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Stormwater Solution Case Study | The Oak Grove Altadena

A Fresh Stormwater Solution & New Development in a Historic California Community


Altadena is a historic turn-of-the-century Los Angeles enclave nestled along the hills of the San Gabriel Mountains. The town’s personality is founded in its natural surroundings, from countless parks and recreational areas to national forests and contributory waterways. Although Altadena’s roots are tied in agricultural development, food production, and dairy processing, the town is now recognized for its legacy of water preservation, agricultural controls/balances, and iconic craftsman architecture. Protecting natural surroundings and resources and finding a sustainable stormwater solution are priorities of the local Arroyo Seco Watershed community.

According to the Arroyo Seco Watershed Organization, “The watershed is a subwatershed of the Los Angeles River Watershed, a basin between the San Gabriel Valley and the San Fernando Valley.”1

The Arroyo Seco watershed is one of California’s most important watersheds. It is designated as an impaired waterway for sedimentation/erosion and aquatic habitat degradation due to urbanization.

stormwater solution

Water quality goals for the watershed and surrounding areas include:

  • Restoring hydrological function
  • Flood control
  • Conserving water resources
  • Improving water quality to enhance natural open areas and recreation

The community’s methods for addressing stormwater greatly affect water quality goals and their progress for the surrounding environment and wildlife.

Stormwater Goals & Challenges

The Oak Grove of Altadena is a new housing development project facing some obvious challenges. Some of these challenges include saving land, architectural aesthetics, water quality, and infrastructure. However, the development will deliver value to the community, including new housing options, infrastructure improvements, and site-controlled water quality and drainage.

The project includes a stormwater management system with natural drainage beds and precast-engineered underground storage tanks to collect and filter stormwater runoff from the site. The system protects the environment by capturing and filtering potential rainwater pollutants before it enters local groundwater aquifers, streams, or other bodies of water. Oak Grove’s design mitigates and controls high volumes of stormwater runoff. The runoff contributes to flooding in low-lying areas, including parts of Altadena, offering the community a return on preferred infrastructure investment.

Stormwater Design

The Oak Grove lot is a very compact space with variable elevations and slopes. This can make drainage details and piping complicated while designing/planning to capture and infiltrate required stormwater volumes. Downstream of all site runoff is a set of cisterns and settling chambers that effectively conserve land and development space.

Diagram 1: Stormwater Drainage Plan

All stormwater collected from roof gutters have downspouts that connect to underground storm drains which feed surrounding bioretention treatment basins. Stormwater from bioretention treatment basins is ultimately discharged into primary stormwater collection systems located underground and within designated ‘green’ areas of the development.

See Diagram 1: The dry well configuration and the basic elements of the stormwater drainage plan.

Stormwater Solution

What are dry well stormwater systems?

Well-designed dry wells can manage a large amount of water volume. Santa Fe Water Systems’ Ultrawell™ dry well system administers a fresh multi-faceted solution to meet complex stormwater goals and manage runoff. The Ultrawell™ dry wells are cost-effective solutions that can handle high volumes of water in a small footprint. They can be custom-built to fit a site’s needs. Ultrawells™ also allow for the capture of water that would otherwise flow off a property or overwhelm stormwater systems and local watersheds.

According to the California Water Resources Control Board, “Dry wells not only aid in stormwater runoff reduction, but they can also increase groundwater recharge, are economical, and have minimal space requirements.”2

Santa Fe Water Systems provides designs and production of the innovative stormwater Ultrawell™ dry well system. This offers engineers and developers an efficient and immediate solution for a wide range of stormwater goals. Contact us today for a project review session or preliminary design.


The Oak Grove of Altadena development is a considerate response to California’s rising housing demand and the need for more affordable housing in Altadena and Los Angeles County. The project created 15 new single-family homes, open space, and protections for valuable existing vegetation and historical trees. It also addressed stormwater management by creating a crucial set of dry wells (infiltration basins) that absorbed water from rainstorms and reduced flooding risks from future storm events.