Rooftop rainwater collection system planned for community garden

For millennia, access to water has meant life for human societies. As urban agriculture takes root in Milwaukee, access to water is no less crucial.

Last year, community gardeners were dealt a stinging challenge when the city of Milwaukee announced it would restrict community access to fire hydrants in the coming years. Permitted spigots attached to hydrants have provided nearby water access for gardens across the city, including Bay View’s Hide House Community Gardens at Deer and Greeley streets.

To wean themselves from hydrants, garden organizers, supported by the Victory Garden Initiative and the Bay View Neighborhood Association, brainstormed a creative solution to meet the water needs for some 115 raised garden plots. They partnered with UW-Milwaukee’s Engineers Without Borders—seven undergraduates who have implemented water systems in Guatemala—who designed a rooftop system to collect water from two raised roof sections of the Hide House building across the street, diverting it into a 250-gallon plastic cistern on the ground. Individual gardeners can tap the cistern as needed.

With the blessing of the Hide House property owners, two 55-gallon rain barrels will be attached to existing gutters. Ten-foot sections of 2.5-inch PVC tubing will conduct rainwater from the barrels to the edge of the building and over the façade down into the cistern.

Engineers without Borders predicts collecting almost 7,000 gallons of water from this 445-square-foot rooftop area during the growing season, based on averaging five years of rainfall data provided by the Metropolitan Milwaukee Sewerage District.

Their plans also called for a similar system to collect rainwater from the existing gutters of the residential duplex immediately north of the gardens, but liability and contract concerns emerged in April, nixing that option. The duplex roof could have contributed another almost 15,000 gallons of water over the course of the growing season, and organizers were optimistic both rooftop sources might make the gardens completely independent of the municipal water supply.

Instead, freestanding rainwater collection structures placed on site will replace the duplex option.

“These structures are easily duplicable and will be cost-effective for any garden to mimic. The only downside is we are not sure if it will meet all of our water demand,” said organizer Melissa Tashjian, who said organizers will still apply for hydrant permit this year.

Organizers estimated using 1,010 gallons of water per week last year. So the other half of the sustainable irrigation plan is to cut that demand in half using clay pot—or olla—irrigation, Tashjian said, a horticultural method that is at least 2,000 years old.

Instead of watering the surface of the soil, gardeners water clay pots embedded in their plots and water “sweats” out underground through the porous clay. Less water is lost to evaporation or sapped up by weeds, and fruit and vegetable plant roots absorb the water over time. To further reduce evaporation, a second pot is secured on top of first so that the system is isolated. Six olla units per four-by-eight-foot plot are anticipated to adequately irrigate each plot.

Tashjian estimated a cost of $1,500 for the clay pots and $1,600 for materials for both collection systems. Pentair is donating cisterns. Assembly should begin in May with completion hoped for by July 1.

In addition, the Hide House roof will host a colony of honeybees donated by Tom Brandstetter and supplied by Charlie Koenen and Jesse Spanaus, who in April moved their Beepods business into the Sweet Water Organics complex at 2151 S. Robinson Ave. The bees will help pollinate gardens and flowering plants within a nine-mile radius.

Charlie Koenen and Jesse Spanaus’ Beepods, a novel system based on ancient technology and designed to be less stressful for both bees and humans, will be featured next issue.

5/5/2011 –  CLARIFICATION: In the print version Jesse Spanaus was unintentionally omitted from mention with regard to Beepods. Spanaus and Koenen are partners in the new enterprise.

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