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Davis R.W.,Cdm Smith
Transportation Research Record | Year: 2014

Recently there has been a trend among toll road agencies to index their tolls to inflation, giving rise to the question of how past tolls compared with inflation. To answer that question, a database including all toll roads in the United States since 1950 was developed. The database was used to analyze historical national average per mile toll rates for passenger cars and commercial vehicles and to compare these rates with rates of inflation. Historical toll road operation trends, including the annual number of agencies and ccnterline mileage since 1950, were also analyzed and discussed in the context of changing federal highway policies over time. To consider inflation from the perspective of drivers and toll ugencics, the U.S. Bureau of Labor Statistics' national-level all urban consumers consumer price index (CTI) and FHWA construction price indexes were used for comparison. It was found that considering typical published electronic or cash toll rates, the national average annual toll increase since 1960 was 3.2% for passenger cars and 3.6% for commercial vehicles. That result compares with an average annual national CTI increase of 4.0% and construction price increase of 3.8% in this period. While current national average toll rates remain significantly lower than the inflation rate, the gap has narrowed in recent years, especially considering commercial vehicle tolls and the drop in construction prices following the recent recession. Source

Bell K.Y.,Cdm Smith | LeBoeuf E.J.,Vanderbilt University
Chemosphere | Year: 2013

This study demonstrates differences in sorptive capacity of volatile organic compound (VOC) trichloroethylene (TCE) onto natural organic matter (NOM) coated and uncoated mineral surfaces above and below the NOM glass transition temperature. TCE sorption isotherms for dry NOM-mineral systems below the NOM glass transition temperature (Tg) demonstrated sorption behavior characteristic of micropore filling, with sorption capacities reduced relative to uncoated mineral matrices. Such differences were not entirely associated with differences in surface areas of the coated and uncoated mineral matrices, but were likely associated with either a blockage of pore space available to the VOC or a kinetic limitation that does not allow the VOC access to the internal porosity of the model soil within the time periods of the experiment. TCE sorption in dry NOM-mineral matrices above the Tg, however, was described in terms of sorption within a more fluid, macromolecular dissolution medium that does not hinder access to mineral surfaces. Such observations have potential important implications for modeling the fate and transport of VOCs in soils and sediment systems. © 2012 Elsevier Ltd. Source

Watts J.L.,Cdm Smith
World Environmental and Water Resources Congress 2014: Water Without Borders - Proceedings of the 2014 World Environmental and Water Resources Congress | Year: 2014

The Greater New Orleans (GNO) area is often referred to as "a bowl of water surrounded by water," an indication of the area's continuous struggle with stormwater management, including the more recent problems of subsidence and sea level rise. To address some of these challenges, the City of New Orleans commissioned the development of an H&H computer model. As envisioned, this evaluation would serve as a baseline and assess possible levels to either exceed service levels or reduce costs. The model has fulfilled its vision and blossomed into more than just a tool for traditional drainage design. The model has been essential in developing plans and proving benefits for several projects in the GNO area, including many green infrastructure projects, and has been used to help prove the benefits of changing the stormwater management paradigm of the GNO area. © 2014 American Society of Civil Engineers. Source

Olsen R.L.,Cdm Smith | Chappell R.W.,Environmental Science Solutions LLC | Loftis J.C.,Colorado State University
Water Research | Year: 2012

Comprehensive water quality investigations to characterize large watersheds include collection of surface water samples over time at various locations within the watershed and analyses of the samples for multiple chemical and biological constituents. The size and complexity of the resulting dataset make overall evaluations difficult, and as a result, multivariate statistical methods can be useful to evaluate environmental patterns and sources of contamination. The most commonly applied multivariate method in watershed studies is principal components analysis (PCA), which uses correlation among multiple water quality constituents to effectively reduce the number of variables. The reduced set of variables may assist in the identification and description of spatial patterns in water quality that result from hydrologic and geochemical processes and from sources of contamination.The utility of PCA for identifying important environmental factors in a given study is obviously affected by sampling design, constituents analyzed, data quality, data treatment prior to PCA, methods of interpreting PCA results, and other factors. Unfortunately no comprehensive evaluations have been performed and no standard procedures exist for dealing with these issues. This paper examines and evaluates the current state-of-the-science by review of 49 published papers dealing with multivariate (typically PCA) techniques to evaluate watershed water quality.Additionally an example PCA for a surface water quality study in the Illinois River Watershed (IRW) is provided to illustrate methods to address the above issues and to evaluate the sensitivity of results to alternative methods. The example PCA evaluations were consistent with two dominant sources of surface water contamination in the IRW: 1) discharge to the streams from municipal wastewater treatment plants and 2) runoff and infiltration from fields with land applied poultry waste. © 2012 Elsevier Ltd. Source

Apell J.N.,University of Florida | Apell J.N.,Cdm Smith | Boyer T.H.,University of Florida
Water Research | Year: 2010

Dissolved organic matter (DOM) and hardness cations are two common constituents of natural waters that substantially impact water treatment processes. Anion exchange treatment, and in particular magnetic ion exchange (MIEX), has been shown to effectively remove DOM from natural waters. An important advantage of the MIEX process is that it is used as a slurry in a completely mixed flow reactor at the beginning of the treatment train. Hardness ions can be removed with cation exchange resins, although typically using a fixed bed reactor at the end of a treatment train. In this research, the feasibility of combining anion and cation exchange treatment in a single completely mixed reactor for treatment of raw water was investigated. The sequence of anion and cation exchange treatment, the number of regeneration cycles, and the chemistry of the regeneration solution were systematically explored. Simultaneous removal of DOM (70% as dissolved organic carbon) and hardness (>55% as total hardness) was achieved by combined ion exchange treatment. Combined ion exchange is expected to be useful as a pre-treatment for membrane systems because both DOM and divalent cations are major foulants of membranes. © 2010 Elsevier Ltd. Source

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