Impermeable paving and hard ground surfaces at the Hall House were contributing to urban runoff. Instead of soaking into the soil, rainwater was lost to storm drains. That fresh water could be captured, stored and reused for irrigating the property in dry weather.
A sustainable solution
The team that designed the site’s best management practices (BMPs) considered the environmental impacts of L.A.’s water use, both locally and in distant places (such as the Owens Valley, Mono Lake and the Bay-Delta) that supply our city with water. This inspired a number of BMPs for the site, including:
If these practices were widely used by residents and businesses in L.A., it would help heal our city by:
- Capturing, cleaning and storing rainwater
- Using the water and then letting it soak into the ground
- Reducing stormwater flows and alleviating flooding
- Improving air quality by reducing the demand for energy
- Saving money by reducing the need for costly imported water
- Creating urban forestry and watershed management jobs
A cistern made of recycled polypropylene collects rainwater from part of the roof and stores it for landscape irrigation. A pump feeds the stored water to the automatic irrigation system.
If there were hundreds of thousands of cisterns around the city, they could be networked to detain stormwater and help control flooding. Authorities could drain the tanks before a big storm, capture a significant portion of the rain and regulate its release to the flood-control system.
The cistern tanks in the back yard.
Retention grading in the front and back yards creates "sunken gardens" that hold rainwater until the ground can absorb it. This BMP works best in soils of medium to high permeability.
At the demonstration home, runoff from the front half of the roof flows to depressions in the front lawn; half of the back of the roof drains to the backyard (the other half drains to the cistern). These depressions can handle a 10-inch flash flood that could occur during a 100 year storm event.
During a more intense storm, excess rainwater flows to the street. In slower-draining soils, the depression can be underlain with coarse aggregate rock to achieve a higher infiltration rate.
The retention grading in the front yard.
A swale is a low-lying or depressed stretch of land. The swale at the demonstration home was designed as a usable space. Swales can also perform a vital waste-reduction function – they can be mulched with local tree trimmings and dropped leaves, thus reducing the amount of green waste that ends up in landfills.
Swales slow the flow of stormwater, filter pollutants and increase the amount of water that can be absorbed by the soil. A swale can be used in any residential setting and may be grassy, vegetated or mulched. Grass requires irrigation in dry months and regular mowing.
The mulched swale in the back yard.
Rainwater flowing down the driveway runs through a grate and into a drywell – a box containing sand and crushed rock that capture pollutants. The grate and drywell help keep motor oil and other pollutants out of the storm drain system and off the beach. They also increase the property’s capacity to absorb stormwater.
The driveway grate and drywell.
Find detailed information about this project in our publication Rainwater as a Resource.