There’s a Volcano on our Project Site

Water is the life blood of any city, but its systems are not always pretty. So the two-million-gallon Forest Park Low Tank was embedded into the hillside to preserve the natural character of the area and leave unfettered views. However, this presented engineering challenges. Overcoming those challenges helped us win a 2017 Grand Award from the American Council of Engineering Companies (ACEC).

Wait—What’s Down There?

The subsurface conditions were quite unusual. Maps showed them as hard volcanic rock, but our geotechnical explorations discovered a new volcanic vent, as yet unmapped. Although of great interest to geologists, volcanic vents are rarely built on. A search of case histories did not find any information to guide the process. We embarked upon an exploration and laboratory testing program to determine if the 100-foot plus pile of cinders would support the tank. We determined that the cinders were fairly uniform across the area, resulting in uniform support for the tank. Our testing further determined the magnitude of loading the cinders could support. With this information we were able to design a foundation that did not require expensive subgrade improvements or pile foundations.

Our high-tech analyses confirmed a low-tech approach would work.

Burying Infrastructure to Preserve the Natural Beauty

In many places, water tanks are constructed within large cuts that many may view as eyesores and which permanently remove natural habitat. This has been accepted over decades as a necessary compromise to provide a robust water supply to our cities. However, this compromise does not need to be accepted. Much like the trend of burying power, communications, and other utilities that were once also overhead, the Forest Park Low Tank demonstrates that water infrastructure can be adapted similarly.

Making the Water Supply Safe

Water is a critical resource in any disaster that disrupts our infrastructure. It’s common knowledge that we cannot survive for more than three days without water. During any natural disaster, it is imperative that our water remain safe and accessible. We completed a site specific seismic hazard (SSSH) as part of our work, so the tank and appurtenant facilities will withstand the next “Big One.”

Defining Ingenuity

Sometimes ingenuity is not devising something new, but applying simple methods to solve a problem. We used performance-based results to guide changes in shoring design, and confirmed landslide mitigation approaches during construction. We avoided designing expensive foundation alternatives, installing bulletproof (and expensive) secant shoring walls, and over-analyzing slope stability prior to construction. And then we buried our best work.

The one thing to remember about this project is that we did not blow our top over an unexpected volcanic vent; instead, we persevered and worked with the design and construction teams to build a successful project…and then buried it out of “site.”Finished project

Towering Hills for Beauty and Strength

Governors Island

Photo: Timothy Schenk

A dozen years ago an American port representative was asked how his port was preparing for rising sea levels. “Well…we aren’t,” he answered, somewhat sheepishly, because he knew they should be. Back then, the public was skeptical of the controversial topic, and frankly many ports had too many other priorities. But now public officials see the situation in a new light. They are taking advantage of waterfront development projects to make property not only more resilient to climate change, but also more beautiful and beneficial to the public.

A perfect example is the 40-acre Governors Island Park and Public Space in New York. West 8, an urban design and landscape architecture firm, transformed the abandoned former military island into a green oasis with an extraordinary 360-degree experience of water and sky that has won numerous awards. Part of the makeover involved creating four tall, dramatic hills from twenty-five to seventy feet high. This meant overcoming a major challenge involving Governors Island history.

Governors Island Park and Public Space

Pumice, or lightweight fill (the light colored material) is placed on the water side of the tallest hill. Image courtesy of West 8

From Subway Dirt to Island

Back in 1637, when a Dutch man bought Governors Island for two ax heads, a string of beads, and some nails, the island was only about 72 acres. In 1901, somebody needed a place to discard the dirt from the excavation of New York’s Lexington Avenue subway line. What better place to put it than Governors Island? The dirt widened the island by 100 acres.

Fast forward to the twenty-first century. Now that the island had been sold back to the people of New York for one dollar, it was possible to take advantage of the island’s potential views, which meant building upwards. To create the new hills, West 8 needed to add 300,000 cubic yards of new fill—enough to fill 40 Goodyear blimps. The challenge was to keep that massive amount of dirt from pushing the island built on subway fill out into the harbor.

Hart Crowser worked with the lead civil engineer to make the hills strong yet light. Twenty-five percent of the new fill is from the demolition of structures and parking lots. This made it sustainable and strong. Pumice lightened the load. Some of the fill was wrapped in geotechnical matting, and the steepest slopes used wire baskets. This allowed hills as high as seventy to be built within twenty feet of the shoreline, and allowed for varying slopes and walkways, where the public can safety enjoy the park.

Governors Island reopened to the public on May 28.

Shaken and Stirred: Northwest Earthquake and Tsunami

Washington 9.0 earthquake--Are you ready? Oregon 9.0 Earthquake--Are you ready?Suddenly the Pacific Northwest is on the national stage for its earthquake and tsunami vulnerability, thanks to a New Yorker article. “The Really Big One,” by Kathryn Schulz, has triggered attention from dozens of local papers and news sites. Yet even before the New Yorker shook the Northwest (pun intended), Oregon Public Broadcasting had been featuring Hart Crowser engineer Allison Pyrch in its “Unprepared” series, to alert the region to the impending disaster in hopes that we will get prepared.

Also, Allison recently gave a presentation for the Lake Oswego Sustainability Network: “Surviving a 9.0, Lessons Learned from Japan and Beyond.” If you are involved in emergency management or just plain interested in massive disasters and their aftermaths, settle in for some powerful visuals and easy-to-follow explanations about earthquakes in Japan and Chile, how the 9.0 earthquake and tsunami will happen in the Pacific Northwest, and what you can to do to be resilient.

Watch the whole “Surviving a 9.0” video to get unusual insight into what’s ahead, or if you’re pressed for time, skip to one of these minute points:

  • 9:00 Jan Castle introduces Allison Pyrch 10:56 Allison Pyrch’s presentation begins with how the Pacific Northwest 9.0 earthquake will happen
  • 14:25 Comparing the Japan and Chile quakes “It didn’t stop shaking for a day”
  • 21:45 Fire damage/natural gas 22:30 Water, wastewater, and electrical systems; liquid fuel; natural gas
  • 24:25 Lifelines/infrastructure/airports “PDX will not be up and running”
  • 28:35 Port damage/economics
  • 31:45 How prepared is the Pacific Northwest? When will it happen? “We are 9 ½ months pregnant”
  • 35:00 What will it look like?
  • 37:32 What you can do
  • 40:30 What businesses can do
  • 42:11 Can you be sustainable without being resilient?
  • 43:33 What about a resiliency rating system similar to LEED?
  • 53:30 Will utilities, transportation, hospitals be useable after the 9.0? “We’re toast”
  • 1:01:30 End of Allison’s presentation; additional information from Jan Castle on how to prepare
  • 1:19:19 How sustainability measures in your home lead to resiliency

Increase Your Points Toward LEED Certification

Federal Center South

Federal Center South, the most energy-efficient office building in the Pacific Northwest, may achieve LEED Platinum. Energy Piles, recycled wood and construction debris, and stormwater infiltration galleries contributed LEED points.

Most LEED points come from efficiency in design and construction areas such as energy, water, materials, and indoor environmental quality. That’s why it may not be obvious how geotechnical engineers and environmental scientists contribute to LEED certification. Since LEED Silver is a requirement for most new public buildings, with LEED Gold the new normal, owners need every possible point. Here are several avenues to gain more:

Sustainable Sites – Several credits are available, including Brownfield Redevelopment (Credit 3); Protect and Restore Habitat, including green roofs (Credit 5.1); and Stormwater Design, including infiltration, reuse, pervious paving, swales, and other LID solutions (Credits 6.1 and 6.2).

Water Efficiency – Credits are typically based on the percentage of reduction in the use of potable water for the new development. Water-efficient landscaping, reuse of rainwater, and capture and reuse of groundwater in the irrigation or building systems can cut water use by 20% or more. Designing efficient filters for graywater recycling can lead to additional points.

Energy and Atmosphere – Credit 2 (On-Site Renewable Energy) allows as many as 3 credits for generating up to 7.5% of the building’s power usage on site. Properly designed ground source heat pump geothermal systems will achieve this goal and these points.

Materials and Resources – Again, several credits are available: Credit 2.1 Construction Waste Management (diverting demolition debris from landfills or incinerators), Credit 3.2 Materials Reuse (reusing salvaged building materials like foundation piles), Credit 4 Recycled Content (using materials such as ground down tires or recycled glass for backfill).

Innovation & Design Process – New or innovative energy saving solutions that have been applied to a site development can be described, justified, and submitted for potential extra points.

Geotechnical and environmental professionals can work with design and construction teams to gain as many as 5 or 6 additional points – and that might be the difference between Silver and Gold, or Gold and Platinum.

Infiltration and Laboratory Testing Support Green Design

Federal Center South Swale

Swale at the new Federal Center South Building in Seattle

Rain gardens and bio-filtration swales are an increasingly important part of the sustainability approach for new construction. They keep rainwater from flowing over impervious surfaces where it can pick up pollutants and carry them to water bodies. This benefit is more and more imperative when it comes to controlling non point source pollution. The Washington State Department of Ecology, for example, has reconfirmed surface runoff as the leading pathway for toxics to get into Puget Sound. (Phase 1 study, Phase 2 study).

Infiltration testing allows you to determine whether a swale will be successful at a given property. An infiltration test involves excavating a test pit (typically 5 feet by 5 feet). A hydrogeologist adds water to the pit, then records how much water is necessary to maintain the water level at the same level over a period of 10 to 12 hours. The hydrogeologist then stops the water flow and measures the drop in water level. The infiltration rate determined from a field test is called a field infiltration rate. To determine the design infiltration rate, the hydrogeologist then adjusts for a number of factors such as site variation, number of tests conducted, degree of long-term maintenance and influent pre-treatment/control, and the potential for long-term clogging from silt and bio-buildup.

Geotechnical laboratory testing is useful for rain gardens, which require a specific mix of soil types that helps scrub some of the contaminants from the rainwater before it reaches a major body of water, yet still allows the water to drain. Rain gardens are also an effective way to store water from large storm events and prevent it from overloading the storm drain and sewer systems in the public streets.