Saturday, March 13, 2010

Sakai and Oishi Nurseries - Part 3

This is the third post in a series; you should read the first post before this chapter. Since 2004 several studies have been completed for the Sakai and Oishi Nurseries. They have focused primarily on the history of the site, the significance of the cut-flower industry in the Bay Area, and the buildings and structures on the two sites. What has not been studied in detail are the various systems that were needed to operate the nurseries – these will be illuminated as part of the HALS work that PGAdesign and Denise Bradley are currently completing.

In part two, I wrote about the pedestrian circulation systems and how they differed on the two sites. I’ve mentioned the other systems. Part 3 is about those systems.

Water Sources and Distribution
Both nurseries have several wells on site, which were the primary source of water. In later years Oishi nursery had a connection to the city main. Pumps drew water up into wooden storage tanks – both on grade and elevated. Water was drawn out of the tanks to supply water lines for irrigating or was routed to the boiler room where it was heated to produce steam.

Water lines fed a manifold of galvanized pipe at the center of each greenhouse that branched at each flower bed and was connected to a plastic pipe and drip or soaker type lines spaced about 8 inches apart in each raised planter. These were used to water the flowers, initially manually and later the operation was automated

Fertilizer was mixed in large steel or plastic tanks and was injected into the water lines when needed. Manually controlled valves would release or shut off the fertilized water as needed.
Water Collection
Irrigation water was collected and channeled into concrete swales or curbed trenches that run outside and parallel to each greenhouse. These trenches, typically 19” wide, are found throughout both nurseries. There are small, wooden bridges where pathways cross these trenches. The water collection system of swales and curbed trenches includes collection pits of varying sizes, typically 36” by 24” and 30” deep. Some of these pits still have pipes running into or over them. These pits collected water or silt.

Steam Distribution
Steam was used to heat the greenhouses and to provide optimal humidity for the flowers.
Steam from the boiler room was pumped into insulated pipes that was routed to each greenhouse. Many of these pipes run overhead, about 10 feet in the air, and were supported on 4 x 4 posts spaced about 15 feet apart. The steam was released inside each greenhouse and the condensate was collected and returned to the boiler for re-use in smaller diameter pipes, also insulated.
Pesticide System
A separate and parallel set of small diameter pipes was used to distribute water that included pesticides or herbicides. These pipes extended to the center of each greenhouse, and from there one of the nursery workers would attach a special hose to a valve and apply the pesticides with a spray nozzle.

Air Circulation and Greenhouse Cooling System
Maintaining optimal temperatures and humidity inside the greenhouses was critical. The components of this system include roof and side windows, large diameter fans, and swamp coolers. Each greenhouse has both roof and side windows with manually operated wheels and pulleys used to open or close the windows. In later years some of these were automated.

Large fans, housed in 5’ by 5’ square box structures were built into the sides or ends of the greenhouses. These would draw air into and out of the greenhouse. To cool the greenhouses large mats were attached to the end or sides of the greenhouse. An overhead PVC pipe with 1/8” diameter holes drilled every 5” was mounted above the mats. Water fed into these pipes then dripped onto the mats to wet them. As the fans drew in air through the dampened mats it cooled the air inside the greenhouse.

In part one I mentioned that at one spot on the Oishi site we counted 9 parallel pipes. Tom Oishi, who met us on our first day on site, was able to identify what six were for: fresh irrigation water from the tanks, out-going steam, returning steam, pesticides, city water, and water that fed the pipe for wetting the mats. I’ll let you know if we figure out what the last 3 were for.
Left: Cooling mats at Oishi Nursery
Right: Raised beds with soaker type irrigation at Sakai Nursery

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