Bioretention for Post-Construction Stormwater Managment

Bioretention areas, also sometimes called rain gardens, are the post-construction stormwater treatment measure of choice for commercial developments in the Bay Area. Civil engineering design often utilizes this Low Impact Development (LID) practice that combines aesthetic landscaping with engineered stormwater management systems designed to remove pollutants through natural processes. According to the San Francisco Bay Water Quality Control Board, “In the San Francisco Bay watershed, urbanization and agricultural runoff is generally considered to be the largest source of pollutants to aquatic systems.” Stormwater in cities picks up debris, oil, chemicals, etc. from impervious streets and sidewalks and washes it down the storm drain and into surrounding bodies of water rather than sinking into the ground like rainfall does in an undeveloped area. According to the C.3 Technical Guidance Handbook, a bioretention area is: "…designed to have a surface ponding area that allows for evapotranspiration and to filter water through 18 inches of engineered biotreatment soil. After the water filters through the engineered soil, it encounters a 12-inch layer of rock in which an underdrain is typically installed. Bioretention areas may be lined or unlined depending on the hydraulic conductivity rate of the underlying soils."

cbls bioretention area

  Bioretention areas are filled with plants that flourish while being partially submerged. The combination of these plants and underlying layers of soil and rock filter out much of the pollutants that would normally go through the storm drain system and into the Bay, as well as allowing some moisture to evaporate back into the atmosphere like it would from an open field or similar undeveloped land. In some bioretention areas, the water can slowly filter back into the ground without the use of an underdrain, further mimicking the way rain would soak into the ground on undeveloped land. bioretentionareasandraingardens3   In 1977, the Clean Water Act was passed, in part to address the negative effects of stormwater runoff in urban and agricultural areas. Under the Clean Water Act, the EPA established the National Pollutant Discharge Elimination System (NPDES), which regulates allowable levels of certain chemical pollutants and requires polluters to obtain permits for chemicals discharged into surface waters. As a result of increased regulation on pollutants entering waterways, many states have adopted sustainable practices like Low Impact Development to encourage more effective stormwater management. Since 2009, bioretention has been the Bay Area’s stormwater management method of choice, replacing bioswales. Bioretention works well on most sites but can be constrained by steep slopes, a high ground water table or soil impermeability. A civil engineer can determine the best stormwater methods for each project. In some situations, flow-through planters have become an acceptable method for treating stormwater when bioretention is not feasible like when in close proximity to a building, or where soil moisture is a possible concern. In sites with size constraints, steep slopes or poorly-draining soils, the smaller size and impervious bottom of a flow-through planter allows for the treatment of stormwater runoff and discharge to a storm drain, much like some bioretention areas. However, flow-through planters are limited in respect to re-use of stormwater and must account for the possibility of overflow. WClibrary   In addition to “cleaning” the water that passes through it, a bioretention area or flow-through planter adds pleasant and aesthetically landscaped greenery to a site. The greenery can also provide a habitat for birds, amphibians and insects. In warmer cities, additional vegetation helps to mitigate some of the “heat island” effect that occurs because of dark city surfaces like asphalt and the minimal evapotranspiration that can occur on these impervious surfaces.  

Stormwater Management and Rainwater Harvesting – An Important Piece of the Bay Area’s Sustainability Puzzle

Green Roof at Facebook Campus The Bay Area is known for its environmentally conscious mindset – that of its citizens, environmental policies and the kind of development the region attracts. Initiatives have developed at municipal levels, such as San Francisco’s ban on plastic checkout bags in 2013 and San Jose’s sustainable city plan. Private companies have also taken similar initiatives, think Facebook’s campus with its 9-acre green roof and Salesforce East’s Platinum LEED status remind us that sustainability is here to stay. Along with environmentally-intelligent development and the regulations that govern it, the need for equitable water management practices at both public and private levels is a growing issue. Currently, the Bay Area’s approach to water management is steadily improving with the help of the region’s development standards and the increase in our collective environmental awareness. Read more

Beyond Bay Area Green Building: Developing “Healthy” Workplaces

1225 Connecticut Ave.JPG Peter Akinosho, a civil engineering student at the University of Georgia, spoke about why he chose the profession: “[Civil engineers] do what we do so people don’t have to worry about their basic needs.” Paramount among these needs is health. We are building structures for tomorrow’s generations, who are more conscious about the benefits of maintaining an active lifestyle, even at work. Especially in the realm of Bay Area green building, tech giants are building headquarters with green roofs equipped for walking meetings, and offer daylighting, yoga, and healthy food. To remain competitive for clients, we developers, architects, and engineers must work together to design and build developments that are not only sustainable but also promote the health of the people who use them. Read more

A Civil Engineering Perspective on Bay Area Growth

Plan for Google expansion. Credit: Big & Heatherwork Studio By Sonia Easaw with Kamal Obeid, S.E., PE Can the San Francisco Bay Area handle the growth? The Bay Area region is one of the most in-demand places in the country to live, especially for professionals in the technology industry. After all, it's the place where tech companies come to grow, and subsequently, the region attracts great talent. However, the increased demand has contributed to a housing shortage, making it unaffordable for many, and it's caused other problems such as traffic congestion and long commute times. Also, environmental conditions are much harder to predict with a warming climate. From a civil engineering perspective, the growth can last if development is well-planned and sustainable. Read more

Sustainable Development: Invest in a Green Roof?

[caption id="attachment_228" align="alignright" width="300"]800px-CalifAcadamyOfSciAug28-2008img0640 California Academy of Sciences[/caption] By Sonia Easaw & Kamal Obeid, SE, P.E. When you think of sustainable development in the California Bay Area, you may think of CEQA, solar panels, and environmentally-friendly hipsters, but green roofs will probably not come to mind. Though San Francisco has some green infrastructure projects, the Bay Area region lags behind areas such as Washington, D.C., which led the country in 2012 with 1.2 million square feet of new green roofs. There are grand exceptions like Facebook's newest campus in the Bay Area that contains a gigantic roof garden complete with trees, walkways, and sitting areas, or the living roof of the California Academy of Sciences. But is it worth investing in a green roof when building in the Bay Area? First, let’s look at the potential benefits of green roofing.

Benefits of Green Roofs for California

CalifAcadSciRoof 0820Beautiful green roofs are more than just aesthetically pleasing. For example, the living roof atop San Francisco’s California Academy of Sciences is made up of 50,000 porous vegetation trays that house an estimated 1.7 million plants, and in turn provide a home for local wildlife such as birds, insects, and other creatures. The green roof also reduces the energy needs for heating and cooling the Academy. Environmentally-responsible owners of many green-roofed buildings enjoy similar benefits such as the following:
  • lower energy costs because the green roof absorbs solar energy and provides excellent insulation;
  • improved local environment;
  • additional space for occupants to garden;
  • efficient use of space in an urban environment;
  • and rainwater harvesting.
You are likely aware of the many benefits that green roofs hold for every city, including cleaner air and water, greener spaces, and healthier communities. For example, the Academy’s green roof captures 100 percent of excess stormwater, thus preventing pollutants in the runoff from getting into the ecosystem. In general, green roofs offer many environmental benefits, including the following:
  • reduce carbon footprints by helping to reverse carbon emissions;
  • provide mechanisms for water conservation and stormwater harvesting;
  • offer landscape-based treatment for stormwater;
  • control and reduces storm peak flows;
  • and cool the local environment.
As mentioned above, some critical benefits that green roofs can provide a drought-stricken California is their ability to harvest water and slow down stormwater runoff. There will be an initial investment the first couple years to irrigate the green roof. However, a rainwater harvesting system built in conjunction with the green roof can divert runoff into tanks for storage, flushing, or irrigation. Now let's take a look at the challenges presented by green roofs.

Challenges of Green Roofs in California

Living Roof A green roof changes the construction and maintenance of a building. Once you introduce a green roof, standards for regular maintenance go up, and waterproofing is especially critical to ensure against leaks. Other wholesale failures include soil erosion, poor drainage, and slope instability. Since a proposed green roof would need saturated soil placed at roof level, significant added weight must be supported by a given building. In seismic zones such as the Bay Area added roof level (top heavy) weights also create a challenge for structural seismic design. All told, when planning a green roof, a significant increase in structural construction cost is to be expected. Last but not least, a green roof will be more expensive than a regular roof, and a thorough cost-benefit analysis would have to be conducted during the planning stages. Some of the cost implications for green roofs include the following:
  • a significant increase in structural construction cost to support the building’s weight and seismic design implications;
  • special waterproofing costs;
  • green roof maintenance costs;
  • and green roof irrigation needs, especially during a dry season.
Emeryville California Stormwater Curb ExtensionTo meet the challenge of the high costs of green roofs and other green infrastructure while dealing with increased stormwater pollution, some cities such as Washington, D.C. have set up a green infrastructure marketplace. Property owners who have green roofs, rain gardens, etc. receive credits they can sell to others who need to offset runoff from their developments. This system is also designed to increase water collection, which would be a great benefit for California. There have not been any general economic incentives for commercial businesses to reduce water usage, but it’s likely in the future that larger consumers of water resources will have to pay more. With the possibility of water rationing, green roofs become more economically appealing for commercial developments. Green roofing is a great and socially responsible idea, especially as commercial businesses are becoming better corporate citizens with sustainable development. However, challenges remain, and it will be interesting to see how Bay Area cities, municipalities, and the private sector work together to make green infrastructure work for everyone. In the meantime, however, there are other "green" ways to get up to code with clean water requirements, such as with bio-retention methods. Perhaps in 50 years sustainable development such as green roofs will become more common in the Bay Area, and not just exist on Facebook's campus or the California Academy of Sciences. Until then, however, it is best to consider both the challenges and benefits on a case-by-case basis before investing in a green roof.

The #1 Sustainable Development Feature for Silicon Valley Tech Companies

By Sonia Easaw, with Kamal Obeid, SE, P.E. Sustainable development for growing high-tech companies in Silicon Valley signifies they meet their present needs without compromising the ability of future generations to meet their needs. But green building is not just a buzzword for Apple, Google, Facebook, and other technology giants--they are incorporating environmentally-friendly features into their new campus developments. However, the number of solar panels or the acres of green space in a new campus is not as important as the impact the development has on the surrounding community. Community-oriented development, or the creation of vibrant communities, is the number one sustainable development feature for new technology company developments. Silicon Valley is privileged to be home to three of the biggest technology companies in the world: Apple in Cupertino, Google in Mountain View, and Facebook in Menlo Park. The most important factor to the surrounding communities, however, is whether the new tech campuses are developed with the future of community in mind.

Fitting Into the Community: New Apple, Google, and Facebook Campuses

Norman Foster - Apple Campus 2 Rendering 05.jpg Apple Inc., the largest company in the world, changed the face of the city of Cupertino, CA. Now they're building a new spaceship-like campus in town, and residents will embrace thousands of new technology workers when the project finishes at the end of 2016. Residents and city leaders, though eager to welcome such growth, are concerned about Apple’s new campus’ potential impact on traffic and local charm. Apple said it would help alleviate increased traffic around the new site, and the City plans to improve pedestrian and bike paths. The City has also set aside more room for housing, by state regulation. But some residents do not like the added burden of growth in the town, and any expansion beyond Apple’s growth has generated backlash. In May 2015, the Cupertino City Council voted to restrict office expansion (except near Vallco Shopping Mall) amid community concerns about the impact of growth on traffic, schools, green spaces, and public transit. Google's New Headquarters: Google rending new campus Early in May, Google made its ambitious expansion plans known to the city of Mountain View, but the City Council rejected most of them. In late May, Google again filed plans, but this time for a project that was not a part of their original proposal. They are planning to construct a translucent domed headquarters on a site they acquired rights to before the City set limits on office expansion in the North Bayshore district. This is a district where thousands of technology workers travel to for jobs at Google, LinkedIn, Intuit, Microsoft, and other places. Google promises to ease City worries of increased traffic congestion by moving people around the district through biking and walking. The plans for the new building includes a publicly accessible nature path that will cut across the giant dome and connect pedestrians and bicyclists. But the City desires a holistic development plan that ties in housing, retail, offices, and public transit, and will hold community meetings this summer to help sort out how Google fits in. Facebook's Menlo Park Campus: [caption id="" align="aligncenter" width="640"] By Austin McKinley (Own work) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons[/caption]Facebook's newest campus in Menlo Park opened its doors in March and contains a nine-acre green roof, with a half-mile walking loop and 400 full-grown trees. The roof also has WiFi and whiteboards outside so employees can enjoy the California climate and work out-of-doors. But with its burgeoning size, Facebook knows the importance of connection with the community.  The City of Menlo Park’s vision is for mixed-use land development with publicly accessible housing, retail, and a hotel, all of which Facebook supports. Facebook executives also want to take advantage of trails, a railway easement, and a tunnel to better connect their campuses and the surrounding Menlo Park neighborhood. Apple, Google, and Facebook each realize that the surrounding community will be significantly affected by development. The shift from insular Silicon Valley campuses to those that simultaneously create vibrant communities within and around them is what every Bay Area city wants. Incorporating a city’s vision for community-oriented building will be the best way to go forward in the future, and is the number one sustainable development feature for every new Silicon Valley technology company.    

Bay Area Future Buildings– Apple’s new “spaceship” campus and Oakland’s Coliseum City

The Bay Area has two up-and-coming building projects that will be quite the spectacle once they are finished. The first--Apple's new headquarters--promises to be the next home for the company for decades to come. The second, a planned massive redevelopment of East Oakland, Calif. called Coliseum City, claims to be the largest transit-oriented development project in California.spaceship-111206-9 Read more