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Low Impact Development: Designing for the Built
Environment Dr. Elizabeth Dougherty
WhollyH2oandAIANorCalJune8,2010
What is Low Impact Development?
LID is an approach to land development (or re-development) that works with nature to manage stormwater as close to its source as possible. LID employs principles such as preserving and recreating natural landscape features, minimizing effective imperviousness to create functional and appealing site drainage that treat stormwater as a resource rather than a waste product.
LID
There are many practices that have been used to adhere to these principles such as bioretention facilities, rain gardens, vegetated rooftops, rain water harvesting, and permeable pavements.
LID
By implementing LID principles and practices, water can be managed in a way that reduces the impact of built areas and promotes the natural movement of water within an ecosystem or watershed. Applied on a broad scale, LID can maintain or restore a watershed's hydrologic and ecological functions.
Implementing LID practices that emphasize rainwater harvesting, which includes infiltration of water into the ground as well as capture in rain barrels or cisterns for later use onsite, at new and redeveloped residential and commercial properties in the urbanized areas of southern California and limited portions of the San Francisco Bay area has the potential to increase local water supplies by up to 405,000 acre-feet (af) of water per year by 2030.(Pacific Institute)
The water savings translate into electricity savings of up to 1,225,500 megawatt hours (MWh), avoiding the release of as much as 535,500 metric tons of CO 2 per year, as the increase in energy-efficient local water supply from LID results in a decrease in the need to obtain water from imported sources of water such as the California State Water Project (SWP) or the use of processes such as ocean desalination, both of which require tremendous amounts of energy.
Water Supply Security Issues
Urban Stormwater pollution, Agricultural water pollution
Bay Delta Health and Supplies
Increasing Population and related water demands
Energy involved in moving water in the state
Aging Infrastructure
Earthquake Disasters (Salinity Increase in Supplies)
Climate Change: reduced Snowpack, increased temperatures, salinity increase in water supplies
Water/Energy Nexus
Water-related energy consumption in the state represents approximately 15%-20% of all energy consumed in California.
Approximately 30 percent of California’s urban and agricultural water needs are supplied by groundwater in an average year, a figure that rises to 40 percent or more during periods of drought.
Federal Clean Water Act In order to prevent the pollution and other harms that result from urban runoff, the Federal Clean Water Act requires municipalities, counties, and other dischargers to impose “controls to reduce the discharge of pollutants to the maximum extent practicable.”
Dischargers must use “management practices, control techniques and system, design, and engineering methods, and such other provisions which are appropriate.”
Aone‐acreparkinglotproduces16Amesmorerunoffthanaone‐acremeadow.
“The EPA views urban runoff as one of the greatest threats to water quality in the country and considers it “one of the most significant reasons that water quality standards are not being met nationwide.”
Clean Water Act/NPDES
As authorized by the Clean Water Act, the National Pollutant Discharge Elimination System (NPDES) permit program controls water pollution by regulating point sources that discharge pollutants into waters of the United States. Point sources are discrete conveyances such as pipes or man-made ditches. Individual homes that are connected to a municipal system, use a septic system, or do not have a surface discharge do not need an NPDES permit; however, industrial, municipal, and other facilities must obtain permits if their discharges go directly to surface waters.
Impervious Surfaces R Us
Oh, that’s better.
Unzip your pavement and let the water in!
Examples of Low Impact Development (AKA: Onsite Water Management)
Reducing Impervious Surfaces (e.g., rooftop gardens, narrower streets, pervious pavement)
Conserving Open Space / Maintaining Groundwater Recharge Areas, Buffer Zones, and Drainage Courses
Installing Rainwater and Graywater systems for water use and reuse and groundwater recharge
Infiltration Swales, Grading Strategies, and Open Drainage Systems (e.g., bioretention)
Reducing the Use of Pipes, Curbs and Gutters
Benefits of Going Local with Water
Reduced energy in cleaning and moving water and cleaning water and moving water
Storm water management, reduced pollutants in local waterways, reduced costs for capital improvements/treatment of combined sewer/stormwater
More water available for public urban tree cover
Groundwater recharge
Urban Heat Sink reduction (concurrent energy reduction due to air conditioning temperature control
* Design for local conditions (terrain, soil composition, local rainfall, water use/needs)
Shifting Norms Always includes a shift in practices, which opens the
door to openness to education and more change.
Increased awareness of the larger context of water supplies
Increased awareness of water use
Shift in use of materials
The ecology of water and where it fits into a larger context of ecology (native plants, soil (infiltration), watersheds, wetlands, species diversity, maintaining a healthy ecosystem
The Golden Moment
New Codes and Ordinances Being Developed
Need Innovation in Design of Systems
Need Innovation in Design of Incorporation
Need to Bring Down Costs
CA Precipitation
In average years, about 193 million acre-feet (MAF)* of rain and snow falls on California.
About 75% of the annual precipitation falls north of Sacramento, while more than 75% of the demand for water is south of the capital city. Most of the rain and snowfall occurs between October and April, while demand is highest during the hot and dry summer months. (CCWD)
Precipitation Map
Rainwater Calculations
A = (catchment area of building)
R = (inches of rain)
G = (total amount of collected rainwater)
(A) x (R) x (600 gallons) / 1000 = (G)
(http://www.rain-barrel.net/rainwater-calculator.html)
Reduce, Reuse, Recycle Rainfall: yearly average (www.allcountries.org)
San Francisco: 19.70
Los Angeles: 17.52
San Diego 9.9
(A) x (R) =
x (600 gallons) / 1000 = (Rainwater Harvesting Potential)
Given a 1000 square foot roof catchment area: San Francisco: 1000 sq ft x 19.70 x 600 = 11,820 gallons
Los Angeles: 1000 sq ft x 17.52 x 600 = 10,512 gallons
San Diego: 1000 sq ft x 9.9 x 600 = 5,940 gallons
Rainwater Systems
GuGers,Guards,FirstFlushDiverters,PrefiltraAon,Tank,ConveyanceSystemtopointofuse(InteriororExteriorLandscapeIrrigaAon,AddiAonalFiltraAonasnecessary
School
Rainwater Rebates (not including irrigation rebates)
City of San Francisco
City of Palo Alto
City of Santa Rosa
City of Marin
Santa Monica
City of Soquel
Scotts Valley Water District
Marin Peninsula Water District
Now, Tucson, Ariz. has passed what may well be the first municipal rainwater-harvesting ordinance in the U.S.
The Tucson rainwater-harvesting ordinance requires that all commercial development and site plans submitted after June 1, 2010 include a rainwater-harvesting plan submitted concurrently with the site and landscape plan.
The plan must also include a landscape water budget that estimates the volume of water required each year for all site landscaping, and an implementation plan to show how rainwater will be harvested on site. The implementation plan will provide water metering of all onsite landscaping via a separate water meter connected to the main water supply, or via an irrigation submeter.
The ordinance further states: “No later than three years from the date of issuance of a final certificate of occupancy, and for every year thereafter, 50% of the estimated yearly landscape water budget shall be provided by rainwater harvested onsite by a rainwater harvesting system…”
The Sun Valley is one of six giant funnel-shaped canopies that are currently springing up in Shanghai in preparation for an Expo. Each of the six cone-shaped valleys stands 40 meters tall, and is constructed from steel and plastic. The structures will funnel daylight to the levels below, and will also be used to collect rainwater, which will then be filtered and used throughout the grounds for irrigation purposes. The giant membranes will also shade the walkway below to help moderate the temperature for visitors.
The pavilion’s exterior will be composed of hundreds of polycarbonate transparent plastic tubes recycled from used CD cases. A misting system will also add to the structure’s appearance and help lower the temperature, purify the air and create a comfortable climate in the pavilion. Mist and water use inside the building will come from collected rainwater, which will be treated for sedimentation and then filtered and stored. Energy will be gathered through a 1,600 square meter solar thermal energy system of heat-collecting tubes on the roof, which will generate electricity through ultra-low temperature power generation.
Beijing
Academy of Sciences Green Roof
The roof also retains 2 million gallons of rainwater, preventing 70% of the rainwater that falls on the roof from becoming runoff.
The water that does run off the roof is collected in basement-level cisterns and reused for roof irrigation. No potable water will be used to irrigate the living roof.
The roof covers an ambitious 197,000 sq. ft. to a depth of 6-7 inches and cost $17 per sq. ft.
The roof’s diverse assemblage of nine indigenous plant species is a new link in an ecological corridor for the City’s wildlife. Habitat space taken away from urban development will be restored for the native plants and animals of the area. For San Francisco, the green roof creates the most concentrated area of native wildflowers within the city.
Academy of Sciences Green Roof: 2.5-acre undulating greenroof
Green Roofs!
Infiltration
Into Landscape
Into the Ground
Through Permeable Pavement
Permeable Pavement
Berms, Bioswales and Rain Gardens
Beautiful Design
Seatlle
Storm Drain Design
Pervious Park
Captures and Infiltrates Rainwater
What is a Rain Garden?
A "rain garden" is a man-made depression in the ground that is used as a landscape tool to improve water quality. The rain garden forms a "bioretention area" by collecting water runoff and storing it, permitting it be filtered and slowly absorbed by the soil.
The bioretention concept is based on the hydrologic function of forest habitat, in which the forest produces a spongy litter layer that soaks up water and allows it to slowly penetrate the soil layer. (must consider soil type and slope)
The site for the rain garden should be placed strategically to intercept water runoff.
Components of a Rain Garden Planting Soil
Organic matter in the form of leaf mulch (20%) blended into a sandy soil (50%) with and about 30% top soil. The planting soil mixture provides a source of water and nutrients for the plants to sustain growth. Clay particles adsorb heavy metals, hydrocarbons and other pollutants.
Plant Selection: Native Species
A planting plan design should include species that tolerate extremes. There will be periods of water inundation and very dry periods. Most riparian plant species will do well in rain gardens. The choice of species should include plants that mimic forest habitat and have an aesthetic landscape value such as flowers, berries, interesting leaves or bark. Groundcovers, perennials shrubs and trees should be incorporated into the planting design.
Natives Attract Natives!
Native flowers, sedges, grasses, bushes and trees that make up the rain garden attract the butterflies, frogs, turtles, toads, and birds, that depend on them for their food and homes. This creates a backyard habitat for you and your family to watch, enjoy and learn from year after year.
Increase Biodiversity!!!
RECYCLE YOUR LAWN
In a recent NASA-sponsored study, researcher Cristina Milesi estimated the area covered by lawns in the United States to be about 128,000 square kilometers (nearly 32 million acres), making it the nation's largest irrigated crop by area
Where are the Birds and the Bees?
Many lawns are composed of a single species of plant, or of very few species, which reduces biodiversity, especially if the lawn covers a large area. In addition, they may be composed primarily of plants not local to the area, which can further decrease local biodiversity.
Lawns are sometimes cared for by using synthetic pesticides and other chemicals, which can be harmful to the environment, especially when misused.
Sprinkler runoff
creates a stream on
the side of a street.
Irrigated lawns have a significant impact on
water supplies in American
cities.
Add Water Efficiency, Gray Water and Recycled Water to
your Palette
Water Efficiency: Showerheads, Faucet Aerators, Flow Reducers, Low Flo Toilets, Waterless Urinals
Greywater Systems
Simple Graywater
Green Building Rating Systems:
• LEED
• GreenPoint rated
• EPA WaterSense for residential
• California Green Building Standards Code (Title 24)
LEED
Of the 69 possible points in LEED, only five are directly associated with water efficiency. These five points are apportioned among three LEED Water Efficiency credits:
Credit 1 – Water-efficient Landscaping, two points
Credit 2 – Innovative Wastewater Technologies, one point
Credit 3 – Water Use Reduction, two points
In LEED for Homes, "Sustainable Sites", stormwater retention and green roofs (vegetated roofs) can earn as many as 7 points.
In the "Water Efficiency" criteria, rainwater harvesting can be worth 4 points, but only if the storage capacity is enough to capture all water from a 1" rain event falling on 50% of the roofed area.
Graywater reuse earns 1 point, but must include a "dosing basin". This means the graywater would have to be pre-treated, which is often quite unnecessary, depending on end use).
Using recycled municipal water for irrigation is worth 3 points.
High-efficiency irrigation, water-wise landscaping, and high-efficiency indoor fixtures are worth as many as 10 points.
For commercial, retail, institutional, or manufacturing buildings the major criteria remain similar, but the point structures are differ depending on the type of construction and its users. The points available for water conservation and reuse in these other building categories are disappointingly minimal.
Under LEED New Construction stormwater design earns only one point, and water use efficiency is worth a total of 10 points.
As some US states grapple with increasing water supply shortages, LEED will need to place a higher priority on large-scale water conservation.
