CH2M Hill Companies, Ltd., also known as CH2M, was an engineering company that provided consulting, design, construction, and operations services for corporations and governments. The company was organized in Delaware, and headquartered at 9191 South Jamaica Street, Englewood, Colorado. In December 2017, the company was acquired by Jacobs Engineering Group. The company played a major role in the Panama Canal expansion project. The company developed, maintained and published its own method for managing projects for clients, called the CH2M Hill Project Delivery System. The firm was named from the initials of its four founders.
A mining tail cover system for controlling toxic substances (e.g. chromium (VI) (Cr 6+ )) in chromium ore processing residue (COPR) requires unsaturated transport modelling with inputs of water retention curves (WRCs) to evaluate the system. This study experimentally characterised the unsaturated properties of unweathered grey-black (GB) and weathered hard-brown (HB) COPR before and after hydration associated with mineralogical changes and estimated chromium transport by employing numerical modelling with the properties. X-ray diffraction (XRD) tests were also performed before and after testing to quantify the mineralogical compounds of materials. The XRD results showed that the brownmillerite decreased with the degree of the hydration. The relationship between the fitting parameters of WRC models and variables, such as the degree of hydration and specific gravity, was investigated. The WRC of GB COPR shows a bimodal shape because of the hydration process during the test. The hydration process transformed the chemical and mineralogical composition of GB COPR, thus influencing its WRC characteristics. Numerical simulations parameterised by WRC properties were conducted to compare unsaturated transport between GB and HB COPR through a sandy cover. HB COPR had a longer transportation time than GB COPR, revealing the importance of considering water retention characteristics in remediation plans.
Anaerobic ponds have the potential to contribute to low carbon wastewater treatment, however are currently restricted by long hydraulic residence time (HRT) which leads to large land requirements. A two-stage anaerobic pond (SAP) design was trialled against a single-stage control (CAP) over four HRTs down to 0.5 days, to determine the lowest HRT at which the ponds could operate effectively. No statistical differences were observed in particulate removal between the ponds over all four HRTs, suggesting solids loading is not a critical factor in AP design. Significantly higher biogas production rates were observed in the SAP than the CAP at 1.5 d and 1.0 d HRT, and microbial community profiling suggests the two-stage design may be facilitating spatial separation of the anaerobic digestion process along reactor length. Hydrogenotrophic methanogensis dominated over aceticlastic, with acetate oxidisation a likely degradation pathway. Experimental tracer studies were compared to CFD simulations, with the SAP showing greater hydraulic efficiency, and differences more pronounced at shorter HRTs. Greater flow recirculation between baffles was observed in CFD velocity profiles, demonstrating baffles can dissipate preferential flow patterns and increase effective pond volume, especially at high flow rates. The study demonstrates the potential of APs to be operated at shorter HRTs in psychrophilic conditions, presenting an opportunity for use as pre-treatments (in place of septic tanks) and primary treatment for full wastewater flows. Two-stage designs should be investigated to separate the stages of the anaerobic digestion process by creating preferential conditions along the pond length.
Damages to port facilities supported by anchored sheetpile walls are commonly observed at moderate to high seismic load levels. Predicting the extent of seismic deformations of anchored sheetpile walls is a necessary step in the performance-based design; however, the lack of straightforward and practical models poses great challenges for this prediction. In this study, a hybrid framework is proposed for developing practical empirical models for predicting seismic deformations of anchored sheetpile walls. First, a 2-D numerical model is calibrated with field case history data. Next, a series of numerical simulations are undertaken to characterize the relationship between the responses (i.e., seismic deformations of anchored sheetpile walls) and the inputs (i.e., variables that affect the responses). The model bias factor and coefficients (i.e., model parameters) in the derived coarse solution model are then characterized probabilistically, and further updated and refined with the collected database of field cases and/or experimental data. Finally, this hybrid framework is demonstrated through the development of data-driven empirical models for predicting seismic deformations of anchored sheetpile walls. The results show that the proposed framework is effective in developing a data-driven empirical model, and the obtained model can be easily updated with additional case history data, as needed, to improve the accuracy.
For millennia the Indus Valley Civilizations have learned how to manage the waters of the Indus River water system. However, climate changes could have unforeseeable effects on the region's growing population, and they could hinder short- and long-term decision making regarding the emerging needs of the energy-food-water nexus. Also, changes in aspects of the variability of monsoons and in the timing and amount of snow and glacier melt may lead to extreme events, such as droughts over the Asian plains and flooding in the neighboring Himalayas. Although global and regional climate models have advanced our knowledge about future changes in the climate system, there are still uncertainties and knowledge gaps in our understanding of the precipitation systems associated with the Asian summer monsoon and the winter and pre-monsoon western disturbances. Hence understanding the summer and winter precipitation variabilities and their connections to the hydrological cycle in the Hindu-Kush-Himalayan region in general and the Indus River Basin in particular is of utmost importance for setting baseline and future timescales.
The Port of Alaska is modernizing its facilities through the Port of Alaska Modernization Program (PAMP). An initial step in the program was implementation of a test pile project (TPP), which involved installation of ten 200-foot long by 48-inch diameter, 1-inch wall, steel pipe piles. The TPP replicated the concept pile design and marine permit conditions. The project included (1) monitoring response of each pile during initial installation and 13 to 38 days after initial pile installation with a pile driving analyzer (PDA) and (2) evaluating the performance of two types of underwater noise attenuation systems (NAS). Key observations from the TPP included doubling of pile capacity for the setup periods, the absence of soil-plug formation during initial driving and restrike, and appreciable decreases in underwater noise from the use of the NAS. This paper summarizes background for and results of the test pile project.
