Sejkora P.,GZA GeoEnvironmental Inc. |
Kirisits M.J.,University of Texas at Austin |
Barrett M.,University of Texas at Austin
Journal of the American Water Resources Association | Year: 2011
Animals, such as birds, are a source of fecal indicator bacteria and pathogens in the environment. Our objective was to determine whether a colony of cliff swallows nesting underneath a bridge would yield a measurable increase in fecal indicator bacteria (specifically Escherichia coli) in the underlying creek. When the swallows were absent, dry-weather concentrations of E. coli upstream and downstream of the bridge (in Austin, Texas) were below the Texas contact recreation criteria. When the swallows were present, dry-weather geometric-mean E. coli concentrations increased significantly from upstream (43 most probable number [MPN]/100ml) to downstream (106MPN/100ml) of the bridge. One exceedance and one near-exceedance of the Texas single-sample contact recreation criterion were observed during the swallows' nesting phase. When the swallows were present, the downstream E. coli geometric-mean concentration in storm events (875MPN/100ml) was significantly higher than the upstream concentration (356MPN/100ml), suggesting that runoff flushes swallow feces from the ground into the creek. Although the loading of E. coli from cliff swallows nesting under bridges can be significant (e.g., dry-weather loading of 3.1×108MPN/day/nest), the zoonotic potential of the cliff swallow must be examined to determine the risk to human health from contact recreation in waters contaminated with cliff swallow feces. © 2011 American Water Resources Association.
Tumer R.,GZA GeoEnvironmental Inc. |
Grynkewicz F.,FGG Consulting LLC FGG
Geotechnical and Structural Engineering Congress 2016 - Proceedings of the Joint Geotechnical and Structural Engineering Congress 2016 | Year: 2016
In 2012, the Novartis Institute for Biomedical Research embarked on a 600 million expansion of its Cambridge, Massachusetts Campus with the addition of a 550,000 square foot complex which includes multiple levels of underground space. To excavate to the maximum depth in excess of 45 feet, the contractor faced several logistical challenges presented by the congested, urban location. These challenges included the shear size of the excavation, which occupied an entire city block, the presence of very soft clay deposits, the close proximity to adjacent buildings and varying structural systems and slab elevations. A support of excavation (SOE) system was designed which consists of a combination of deep soil mix wall and steel sheet piling to support a total excavation area of about 3.2 acres (138,500 sq ft). Since the use of tiebacks was limited due to the site location, the SOE was mostly supported by internal bracing; with single strut lengths reaching 240 feet. Finite element models were developed to account for soil non-linearity, SOE stiffness, and varying depths of excavation. With strut loads up to 1,200 kips, an instrumentation system provided real time data acquisition of the loads in the bracing and deflections of the SOE. The monitoring data were comparable to the stresses and deformations predicted by finite element model. © ASCE.
Lutenegger A.J.,University of Massachusetts Amherst |
Khalili J.,GZA GeoEnvironmental Inc.
Geotechnical Special Publication | Year: 2015
Results of axial tension (uplift) tests on driven open-end pipe piles and H-Piles with difference surface coatings are presented. Piles included plain steel, galvanized steel and piles coated with Slickcoat, a silicone epoxy surface coating. Open-end pipe piles with outside diameters of 2.875 in. and 4.5 in. and H-piles consisting of standard steel W6x9 sections were evaluated. Piles were installed using a simple gravity drop hammer. Uplift tests were conducted at four sites consisting of both clay and sand to evaluate the influence of surface coating on the short-term behavior and long-term behavior. Short-term tests were performed seven to ten days after driving; long-term tests were performed on the same piles 200 to 400 days after driving. Axial tension tests were performed to failure for each pile. A comparison of the installation driving records is presented which shows a similarity in driving resistance for the different surface coatings. Load tests are also presented and show that the Slickcoat coated piles gave a substantial decrease in shaft resistance for both short-term and long-term behavior as compared with plain or galvanized piles.
Davids W.G.,University of Maine, United States |
Sandford T.,University of Maine, United States |
Ashley S.,SW Cole Engineering Inc. |
Delano J.,GZA GeoEnvironmental Inc. |
Lyons C.,E Pro Engineering
Journal of Bridge Engineering | Year: 2010
Integral abutment bridges (IABs) with short steel H-pile (HP) supported foundations (≤4 m of pile depth) are economical for many environmentally sensitive sites with shallow bedrock. However, such short piles may not develop an assumed, fixed-end support condition at some depth below the pile cap, which is inconsistent with traditional pile design assumptions involving an equivalent length for bending behavior of the pile. In this study, the response of an IAB with short HP-supported foundations and no special pile tip details such as drilling and socketing is investigated. Instrumentation of a single-span IAB with 4-m-long piles at one abutment and 6.2- to 8.7-m-long piles at the second abutment is described. Instrumentation includes pile strain gauging, pile inclinometers, extensometers to measure abutment movement, earth pressure cells, and thermistors. Pile and bridge response during construction, under controlled live load testing, and due to seasonal movements are presented and discussed. Abutment and pile head rotations due to self-weight, live load, and seasonal movements were all found to be significant. Measured abutment movements were likely affected by both temperature changes and deck creep and shrinkage. Based on the field study results presented here, moderately short HPs driven to bedrock without special tip details appear to perform well in IABs and do not experience stresses larger than those seen by longer piles. © 2010 ASCE.
Bowman D.C.,GZA GeoEnvironmental Inc. |
Bowman D.C.,University of North Carolina at Chapel Hill |
Wilcock W.S.D.,University of Washington
Antarctic Science | Year: 2014
An ocean bottom seismometer (OBS) network was deployed for 1 month at Deception Island volcano, Antarctica, in early 2005. Although only two volcano-tectonic and three long-period events were observed, the three OBSs located > 2 km apart inside the caldera detected over 3900 events that could not be attributed to known volcanic or hydrothermal sources. These events are found on one instrument at a time and occur in three types. Type 1 events resemble impulsive signals from biological organisms while type 2 and type 3 events resemble long-period seismicity. The largest number of events was observed in a region of volcanic resurgence and hydrothermal venting. All three types occur together suggesting a common cause and they show evidence for a diurnal distribution. The events are most likely to be due to aquatic animals striking the sensors, but a geological source is also possible. In the first case, these signals indicate the presence of a biological community confined to the caldera. In the second case, they imply widespread hydrothermal activity in Port Foster. Future OBS experiments should bury the seismometers, include a hydrophone, deploy instruments side-by-side, or include a video camera to distinguish between biological and geological events. © Antarctic Science Ltd 2013.