Time filter

Source Type

Allentown, PA, United States

Roessler E.C.,Michael Baker Inc.
ASABE - TMDL 2010: Watershed Management to Improve Water Quality | Year: 2010

Fecal coliform TMDLs were developed for three small shellfish areas along the White Oak River in North Carolina. The TMDLs were developed using mechanistic modeling approaches (LSPC and Tidal Prism Model) and called for loading reductions of 14%, 55%, and 70%. Site-specific implementation strategies were developed for each area in an effort to meet the TMDLs. It is possible to quantify the effect of structural BMPs (e.g., bioretention areas and constructed wetlands) but not non-structural BMPs (e.g., landowner education). It appears that the TMDL for Dubling Creek can be met, even though there are few anthropogenic sources of bacteria in the catchment, by installing pet waste stations around a walking trail and retrofitting a pond outlet. However, meeting the TMDLs in the more developed catchments, Boathouse Creek and Hills Bay embayment, appears to be problematic at this stage. Not only would every developed parcel need a retrofit BMP, but apparent wildlife loading in the vicinity of the shellfish waters would need to be reduced. The lone NPDES-permitted source in the area is the North Carolina Department of Transportation (NCDOT). Reductions of 60-72% were sought from NCDOT roads and stormwater pipes in the developed catchments. Since loading from NCDOT property is estimated to compose a minor portion of the total, higher, less achievable, reductions would have minimal effect. The small size of the three catchments (0.23-0.85 mi2) enabled close examination of how and where to reduce bacteria loading. Tracking TMDL implementation through monitoring will help determine if the TMDLs were set at appropriate levels and if the expected reductions from the recommended management strategies are being achieved. Source

Fagert J.,Case Western Reserve University | Zhang B.,Michael Baker Inc. | Gao Q.,Case Western Reserve University | Yu X.,Case Western Reserve University
Geotechnical Special Publication | Year: 2014

This paper describes the results from a preliminary study targeted to developing a high-resolution distributed moisture sensor. The sensor is for measuring the moisture distribution with sufficient spatial and temporal resolution so that it can detect the earthquake-induced void redistribution and the consequent onset of ground liquefaction. Such a sensor is currently unavailable. Therefore, an important application of this sensor is to establish the liquefaction criteria due to void redistribution, which may occur under stratified ground conditions. The sensing principles are described. A feasibility analysis is conducted to improve the sensor design to achieve the desired resolution. A few prototype sensor designs are described. The results indicate a spiral shaped design further increased the spatial resolution. The sensor is under further refinement and testing to gauge its feasibility for practical applications. © 2014 American Society of Civil Engineers. Source

Morar D.L.,Michael Baker Inc. | Aydilek A.H.,University of Maryland University College | Aydilek A.H.,Antalya International University | Seagren E.A.,Michigan Technological University | Demirkan M.M.,Paul C. Rizzo Associates Inc
Journal of Environmental Engineering (United States) | Year: 2012

One potential beneficial reuse of high-carbon-content (HCC) fly ashes is in reactive barrier applications for remediation of contaminated groundwater. However, leaching of metals from coal fly ashes into the environment is of concern. A series of column leach tests (CLTs) and batch water leach tests (WLTs) were performed to investigate the potential leaching of metals from HCC fly ashes during reactive barrier applications. Fly ash content and pH were two key factors affecting the amount leached in WLTs. Leaching of metals in CLTs exhibited a first flush, followed by a tailing elution pattern, for all fly ashes. Attempts to correlate the WLT and CLT data indicated that scale-up of the WLT results to the column experimental setup provided a better prediction of the leachable amount in CLTs compared with a direct comparison of concentrations. Nevertheless, caution should be exercised when building correlations because of the different testing conditions in the two test setups. © 2012 American Society of Civil Engineers. Source

Kang J.,Grande Rio University | King S.E.,Michael Baker Inc. | McLaughlin R.A.,North Carolina State University
Journal of Environmental Management | Year: 2016

Due to stringent water quality regulations on stormwater discharges, there is increasing interest in chemically-assisted settling of suspended sediments at construction sites. This study investigated settling characteristics of flocculated sediment by polyacrylamide (PAM) in a top-loading settling tube. Studied sediment materials were obtained from construction sites in North Carolina, USA: Coastal Plain loamy sand (CPLS), Piedmont sandy clay loam (PSCL), Piedmont silt loam (PSL), and Mountain clay loam (MCL). The four different sediment suspensions mixed with and without dissolved PAM were introduced to the top of the column individually. During a 1-h settling period, samples were taken at 1-m depth from surface at various times and analyzed for total suspended solids (TSS). Flocculated sediment by PAM greatly increased its settled TSS fraction up to 95-97% only in 1-min settling period compared to those of unflocculated sediment (16-72%). The settling improvement by PAM was profound in the finer-textured soils (PSL and MCL) by increasing their median particle settling velocity (>2 cm s-1) compared to unflocculated counterparts (<1.1 cm s-1). Estimated surface area requirement of sediment basin suggested that the basins receiving flocculated sediment could be reduced in size (surface area) by 2- to 4-times compared to those receiving unflocculated sediment. Our results suggests that current sediment basin design could be modified when chemically-assisted settling is implemented, taking up less space and cost in construction sites. © 2015 Elsevier Ltd. Source

Liu Z.,Case Western Reserve University | Yu X.,Case Western Reserve University | Sun Y.,Case Western Reserve University | Zhang B.,Michael Baker Inc.
Journal of Cold Regions Engineering | Year: 2013

The writers have derived a unified governing equation for freezing saturated soils. This equation considers the governing mechanisms with respect to individual thermal and hydraulic fields. The writers included coupling effects such as the thermodynamic equilibrium on the water-ice interface. The morphology of the solid matrix and the physical chemistry of the water-ice interface have also been incorporated. The equation is comprised of terms with clear physical meanings. Typical properties that are indicative of freezing soils, e.g., segregation potential, can be derived from this equation. The writers discuss the material properties that are required for implementation of the equation. For the conventional parameters in the equation, i.e., thermal conductivity, heat capacity, and hydraulic conductivity, the corresponding mathematical descriptions were investigated. The functions for prediction of these parameters during the soil freezing process are presented. The writers have also proposed a relationship between the temperature and unfrozen water content for characterization of freezing saturated soils. The writers propose that the measurement of this relationship be conducted with a new technique that uses a thermo-time domain reflectometry (TDR) sensor. The writers have described detailed sensor and experiment designs for measuring this new relationship and have compared the results with data that were measured with a standard method. © 2013 American Society of Civil Engineers. Source

Discover hidden collaborations