CH2M HILL is an American engineering company that provides consulting, design, construction, and operations services for corporations, and federal, state, and local governments. The firm's headquarters is in Meridian, an unincorporated area of Douglas County, Colorado in the Denver-Aurora Metropolitan Area. The postal designation of nearby Englewood is commonly listed as the company's location in corporate filings and local news accounts. As of December 2013 CH2M HILL had approximately 26,000 employees and 2013 revenues totaled $5.88 billion. The firm is employee-owned, with an internal stock market that operates buy/sell events quarterly. Wikipedia.
Rojas H.A.,CH2M HILL |
Foley C.,Marquette University |
Pezeshk S.,University of Memphis
Earthquake Spectra | Year: 2011
An automated performance-based design methodology to optimize structural and nonstructural system performance is outlined and it is shown that it can be used to enhance understanding of structural steel system design for minimum life-cycle costs. Performance is assessed using loss probability with direct economic loss expressed as a percentage of the building replacement cost. Time-based performance assessment is used to compute the expected annual loss of a given steel framing system assuming exposure to three seismic hazard levels. Damage to the structural system, nonstructural displacement-sensitive components, and nonstructural acceleration-sensitive components is characterized using fragility functions. A steel building with three-story, four-bay topology taken from the literatureis used to demonstrate application of the algorithm with subsequent comparison of designsobtained using the proposed methodology and others found in the literature. © VC 2011, Earthquake Engineering Research Institute.
Miranda J.C.,CH2M HILL
Structural Control and Health Monitoring | Year: 2012
This paper establishes the theoretical basis for a method of selecting design parameters of damping maximized tuned mass dampers (TMDs) intended to reduce the seismic response of structures. Given that increased damping decreases the seismic response of conventional structures, the method maximizes the damping that is physically feasible for the TMD, and consequently for the structural system, and provides parameters that are intrinsic to the system and excitation independent. This is achieved using a physical interpretation of the system's eigenproblem, and by establishing the correspondence between factors of the characteristic equations expressed with structural as well as with modal properties. The resulting parameters for the modal damping maximized TMD are simple, are obtained in closed forms, and are derived in a straightforward manner. Copyright © 2011 John Wiley & Sons, Ltd.
Mebane C.A.,U.S. Geological Survey |
Dillon F.S.,CH2M HILL |
Hennessy D.P.,Anchor QEA LLC
Environmental Toxicology and Chemistry | Year: 2012
The authors conducted 150 tests of the acute toxicity of resident fish and invertebrates to Cd, Pb, and Zn, separately and in mixtures, in waters from the South Fork Coeur d'Alene River watershed, Idaho, USA. Field-collected shorthead sculpin (Cottus confusus), westslope cutthroat trout (Oncorhynchus clarkii lewisi), two mayflies (Baetis tricaudatus and Rhithrogena sp.), a stonefly (Sweltsa sp.), a caddisfly (Arctopsyche sp.), a snail (Gyraulus sp.), and hatchery rainbow trout (Oncorhynchus mykiss), were tested with all three metals. With Pb, the mayflies (Drunella sp., Epeorus sp., and Leptophlebiidae), a Simuliidae black fly, a Chironomidae midge, a Tipula sp. crane fly, a Dytiscidae beetle, and another snail (Physa sp.), were also tested. Adult westslope cutthroat trout were captured to establish a broodstock to provide fry of known ages for testing. With Cd, the range of 96-h median effect concentrations (EC50s) was 0.4 to >5,329μg/L, and the relative resistances of taxa were westslope cutthroat trout ≈ rainbow trout ≈ sculpin << other taxa; with Pb, EC50s ranged from 47 to 3,323μg/L, with westslope cutthroat trout
Senner R.,CH2M HILL
Environmental Impact Assessment Review | Year: 2011
Evaluating and comparing development alternatives with regard to sustainability is an important goal for comprehensive project appraisal. In the United States, this component has been largely missing from standard environmental impact assessment practice. Cumulative effects assessment provides a way to appraise the sustainability of project alternatives in terms of their probable contributions to long-term trends affecting the condition of valued environmental components. Sustainability metrics and predictors are being developed as criteria for rating systems and evaluation processes that are applied to community planning, building design, and transportation infrastructure. Increasing interest in adaptive management is also providing cost-effective solutions to optimizing safety and function throughout the long-term operation of a facility or infrastructure. Recent federal legislation is making it easier to integrate sustainability features into development alternatives through early, community-based planning. © 2011 Elsevier Inc.
Daigger G.T.,CH2M HILL
Water Science and Technology | Year: 2011
The modern age of wastewater treatment modelling began with publication of the International Water Association (IWA) Activated Sludge Model (ASM) No.1 and has advanced significantly since. Models are schematic representations of systems that are useful for analysis to support decision-making. The most appropriate model for a particular application often incorporates only those components essential for the particular analyses to be performed (i.e. the simplest model possible). Characteristics of effective models are presented, along with how wastewater modelling is integrated into the wastewater project life cycle. The desirable characteristics of wastewater treatment modelling platforms are then reviewed. Current developments of note in wastewater treatment modelling practice include estimates of greenhouse gas emissions, incorporating uncertainty into wastewater modelling and design practice, more fundamental modelling of process chemistry, and improved understanding of the degradability of wastewater constituents in different environments. Areas requiring greater emphasis include increased use of metabolic modelling, characterisation of the hydrodynamics of suspended and biofilm biological treatment processes, and the integration of biofilm and suspended growth process modelling. Wastewater treatment models must also interface with water and wastewater management software packages. While wastewater treatment modelling will continue to advance and make important contributions to practice, it must be remembered that these are complex systems which exhibit counter-intuitive behaviour (results differ from initial expectations) and multiple dynamic steady-states which can abruptly transition from one to another. © IWA Publishing 2011.