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

East Bay Development vs. Community Interests

By Kamal S. Obeid, SE, P.E. Santos Farm, Fremont, CA. I first started as a civil engineer during the 1980s. At that time, Fremont, California, located in the East Bay of California’s San Francisco Bay Area, was a sleepy suburban community in the backdrop of the larger region. The not-too-distant Silicon Valley was in the throes of a recession. The historical farming community was evolving with acres of land being developed into subdivisions and ancillary commercial strip center development. Large areas of pristine open space were under threat from encroaching suburbia. The City of Fremont government, actively dealing with development pressure and market forces, was also beginning to steer the City away from unplanned, market-driven development. 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

Silicon Valley Construction: What’s tech got to do with It?

Silicon Valley Construction: Google's Plan The technology sector and Silicon Valley construction have always had a symbiotic relationship. The agreement between companies such as Google and Bay Area development has usually been good, for the most part. Since the time of Steve Jobs in his garage working to develop the Apple computer, to the hardware revolution that gave the Valley its name, technology has attracted the best, and the brightest to this part of California, and construction usually followed. Read more

Downtown Fremont CA Emerges

Sign drapes edge that reads Downtown Fremont on the Rise, new retail and residences coming soon In 1956, five townships came together to form Fremont, California. Sixty years later, the City is becoming more of an urban place than a suburb, especially with an additional new transit station and associated development. However, the City has lacked a central place, or downtown, to bring everyone together. In fact, the center of the City is walking distance from an existing local BART (Bay Area Rapid Transit) station, but the land has historically been underutilized, filled with large surface parking lots and underused retail shopping centers. However, after years of planning, the possibility of a Downtown Fremont CA is emerging. Read more

Civil Engineering: Rethinking Water Projects

Folsom Dam USACE 2004 By Sonia Easaw with Kamal Obeid, PE, S.E. Water storage on a municipal scale in the West used to involve building dams and reservoirs such as the Folsom Dam, which would gush with water from the melting snow of the Sierra Nevada mountains. Now the snowpack is at its lowest measured record, and the water levels of the reservoir may run so low this year that pumps will have to be installed to push water through the dam. Unfortunately, these warming conditions are likely to continue. In response to the “new normal” of drought conditions, the community of civil engineers and local jurisdictions must take a sustainable approach and rethink infrastructure to deal with potential severe water shortages. With the drought looming overhead (and below), here are four examples of water projects throughout the Bay Area and California involving desalination, groundwater recharge, stormwater capture, and recycled water.


Carlsbad desalination plant2 Salt water from the San Francisco Bay has been seeping into the groundwater basins that serve the cities of Alameda County (cities of Fremont, Newark, and Union City). Back in 2003, the Alameda County Water District, or ACWD, built the small Newark Desalination Facility to treat the brackish water. The effort proved fruitful when the plant supplied much-needed water to areas of the County during the drought and saved the ACWD about $4 million dollars a year. The plant uses a reverse osmosis membrane filtration process that requires high-pressure pumps that consume a lot of energy and contribute to additional carbon consumption. The energy-intensive, and therefore, expensive desalination process has also been known to pose a threat to ecosystems--the brine byproduct of desalination (a highly concentrated saltwater solution) can be dangerous to sea life if not properly mixed back into the ocean. Supplying the County with clean water during drought periods was a resulting benefit of the small desalination plant but may not have been the primary reason for why it was built. There are some California jurisdictions, however, that have considered desalination treatment plants as a larger fix for water shortages. A one billion dollar desalination plant will be unveiled in Carlsbad, Calif. in 2016--what will be the largest one in the nation--and will supply San Diego County with seven percent of its water. However, desalination is considered more of last resort after other water conservation methods have been employed.

Groundwater Recharge

Groundwater flow How do you capture and store clean water on a massive scale in a sustainable way? There are many ways of capturing and storing fresh water for municipalities, such as increased stormwater capture, reservoir expansion, or groundwater recharge and storage. A practical alternative to desalination in California is expanding the water supply beneath our feet. This method of recharging groundwater has been found to be much cheaper than other water supply options and offers more local control. Groundwater levels have been declining across the state because of the drought but also because of overuse, and so recharge becomes especially important to replenish the water into the groundwater basins or aquifers. Groundwater recharge can also be a barrier to seawater intrusion and help restore local ecosystems. Some disadvantages to groundwater recharge include the financial costs to local communities though it is cheaper than surface storage or importing water. Also, natural recharge from rain and snow is not as readily available during times of drought, and so artificial recharge is the next option. But where will the water for artificial recharge come from, especially when the surface water from streams and rivers are not at peak-flow? Alternative water sources for groundwater recharge include treated wastewater, runoff from agricultural uses, and past stormwater capture. Alameda Creek in Niles Canyon 2626 Alameda County Water District (ACWD) considers recharge as a top priority for groundwater management. With the help of inflatable dams, water from the Alameda Creek is diverted into Quarry Lakes Regional Recreation Area for groundwater recharge. Rubber Dam No. 1 was installed back in 1971, and its fabric membrane was recently replaced this summer. The dam structure was upgraded to increase capacity (a project on which Landtech Consultants served as structural engineer of record).

Stormwater Capture

Tank Baustelle 2010 It may seem as if never rains in California, especially during drought years. But, stormwater is a good potential source of water that if captured and stored properly will be a valuable addition to water reserves. Los Angeles County adopted new rules in June 2015 for stormwater capture and reuse, which could serve as a model for the rest of the State. Though there is regulation monitoring the pollution of stormwater that flows into drains, the idea of capturing rainwater for reuse in California is a relatively new one. Rainwater harvesting supports a sustainable method of water management, and has been successful in other parts of the world such as Australia.

Recycled Water

Recycled water overflow from Aquacycle thickener (6324881971) Recharging groundwater and stormwater capture are necessary measures, but how about increasing water supply in the short term? Los Angeles County is considering additional water obtained through unconventional, though perhaps more sustainable, means. The County is talking with the Metropolitan Water District of Southern California (MWD) about a potential large recycled water programwhich would recycle treated sewage. If it succeeds, it would be one of the biggest programs of its kind. Frequently, treated sewage is flushed back into the Pacific Ocean, but reuse systems can transform the water for other uses such as agricultural irrigation, other irrigation, and fire suppression systems. The Santa Clara Water District already recycles water with the Silicon Valley Advanced Purification Center, the largest plant of its kind in Northern California. The facility receives treated water from a nearby wastewater treatment plant and further purifies the water with advanced techniques such as reverse osmosis, microfiltration, and ultraviolet disinfection. The result is eight million gallons of water. VIEW OF AMERICAN RIVER, SHOWING REMAINS OF OLD FOLSOM DAM, HEADGATES AND CANAL. NEW FOLSOM DAM IS IN THE BACKGROUND - Folsom Powerhouse, Adjacent to American River, HAER CAL,34-FOLSO.V,2-95 (CT) The Bureau of Reclamation, created in 1902, developed the network of the 20th-century water infrastructure of dams, reservoirs, and aqueducts in the West. However, as climate change becomes our new reality, the community of civil engineers and municipalities must rethink water networks for the warming 21st century. Recycling water and recharging groundwater are practical, sustainable, and cost-effective methods and allow for more local control of the water supply. As civil engineers learn new skills to adapt to changing water infrastructure, the entire community can work together to increase California’s future water supply.

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 (], 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.