VTechWorks Repository :: Browsing by Author "Sample, David J."

Browsing by Author "Sample, David J."

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Applicability of Stormwater Best Management Practices in the Virginia Coastal Plain
Johnson, Rachael Diane (Virginia Tech, 2016-06-06)
The Virginia Runoff Reduction Method (RRM) was adopted in 2014 as a compliance tool for evaluation of stormwater volume and quality, and necessitates use of urban stormwater best management practices (BMPs) to meet regulatory standards. Coastal Virginia is characterized by flat terrain, shallow water tables, and low permeable soils that may limit the application of BMPs as recommended by state regulations. Soil morphological features are often used to estimate the seasonal high water table (SHWT) for initial feasibility, but existing soil data misrepresented expected SHWT depths in the Virginia Beach, VA, study area. A GIS-based methodology relying on perennial surface water elevations and USGS groundwater monitoring data was developed to estimate the SHWT depth in Virginia Beach. The SHWT map was shown to be consistently more reliable than available predictions based on soil morphology, and was used as input to a BMP siting tool. The tool, known as BMP Checker, was developed to explore how flat terrain, shallow water tables, and poor soils influence BMP siting in coastal Virginia. The BMP Checker algorithm was validated on 11 Virginia Beach sites before application on 10,000 ft2 (929 m2) area sections across the city. Citywide application showed that the most widely applicable BMPs in the study area include wet ponds that intercept groundwater and constructed wetlands. Conversely, sheet flow to conservation area and infiltration practices are the least applicable. Because the RRM assigns more credit to infiltration-based practices, sites in Virginia Beach may find it difficult to meet regulatory standards.
Assessing Green Infrastructure Needs in Hampton Roads, Virginia and Identifying the Role of Virginia Cooperative Extension
Robinson, Daniel J. (Virginia Tech, 2018-08-08)
The Hampton Roads region of southeast Virginia is largely defined by its abundant water resources. These water resources are also a source of unique issues for the region. Specifically, water quality challenges related to the Chesapeake Bay and recurrent flooding are the major concerns. Green infrastructure (GI) has emerged in recent years as an alternative to traditional stormwater conveyance and detention focused systems. GI practices focus on integrating infiltration, evapotranspiration, and other components of the water cycle into more conventional stormwater management systems. These systems provide several positive benefits, including local water quality and quantity control, community revitalization, and various public health benefits. In addition, GI implementation has seen strong levels of support from the Cooperative Extension System, with Extension faculty and staff around the U.S. supporting local municipalities through GI research, promotion, and program development. Despite widespread interest, GI has been slow to be adopted due to various barriers to its implementation. This study sought to identify the major barriers to the implementation of GI practices in Hampton Roads by conducting a needs assessment. Municipal stormwater staff were invited to participate in an online survey aimed at identifying the most significant barriers in the region. At the same time, local staff with Virginia Cooperative Extension (VCE) were interviewed to explore their potential to become involved in promoting GI adoption in Hampton Roads. Survey respondents and interview participants found common ground in identifying costs, funding, and maintenance issues as the most significant barriers to GI implementation in Hampton Roads. In addition, VCE staff were found to be well suited to support widespread GI adoption in the region, having familiarity with the GI concept and access to unique resources in the form of knowledgeable Master Gardener volunteers and connections to Virginia Tech. Recommendations for VCE involvement in promoting GI in Hampton Roads include conducting cost studies, developing and hosting maintenance training programs, and taking advantage of partnerships to identify and obtain funding from diverse sources. By focusing on these widely acknowledged challenges at the regional scale, VCE can support GI implementation throughout all of Hampton Roads.
Assessing nitrogen and phosphorus removal potential of five plant species in floating treatment wetlands receiving simulated nursery runoff
Spangler, Jonathan T.; Sample, David J.; Fox, Laurie J.; Albano, Joseph P.; White, Sarah A. (2019-02)
The feasibility of using floating treatment wetlands (FTWs) to treat runoff typical of commercial nurseries was investigated using two 8-week trials with replicated mesocosms. Plants were supported by Beemat rafts. Five monoculture treatments of Agrostis alba (red top), Canna x generalis Firebird' (canna lily), Carex stricta (tussock sedge), Iris ensata Rising Sun' (Japanese water iris), Panicum virgatum (switchgrass), two mixed species treatments, and an unplanted control were assessed. These plant species are used for ornamental, wetland, and biofuel purposes. Nitrogen (N) and phosphorus (P) removals were evaluated after a 7-day hydraulic retention time (HRT). N removal (sum of ammonium-N, nitrate-N, and nitrite-N) from FTW treatments ranged from 0.255 to 0.738gm(-2)d(-1) (38.9 to 82.4% removal) and 0.147 to 0.656gm(-2)d(-1) (12.9 to 59.6% removal) for trials 1 and 2, respectively. P removal (phosphate-P) ranged from 0.052 to 0.128gm(-2)d(-1) (26.1 to 64.7% removal) for trial 1, and 0.074 to 0.194gm(-2)d(-1) (26.8 to 63.2% removal) for trial 2. Panicum virgatum removed more N and P than any other FTW treatment and the control in both trials. Results show that species selection and timing of FTW harvest impact the rate and mass of nutrient remediation. FTWs can effectively remove N and P from runoff from commercial nurseries.
Assessing Per- and Polyfluoroalkyl Substances (PFAS) Presence and Distribution in the Stormwater Systems of Socioeconomically Disadvantaged Coastal Communities
Blackburn, Savanna; Harrison, Michael (Virginia Tech, 2024-05-01)
This interdisciplinary study investigates the presence of Per- and Polyfluoroalkyl Substances (PFAS) in socioeconomically disadvantaged communities within two coastal municipalities in the Virginia Coastal Plain. Utilizing a field and laboratory approach, the research aims to assess the distribution and concentration of 30 PFAS compounds across multiple environmental receptors. Initial grab-sampling conducted across four distinct sites provided preliminary data on a wide range of PFAS, employing targeted analytical techniques to evaluate their presence. The significance of the study is underscored by the ecological and public health risks associated with PFAS contamination. Results from the analysis revealed variable concentrations of PFAS compounds across the sampled locations, suggesting a relationship between urban infrastructure, environmental justice areas, and PFAS distribution. These findings contribute to the existing body of knowledge on PFAS environmental behavior, risks, and management, highlighting the need for continued monitoring and research. Additionally, the study demonstrates the critical role of interdisciplinary collaboration in addressing complex environmental health issues, providing a foundation for future research and targeted sampling strategies to mitigate PFAS risks in urban coastal settings.
Assessing the Effects of Climate Change on Water Quantity and Quality in an Urban Watershed Using a Calibrated Stormwater Model
Alamdari, Nasrin; Sample, David J.; Steinberg, Peter; Ross, Andrew C.; Easton, Zachary M. (MDPI, 2017-06-27)
Assessing climate change (CC) impacts on urban watersheds is difficult due to differences in model spatial and temporal scales, making prediction of hydrologic restoration a challenge. A methodology was developed using an autocalibration tool to calibrate a previously developed Storm Water Management Model (SWMM) of Difficult Run in Fairfax, Virginia. Calibration was assisted by use of multi-objective optimization. Results showed a good agreement between simulated and observed data. Simulations of CC for the 2041–2068 period were developed using dynamically downscaled North American Regional CC Assessment Program models. Washoff loads were used to simulate water quality, and a method was developed to estimate treatment performed in stormwater control measures (SCMs) to assess water quality impacts from CC. CC simulations indicated that annual runoff volume would increase by 6.5%, while total suspended solids, total nitrogen, and total phosphorus would increase by 7.6%, 7.1%, and 8.1%, respectively. The simulations also indicated that within season variability would increase by a larger percentage. Treatment practices (e.g., bioswale) that were intended to mitigate the negative effects of urban development will need to deal with additional runoff volumes and nutrient loads from CC to achieve the required water quality goals.
Assessing the Efficacy of Stream Restoration and SCM Retrofitting for Channel Stability in Urbanized Catchments
Towsif Khan, Sami; Thompson, Theresa M.; Sample, David J. (2024-05-29)
The hydrological benefits of catchment-scale implementation of stormwater control measures (SCMs) in mitigating the adverse effects of urbanization are well established. Nevertheless, recent studies indicate that Maryland's stormwater regulations, mandating the combined use of distributed and end-of-pipe SCMs, fall short in maintaining channel stability, despite their effectiveness in reducing runoff from impervious surfaces. The study objective was to evaluate the incremental impact of SCM retrofits and stream restoration on channel stability in a small, urbanized catchment (0.9 sq. km) in Montgomery County, Maryland, USA. This study employed a refined, well-calibrated, coupled hierarchical modeling approach, integrating a watershed-scale Storm Water Management Model (SWMM) with the Hydrologic Engineering Centers River Analysis System (HEC-RAS). A comprehensive methodology was developed using the calibrated SWMM and HEC-RAS models. The modeling results revealed that only retrofitting SCMs with multi-stage outlet structures designed to maintain the pre-development mobility of bed particles may not effectively reduce channel degradation. Conversely, stream restoration practices, including the removal of legacy sediments from the floodplain, significantly mitigated channel instability. Notably, the combination of SCM retrofitting, aimed at matching the sediment transport capacity of the predevelopment state, and stream restoration practices did not yield better results compared to stream restoration alone. This finding suggests that for streams impacted by legacy sediments, floodplain restoration alone might suffice to achieve channel stability, eliminating the need to retrofit SCMs designed under existing regulations.
An Assessment of Floating Treatment Wetlands for Reducing Nutrient Loads from Agricultural Runoff in Coastal Virginia
Spangler, Jonathan Travis (Virginia Tech, 2017-07-18)
Floating treatment wetlands (FTWs) are an innovative best management practice that can enhance the performance of traditional retention ponds by increasing removal of the nutrients nitrogen (N) and phosphorous (P). FTWs consist of floating rafts on which wetland plants are planted, allowing the roots to be submerged below the water surface while the shoots remain above. A growing body of research has documented FTW performance with regard to urban runoff treatment, however evaluation of FTW effectiveness for treatment of agricultural runoff has received less attention. Due to high fertilization and irrigation rates, commercial nursery runoff contains much higher concentrations of N and P than runoff from urban areas. We conducted this study over two growing seasons (2015 and 2016) to assess the effectiveness of FTWs for use in commercial nursery retention ponds. In the first study we used two different nutrient concentrations, one to simulate nursery runoff (17.1 mg∙L-1 TN and 2.61 mg∙L-1 TP) and one to simulate concentrations that fall between urban and nursery runoff (5.22 mg∙L-1 TN and 0.52 mg∙L-1 TP). Four treatments were used: 1) Pontederia cordata planted in cups supported by a Beemat, 2) Juncus effusus planted in cups supported by a Beemat, 3) a Beemat with no plants, and 4) no treatment (open-water). Performance was evaluated based on a 7-day hydraulic retention time (HRT). Pontederia cordata removed between 90.3% and 92.4% of total phosphorus (TP) and 84.3% and 88.9% total nitrogen (TN), depending on initial loads. These reductions were significantly more than other treatments at both high and low nutrient loading rates. Juncus effusus performed better than the control treatments for TP removal at low nutrient concentrations, but did not perform any better than the control at higher nutrient loads. In the second study, conducted in 2016, we evaluated different plant species over two 8-week trials using simulated nursery runoff. We used five monoculture FTWs with the following species: Agrostis alba, Canna ×generalis, Carex stricta, Iris ensata, and Panicum virgatum. Additionally, two treatments were created from mixed species plantings and the final treatment consisted of an open water control mesocosm. Nutrient removal performance was evaluated over a 7-day HRT. P removal (phosphate-P) by FTW treatments ranged from 26.1% to 64.7% for trial 1 and 26.8% to 63.2% for trial 2. Trial 1 N removal (sum of ammonium-N, nitrate-N, and nitrite-N) efficiencies ranged from 38.9% to 82.4%, and trial 2 ranged from 12.9% to 59.6%. Panicum virgatum removed significantly more N and P than the control and any other FTW treatment in the second study. Both studies indicated, depending upon plant species, that FTWs can effectively remove nitrogen and phosphorous from urban and commercial nursery retention ponds.
Assessment of Sediment and Salinity in the Lower Mekong River Basin
Chowdhury, Md Mahabub Arefin (Virginia Tech, 2023-01-06)
The Mekong River Basin (MRB) is famous for its rice farming and export and produces more than 20 million tons of rice per year. Rice production depends on climate, irrigation, soil fertility. However, this region is adversely impacted by several environmental concerns like nutrient deficiency from sediment and saltwater intrusion. The decrease in sediment deposition in the Mekong basin is caused by a number of factors. In China, Lao PDR, and Vietnam, the hydropower generation from dams has improved people's overall living standards, leading in more dams being built or planned in the future. However, dam construction work is adversely impacting the overall salinity condition in this region by reducing upstream flow. Upstream lower flows during the dry season contributes to the increased salinity in the lower Mekong Delta. In addition to these, multiple dams in the upper and middle region of the Mekong basin are trapping sediments and decreasing it in the lower zones. This study found that the reservoirs, built by China between 2008-2015, has reduced the sediment load at all five stations considered in the study. When a reservoir is removed from the model, the sediment load is increased which showed the substantial impact of reservoir construction on sediment load in this area. The landuse pattern is another factor for variability of the sediment yield in the study area. Forest area contributes to higher sediment production whereas agricultural area results in lower sediment yield. The GFDL RCP (4.5) and GFDL RCP (8.5) future climate change projection scenarios used in this study also demonstrated substantial variability in the precipitation pattern for the study region. GFDL RCP (4.5) scenario resulted in a lower sediment yield during the dry season. On contrary to that, GFDL RCP (8.5) showed higher sediment yield due to higher precipitation during the wet season. The severe salinity impact was observed in the Cai Nuoc, Nam Can, and Thanh Phu districts. In Ca Mau province, the observed salinity is highest among the provinces of the study area during dry season (February to May), about 12-14 PPT (parts per thousand) whereas the lowest level of salinity (less than 1 PPT) was observed in the Dong Thap and Vinh Long provinces. This salinity intrusion is adversely impacting the rice production in the study area. In the year 2000, rice production in the Ca Mau province was about 100-150 thousand tons. But salinity intrusion is drastically reducing the rice production in this area, about 10-30thousand tons per year during 2015-2017. Rice production is increasing in the upper deltaic part of the Mekong Delta region where preventive measures were taken.
Basic Principles of Watershed Restoration and Stormwater Management in the Chesapeake Bay Region
Dindinger, Jennifer; Kyler, Kristen; Rockler, Amanda; Sample, David J.; Fox, Laurie J.; Hughes, Shereen (Virginia Cooperative Extension, 2020-12-08)
This publication will provide an overview of the most relevant urban stormwater management and watershed restoration issues, common mitigating practices, and regulations relevant to the Chesapeake Bay watershed.
Best management practice fact sheet 10: Dry Swale
Sample, David J.; Fox, Laurie J.; Hendrix, Carol (Virginia Cooperative Extension, 2020)
A wet swale is an engineered, BMP arranged in a straight line that is designed to reduce stormwater pollution. It consists of a shallow, gently sloping channel with broad, vegetated, side slopes and slow flows. Wet swales typically stay wet because the bottom of the swale is below the water table. This is done to encourage the growth of wetland vegetation.
Best management practice fact sheet 11: Wet Swale
Sample, David J.; Fox, Laurie J.; Hendrix, Carol (Virginia Cooperative Extension, 2020)
A dry swale is a shallow, gently sloping channel with broad, vegetated side slopes. Water flow is slowed by a series of check dams. A dry swale provides temporary storage, filtration, and infiltration of stormwater runoff. they should remain dry during periods of no rainfall. It is a BMP designed to reduce pollution runoff reduction and pollutant removal and is part of a site's stormwater treatment practice.
Best management practice fact sheet 12: Filtering practices
Sample, David J.; Fox, Laurie J.; Hendrix, Carol (Virginia Cooperative Extension, 2020)
A stormwater filtering practice treats stormwater runoff by passing it through and engineered filter media consisting of either sand, gravel, organic matter, and/or a proprietary manufactured product, collecting it in an underdrain, and then discharging the effluent to a stormwater conveyance system.
Best management practice fact sheet 15: Extended detention ponds
Sample, David J.; Fox, Laurie J.; Hendrix, Carol (Virginia Cooperative Extension, 2020)
Extended detention ponds (EDs) are dry detention ponds that provide 12 to 24 hours of runoff storage during peak runoff events. Releases from the ED ponds are controlled by an outlet structure. During a storm event, as the discharge restriction is reached, water backs up into the ED pond. The pool slows flow velocities and enables particulate pollutants to settle. Peak flows are also reduced.
Best Management Practice Fact Sheet 16: Step Pool Stormwater Conveyance
Hickman, Elizabeth L.; Thompson, Theresa M.; Sample, David J. (Virginia Cooperative Extension, 2021-09-03)
Urban development results in increased impervious surfaces, causing an increase in runoff and degradation of water quality and stream habitat. Stormwater control measures (SCMs), also known as urban best management practices (BMPs) are used to reduce these impacts. In Virginia, 15 SCMs have been approved for use in site development, and a corresponding fact sheet was developed for each. New technologies are continually being developed and implemented within SCMs, so a new series for these “Innovative Stormwater BMPs”, was created. The 2nd in this series addresses Regenerative Step Pool Storm Conveyance (RSPSC). RSPSC is a unique technology being implemented to reduce erosion, recharge groundwater, and improve water quality and stream habitat at stormwater outfalls.
Best management practice fact sheet 1: Rooftop disconnection
Sample, David J.; Fox, Laurie J.; Hendrix, Carol (Virginia Cooperative Extension, 2019)
Discussion of rooftop disconnection and compost amended flow paths
Best management practice fact sheet 2: Grass channels
Sample, David J.; Fox, Laurie J.; Hendrix, Carol (Virginia Cooperative Extension, 2019)
Discussion of grass channels as a storm water conveyance system
Best management practice fact sheet 2: Sheet flow to open space
Sample, David J.; Fox, Laurie J.; Hendrix, Carol (Virginia Cooperative Extension, 2019)
Discussion of Sheet flow to open space (SOS) drainage practices
Best management practice fact sheet 5: Vegetated roofs
Sample, David J.; Fox, Laurie J.; Hendrix, Carol (Virginia Cooperative Extension, 2019)
Discussion of vegetated roofs which reduces storm water runoff and pollution.
Best management practice fact sheet 6: rainwater harvesting
Sample, David J.; Fox, Laurie J.; Hendrix, Carol (Virginia Cooperative Extension, 2019)
Discussion of devices that intercept, divert, store, and release collected roof runoff from rainfall for later use as an alternative water supply
Best management practice fact sheet 8: Infiltration practices
Sample, David J.; Fox, Laurie J.; Hendrix, Carol (Virginia Cooperative Extension, 2019)
Discussion of infiltration practices which provide temporary surface and/or subsurface storage, allowing infiltration of runoff into the soil.