Alex K. Manda

Evolution of multi-well pad development and influence of well pads on environmental violations and wastewater volumes in the Marcellus shale (USA).

A majority of well pads for unconventional gas wells that are drilled into the Marcellus shale (northeastern USA) consist of multiple wells (in some cases as many as 12 wells per pad), yet the influence of the evolution of well pad development on the extent of environmental violations and wastewater production is unknown. Although the development of multi-well pads (MWP) at the expense of single well pads (SWP) has been mostly driven by economic factors, the concentrated nature of drilling activities from hydraulic fracturing and horizontal drilling operations on MWP suggests that MWP may create less surface disturbance, produce more volumes of wastewater, and generate more environmental violations than SWP. To explore these hypotheses, we use geospatial techniques and statistical analyses (i.e., regression and Mann-Whitney tests) to assess development of unconventional shale gas wells, and quantify environmental violations and wastewater volumes on SWP and MWP in Pennsylvania. The analyses include assessments of the influence of different types of well pads on potential, minor and major environmental events. Results reveal that (a) in recent years, a majority of pads on which new wells for unconventional gas were drilled are MWP, (b) on average, MWP have about five wells located on each pad and thus, had the transition to MWP not occurred, between two and four times as much land surface disturbance would have occurred per year if drilling was relegated to SWP, (c) there were more environmental violations on MWP than SWP, but when the number of wells were taken into account, fewer environmental violations per well were observed on MWP than on SWP, (d) there were more wastewater and recycled wastewater volumes per pad and per well produced on MWP than on SWP, and (e) the proportion of wastewater that was recycled was higher on MWP than SWP. This study sheds light on how the evolution from SWP to MWP has influenced environmental violations and wastewater production in a field that has undergone rapid development in recent years.

A method of estimating bulk potential permeability in fractured-rock aquifers using field-derived fracture data and type curves

A method is devised for estimating the potential permeability of fracture networks from attributes of fractures observed in outcrop. The technique, which is intended as a complement to traditional approaches, is based on type curves that represent various combinations of fracture lengths, fracture orientations and proportions (i.e., intensities) of fractures that participate in flow. Numerical models are used to derive the type curves. To account for variations in fracture aperture, a permeability ratio (R) defined as the permeability of a fracture network in a domain divided by the permeability of a single fracture with identical fracture apertures, is used as a dependent variable to derive the type curves. The technique works by determining the point on the type curve that represents the fracture characteristics collected in the field. To test the performance of the technique, permeabilities that were derived from fractured-rock aquifers of eastern Massachusetts (USA) are compared to permeabilities predicted by the technique. Results indicate that permeabilities estimated from type curves are within an order of magnitude of permeabilities derived from field tests. First-order estimates of fracture-network permeability can, therefore, be easily and quickly acquired with this technique before more robust and expensive methods are utilized in the field.RésuméUne méthode a été élaborée pour estimer la perméabilité d’ensemble de réseaux de fractures à partir de caractéristiques de fractures observées sur affleurement. La technique, qui se veut être un complément aux approches traditionnelles, est basée sur des abaques représentant des combinaisons variables de longueurs, orientations et proportions (i.e. densité de fracturation) des fractures qui contribuent à l’écoulement. On a utilisé des modèles numériques dérivés d’abaques. Pour tenir compte des variations d’ouverture de la fracturation, un ratio de perméabilité (R) défini comme la perméabilité d’un domaine de réseau de fractures divisé par la perméabilité d’une fracture unique d’ouverture identique, a été utilisé comme variable dépendante dérivant des abaques. La technique fonctionne en déterminant le point sur l’abaque type qui représente les caractéristiques de la fracturation relevées sur le terrain. Pour tester la performance de la technique, les perméabilités d’aquifères fracturés de l’Est Massachusetts (USA) ont été comparées avec les perméabilités prévues par la technique. Les résultats indiquent que les perméabilités estimées à partir des abaques sont dans l’ordre de grandeur des perméabilités issues de tests de terrain. Des estimations de premier ordre de la perméabilité du réseau de fractures peut, par conséquent, être aisément et rapidement acquises avec cette technique avant que des méthodes plus lourdes et coûteuses soient utilisées sur le terrain.ResumenSe diseñó un método para estimar la permeabilidad potencial de redes de fracturas a partir de atributos de las fracturas observadas en afloramientos. La técnica, que se intenta como un complemento a los enfoques tradicionales, está basada en curvas tipo que representan varias combinaciones de longitudes, orientaciones y proporciones (por ejemplo intensidades) de fracturas que participan en el flujo. Se utilizan modelos numéricos para desarrollar las curvas tipo. Para tener en cuenta las variaciones en las aperturas de las fracturas, se utilizó una relación de permeabilidad (R) definida como la permeabilidad de una red de fracturas en un dominio dividido por la permeabilidad de una fractura simple con idénticas aperturas de fracturas, como una variable dependiente para desarrollar las curvas tipo. La técnica trabaja determinando el punto sobre la curva tipo que representa las características de la fractura recogidas en el campo. Para probar la performance de la técnica se comparan las permeabilidades que fueron desarrolladas de los acuíferos de rocas fracturadas del este de Massachusetts (EEUU) a las permeabilidades predichas por la técnica. Los resultados indican que las permeabilidades estimadas a partir de las curvas tipo están dentro del orden de magnitud de permeabilidades deducidas de los ensayos de campo. Las estimaciones de primer orden de la permeabilidad de redes de fractura, pueden, por lo tanto, ser fácil y rápidamente adquiridas con esta técnica antes de utilizar métodos de campo más robustos y costosos摘要通过在野外露头观察到的裂隙的特征来评估裂隙网络的潜在渗透性的方法在本文中被提出。这种技术是基于标准曲线的,是对传统方法的一种补充,标准曲线代表了裂隙的长度、裂隙的走向和与地下水流动有关的裂隙的规模(即密度)的不同组合。用数值模型来获得标准曲线。为了解释裂隙开度的变化,定义了渗透性比值(R),渗透性比值是区域上裂隙网的渗透系数与具有相同裂隙开度的单一裂隙渗透系数的比值,渗透性比值也作为获得标准曲线的因变量。这种技术的工作原理是确定标准曲线上能代表在现场获得的裂隙特征的点。为了测试这种技术的效果,把从美国马萨诸塞州东部获得的裂隙含水层的渗透率和通过这种技术预测得到的渗透率进行了对比。结果表明,利用标准曲线评估获得的渗透系数和通过现场测试得到的渗透系数在同一个数量级上。因此,在利用更成熟更昂贵的方法之前,利用这种技术,可以方便快捷地获得裂隙网络渗透系数的一级估计值。ResumoÉ desenvolvido um método para estimar a permeabilidade potencial de redes de fratura através de atributos de fraturas observadas em afloramento. A técnica, que é concebida como um complemento para as abordagens tradicionais, baseia-se em curvas tipo que representam várias combinações de comprimentos de fratura, orientações de fratura e proporções (isto é, intensidades) de fraturas que facilitam o fluxo. São utilizados modelos numéricos para obter as curvas tipo. Para ter em conta as variações de abertura das fraturas, uma relação de permeabilidade (R) definida como a permeabilidade de uma rede de fraturas de um domínio dividida pela permeabilidade de uma fratura simples com idêntica abertura da fratura, é usada como uma variável dependente para obter as curvas tipo. A técnica funciona através da determinação do ponto na curva tipo que representa as caraterísticas das fraturas recolhidas no campo. Para testar o desempenho da técnica, as permeabilidades que foram derivadas a partir de aquíferos rochosos fraturados do leste de Massachusetts (EUA) são comparados com permeabilidades previstas pela técnica. Os resultados indicam que as permeabilidades estimadas a partir das curvas tipo estão dentro da ordem de grandeza da magnitude das permeabilidades obtidas a partir de ensaios de campo. Estimativas de uma primeira ordem de grandeza da permeabilidade da rede de fraturas podem, portanto, ser fácil e rapidamente obtidas com esta técnica, antes de métodos mais robustos e dispendiosos serem utilizados no campo.

Groundwater and stream E. coli concentrations in coastal plain watersheds served by onsite wastewater and a municipal sewer treatment system

The goal of this study was to determine if onsite wastewater treatment systems (OWS) were influencing groundwater and surface water Escherichia coli concentrations in a coastal plain watershed. Piezometers for groundwater monitoring were installed at four residences served by OWS and five residences served by a municipal wastewater treatment system (MWS). The residences were located in two different, but nearby (<3 km), watersheds. Effluent from the four septic tanks, groundwater from piezometers, and the streams draining the OWS and MWS watersheds were sampled on five dates between September 2011 and May 2012. Groundwater E. coli concentrations and specific conductivity were elevated within the flow path of the OWS and near the stream, relative to other groundwater sampling locations in the two watersheds. Groundwater discharge in the OWS watershed could be a contributor of E. coli to the stream because E. coli concentrations in groundwater at the stream bank and in the stream were similar. Stream E. coli concentrations were higher for the OWS in relation to MWS watersheds on each sampling date. Water quality could be improved by ensuring OWS are installed and operated to maintain adequate separation distances to water resources.

Rescuing degrading aquifers in the Central Coastal Plain of North Carolina (USA): Just process, effective groundwater management policy, and sustainable aquifers

Strategic management of degrading coastal aquifers in eastern North Carolina (USA) became imperative after a severe imbalance occurred between withdrawal and recharge rates. To ameliorate this growing problem, an aggressive water policy was developed through public input by creating the Central Coastal Plain Capacity Use Area (CCPCUA) to maintain beneficial use of groundwater resources. Insights from social psychology, and socio-legal studies are used to evaluate how procedural justice and public participation played major roles to resolving groundwater resource management problems. A mixed methods approach uses archival data and interviews with various rule-making participants to assess the process of stakeholder involvement that led to creation of the policy. In addition, data analysis techniques are utilized to evaluate the effects of the policy on aquifer health (through water levels) over a ∼10 year period. Results suggest that not only did a stakeholder group participate in a process that was deemed fair, understandable, and relatively easy to administer for users and regulators, but public participation resulted in an effective plan that ensures the long-term sustainable use of groundwater. Declining groundwater withdrawals and recovering water levels suggest that the rule is achieving its intended goal of protecting the aquifers from depletion and degradation. This paper touches on global themes that are essential to water demand and consumption, water management techniques, and water resources protection.

Influence of Sewered Versus Septic Systems on Watershed Exports of E. coli

Elevated bacteria concentrations have led to the impairment (e.g., closures of shellfisheries and recreational beaches) of coastal waters. Although many previous studies have suggested that wastewater inputs can lead to elevated fecal indicator bacteria (FIB) concentrations in surface waters, few studies have quantified wastewater-associated FIB exports at the watershed scale. The goal of this study was to estimate bacterial exports at the watershed scale based on wastewater management approach (septic vs. sewer). Six watersheds (three exclusively on septic and three exclusively served by a sewer system) were selected for water quality assessment and comparison. Streams were monitored approximately monthly from August 2011 to June 2012 during baseflow conditions. Additionally, three storms were monitored. Samples were collected in sterile 100-mL bottles and analyzed for Escherichia coli concentrations. Discharge from streams was measured and bacterial exports were estimated by multiplying discharge by E. coli concentration. The results revealed that (1) during baseflow conditions, septic watersheds contained elevated stream discharge and E. coli concentrations and exports as compared to sewer watersheds; (2) warmer months had elevated E. coli watershed exports compared to colder months in both septic and sewer watersheds; and (3) storms significantly increased watershed E. coli exports in both septic and sewer watersheds. Storms significantly increased watershed E. coli exports in both septic and sewered watersheds, but E. coli counts in sewered watersheds were considerably greater likely due to greater impervious surface coverage and or leaky sewer infrastructure. These findings in conjunction with previous studies suggest that septic systems may play a pivotal role in the delivery of FIB to receiving waters, particularly during baseflow conditions.

Refining management strategies for groundwater resources

Accessible potable water resources are imperative to global health. However, despite years of management interventions, groundwater resources remain threatened by overexploitation and contamination due to increasing human population, urban, industrial and agricultural development, and climate change and sea level rise. Population dynamics accompanied by climate change will place greater stresses on groundwater resources and lead to increased threats of pollution, salt-water intrusion, and declining water levels due to large withdrawal volumes (Green et al. 2011; Taylor et al. 2013). The ultimate goal for resource managers is sustainability. Regardless of the resource, sustainability has become the buzzword for environmental health, yet is a difficult term to understand (Sophocelous 2000). In 1987, the United Nations defined sustainable development as that which “meets the needs of the present without compromising the ability of future generations to meet their own needs (Brundtland 1987).” This view, calls for both short and long-term perspectives for resource management. It also begs the difficult incorporation of criteria measured in qualitative and quantitative terms with inconsistent measurement units (Ashley 2008; Ryu et al. 2009). Yet, it is a shortsighted and human-centric view driven by human needs. In contrast, Alley et al. (1999) defined groundwater sustainability as the “development and use of ground water in a manner that can be maintained for an indefinite time without causing unacceptable environmental, economic, or social consequences.” This broader world-view incorporates all aspects of the environment, including, but not limited to humans. The literature is rife with broad descriptions and examples of interventions for resource sustainability (e.g., Alley et al. 1999; Sophocleous 2000; Alley and Leake 2004; Unver 2007; McCarthy 2008; Ryu et al. 2009; Mukheibir 2010; Sophocleous 2010; Gleeson et al. 2012; Mays 2013). Many of the strategies are crossdisciplinary and are not groundwater specific (e.g., Ambler 2002; Ashley et al. 2008; Mihelcic 2008; Petrini and Pozzebon 2009; Stainer and Stainer 2009; Weidmann et al. 2009; Leon-Soriano et al. 2010); however, a comprehensive framework that allows resource managers to quantify and adapt to rapidly changing environmental, social and economic conditions, while relating specifically to groundwater resources is lacking. Here, concepts are borrowed from other disciplines to argue that refined and flexible groundwater management philosophies incorporating proven methodologies can help model, develop and evaluate groundwater resource strategies. Major organizational changes are required to meet the challenges of temporally and spatially changing groundwater supplies and demands. Basic groundwater management norms are reexamined to include strategies to maintain variously scaled projects, over both short and long timescales, while incorporating changing environmental, social and economic conditions. Only through steadfast intention, improved groundwater use, evaluation, and management philosophies coupled with efficient resource practices, resource allocation, and pricing, will water managers successfully achieve groundwater sustainability. In addition to well-established groundwater management protocols (e.g., Alley et al. 1999; Gleick 2003; Sophocleous 2010), the following elements vital to achieving sustainability are proposed: (1) well-defined long-term goals for the future with varying temporally and spatially measurable benchmarks (vision), (2) innovative management strategies (adaptation and integration), (3) empowerment and education (cooperation), and (4) Received: 17 April 2014 /Accepted: 30 July 2014 Published online: 15 August 2014

In situ measurements of wind-driven salt fluxes through constructed channels in a coastal wetland ecosystem

Department of Geological Sciences, East Carolina University, Graham 101, East 5th Street, Greenville, NC 27858, USA 2 Institute for Coastal Science and Policy, East Carolina University, Flanagan 387, East 5th Street, Greenville, NC 27858, USA Department of Biology, East Carolina University, N108 Howell Science Complex, East 5th Street, Greenville, NC 27858, USA 4 Institute for Coastal Science and Policy, East Carolina University, Howell S211, East 5th Street, Greenville, NC 27858, USA Correspondence Alex K. Manda, Department of Geological Sciences, East Carolina University, Graham 101, East 5th Street, Greenville, NC 27858, USA. Email: mandaa@ecu.edu Funding information East Carolina University Intramural Award

CHARACTERIZATION OF HETEROGENEITIES AT THE RESERVOIR SCALE: SPATIAL DISTRIBUTION AND INFLUENCE ON FLUID FLOW

The theory behind how chemically reactive tracers are used to characterize the velocity and temperature distribution in steady flowing systems is reviewed. Kinetic parameters are established as a function of reservoir temperatures and fluid residence times for selecting appropriate reacting systems. Reactive tracer techniques are applied to characterize the temperature distribution in a laminar-flow heat exchanger. Models are developed to predict reactive tracer behavior in fractured geothermal reservoirs of fixed and increasing size.