Bolin of the Los Angeles office of Syska Hennessy. "We ended up with a system that can collect, filter and hold up to 4 in. of rain from any single storm on the entire site."

In addition to serving as principal-in-charge, Bolin was the project manager and lead mechanical engineer for the project, which is seeking silver certification from the Unites States Green Building Council's LEED® green building rating system.

"We worked with the landscape architect to ascertain what its irrigation demand would be throughout the year, and they selected their plant palette based on the irrigation needs that would match the amount of water that we were collecting throughout the year," he added. "So it was a very well integrated system."

Bolin said many cities in Southern California in California require filtering the first .25 in. of storm water, but Santa Monica upped its requirement to .75 in. since, as a coastal city, it depends on clean beaches for a healthy tourism trade. Santa Monica averages about 15 in. of rainfall a year, but the amount comes in a three- to four-month period during the winter.

Bolin said the first .75 in. of rain equals about 50,000 gallons.

The collection system consists of a series of filters in the downspouts and drains that collect all of the hydrocarbon material and various other materials before it enters into an underground cistern measuring 60 ft. by 80 ft. by 10 ft. The surface parking lot has a multi-chamber water clarifier that removes sand, oil and grease.

Bolin said that there will be a water-testing protocol on a weekly basis that will take water samples to examine the quality --not just from a discharge point of view, but also for irrigation purposes because different plants require different pH levels.

"Adjustments can be made to the pH of the water," he said.

Santa Monica-based Morley Builders, the project's general contractor, began the construction phase of the 110,000-sq.-ft. library two years ago. The new library, on Santa Monica Boulevard, replaces the existing one on Fifth Street.

The new library is scheduled to open in January.