Rainwater Harvesting A Local Water Management Strategy

Water Conservation ShowcaseSarah MinickMarch 2009

OUTLINE

• Stormwater in San Francisco

• Low Impact Design – keeping water on site

• Stormwater Design Guidelines

• Rainwater Harvesting

• Project examples

SAN FRANCISCO WATERSHEDS

San Francisco Context –

Urban Hydrology w/ lid

LOW IMPACT DESIGN (LID)

Intensive

eco-roof

Rain

screen

Permeable

paving

Rainwater

harvesting

In-street

planter

LESS WATER IN, LESS WATER OUT-

Using local resources in our San Francisco watersheds.

• Policies & Guidelines– Stormwater Design Guidelines, Better

Streets Plan, Rainwater Harvesting MOU– Green Building Ordinance– Sewer System Master Plan– NPDES Permit

• Community Involvement– Urban watershed planning charrette– Small grants

• Demonstration Projects– Multi-purpose projects

• Private Development– Remove barriers to innovation– Regulate and provide incentives

MECHANISMS FOR CHANGE

LEED Credits SS6.1 Stormwater quantity control SS6.2 Stormwater quality control SS5.1 Protect or restore habitat SS5.2 Maximize open space SS7.1 Urban heat island effect - non-roof SS7.2 Urban heat island effect – roof WE1.1 Water efficient landscaping - reduce by 50% WE1.2 Water efficient landscaping - no potable water use or no irrigationWE2 Innovative wastewater technologies WE3.1 Water use reduction - 20% reduction WE3.1 Water use reduction - 30% reduction

Total stormwater-related credits 11

Stormwater Control Plan

Size treatment

controls

Plan for operations and

maintenance

Develop a site design Select and locate

source controls

Select and locate

treatment controls

Characterize existing

conditions

Vegetation Palette

Species adapted to clay soils

Photo: Rana Creek Living Architecture

Flow-through planters and stormwater discharge detail, Emeryville, CA.

Rain gardens and permeable paving, Mint Plaza, San Francisco, CA.

Rain gardens and creek daylighting, Tryon Creek Headwaters, Portland, OR.

Green roofs and bioretention planters, South Waterfront, Portland, OR.

Photo

: In

grid S

evers

on

Photo

: M

arg

o B

ors

Photo

: M

ara

Seili

ng

•Decrease the volume of potable water used for irrigation and toilet flushing

•Decrease the burden on San Francisco’s combined sewer

•Recharge groundwater

•Help reduce flooding and combined sewer discharges

•Broaden San Francisco’s water portfolio

Rainwater Harvesting

GreenPoint Rated is backed by third party verification to assure your home is better for you and the environment.

Rain water harvesting meets the follow GreenPoint Rated Measures:

P.C3 - Rain Water Harvesting System

1 Point for 50-350 gallons

2 Points for >350 gallons

For more information please visitwww.GreenPointRated.org

• Rainwater harvesting MOU

• Regulatory requirements (SDG)

• Rain barrel subsidy

• Education and outreach

Program elements

Rainwater harvesting system

1. Catchment area (roof)

2. Conveyance (scupper, gutter, downspout)

3. Roof washer

4. Storage (barrel, cistern, tank)

5. Distribution (pipes and pumps)

6. Use (irrigation, toilet flushing, vehicle washing, etc.)

7. Overflow (landscape or collection system)

Rainwater Harvesting MOU• Describes the commitments by

the participating agencies

• Allows non-potable use of rainwater with first flush diversion only

• Describes required system components

• Lists safety and maintenance, labeling, and permitting requirements

• Responsibility for design, installation, and maintenance lies with the system owner

SYSTEM COMPONENT REQUIREMENTS• Roof surfaces serving as catchments for water shall not include copper or materials treated

with fungicides or herbicides

• Gutters must be fully screened, continuous grade

• Storage containers, tank liners, and tank coatings must be listed as food grade, or be approved for potable water storage

• Storage containers must be opaque, water tight, vented, completely covered and screened

• All openings must be screened

• For above-ground systems, spigot and/or hose bibb for drawing water must be at least 4 inches from the bottom and must be labeled “NON-POTABLE”

• Overflow device must be equal in size to the total of all inlets and must lead to an approved discharge location

• First flush diverter must be automatic self-draining with clean out

• Air gap located where the rainwater enters the system

• Safety labels (non-potable, vector hazard, drowning hazard icons shown below)

• Installation of gutters, leaders, downspouts, piping, fittings, valves, and screens must comply with California Plumbing Code

• All plumbing materials must be listed with a recognized testing agency such as NSF or ANSI

• University of Southern California approved backflow prevention device located at the service connection with no fixtures between it and the water meter

• Outdoor spigots must have an atmospheric vacuum breaker attached

Permitting

• Plumbing permits are required for all systems connected to indoor plumbing, regardless of size

• Electrical permits are required for all systems using pumps or other electrical equipment or controls

• Building permits are required for cistern footings, foundations, enclosures, and roof structures

• Grading and erosion control permits may be required for underground facilities

DESIGN FOR COMPLIANCE• Rainfall depth = .75 inches• Volume = 7,103 ft3 of rainwater

(about 53,134 gallons) • Imagine a 30’ x 20’ x 12’ box

How much water are we talking about?DESIGN FOR MAXIMUM CAPTURE• Design storm = 21 inches• Volume = 198,888 ft3 of rainwater

(about 1,487,786 gallons – enough to flush toilets for 500 people for a full year!)

• Imagine a 1.5-acre reservoir about 3 feet deep

133,706 ft2 (about 3 acres)

Langston Brown Community Center and High School, Arlington, VA has two 24-foot-tall 11,000-gallon cisterns that store rainwater.

Photos: http://mrgreenbiz.wordpress.com/2008/10/05/

Chartwell School, Monterey, CASize: 5,000 gallons

Primary use: toilet flushing overflow/bypass line feeds the irrigation system

Photos: courtesy of Sherwood Design Engineers

DaVinci Water Gardenoutdoor learning lab

Thanks for having me!

Contact information:Sarah Minick

sminick@sfwater.org

http://stormwater.sfwater.org