MWH Americas Inc.

Dallas, TX, United States

MWH Americas Inc.

Dallas, TX, United States

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Yang L.,MWH Americas Inc. | Woods R.D.,University of Michigan
Canadian Geotechnical Journal | Year: 2015

The shear modulus and damping of cemented clay are investigated using ultrasound transducers, bender elements, and a resonant column device. The model SimSoil-CC, based on the Pestana and Salvati (published in 2006) model SimSoil, is proposed to represent the maximum shear modulus and stress–strain behavior (under cyclic loading conditions) at small strains for the cemented clay. The model can also be used for uncemented clay when the cementation parameter is set to zero. Model parameters are determined for three types of clay (kaolinite, bentonite, and the equal mix of kaolinite and bentonite) and two types of cementation agents (type III Portland cement and gypsum). The model SimSoil-CC is validated using the laboratory test data of this study and data from other studies in literature. The SimSoil-CC model can be very useful for performing earthquake site response analysis for naturally cemented clay sites or sites that have been improved by cementation. In addition, a relationship between the cementation parameter acc(CC)2 (acc, cement material constant; CC, dry cement content) and the unconfined compression strength is proposed. The relationship simplified modeling for naturally cemented clay soil or cemented clay whose cement contents and cementation type are otherwise difficult to determine. This research advances the understanding of cemented clay by providing a database of test results and creation of a model that can be used to predict the response of cemented clay soils to dynamic loads.


Doyle B.R.,MWH Americas Inc.
2012 Proceedings - North American Tunneling, NAT 2012 | Year: 2012

The GBR concept has become widely accepted in the tunneling industry since ASCE first published the guide "Geotechnical Baseline Reports for Underground Construction" in 1997. While the ASCE guide is clear on GBR concepts, it is not definitive on how a GBR should be prepared. Tunnel designers have yet to reach a consensus on what constitutes a proper GBR. The author is in complete agreement with the objectives of the GBR concept, but proposes to narrow the range of interpretation as to what constitutes a proper GBR, by clarifying potential ambiguities of the ASCE guide.


Barnhurst J.E.,MWH Americas Inc.
Pipelines 2013: Pipelines and Trenchless Construction and Renewals - A Global Perspective - Proceedings of the Pipelines 2013 Conference | Year: 2013

The wastewater system backbone of the New Orleans Sewerage & Water Board (the Board) is comprised of large-diameter, steel force mains in diameters from 54- to 72-inch size. During Hurricanes Katrina and Rita, the town and associated infrastructure experienced damages associated with the flooding resulting from these storms. In 2005, two back-to-back major storms inflicted great damage on the City and the surrounding area. On August 29, 2005, Hurricane Katrina hit the Louisiana coastline as a Category 4 storm. The water level in Lake Pontchartrain peaked at 8.6 feet (7.6 feet above the normal sea level). Breaches in the levees built to protect the City occurred at the 17th Street Canal, the London Avenue Canal, and the Industrial Canal. The breaches led to flooding in nearly 80 percent of the City with water depths reaching 25 feet in some areas and adding very large external loads to the existing forcemains. Less than a month later, Hurricane Rita made landfall on September 24, 2005, as a Category 3 storm. Levees were again overtopped in at least three locations along the Industrial Canal, re-flooding the City's Lower Ninth Ward, a few neighborhoods surrounding Lake Pontchartrain, and neighboring St. Bernard Parish. © 2013 American Society of Civil Engineers.


Xiao Y.,University of British Columbia | Roberts D.J.,University of British Columbia | Zuo G.,University of Houston | Badruzzaman M.,MWH Americas Inc. | Lehman G.S.,MWH Americas Inc.
Water Research | Year: 2010

A salt-tolerant, perchlorate- and nitrate-reducing bacterial culture developed previously was used to inoculate two acetate-fed fluidized bed reactors (FBRs) which treated a 6% ion-exchange regenerant brine containing 500 ± 84 mg-N/L nitrate and 4.6 ± 0.6 mg/L perchlorate. The reactors were operated in series in continuous flow mode for 107 days after an acclimation period of 65 days. Pilot operation data suggest that complete denitrification was achieved after 70 days of operation, but significant perchlorate removal was not observed. Molecular analysis of the inoculum culture and biomass from the pilot plant samples using denaturing gradient gel electrophoresis (DGGE) and fluorescence in situ hybridization (FISH) revealed that the composition of the biomass in the pilot-plant was evolving with time in each FBR. The total number of Azoarcus/Denitromonas decreased in the first reactor with time and position in the bioreactor during acclimation and operation. FISH analysis clearly revealed that the number of Halomonas which was the dominant nitrate-reducing organism increased in the first reactor. This indicates a shift towards nitrate reduction which corresponds to the operation data. Both DGGE and FISH demonstrated that the Azoarcus/Denitromonas was still present in the second bioreactor, which indicated that the removal of nitrate in the first reactor was allowing the perchlorate-reducing organisms to establish themselves in the second reactor. The study also suggests that FISH was more effective for analysis of the composition of these cultures and it would be a better tool for the routine monitoring of cultures. © 2010 Elsevier Ltd.


Oppenheimer J.,MWH Americas Inc. | Eaton A.,MWH Laboratories | Badruzzaman M.,MWH Americas Inc. | Haghani A.W.,MWH Laboratories | And 2 more authors.
Water Research | Year: 2011

Urban watersheds are susceptible to numerous pollutant sources and the identification of source-specific indicators can provide a beneficial tool in the identification and control of input loads, often times needed for a water body to achieve designated beneficial uses. Differentiation of wastewater flows from other urban wet weather flows is needed in order to more adequately address such environmental concerns as water body nutrient impairment and potable source water contamination. Anthropogenic compounds previously suggested as potential wastewater indicators include caffeine, carbamazepine, N,N-diethyl-meta-toluamide (DEET), gemfibrozil, primidone, sulfamethoxazole, and TCEP. This paper compares the suitability of a variety of anthropogenic compounds to sucralose, an artificial sweetener, as wastewater indicators by examining occurrence data for 85 trace organic compounds in samples of wastewater effluents, source waters with known wastewater point source inputs, and sources without known wastewater point source inputs. The findings statistically demonstrate the superior performance of sucralose as a potential indicator of domestic wastewater input in the U.S. While several compounds were detected in all of the wastewater effluent samples, only sucralose was consistently detected in the source waters with known wastewater discharges, absent in the sources without wastewater influence, and consistently present in septic samples. All of the other compounds were prone to either false negatives or false positives in the environment. © 2011 Elsevier Ltd.


Hirani Z.M.,MWH Americas Inc. | DeCarolis J.F.,MWH Americas Inc. | Adham S.S.,ConocoPhillips | Jacangelo J.G.,MWH Americas Inc. | Jacangelo J.G.,Johns Hopkins University
Water Research | Year: 2010

A pilot study was conducted over a period of 18 months at the Point Loma Wastewater Treatment Plant (PLWWTP) in San Diego, CA to evaluate the operational and water quality performance of six selected membrane bioreactor (MBR) systems at average and peak flux operation. Each of these systems was operated at peak flux for 4 h a day for six consecutive days to assess peak flux performance. Virus seeding studies were also conducted during peak flux operation to assess the capability of these systems to reject MS-2 coliphage. When operating at steady state, these MBR systems achieved an effluent BOD concentration of <2 mg/L and a turbidity of <0.1 NTU. Peak flux for the MBR systems ranged from 56 to 76 L/m2/h (liters per square meter per hour) with peaking factors in the range of 1.5-3.2. When switching from average to peak flux operation, a reversible drop of 22-32% in temperature-corrected permeability was observed for all submerged MBR systems. The percent drop in permeability increased as MLSS concentration in the membrane tank increased from 11,100 mg/L to 15,300 mg/L and was observed to be highest for the system operating at highest MLSS concentration. Such trends were not observed with an external MBR system. Each MBR system was able to sustain a 4-h-a-day peak flow for six consecutive days with only moderate membrane fouling. The membrane fouling was quantified by measuring the drop in temperature-corrected permeability. This drop ranged from 13 to 33% over six days for different submerged MBR systems. The MBR systems achieved microbial removal in the range of 5.8-6.9 logs for total coliform bacteria, >5.5 to >6.0 logs for fecal coliform bacteria and 2.6 to >3.4 logs for indigenous MS-2 coliphages. When operating at peak flux, seeded MS-2 coliphage removal ranged from 1.0 to 4.4 logs, respectively. The higher log removal values (LRVs) for indigenous MS-2 coliphage among different MBR systems were probably the result of particle association of indigenous coliphage. Differences in membrane pore size (0.04-0.2 μm) amongst the MBR systems evaluated did not have a substantial impact on indigenous MS-2 coliphage removal, but seeded MS-2 coliphage removal varied among the different MBR systems. © 2010 Elsevier Ltd.


Oneby M.A.,MWH Americas Inc. | Bromley C.O.,MWH Americas Inc. | Borchardt J.H.,MWH Americas Inc. | Harrison D.S.,MWH Americas Inc.
Ozone: Science and Engineering | Year: 2010

Ozone is a strong oxidant used to treat a variety of constituents in potable water, wastewater, water reuse, and industrial water treatment applications. Ozone is effective at oxidizing a wide range of organic and inorganic compounds and disinfection. Well-known in potable water treatment, with about 400 US installations and 3,000 world-wide, ozone has limited application at wastewater treatments, with less than 10 operating facilities in the US. The ability of ozone to significantly reduce low level concentrations of trace organic compounds, including endocrine disrupting chemicals (EDCs), pharmaceuticals and personal care products (PPCPs), and other emerging contaminants have increased interest in applying ozone in potable water and wastewater treatment. Treating at the point source discharge rather than the water supply intake may be more effective. A recent American Water Works Research Foundation (AwwaRF) report indicated high removals of many EDCs and PPCPs at typical disinfection doses. Several wastewater utilities have installed or are in the process of installing ozone to treat secondary effluent. These utilities are using ozone in a variety of ways: as a primary disinfectant, for treatment of microconstituents, and in combination with other processes (e.g. membranes and UV) to produce high-quality water for indirect potable reuse (IPR). The different applications, treatment goals and basis of process selection are compared and contrasted. Secondary benefits of ozone treatment of secondary effluent, including the use of off-gas in biological treatment is also discussed. © 2010 International Ozone Association.


Turker U.,Eastern Mediterranean University | Alsalabi B.S.,MWH Americas Inc. | Rizza T.,Lefkosa
Environmental Earth Sciences | Year: 2013

The groundwater of the deep Yeşilköy aquifer is the only water resource for agricultural and domestic consumption at the Karpaz Peninsula of Cyprus, which stretches approximately 100 km from the northeast of capital Nicosia to the northern tip of Cyprus. During the last decade, over-pumping and following dry periods have depleted the groundwater resources and the water surface elevation of the aquifer has dropped. The aim of this study is to understand the behavior of the Yeşilköy aquifer in the last decade for the proper management of groundwater resources. This has been achieved based on well survey and field survey studies, monitoring programs followed by pumping tests, and safe yield analysis. Most of the research effort has been focused on field and well survey studies to quantify agricultural water consumption and abstraction rates from the aquifer. A long-term groundwater level monitoring program, short-term continuous groundwater monitoring and pumping tests provided information for the regression analyses while deriving a sixth order polynomial relationship between the period parameter and the head parameter. The equation was helpful to predict the short-term behavior of the water level when the present hydrogeological conditions prevail. The pumping test results satisfied the hydraulic properties of calcarenite formation yielding T = 1,782 m2/day and S = 0. 0012. The results of safe yield analysis show that the annual deficit of the aquifer is 0. 496 million cubic meters (MCM), which is equivalent to a 0. 6 m drop in groundwater levels per year. Finally, the resultant annual safe yield of the aquifer is estimated as 0. 84 MCM. © 2012 Springer-Verlag.


Subramani A.,MWH Americas Inc. | Badruzzaman M.,MWH Americas Inc. | Oppenheimer J.,MWH Americas Inc. | Jacangelo J.G.,MWH Americas Inc. | Jacangelo J.G.,Johns Hopkins University
Water Research | Year: 2011

Energy is a significant cost in the economics of desalinating waters, but water scarcity is driving the rapid expansion in global installed capacity of desalination facilities. Conventional fossil fuels have been utilized as their main energy source, but recent concerns over greenhouse gas (GHG) emissions have promoted global development and implementation of energy minimization strategies and cleaner energy supplies. In this paper, a comprehensive review of energy minimization strategies for membrane-based desalination processes and utilization of lower GHG emission renewable energy resources is presented. The review covers the utilization of energy efficient design, high efficiency pumping, energy recovery devices, advanced membrane materials (nanocomposite, nanotube, and biomimetic), innovative technologies (forward osmosis, ion concentration polarization, and capacitive deionization), and renewable energy resources (solar, wind, and geothermal). Utilization of energy efficient design combined with high efficiency pumping and energy recovery devices have proven effective in full-scale applications. Integration of advanced membrane materials and innovative technologies for desalination show promise but lack long-term operational data. Implementation of renewable energy resources depends upon geography-specific abundance, a feasible means of handling renewable energy power intermittency, and solving technological and economic scale-up and permitting issues. © 2011 Elsevier Ltd.


Heidari T.,MWH Americas Inc. | Heidari T.,Clemson University | Andrus R.D.,Clemson University
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2012

Liquefaction potential of four Pleistocene beach sand deposits in the Greater Charleston area, South Carolina, is assessed. The assessment is based on a review of 51 sites of conspicuous craterlets and horizontal ground displacement that occurred in beach sand deposits during the 1886 Charleston earthquake and an analysis of 82 seismic cone penetration tests with pore-pressure measurements. Of the 51 ground failure sites, 23 are associated with the Ten Mile Hill beds; 13 with the Wando Formation; 13 with the Silver Bluff terrace and younger deposits that lie adjacent to the harbor, rivers, and creeks; and two with the Ladson Formation. Liquefaction potential is analyzed using the seismic cone data with and without correction for age-related processes (diagenesis) and then expressed in terms of the liquefaction potential index (LPI). Probability curves are developed from the LPI calculations for different earthquake ground-shaking parameters. The probability curves for the Wando Formation overpredict liquefaction potential when no corrections for diagenesis are made. When corrections for diagenesis are made, the probability curves for all four sands generally agree with the observed field behavior. © 2012 American Society of Civil Engineers.

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