Author: Ashley Sullivan

OTO Sponsors Net Positive Symposium at Hampshire College

June 28, 2018 Ashley Sullivan

O’Reilly Talbot & Okun Associates, Inc. participated as a sponsor in the Net Positive Symposium for Higher Education, held at one of our recently completed projects, the R.W. Kern Center on the beautiful Hampshire College campus in Amherst, Massachusetts.  The R.W. Kern Center   is Living Certified by the International Living Future Institute, meaning that:

  • The building includes regenerative spaces that connect occupants to light, air, food, nature, and community;
  • The building is self-sufficient and remains within the resource limits of the site. A “Living Building” produces more energy than it uses, and collects and treat water on site; and
  • The building is healthy and beautiful.

You can read more about the R.W. Kern Center in the certified case study here.  The building contains a number of features to meet the “imperatives” of each of performance areas.  The building includes composting toilets and treats all its grey water on site via filtering through indoor planters in the building’s common space, and through an onsite wetland.  Thermal efficiency and a rooftop solar array are included in a net-zero energy demand for the building.  Biophilic design elements mimic the beauty of the college campus, and exposed structure and systems allow visitors to see components of the building typically covered behind ceilings and walls (who knew piping systems could be so elegant?).  Materials used in the building are locally sourced and any materials that have adverse effects on human health and the environment are avoided.

The symposium was held over two days, and included tours of the Kern Center and the Hitchcock Center (another Living Building in Amherst, Massachusetts).  The symposium highlighted projects at Hampshire College, Smith College, and Williams College, and their approach to sustainable, resilient, healthy, innovative, and equitable design.  On the 2nd day, a variety of small group lectures were held throughout the day covering many aspects of sustainable design and education, as well as design, development, implementation, and construction aspects of the Kern Center and other Living Building Certified projects.   Attendees included sustainability directors, faculty/educators, students operations staff, and design and construction professionals, and many others.

OTO was fortunate to be a part of the design, construction and commissioning teams for both the R.W. Kern Center and the Hitchcock Center.  OTO provided both environmental and geotechnical engineering services, as well and indoor air quality testing services during commissioning and certifications.  We would like to thank our clients (Hampshire College and Hitchcock Center for the Environment) and other members of the team, most notably Bruner/Cott & Associates, Inc. (architects for Kern Building) and designLAB architects, inc., (architects for Hitchcock Center), and Wright Builders (General Contractor).

OTO is a proud sponsor of the International Living Future Institute and we look forward to more Living Building Projects in the northeast.

Felt at Kern
Photograph of artwork by artist Janice Arnold (JA Felt) which includes 100 feet of dyed felt cloth hung above the staircase at the R. W. Kern Center.

 

 

 

Settlement of Structures Part 2 – “The Fix”

April 2, 2018 Ashley Sullivan

In Part I of this topic, we discussed the assessment and the identification of the cause of settlement of existing structures.  Once the causes have been identified, we can then provide alternatives to prevent on-going settlement, if needed.  This post will discuss a few of the engineering solutions that are available to mitigate a settlement problem of an existing structure.

It should be mentioned that we do not always propose mitigation or remediation.  For instance, if the settlement of the foundation appears to be due to the placement of compacted engineered fill in the 1960s (during construction) over soft compressible clay, OTO likely may recommend that the client delay large and expensive repairs and mitigation, and instead monitor the rate settlement over the next couple of years. In these instances, the rate of settlement often has decreased to negligible amounts and further significant settlement may be unlikely.  At that time, we often recommend that the owner proceed with larger structural and cosmetic repairs.

If settlement concerns appear to be due to improper drainage and the introduction of large amounts of water into the soil mass, OTO will provide recommendations for correcting the drainage problems.  We often can provide local contractor names, upon request, to help repair or install new drainage systems.   Often times, these repair or maintenance tasks can be performed by the owner or facilities manager.

If the cause of the building settlement is the presence of an unsuitable bearing layer, such as loose, non-engineered fill that may continue to compress, or a thick organic peat layer that may continue to degrade, we will recommend a mitigation alternative such as a deep foundation or a soil improvement technique.

A deep foundation system transfers loads through the unsuitable layer to a firm bearing layer, such as driving pilings through a clay layer to bear on a layer of dense sand or bedrock.  Deep foundation alternatives to mitigate the settlement of existing buildings may include helical piles or mini piles.  Helical piles consist of a central steel shaft with horizontal bearing plates (8 to 14 inches in diameter) welded to the shaft at spacings on the order of 12 inches, which are augered into the soil. Mini piles are drilled, cast in place, cement grouted shafts. The piles are constructed by drilling and advancing casing (three to ten inches in diameter) to a selected depth or bearing stratum, installing a steel reinforcing bar down the center of the casing, and injecting cement grout into the casing.  The grout is pumped into the borehole at high pressure, starting at the bottom of the casing and moving upward in order to displace drilling mud or any remaining soil cuttings from the borehole. As the grout is pumped into the borehole, the casing is pulled up to a selected depth at the top of the “bond zone,” allowing contact between the grout and the surrounding soil. Helical or mini-piles are typically connected to the existing footings using an underpinning bracket.

Soil improvement techniques, which improve the existing loose soil so that it can function as a suitable bearing layer, may include pressure or compaction grouting.  In compaction grouting, the soils within the improvement zone are densified and strengthened by a systematic, pressurized injection of controlled low mobility cement grout. The goal of the process is to achieve increased strength of the soil mass.

Compaction Grouting Ashley Blog II
Compaction grouting in progress at an industrial facility

Many factors must be considered in order to recommend the most appropriate engineered solution for settlement issues.  OTO will often discuss existing building and soil conditions and proposed mitigation techniques with specialty geotechnical contractors to evaluate possible alternatives costs.  OTO maintains relationships with most of the foundation specialty contractors in New England and often can provide two or three independent contractor contacts to the client so that competitive cost information can be obtained.  Once the mitigation alternative and contractor is chosen, OTO can assist during construction by documenting the installation and addressing any concerns that arise.

If you have other questions about building settlement, contact Ashley Sullivan at 413-276-4253 or sullivan@oto-env.com to see how OTO can help!

 

 

 

Geotechnical Engineering Series: Building Settlement issues in Western New England

January 9, 2018 Ashley Sullivan

 

The OTO geotechnical group will feature a series of blogs discussing soil settlement concerns and mitigation.  Topics will include forensic studies and remediation alternatives for existing building settlement and damage, as well as providing geotechnical engineering solutions for new construction to mitigate settlement concerns.

 

Part I:  Soil Detectives! Assessment of Settlement of Existing Foundations – Ashley Sullivan, PE

The geotechnical engineers at OTO spend a good portion of their time providing geotechnical engineering solutions to mitigate potential settlement for new structures.  In addition, we are often called in to assess situations where structural damage has already occurred due to the settlement of an existing building.  Our role in these situations is to determine whether foundation settlement is a cause of the structural damage, and more importantly, what was the cause of the foundation settlement.  We then will provide alternatives to mitigate on-going settlement and allow the structures to be productively used.  We work closely with owners, structural engineers, architects and sometimes real estate agents.  These are always interesting projects, since they allow us to put on our detective cap and practice forensic geotechnical engineering.

 

Often times, the OTO geotechnical engineer is not the first phone call, in that the client has already reached out to a structural engineer or architect. The structural engineer will often assess the aboveground building components such as columns and beams to determine whether these load-bearing components are sized correctly and functioning properly.  If the structural components appear to be adequate, the team may start to look at the foundations and ground conditions. This is where OTO can be a valuable asset to the project.

 

Once our services are engaged, we first gather as much information as is readily available regarding the history of the building and likely subsurface conditions. We look for information regarding construction (year built, materials), type of damage observed (cracks, doors and windows that won’t close, leaning walls, etc.), and timelines (immediate/sudden settlement, on-going settlement over long time span, etc.).  We also discuss any changes in site conditions, such as increased building or fill loads, or recent nearby construction work.  Before we leave the OTO’s office, our geotechnical engineer will put some thought into anticipated soil conditions.  We will access OTO’s database of soil boring and test pit information to review conditions at any nearby sites, review both on-line and OTO’s library of published soil and bedrock geology maps, along with historical Sanborn Fire Insurance and USGS topographical maps.  With our experience and the help of published/public information, we often can take an educated guess as to what soil conditions are anticipated at the particular site.

 

Shortly after receiving the initial call, we normally perform a site visit to obtain a firsthand look at the problem area.  We typically review topography and look for indications of fills, changes in drainage (sink holes, soft ground), or slope instability/erosion (bent tree trunks, surficial slips).  At that time, we determine the best approach for investigations, such as the type and approximate locations for invasive testing and/or a settlement monitoring program.  Investigations may include test pits, soil borings and a review of existing subsurface utilities and drainage.  A monitoring program may include the installation of points installed on a building and nearby ground surface, which will be to be surveyed periodically over time to determine trends in the amount and rate settlement.

Door and slab example
An uneven door or cracked or uneven concrete can be a good field indicator of settlement.

Many times, the test pits or soil borings with accompanying laboratory tests quickly reveal the cause of the problem.  Some examples of potential causes include:

  • A pocket of peat, soft clay or loose, non-engineered fill that has compressed under the building load.
  • A buried layer of decomposed organics, trash or other deleterious material that has compressed over time, and will further degrade over time.
  • A soft compressible layer of fine grained soil that has consolidated under the weight of the new structure or fill loads.
  • Wet, loose, granular soils indicate a possible “wash out” condition due to a drainage pipe break and the introduction of water into the soil matrix.

 

We then continue the investigations to determine the nature and extent of the unsuitable conditions.  After the assessment is complete, the geotechnical engineers can start the next phase of the evaluation, “The Fix”, which will be discussed in a future blog post.

 

Do you have a building that is settling?  Contact Ashley Sullivan at 413-276-4253 or sullivan@oto-env.com to see how OTO can help!