Award-Winning 21st Street Turns Roadway Into “Green and Complete Street”

By Land8: Landscape Architects Network on July 8, 2015 No Comments / 8599 views

21st Street, by SvR Design Company and Cannon, in the City of Paso Robles, California. Sustainability, ecological balance, climate, social interactions, community involvement, health and economic benefits, and aesthetics are the challenges an architect struggles with when deliberating the design of a project. It’s like a brainstorming exercise to incorporate all of these multidisciplinary yet integral aspects into a single project. When successful, this process can produce a project such as the 21st Street Complete and Green Street Project. In 2011, the City was awarded a $1 million grant and hired Cannon, a full-service, local engineering and landscape architecture firm, to take the concept plan through design development and prepare construction documents. SvR was retained to work with Cannon and provide technical guidance and review for each design submittal, to ensure appropriate implementation of green infrastructure strategies. It is located in the heart of the City of Paso Robles in San Luis Obispo County, California. The project’s name itself implies the use of “green elements” in its infrastructure. The sensitivity in the use of green elements and eco-friendly design is why it won the 2014 Green Innovation Award.

Looking down the center of the reconfigured street during a storm, water winds between rail baffles designed to evoke the region’s railroad history, slow the water flowing through the system, and allow for deposition and removal of sediment. Image credit: Cannon

21st Street, the City of Paso Robles, California

In the past, 21st Street experienced frequent and severe flooding, poor pavement conditions, discharge of sedimentation into the Salinas River, and inadequate facilities for bicycle and pedestrian traffic. To improve this, the city of the City of Paso Robles, in partnership with the Central Coast Low Impact Development Initiative and SvR Design Company, developed a conceptual design for a green/complete street. The city obtained an Urban Greening Grant in the amount of $993,000 and, with additional funding from the city, transformed the conceptual design into a reality. Related Articles:

Once the buried stream is daylit, riparian channel plantings and more generous drought tolerant landscape strips on both sides of the street provide a gracious public realm. Image Credit: SvR Design Company

Management of Stormwater Runoff The design of stormwater management is exemplary: The contaminated runoff from the impervious surfaces was addressed separately from the overflow from Mountain Springs Creek to control the quality and quantity of the runoff. The Engineered Median Channel High-volume, high-velocity water flow from the creek to the landscaped channel in the median of the street imitates the flow of the creek watershed while at the same time recharging groundwater through underlying infiltration trenches and engineered mixes of soil. Due to this, from the last nine rain events, approximately 250,000 gallons of water has recharged into the groundwater basin — equal to the amount of potable water for a four-person family for an entire year. The Pervious Pavers Impervious pavers were replaced with pervious pavers over a pedestrian area of 26,000 square feet to seep up stormwater. The designers intentionally didn’t install underdrains, leaving the water to percolate into the depressed bio-retention areas at the edge of the street. These areas can treat more than 500,000 gallons of water for every rainfall greater than 0.5 inches. Through Infiltration, pollutants are removed. If the water flows through to the Salinas River through the open channel, water pollution caused by sedimentation can be reduced.

Bike rack/art elements incorporating repurposed salvage pieces were created by local artist, Matt Canaday. Image credit: Cannon

Complete Streets Complete Streets are designed to ensure safe and comfortable access for users of all ages and abilities. Following the policy’s aims, three-quarters of a mile of new marked bike lanes, ADA pathways, and a railroad crossing. Crosswalks and widened walkways were added to improve mobility. But I think little attention was paid to the access of physically challenged people who require curb ramps with tactile surfaces indicating changes in level. To protect the bio-retention areas from unwanted subsurface water, other design elements such as deepened curbs, impermeable liners, and trench dams were installed. These measures will also help keep the asphalt road dry, prolonging its lifespan. Sense of Place It was really great to know that despite submissions from national firms, the city selected local firms, allowing those companies to develop their skills in these new concepts. Also, local and recycled materials were used, creating economic benefits for local residents. Moreover, from the conceptual level to the final phase of the design, many workshops were held to raise awareness among city residents. Their input and feedback played a key role in the street’s construction — which is a great way to foster emotional attachment to a place.

Gabion seat walls filled with a mix of concrete waste from the demolition are faced with locally sourced Adelaida stone. Custom steel and sustainable wood benches offer residents places to sit and linger along the corridor. Image credit: Cannon

Native Trees, Plants Trees and plants were not only used to enhance aesthetic appeal but to serve different functions. For bio-retention areas, drought-tolerant native plants were added to alleviate soil erosion. Eighty-one large native trees were also planted to increase shade and reduce the amount of heat radiated from the pavement. Although numerous new trees were added, existing trees weren’t forgotten. The Spanish meaning of the City of Paso Robles is “the pass of the oaks”. To celebrate that legacy, an ordinance was passed to preserve the existing oak trees, which is undoubtedly an acclaimed design decision.

Native and adapted plantings to California’s Central Coast climate reduce irrigation demands along the street while maintaining the stream channel, slowing and cleaning stormwater, and calming adjacent traffic. Image credit: Cannon

Street Amenities For wider use of local materials, contemplative seating areas were constructed, including Gabion basket retaining walls using local Adelaida stone and recycled concrete. Biking racks and high-efficiency decorative streetlights were added to enhance aesthetic appeal. Interpretive signs were also included to explain the landscape process. Truly, the innovative and ecofriendly features of stormwater control and management have set an example for landscape projects. Apart from that, the strong initiatives taken by the city for the betterment of its residents surely teach us a lot about the impacts of well-thought-out design in our lives!

Full Project Credits for 21st Street:

Project Name: 21st Street Designers: SvR Design Company and Cannon Location: The City of Paso Robles, California Budget: $2.5 million Date of Construction: 2010-2011 Awards: 2014 Green Innovation Award Client: The City of Paso Robles Show on Google Maps

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