Redesign of 21st Street, Paso Robles, California

The City of Paso Robles, California redesigned a downtown street utilizing complete and green street design principles to better manage precipitation and stormwater runoff in a natural drainage area.  The 21st Street redesign project has proven successful as a means of stormwater management.  In a three-month period, the street’s new features, which include pervious pavement, street trees, and a stream channel in the middle of the street, helped mitigate flooding from nine significant rain events, and recharged approximately 250,000 gallons of stormwater into the region’s groundwater basin. The Project was awarded a 2014 Green Innovation Award by the Central Coast Chapter of the US Green Building Council.

The commercial and residential street is located in the city’s more densely developed downtown area.  The street was developed in a natural drainageway, and therefore a large segment of land in Paso Robles drains to 21st street.  Due to a large amount of impervious paved area, the existing design did not allow for stormwater infiltration and was vulnerable to flooding. Large storm events would cause street flooding, erosion, traffic hazards, and road closures.

The City commissioned a concept plan from SvR Design Company to design a complete, green street for five contiguous blocks of 21st street.  The City’s objectives for the redesign project were to:

  • Reduce stormwater discharge into the Salinas River;
  • Increase groundwater recharge to improve water supply and aquifer health;
  • Address climate change and improve air quality with added vegetation and reduced vehicle use;
  • Improve active transit (pedestrian and bicycle) mobility and safety; and
  • Encourage infill and redevelopment.

The completed 21st Street redesign reduced impervious surface area by 26,000 square feet, improving stormwater management and groundwater recharge. For every rain event over 0.50 inches, the project results in bioretention and infiltration of over 50,000 gallons of runoff. The design includes linear parks with shade trees, bioretention areas with native plantings, and pervious sidewalks. Native-plant landscaping that requires little water to survive was used to replace asphalt in some areas, and 81 large native trees were planted, which will help increase shade and reduce pavement heat in the future. Additionally, a center median stream channel is able to capture higher velocity stormwater flows to further increase groundwater recharge and alleviate street flooding. The channel includes a cobblestone bottom to help prevent erosion, and old rail ties incorporated into the design help control the velocity of the runoff. The design also narrowed the roadway and incorporated new bike lanes to promote active transportation, and storyboards along the street help promote public awareness of the project.

The City of Paso Robles employed local consultants and construction firms for the redesign project, building from the early concept work of Seattle-based SvR Design Company. The City held numerous regular stakeholder and community engagement meetings throughout the progress of the project to ensure the public was informed. The project was developed from 2010 to 2011 at the cost of $2.5 million, and was partially funded by an Urban Greening Grant from the State of California.

 

This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on January 29, 2016.

 

Publication Date: 2013

Sectors:

Resource Category:

Resource Types:

  • Best practice
  • Case study

States Affected:

Impacts:

Go To Resource