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Walnut Creek, CA, United States

Chang T.J.,Ohio University | Bayes T.D.,Brown and Caldwell
Journal of Irrigation and Drainage Engineering | Year: 2013

The loss of topsoil in the United States has resulted in low crop yield, reduction of reservoir capacity, cost increase of water treatment, and detrimental effects on aquatic life and wildlife habitats. An initial step for taking conservation measures in any watershed is to identify locations where erosion protection measures are needed. Applying the Revised Universal Soil Loss Equation (RUSLE) and a geographic information system (GIS), this study attempts to locate the most erodible locations, namely erosion hotspots, for a watershed. Using GIS, the watershed is divided into 25 × 25-m grids and the RUSLE, including rainfall-runoff erosivity factor, soil erodibility factor, combined slope length and slope steepness factor, cover management factor, and support practice factor, is applied for the estimation of soil erosion potential for each grid cell. By ranking these grid values of erosion potential in a descending order, the top 1% and corresponding locations are defined as the erosion hot spots, which can be expressed in an erosion hotspot map. Applying this method to the Charles Mill Lake Watershed in Ohio, it is found that the erosion hotspots for the watershed under investigation are generally located in the areas of strip mine and cropland/pasture. © 2013 American Society of Civil Engineers. Source

Tunnel professionals should inform project stakeholders on the reality that tunnel projects are not 100 percent devoid of the need for excavations or public inconveniences during both design and construction phases. Competing stakeholder objectives to limit these disruptions must be weighed against the need to mitigate risks and to produce a constructible, operable and maintainable end product. Perhaps the approach we should take with stakeholders, also known as Authorities Having Jurisdiction (AHJs), is sharing memorable case studies that bring to life the potential risks so often buried within lengthy risk registers. This paper provides a sobering case study describing what can occur if the presence and/or location of utilities and other obstructions are not fully understood due to restrictions placed on exploration or mining operations. In this instance, the Microtunnel Tunnel Boring Machine (MTBM) encountered a buried concrete structure, followed by rows of abandoned wood piles, before finally colliding with an active high-pressure gas main under a bustling coastal highway. Multiple stakeholders imposed tight logistical and other work restrictions, compounding the difficulties experienced during the drive. However, the difficulties were effectively managed through the project team's proactive collaboration and communication with everyone involved. Copyright © (2016) by the Society for Mining, Metallurgy and Exploration All rights reserved. Source

Beggs R.A.,Brown and Caldwell | Hills D.J.,University of California at Davis | Tchobanoglous G.,University of California at Davis | Hopmans J.W.,University of California at Davis
Journal of Contaminant Hydrology | Year: 2011

Subsurface drip irrigation systems apply effluent from onsite wastewater systems in a more uniform manner at a lower rate than has been possible with other effluent dispersal methods. The effluent is dispersed in a biologically active part of the soil profile for optimal treatment and where the water and nutrients can be utilized by landscape plants. Container tests were performed to determine the fate of water and nitrogen compounds applied to packed loamy sand, sandy loam, and silt loam soils. Nitrogen removal rates measured in the container tests ranged from 63 to 95% despite relatively low levels of available carbon. A Hydrus 2D vadose zone model with nitrification and denitrification rate coefficients calculated as a function of soil moisture content fit the container test results reasonably well. Model results were sensitive to the denitrification rate moisture content function. Two-phase transport parameters were needed to model the preferential flow conditions in the finer soils. Applying the model to generic soil types, the greatest nitrogen losses (30 to 70%) were predicted for medium to fine texture soils and soils with restrictive layers or capillary breaks. The slow transport with subsurface drip irrigation enhanced total nitrogen losses and plant nitrogen uptake opportunity. © 2011 Elsevier B.V. All rights reserved. Source

Parker D.S.,Brown and Caldwell
Water Environment Research | Year: 2011

Innovative wastewater treatment technologies are developed to respond to changing regulatory requirements, increase efficiency, and enhance sustainability or to reduce capital or operating costs. Drawing from experience of five successful new process introductions from both the inventor/developer's and adopter's viewpoints coupled with the application of marketing analysis tools (an S curve), the phases of new technology market penetration can be identified along with the influence of market drivers, marketing, patents and early adopters. The analysis is used to identify measures that have increased the capture of benefits from new technology introduction. These have included funding by the government for research and demonstrations, transparency of information, and the provision of independent technology evaluations. To reduce the barriers and speed the introduction of new technology, and thereby harvest the full benefits from it, our industry must develop mechanisms for sharing risks and any consequences of failure more broadly than just amongst the early adopters. WEF and WERF will continue to have the central role in providing reliable information networks and independent technology evaluations. Source

Coats E.R.,University of Idaho | Gregg M.,Brown and Caldwell | Gregg M.,University of Idaho | Crawford R.L.,University of Idaho
Bioresource Technology | Year: 2011

The investigations presented and discussed herein establish an enhanced understanding on volatile fatty acid (VFA) production as a function of dairy manure fermenter organic loading (OL) and retention time (RT), first through a factorial of 64 fermentation potential (FP) batch tests, followed by analysis of a continuously operated pilot-scale fermenter. The maximum observed net FP - 0.103mg VFA produced (as COD) (mg VS applied) -1 - occurred at an OL of 40.7gVSL -1 and at a RT of 6days. The pilot-scale fermenter exhibited an average yield of 0.09mg VFA (as COD) synthesized (mg VS applied) -1, with average effluent total VFA concentrations of 6398mg VFA (as COD) L -1. The research demonstrates that FP tests are an effective method to optimize continuously operated dairy manure fermenters, and that dairy manure fermentation can yield large quantities of organic acids at short RTs and high OL rates. © 2010 Elsevier Ltd. Source

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