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Henderson, NV, United States

Kalra A.,Southern Illinois University Carbondale | Sagarika S.,Atkins North America Inc. | Ahmad S.,University of Nevada, Las Vegas
World Environmental And Water Resources Congress 2016: Hydraulics and Waterways and Hydro-Climate/Climate Change - Papers from Sessions of the Proceedings of the 2016 World Environmental and Water Resources Congress | Year: 2016

We investigated the changes in streamflow (water-year basis) and evaluated the spatial and temporal relationship of the streamflow (averaged for three seasons) across the U.S. with Pacific and Atlantic Ocean climate variability using data from 240 naturalized flow stations for the period 1951 to 2010. Statistical tests (Mann-Kendall and Pettitt's Tests) were used to evaluate the gradual (trend) and abrupt (step) changes. Walker test was used to compute the field significance. The coupled relationship between oceanic-atmospheric indices [Sea surface temperature (SST) and geopotential height at 500-mbar (Z500)] and the seasonal continental U.S. streamflow was evaluated utilizing singular value decomposition. Majority of streamflow stations in the eastern U.S. showed increasing streamflow trend, while most of the stations in Pacific Northwest showed trend that were decreasing. Early period of 1970s and late period of 1980s were detected with shift, following the long term trend. Z500 represented the seasonal variability in streamflow better, compared to SST. Strong correlation with the streamflow stations in the Midwest, Arkansas-White-Red, Souris-Red-Rainy, Pacific Northwest regions were noticed mainly by the Pacific and Atlantic Z500. Strong correlations between Pacific SST and the streamflow stations in southern South-Atlantic-Gulf, Midwest and regions of Pacific Northwest were detected. Likewise, the SST of the Atlantic Ocean showed statistically significant correlations with the New England, Midwest and regions of South-Atlantic-Gulf. The findings from the current study helped in understanding the long term changes and can be used to improve streamflow forecasting models, which may help managing water resources in response to climate change. Source


Clare J.,MWH Americas Inc. | DeKrom P.,Atkins North America Inc.
Proceedings - Rapid Excavation and Tunneling Conference | Year: 2013

The planning and execution of a soft ground tunnel connection 91 m (300 ft) below a residential neighborhood required intricate planning, accurate and confident tunnel survey as well as TBM guidance control. TBM abandonment also necessitated deformation analysis and prediction to establish a sequence for stripping of the TBM interior. TBM abandonment required resistance to high pressure groundwater, drilling and ground freezing loads. Paper presents a review of technical issues and lessons learned from a challenging and risky endeavor. Source


Ingargiola J.,DHS Inc | Perotin M.,Atkins North America Inc.
Forensic Engineering 2012: Gateway to a Better Tomorrow - Proceedings of the 6th Congress on Forensic Engineering | Year: 2013

For more than 30 years, the Federal Emergency Management Agency (FEMA) Building Science Branch of the Federal Insurance and Mitigation Administration has studied the performance of buildings affected by disasters of national significance, including flooding, tornadoes, hurricanes, and terrorist attacks. The Mitigation Assessment Team (MAT) Program draws on the combined resources of the Federal, State, and local governments and the private sector to quickly assemble and deploy teams of investigators following natural and manmade hazard events. The teams conduct field investigations at disaster sites to determine the causes of structural failure and success. Using the information and observations collected in the field, MATs work closely with local and State officials to develop recommendations for improvements in building design and construction, code development and enforcement, and mitigation activities that will lead to greater resistance to hazard events. © ASCE 2013. Source


Elliott H.A.,Pennsylvania State University | Taylor M.,Atkins North America Inc.
Water Science and Technology | Year: 2014

Stabilization and dewatering methods for wastewater solids determine the concentration and nature of phosphorus (P) in biosolids and in-plant sidestreams recycled to the liquid treatment facility. Because water treatment residuals (WTR) exhibit strong immobilization of soluble P, this study evaluated the impact of co-dewatering WTR and biosolids on the P partitioning during dewatering and the environmental lability of biosolids-P measured by water-extractable P (WEP). Overall, P progressively partitioned into the water-insoluble particulate-bound form in dewatered cake with increasing blending ratio (BR) - defined as the dry mass ratio of WTR to biosolids. The reject water total P (TP) content from dewatering biosolids alone (250 mg L -1) was reduced to 60 mg L-1 for a BR = 1.5. Polymer addition resulted in statistically (α = 0.05) lower reject liquid TP, suggesting the cationic polyelectrolyte contributed to P binding. The WEP of the dewatered cake (∼20% solids) dropped from 2.36 g kg-1 (biosolids only) to ∼0.14 g kg-1 for BR = 1.5, meaning the P in land-applied co-processed cake is less susceptible to solubilization by surface runoff compared to unamended biosolids. Co-dewatering can reduce P in return flows and fix P in the dewatered solids in a form less prone to off-site migration following land application. © IWA Publishing 2014. Source


Trademark
Atkins North America Inc. | Date: 2012-08-30

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