Mountain Scholar :: Browsing by Author "Stednick, John, committee member"

Browsing by Author "Stednick, John, committee member"

Now showing 1 - 20 of 22

Open Access
A comparison of electrocoagulation and chemical coagulation treatment effectiveness on frac flowback and produced water
(Colorado State University. Libraries, 2015) Hutcherson, John Ryan, author; Carlson, Ken, advisor; Omur-Ozbek, Pinar, committee member; Stednick, John, committee member
Development and production of tight shale for crude oil and natural gas is increasing rapidly throughout the United States and especially in the Wattenberg field of Northern Colorado. Hydraulic fracturing is used to stimulate the shale formation, which allows previously trapped oil and gas to flow to the surface. According to Goodwin (2013), approximately 2.8 million gallons of water are required to hydraulically fracture a horizontal well. Freshwater makes up the vast majority of water used to create these fracturing fluids with a small portion coming from recycling of previously used fracturing fluid. In a semi-arid climate such as Northern Colorado, there are multiple demands for freshwater, often exceeding the supply. Once a well is fractured, water flows back to the surface along with the targeted oil and gas. This fluid is typically referred to as flowback or produced water. In some areas around the United States as much as 10 barrels of water flows to the surface for every barrel of oil recovered. For the purposes of this research, flowback is defined as water that flows to the surface within the first 30 days after fracturing. After fracturing, up to 71% of the water (produced water) used to fracture the well flows back to the surface along with oil and gas, with approximately 27% flowing back in the first 30 days (Bai et al, 2013). The flowback and produced water is currently being disposed of either by deep underground injection or in evaporation ponds. There has been very little effort to capture, recycle, and reuse this flowback or produced water as it has traditionally been considered a waste product. Due to the limited freshwater supply in Colorado, recycling and reuse should be explored in greater detail and with a sense of urgency. The ultimate goal for the oil and gas industry should be to recycle and reuse 100% of flowback and produced water in the creation of hydraulic fracturing fluid for other production wells, creating a closed-loop system. Before flowback and produced water can be reused, treatment of the water is required. Treatment for reuse typically consists of removal of solids, organic compounds, and some inorganic ions. Historically, chemicals have been the dominant method used for coagulation to remove solids, as they are readily available and in many cases can be cheaper than other methods. Electrocoagulation (EC) is now also being considered as a produced water treatment method. EC involves running electric current across metal plates (sacrificial anodes) in a solution, which creates an in situ coagulant dose (Emamjomeh and Sivakumar 2008). There is a time component to water quality changes over the life of a well. Early flowback typically has higher concentration of aluminum, solids, and total organic carbon (TOC) as it is influenced mostly by the makeup of the fracturing fluid. At some point around the 30-day mark, a transition in water quality begins. The formation or connate water seems to have a greater influence on water quality than does the fracturing fluid. Treatment seems to correlate to the changing water quality, as treatment is less effective on the early flowback compared to produced water. TOC and low ionic strength may be the reason early flowback is more difficult to treat. Also, chemical coagulation (CC) is more effective than EC at removing TOC and aluminum in early flowback water compared to EC, while EC is more effective at removing iron. However, both treatments are effective after day 27.
Open Access
A paleohydrologic investigation in the vicinity of Harpers Ferry, West Virginia
(Colorado State University. Libraries, 1992) Fuertsch, Susan Jane, author; Wohl, Ellen E., 1962-, advisor; Salas, J. D. (Jose D.), committee member; Stednick, John, committee member
A paleohydrologic investigation of the Shenandoah River in the vicinity of Harpers Ferry, West Virginia, was conducted in response to the recent periodic floods that devastate the community. The study reach was approximately 7.5 km long and consisted of thirty-two surveyed cross-sections. Gaging stations established in 1895 at Millville, West Virginia and in 1882 at Harpers Ferry, West Virginia record flows ranging from a maximum of 6,509 m³s¯' , to a minimum of 2 m³s¯'. The average annual peak discharge for a seventy-year water record was 1,244 m³s¯'. Botanical flood evidence preserved as adventitious sprouts, tree scars and eccentric rings were documented in thirty-seven trees. A flood chronology established from these data extended from 1896 to 1955 after which no botanical indicators were found. Botanical indicators did not extend the systematic record, but they did provide an accurate, although not complete, flood chronology. The completeness of the botanical flood record is highly Sedimentological flood evidence was limited within the study area due to the influence of a humid-temperate climatic regime, which is not conducive to the stratigraphic preservation of individual flood depositional units. Human habitation of the area began in 1733; therefore, qualitative historical records were plentiful. Various historical records were cross-referenced to yield the most complete flood history. The correlation between the various sources was extremely high, demonstrating the comprehensiveness of the record. The historical flood record extends from 1748 to the beginning of the systematic record in 1896. The ability to determine accurate flood stages from paleoflood indicators varied highly. Botanical indicators were found to yield very inaccurate and inconsistent flood stages, and only minimum values of flood stage could be obtained from these data. Historical data did yield accurate stages; however, these stages did not necessarily yield accurate discharge values, depending upon the stationarity and hydraulic complexity of the area.
Open Access
A test of general shear versus folding for the origin of a cryptic structural feature, Nason terrane, Washington
(Colorado State University. Libraries, 2013) Jackl, Max Alexander, author; Magloughlin, Jerry, advisor; Ridley, John, committee member; Baird, Graham, committee member; Stednick, John, committee member
The Nason terrane of the Cascades Crystalline Core is a complex tectonostratigraphic terrane that has been the topic of much study due to its long deformational history and importance in the debate surrounding the Baja B.C. hypothesis. Structural patterns along Nason Ridge in the central part of the terrane have been interpreted as the result of either the presence of a major shear zone or the development of fold interference patterns. Distinguishing fold-controlled lineations from shear zone produced lineations can be a complex, but important problem. This study aims to provide a better understanding of high-temperature deformation which may be obscured due to extensive recrystallization. Outside of the cryptic zone the foliation is steeply dipping and striking to the NW with lineations which are subhorizontal. Previous observations revealed a structural zone ~1 km wide striking NW-SE. Within the zone, fold hinges and mineral lineations are typically subvertical with mineral lineations clustering tightly and trending NE, indicating that this zone has a fundamentally different structural fabric than the surrounding terrane. Fold hinge lines are more dispersed along the trend of the zone, possibly reflecting incomplete rotation of pre-existing fold hinges into a near vertical orientation. Anisotropy of magnetic susceptibility analysis indicates the magnetic fabric correlates well with lineations and foliations measured in the field, and lineations likewise shallow to near horizontal outside the zone. Quantification of the strength of the AMS fabric reveals an oblate spheroid, which is interpreted as a proxy for an oblate strain ellipsoid, indicating the presence of a component of pure shear. Asymmetrical microstructural features present include tailed porphyroclasts, mineral fish, and domino clasts. Sense of shear indicators agree with the hypothesized NE-side-up motion (Magloughlin, 1990). Electron backscatter diffraction analysis reveals biotite and amphibole possess a lattice preferred orientation (LPO), whereas quartz and plagioclase have a nearly random crystallographic fabric. The biotite and amphibole LPO was used to determine NE-side-up sense of shear in thin sections from the cryptic zone. It is clear from the agreement between outcrop scale structures, magnetic fabric, microstructures, and crystallographic fabric that a significantly different structural fabric is tightly localized on the zone. The highly focused nature of the zone and the lack of structures typically created by fold interference indicates that superposed folding is unlikely. These data, coupled with geothermobarometric constraints, point to a zone of displacement best characterized by northeast-side-up general shear.
Open Access
Analysis of produced water from three hydraulically fractured wells with different levels of recycled water
(Colorado State University. Libraries, 2016) McCormick, Brian E., author; Carlson, Kenneth, advisor; Sharvelle, Sybil, committee member; Stednick, John, committee member
With the growing use of hydraulic fracturing, injecting large amounts of water into oil and natural gas reservoirs to increase the quantity of oil and natural gas extracted, large amounts of water with low water quality are being created. This water has to be disposed of and many disposal methods have environmental concerns. One method of disposal is treating the water to remove the contaminants that have environmental concerns. Treatment of produced water for reuse, which will be identified as recycled water, as a fracturing fluid is becoming an increasingly important aspect of water management surrounding the unconventional oil and gas industry since the treatment does not have to be as robust as it would for disposal into surface water. Understanding variation in water quality due to fracturing fluid and produced water age are fundamental to choosing a data driven, water management approach. For these reasons, Noble Energy partnered with CSU to analyze the water quality differences between four wells with different levels of recycled water usage in a previous study. In that study, the findings showed a higher organic content of the produced water in the early period due to the presence of emulsified oil. The higher organic content of that produced water was the reason for using recycled water at more wells to determine if the higher organic content was repeatable at a different site. For this study, one well was 100 percent fresh water, another well was one part recycled water and five parts fresh water, and the last well was one part recycled waters and seven parts fresh water. Based on the data, the inorganic constituents vary more than the organic material. Inorganic variance being greater than organic makes sense due to the fact that the organic matter comes mainly from the fracturing fluid’s gel or slickwater component (Sick 2014), despite the organic variance seen in the previous study (White 2014). The inorganic matter mainly comes from the recycled water as seen from the ANOVA testing indicating significant difference between the wells, which is not treated to fresh water levels, and the data from the three wells shows a significantly higher value for the wells fractured with recycled water. A good illustration of the difference in the produced water quality that can be tied to the fracturing water quality is the TDS that was between four and six times higher in the fracturing fluid’s base fluid due to the use of recycled water. Of the inorganic constituents measured, aluminum, silicon, zinc, ammonium and sulfate were the only ones that did not show a statistically significant difference between the fresh water well and the recycled wells as indicated by a p value of 0.05 from an ANOVA test. None of the organic constituents showed significant statistical difference between the recycled wells and fresh water well, but they did vary over time indicating that the reactions and interactions with the geological formation affected the wells at a different rate. The wells did show a statistical difference both between the wells and over time, however, not in the way that was hypothesized as the organic material did not vary based on the wells. Total organic carbon (TOC), dissolved organic carbon (DOC), oil range organics (ORO), diesel range organics (DRO) and gasoline range organics (GRO) all had values 0.367, 0.758, 0.349, 0.768 and 0.707, respectively. The organics showed more significant difference over time with TOC, GRO, and ORO with p-values of 0.005, 0.012, and 0.029, respectively. However, the inorganic data did show significant difference between wells as well as over time. The inorganic constituents boron, barium, bromide, calcium, iron, potassium, magnesium, chlorine, strontium, sodium, and bicarbonate all had p-values of less than 0.01 except for chlorine which was 0.014. Potassium was the only constituent in that list that was not significantly different over time, but silicon and ammonium, which did not differ by well, did show significant difference over time. All of the inorganic constituents were very significantly different over time with no p-value over 0.01. The impact of this on the water management strategies shows that the understanding of the produced water quality and the factors that impact that is still largely unknown. More sampling and testing for well variability based on the ratio of recycled water in the fracturing fluid will allow more data and a better data driven management approach.
Open Access
Characterization and prediction of long-term arsenic mobility, dissolution, and kinetic behavior in arsenic contaminated floodplain deposits of Whitewood Creek and the Belle Fourche River, South Dakota
(Colorado State University. Libraries, 2021) Ji, Mu, author; Ridley, John, advisor; Stednick, John, committee member; Borch, Thomas, committee member; Gallen, Sean, committee member
From 1877 to 1977, the Homestake Mine discharged over 100 million tons of arsenic-rich mine-wastes from Lead, South Dakota into Whitewood Creek (WWC), which joins the Belle Fourche River (BFR). Arsenopyrite and other arsenic-bearing minerals were deposited in tailings (containing between 0.12% to 0.35% arsenic) and mixed with uncontaminated alluvium along the floodplains of WWC and the BFR as overbank deposits and filling abandoned meanders. Since it is not feasible to remove millions of tons of contaminated sediments from the area, an understanding of arsenic mobility on long timescales is vital. Many studies have laid the framework for factors controlling arsenic mobility appropriate to fluvial sedimentary systems; investigating mechanisms of arsenic mobilization, adsorption/desorption kinetics, and the effects of pH, changing redox conditions, etc., however, these studies were conducted on relatively short time scales and did not quantify arsenic mass-budget on field-scales. This study focuses on the long-term retention, dissolution, and kinetic behavior of arsenic from mine tailings. The uniqueness of this site enables arsenopyrite dissolution behavior to be constrained over a 135-year timespan (1877-2012). This allows for the investigation of changes in arsenic's residence sites, its rate of release into the environment, calculation of its transport mass-budget, and elucidation of how natural processes have or have not remediated arsenic contamination over a span of 35 years since the deposition of tailings have ceased (1977-2012). For this investigation, sediment, surface water, and seep water samples were collected along reaches of WWC and the BFR for analysis of arsenic and other geochemical constituents. Sequential extractions of the sediments were performed to determine the mineralogical setting of the arsenic as well as the proportion of arsenic available at different rates of release into the environment. Additionally, various historical data (discharge levels, geochemical analyses of water and sediment samples) were compiled from the United States Geological Survey database. Regressions were applied to historical data to estimate the rate of physical and chemical arsenic removal from the WWC watershed. Sediments collected along the floodplains of WWC and the BFR exhibited arsenic concentrations ranging from approximately 100 to 4,000 mg/kg. The results from the sequential extractions applied to the sediments suggest arsenic is predominantly located in residence sites that are not easily accessible, and arsenic is not readily mobilized or released into solution in large quantities under normal environmental conditions seen in WWC and the BFR. An average of 16% of the arsenic is weakly bound to readily exchangeable surface sites, water-soluble secondary minerals and available for rapid release, or is adsorbed to exchange sites that easily exchange PO43- ions for adsorbed arsenic oxyanions, is weakly bound in amorphous to poorly crystalline fine-grained metal oxides/hydroxides, reducible phases, and easily soluble carbonates. An average of 24% of the arsenic is moderately strongly bound in weakly soluble secondary minerals like clays or crystalline fine-grained metal oxides/hydroxides and will be released relatively slowly with time. The remaining 60% of arsenic is interpreted to be relatively immobile and locked in arsenopyrite in part due to the formation of metal oxyhydroxide coating, which slows down the degradation of the mineral. These interpretations are supported by the elevated but still relatively low total arsenic concentrations (EPA MCL for arsenic is 0.01 mg/L) of in-stream water in WWC (averaging 0.037 mg/L) and in the BFR (averaging 0.021 mg/L), considering that in-stream sediments carried by WWC and the BFR have high arsenic concentrations (264 to 694 mg/kg). Based on regressions applied to 30 years of historical sediment transport and arsenic concentration in solution and in sediment load (1982-2012), the average annual total arsenic load transported out of WWC during these 30 years was estimated to be between 34 to 71 megagrams (Mg) per year. At this rate, based on the 17,400 to 50,800 Mg of arsenic that remain in storage along the floodplains of WWC, complete arsenic transport out of the floodplains of WWC would range between 250 to 1,500 years. The actual rate of arsenic removal is expected to be longer because the model is based on a uniform movement of uniformly distributed sediment, and historical patterns may not be reflective of future trends, as evidenced by the decline in suspended arsenic transport rate starting in the early- to mid-1980s. The constant shifting of the stream creates abandoned meanders along WWC that can store contaminated sediment where the stream no longer has access. Conversely, as the meanders shift over time, the once-abandoned meanders could be again accessed by WWC. The majority of suspended sediment transport occurs during flood events; approximately 88% of the total arsenic load moved during the years between 1983 to 2012 occurred in only 3 of the years (1983, 1984, and 1995). Thus, the rate of arsenic transport for the next 30-year period is uncertain and could be lower if the number of flood events remains low. Although the WWC area once experienced heavy environmental degradation during the period of active mining, natural processes have allowed for relatively stable current environmental conditions. However, the physical transport of arsenic-contaminated sediment and the slow release of arsenic to the environment endures downstream to the BFR into the Cheyenne River and Lake Oahe and will continue for many generations.
Open Access
DC electrical resistivity constraints on hydrostratigraphy in the lower South Platte River alluvial aquifer in northeastern Colorado
(Colorado State University. Libraries, 2013) Lonsert, Reece, author; Harry, Dennis, advisor; Stednick, John, committee member; Ronayne, Michael, committee member
This study uses DC Electrical Resistivity Tomography (ERT) to delineate hydrostratigraphic units within the lower South Platte River alluvial aquifer. The geophysical investigation was conducted at Tamarack Ranch State Wildlife Area in northeastern Colorado, where the South Platte River is artificially recharged via pumping to surface recharge ponds and groundwater flow through the underlying unconfined alluvial aquifer system. Twenty-seven ERT profiles collected within a 4.2 km2 study area on the south bank of the South Platte River define 3 different electrostratigraphic units. The ERT data was correlated with drilling logs and laboratory resistivity measurements to develop a hydrostratigraphic model and confining bedrock surface map. Results indicate 7-25 m thick eolian sand deposits (50-800 ohm-m) serve as infiltration zones and do not readily store groundwater. These eolian deposits form up to 15 m high sand hills in the southern half of the study area, and underlie recharge ponds that are used as water sources for artificial recharge of the river. The underlying alluvium (20-3890 ohm-m) varies from 10-70 m thick and functions as the primary groundwater storage unit. A 10-20 m thick intermittent conductive zone (25-80 ohm-m) occurs within the upper part of the alluvial layer that underlies the sand hills, and is interpreted to be caused by clay deposits that potentially influence initial groundwater flow paths emanating from the recharge ponds. The alluvium is underlain by highly conductive siltstone and claystone bedrock formations (1-60 ohm-m) that confine the aquifer system. The bedrock surface is complexly eroded (1055-1110 m.a.s.l.) and is characterized by prominent large-scale paleo-topographic lows (at typical scales of 700 m wide, 35-40 m deep and 700 m wide, 20-25 m deep) that occur on the northern bank of an incised paleo-channel. These features are interpreted to represent a paleo-topographic surface formed by groundwater outflow in the form of piping and sapping networks. The rugged bedrock topography establishes a previously unrecognized first order control on groundwater flowpaths within the unconfined alluvial aquifer.
Open Access
Development of a watershed modeling selection program and simple equations as an alternative to complex watershed modeling
(Colorado State University. Libraries, 2013) Cho, Yongdeok, author; Roesner, Larry A., advisor; Grigg, Neil S., committee member; Arabi, Mazdak, committee member; Stednick, John, committee member
Population pressures, land-use conversion and its resulting pollution consequences appear to be the major diffuse pollution problems of today. Research also indicates that the increase in imperviousness of land due to urbanization increases the volume, rate of stormwater runoff causing increased channel erosion and flooding downstream, water quality contamination, aquatic biota, and drinking water supplies. In the past, negative impacts were never seriously considered as urbanization increased, but the attitude of citizens and governments are changing and people now want to retain, restore or rehabilitate existing waterways, and manage future urban and rural development in order to improve environmental conditions. Water quality management in the contributing watersheds is vital to the management of water quality in the main stem rivers. Hence, policy makers should decide which places should be considered for restoration projects based on priority analyses. To carry out these evaluations in Korea, mathematical models are needed to forecast the environmental results after applying watershed restoration measures. However, the scope of sophisticated watershed modeling is very complicated, expensive and time consuming, and not really required for planning level decision making. Therefore, simpler evaluation methods should be applied, that can adequately discern for planning purposes the changes in aquatic environmental quality that can be expected in different watersheds after adapting restoration or protective measures. Thus, this research proposed to create a simple equation specifically for watershed planning. To create such a simple equation, three main tasks were undertaken. The tasks are as follows: (1) the creation of a selection program for available watershed models, (2) establish simple equations to be used instead of watershed models, and (3) verify the simple equations by comparing them with a physically based model (HSPF). In regards to the first task mentioned above, this dissertation presents a review of thirty three watershed models available for watershed planning and shows that these watershed models can not easily be applied to large-scale planning projects that are being undertaken by South Korea like the Four River Restoration Project. One of the main reasons for their inapplicability is that they require vast amounts of data and significant application effort to be used in a prioritization project involving many watersheds (Roesner, personal commucation). In addition, it is vital to select an appropriate watershed model that are realistically models a watershed's conditions and more specifically, to match users' needs. However a selection program has not yet developed, as well. Therefore, eight factors were selected for task 1 to examine the specific characteristics of each of the 33 watershed models in great detail. Based on the results of the 8 factors proposed, the selection program was developed to screen which will be most useful to a project. Based on these literature reviews of the 33 available watershed models but unrealistically complex models, it was determined that a simpler model utilizing accessible base data, such as land use type, is needed to evaluate and prioritize watersheds in the feasibility stage of a spatially large projectstudies for national based projects (i.e. National level). A correlation study between land use types and water quality parameters has been published (Tu, 2011, Mehaffey et al., 2005, Schoonover et al., 2005, etc.), however, the research examined the correlation between land usage and water quality in great detail, but did not address any correlations to implement real-based watersheds. Therefore, Task 2 is the development of simple equstions, for this task, two important sub-tasks were undertaken 1) Hydrology (rainfall), geology (slope), and land usage data were analyzed to verify their relationships with the water quality (BOD, COD, T-N, T-P) in the watershed, and 2) Simple Equations were constructed based on Statistical Methods (Excel Solver, Statistical Analysis Systems) and Data Mining (Model Tree, Artificial Neural Network, and Radial Based Function) in order to prove their accuracy. Thus, if the equations are accurate, they can be used to prioritize basins within a watershed with respect to their impact on water quality in the mainstem river. For the final task, task 3, Simple Equations were verified by comparing them with a physically based model, HSPF, based upon the real-based watersheds which are located in South Korea in order to prove the Simple Equations are capable of being a reliable alternative to physically based models. These simple equations could be used to allow management to identify and prioritize restoration and rehabilitation areas in a watershed even though sufficient data had yet been collected to satisfy the requirements of a physically based model.
Open Access
Development of predictive geosmin models in northern Colorado lakes, reservoirs, and rivers
(Colorado State University. Libraries, 2014) Parr, Glenn, author; Omur-Ozbek, Pinar, advisor; Catton, Kimberly, advisor; Stednick, John, committee member
Geosmin is a taste and odor (T&O) compound that is naturally occurring, produced by bacteria, and released into drinking water source waters. Geosmin in many parts of the country is a seasonal issue, so drinking water providers often look for temporary solutions to the T&O caused by geosmin. Being able to predict when geosmin will be an issue is vital if drinking water providers are going to succeed in using temporary mitigation methods. Therefore research is being performed to develop predictive models. This study is a broad sampling of Northern Colorado water bodies investigating the role of watershed and elevation, as well as biotic and abiotic water quality parameters. Water quality and zooplankton samples were collected from 20 different lakes and reservoirs as well as 20 sites on 4 rivers in Northern Colorado. Statistical models were developed using Multiple Linear Regression and Principal Component Analysis. Models show significant correlations between geosmin and zooplankton, particularly the species Nauplii and Daphnia in the lakes and reservoirs data. Modeling of the river data revealed geosmin relationships with elevation and dissolved oxygen, but did not show a significant correlation with stream flow. As expected from previous studies month of the year was also shown to be a significant factor.
Open Access
Estimates of sublimation in the Upper Colorado River basin
(Colorado State University. Libraries, 2013) Phillips, Morgan, author; Cotton, William, advisor; Stednick, John, committee member; Schumacher, Russ, committee member
Snowpack stored in mountain environments is the primary source of water for the population of much of the western United States, and the loss of water through direct evaporation (sublimation) is a significant factor in the amount of runoff realized from snow melt. A land surface modeling study was carried out in order to quantify the temporal and spatial variability of sublimation over the Upper Colorado River basin through the use of a spatially distributed snow-evolution model known as SnowModel. Simulations relied on forcing from high resolution atmospheric analysis data from the North American Land Data Assimilation System (NLDAS). These data were used to simulate snow sublimation for several years over a 400 by 400 km domain in the Upper Colorado River Basin at a horizontal resolution of 250 m and hourly time-steps. Results show that total volume of sublimated water from snow varies 68% or between 0.95 x 107 acre feet in WY 2002 to the maximum of 1.37 x 107 acre feet in WY 2005 within the ten years of the study period. On daily timescales sublimation was found to be episodic in nature, with short periods of enhanced sublimation followed by several days of relatively low snowpack water loss. The greatest sublimation rates of approximately 3 mm/day were found to occur in high elevation regions generally above tree line in conjunction with frequent windblown snow, while considerable contributions from canopy sublimation occurred at mid-elevations. Additional sensitivity runs accounting for reduced canopy leaf area index as a result of western pine beetle induced tree mortality were also carried out to test the models sensitivity to land surface characteristics. Results from this comparison show a near linear decrease in domain total sublimation with reduced LAI. Model performance was somewhat satisfactory, with simulations underestimating precipitation and accumulated SWE, most likely due to biases in the precipitation forcing and errors in determining precipitation phase.
Open Access
Estimation of unconfined aquifer hydraulic properties using gravity and drawdown data
(Colorado State University. Libraries, 2011) Woodworth, Joshua, author; Harry, Dennis, advisor; Sanford, William, advisor; Stednick, John, committee member
An unconfined aquifer test using temporal gravity measurements was conducted in shallow alluvium near Fort Collins, Colorado on September 26-27, 2009. Drawdown was recorded in four monitoring wells at distances of 6.34, 15.4, 30.7, and 60.2 m from the pumping well. Continuous gravity measurements were recorded with a Scintrex® CG-5 gravimeter near the closest well, at 6.3 m, over several multi-hour intervals during the 27 hour pumping test. Type-curve matching of the drawdown data performed assuming Neuman's solution yields transmissivity T, specific yield Sy, and elastic component of storativity S estimates of 0.018 m2s-1, 0.041, and 0.0093. The gravitational response to dewatering was modeled assuming drawdown cone geometries described by the Neuman drawdown solution using combinations of T, Sy, and S. The best fitting gravity model based on minimization of the root mean square error between the modeled and observed gravity change during drawdown resulted from the parameters T =0.0033 m2s-1, Sy =0.45, and S =0.0052. Conservative precision estimates in the gravity data widen these estimates to T =0.002-0.006 m2s-1, Sy =0.25-0.65, and S =0-0.2. Drawdown conforming to the Neuman solution was forward modeled using combinations of T, Sy, and S. Minimization of the root mean square misfit between these forward models and observed drawdown in the monitoring wells results in T =0.0080 m2s-1, Sy =0.26, and S =0.000004. Discrepancy between type-curve matching results, gravity analysis results, and drawdown modeling is attributed to heterogeneity and anisotropy within the aquifer, and a relatively large amount drawdown compared to initial saturated thickness, conditions which fail the Neuman solution assumptions. In this aquifer test, gravity was most sensitive to transmissivity, less sensitive to specific yield, and insensitive to the specific storage-saturated thickness quotient. Simultaneous deployment of multiple gravity stations during similar tests should better constrain gravity analysis aquifer property estimates of transmissivity and specific yield.
Open Access
Evaluation of spatially dependent on-site detention basin policies
(Colorado State University. Libraries, 2015) Augustine, Andrew John, author; Roesner, Larry, advisor; Niemann, Jeffrey, committee member; Gironás, Jorge, committee member; Stednick, John, committee member
Stormwater detention basins are typically used for stormwater control in many communities across the United States. They are commonly constructed downstream of every new development to control post-development runoff, and are called "on-site" detention basins. It has been shown by multiple authors in the literature that the design of on-site detention basins with no consideration of their location (non-spatially dependent policies, or Non-SD) in the watershed can actually increase peak flows above post-development peaks that would occur in the absence of on-site detention basins. This is caused by on-site detention basins delaying the peak release of a particular subwatershed and combining with other peak flows in the watershed (McCuen 1974; McCuen 1979; Emerson et al. 2005). Strategies to combat this problem have been reported, but metrics used to judge their success are limited to the main channel of the watershed or the watershed outlet only, leaving its impact in the remaining other watershed locations unknown. In addition, some strategies have recommended increasing the storage of on-site detention basins, but this approach would increase construction and maintenance costs and reduce the amount of land available to developers. Validation of increased peak flows throughout the watershed when Non-SD policies are used to design on-site detention basins compared to no on-site detention in the watershed was investigated first. The Non-SD policies used in this study controlled the post-development 10 and 100-year peak flows to flows at or below their respective pre-development peak flows (Non-SD 1), and controlled the post-development 100-year peak flow to flows at or below the 2-year pre-development peak flow (Non-SD 2). Next, spatially dependent policies (SD policies) were created by altering the peak flow release from on-site detention basins that would have occurred under a Non-SD policy based on its location in the watershed. These peak flows were altered using a linear model and a piece-wise linear model. Results from SD policies were compared to those from Non-SD policies. Metrics used to evaluate the effectiveness of the on-site detention basin policies (both SD and Non-SD) were peak flows throughout the watershed and total watershed storage. All policies were tested on a watershed in Fort Collins, Colorado using the Urban Morpho-climatic Instantaneous Unit Hydrograph model. Results indicate that Non-SD polices effectively reduce peak flows throughout the watershed, and do not increase peak flows compared to a policy that uses no on-site detention. When compared against Non-SD 1, SD policies derived from the linear equation were successful at reducing peak flows at some 2nd and 3rd order channel and pipe intersections in the upper half of the watershed, while increasing peak flows at 2nd order channel and pipe intersections in the lower half of the watershed. The remaining intersections were not effected by this SD policy, and the total watershed storage was shown to increase. SD policies derived from the piece-wise linear model increased peak flows at 2nd order channel and pipe intersections in the lower half of the watershed. The remaining intersections were not affected by this SD policy, and watershed storage was shown to slightly decrease. When compared to Non-SD 2, SD policies had little to no effect on peak flows at any location in the watershed or on the watershed storage.
Open Access
Evaluation of ultrasonic snow depth sensors for automated surface observing systems (ASOS)
(Colorado State University. Libraries, 2005) Brazenec, Wendy Ann, author; Fassnacht, Steven R., advisor; Doesken, Nolan, committee member; Kelly, Gene, committee member; Stednick, John, committee member
In the 1990's the National Weather Service deployed automated surface observing systems at hundreds of airport locations across the country. Prior to the automation, human observers made snow observations every six hours. Once the automated systems were deployed, snow measurements ceased due to the lack of an automated sensor to measure snow. This study explored how well ultrasonic snow depth sensors compared to manual snow observations at nine sites across the country. This study had four objectives: 1.) Develop a method of quality assurance and quality control 2.) Identify factors which affect sensor performance 3.) Compare automated sensors to manual observations of snow depth 4.) Derive an algorithm to estimate six hour snowfall from automated sensor snow depth. A reliable data smoothing/processing technique was achieved using filtering of large variability and smoothing with a moving average to smooth small variations in snow depth. Factors found to affect sensor performance included: snow crystal type, wind speed, blowing/drifting snow, uneven snow surface, extremely low temperatures, and intense snowfall. The Judd and Campbell sensors both did a satisfactory job measuring snow beneath the sensor within ±0.4 inches. Two separate algorithms were created due to differing degrees of precision between the two sensors. It was found that the Campbell sensor did a better job at estimating six hour snowfall than the Judd using an algorithm that calculated snowfall over 5 minute periods and applying a temperature based compaction model to the estimated snowfall. The Campbell agreed with the manual data with an average mean absolute error between measurements of 0.23 inches. The Judd sensor results improved by using an algorithm which calculated snowfall using the change in snow depth over sixty minutes, however, the Campbell results were better using the five minute snowfall algorithm. Overall, both sensors accurately depicted the snow depth on the ground, however the Campbell sensor was more accurate at predicting six hour snowfall using the algorithms presented in this research.
Open Access
Examining emerging water quality markets through a collective action lens
(Colorado State University. Libraries, 2018) Kraft, Katherine L., author; Cheng, Antony, advisor; Jones, Kelly, committee member; Stednick, John, committee member
Water quality trading (WQT) is a collective action mechanism increasingly employed to address water quality concerns arising from nonpoint source pollution. Yet, many established WQT programs have experienced little or no trading activity. Collective action theory regarding common property resources (CPR) suggests that the external variables comprising a collective action institution's context dictate how effectively an institution can organize and perform. Because successful emergence is a precursor to successful performance and endurance down the road, understanding how and why external variables affect WQT collection action during early formative stages can provide insights into why some WQT programs may struggle to function and perform to their anticipated potential as they mature. However, few efforts have empirically examined WQT programs in terms of the external variables known to influence CPR collective action emergence, performance, and durability. In addressing this void, I use an in-depth case study approach of two incipient WQT initiatives in the western U.S. to assess if and how the manifestation of external variables considered to be enabling conditions for successful CPR collective action influences the development of emerging WQT programs. This research finds theory regarding CPR collective action enabling conditions useful in understanding the development trajectories of emerging WQT programs. Results suggest that the absence of enabling conditions and strong constitutional rules can undermine the ability of decentralized political systems to support emergent WQT programs. Contrarily, centralized systems with well-defined rules and roles may provide more stable scaffolding for institutional development. These findings demonstrate how the quality of constitutional rules interacts with other external variables, including policy norms, agency allocation, collective choice rules, and social capital, to dictate the evolution and eventual performance of emergent WQT programs and CPR collective action institutions more broadly.
Open Access
Hydrogeologic characterization of an alpine glacial till, Snowy Range, Wyoming
(Colorado State University. Libraries, 2011) Houghton, Tyler B., author; Ronayne, Michael, advisor; Stednick, John, committee member; Sanford, William, committee member
Characterization of sediment hydraulic properties is essential to understanding groundwater movement. In many mountain watersheds, surficial geologic material, such as glacial till, plays an important role in water and nutrient chemical cycling. Hydraulic properties of alpine glacial tills are infrequently measured, requiring efforts to characterize this complex geologic material. This research involved the use of multiple measurement techniques to determine the saturated hydraulic conductivity of surficial glacial tills at the Glacier Lakes Ecosystem Experiments Site (GLEES) in south-central Wyoming. During the summer of 2010, three in situ methods (double-ring infiltrometer, mini disk infiltrometer, and Guelph permeameter) were used to measure field-saturated hydraulic conductivity (K sat) at 32 locations around GLEES. Estimated K sat values obtained with the double-ring infiltrometer had a geometric mean of 0.12 cm/min and range of 0.007 to 0.40 cm/min. The Guelph permeameter had a geometric mean of 0.094 cm/min and range of 0.003 cm/min to 0.776 cm/min, and the mini disk infiltrometer obtained estimates with a geometric mean of 0.014 cm/min and ranged from 0.002 cm/min to 0.043 cm/min. The double-ring infiltrometer and Guelph permeameter measure K sat at a physical scale that is large enough to incorporate the large mixture of particle sizes that comprise the till. With a smaller physical measurement scale, the mini disk is predominantly influenced by the fine-grained fraction of the till. Using geometric mean K sat values obtained with the double-ring and mini disk infiltrometers and available snowpack data from the 2005 water year, a physically-based hydrologic and energy-balance model was used to simulate snowpack depletion, soil moisture changes, and groundwater recharge. Simulated sediment moisture changes were used to estimate vertical flow rates toward the water table. Using a higher K sat obtained at a larger physical measurement scale, the calculated flow rate 2 m below the surface is approximately three times that of the low K sat scenarios. Thus, the scale dependency of hydraulic conductivity is important when quantifying groundwater recharge in mountain watersheds.
Open Access
Impacts of wildfires and retardants on surface water quality
(Colorado State University. Libraries, 2016) Morgensen, Brent D., author; Omur-Ozbek, Pinar, advisor; Carlson, Ken, committee member; Stednick, John, committee member
Wildfire retardant is one of the most beneficial tools used to prevent the spread of wildfire, yet its presence has been found to be of big concern when dropped into aquatic habitats. Many retardants are composed mainly of ammonium and phosphates, which can lead to troubles with eutrophication and fish kills at high doses. Iron is often included to help with the identification of retardant drops, but can result in aesthetic issues when gotten into waterways. Despite the risks associated with its use, retardant is still a needed tool to help reduce the spread of wildfire and the effects of wildfire on the increase of organics, nutrients, and metals into waters. This study aims to quantify the effects of wildfire and wildfire retardant on the quality of surface waters. A rainfall simulation was performed on soil plots to observe the influence of wildfire and wildfire retardant on the quality of runoff using Phos-Chek® LC-95A retardant. Soil plots were collected from a tallgrass prairie in Pingree, CO and plots were modified to simulate rainfall over unburned plots without retardant (Uwo), unburned plots with retardant (Uw), burned plots without retardant (Bwo), and burned plots with retardant (Bw). A Norton Ladder Type Rainfall Simulator was used to simulate rainfall over the plots at 165 mm/hr for 15 min and the runoff was collected and analyzed for ammonia, orthophosphate (Pi), Fe, and TOC immediately following the experiment. The experiment was performed on 3 consecutive days and the entire process of the experiment was performed on the same plots 2 months after the first set of runs. Retardant use showed a significant increase in nutrient and iron concentrations for unburned plots, while a significant increase was found for Pi concentrations in burned plots. Burned plots showed a noticeable increase in TOC compared to unburned plots, but retardant showed no influence on either. The second part of this study analyzed the leachate from soils collected from the burn area of the Royal Gorge on 3 separate occasions. Samples were collected from Uwo, Uw, Bwo, and Bw sites, as well as an unburned site with a high application of retardant (UwH). Nutrients and Fe were found to increase noticeably from Uwo to Uw + UwH soil, while ammonia was generally found to be higher in Bw than Bwo. Retardant was found to have no noticeable influence on TP and Fe in the first analysis, but Bw was found to show lesser concentrations than Bwo as the analyses carried on. Concentrations of Mn were generally less in Bw than Bwo for all of the analyses. These results show that concern is warranted when retardant is dropped near waterways.
Open Access
Model for evaluating the effectiveness and life cycle costs of stormwater best management practices
(Colorado State University. Libraries, 2010) Olson, Christopher C., author; Roesner, Larry, advisor; Grigg, P. E., committee member; Stednick, John, committee member
Structural best management practices (BMPs) are devices designed and implemented for the purpose of reducing or eliminating the effects of urbanization on receiving waters. Structural BMPs each have their own unique effectiveness and costs, however BMPs are rarely evaluated or selected for their long-term cost effectiveness because most of the information required to do so is not readily available to the decision maker. The purpose of this model is to integrate the best available information on BMP costs and effectiveness into a tool that decision makers can use when selecting what type of BMP to implement under certain circumstances. A spreadsheet model was developed using relatively few required inputs to describe the watershed and BMPs to be implemented. The model computes the number and size of BMPs required for the watershed, the annual pollutant load reduction and runoff volume reduction expected from implementing the BMPs and the net present value of the life cycle costs of the BMPs. These outputs can be used to determine BMP cost effectiveness, computed as cost per pound of pollutant removed or cost per volume of runoff reduced. The model was applied to two theoretical stormwater management planning scenarios. The first application seeks to determine the unit cost of land at which it is less costly to use underground hydrodynamic separators instead of an extended detention basin in a highly urbanized watershed, assuming that both BMPs meet a minimum water quality requirement. The results show that hydrodynamic separators are less expensive when land costs exceed approximately $1.5 million per acre, however the cost effectiveness ($ per lb of pollutant removed) was not evaluated under this scenario. In the second application four different BMPs were evaluated to determine the most cost effective at removing 60% of the total suspended solids (TSS) generated from a highly developed watershed. The four BMPs evaluated (hydrodynamic separator, porous landscape detention, sand filter vault and inlet inserts) were chosen because they can be retrofitted into an existing development more easily than many other BMPs. Using an iterative procedure, the BMPs were applied to a certain percentage of the watershed until the annual TSS load discharged to the receiving waters was reduced to approximately 60%. The results suggest that porous landscape detention is the most cost effective BMP at approximately $4.20 per lb of TSS removed annually. Inlet inserts were the second most expensive at $6.00 per lb of TSS removed annually, despite having the lowest initial capital costs. The latter result shows the importance of including long-term operations and maintenance costs when selecting BMPs.
Open Access
Motorized winter recreation impacts on snowpack properties
(Colorado State University. Libraries, 2011) Heath, Jared Tucker, author; Fassnacht, Steven, advisor; Elder, Kelly, committee member; Stednick, John, committee member; Wilson, Kenneth, committee member
Winter recreation, consisting of snowshoeing, skiing, snowboarding, and snowmobiling, has been increasing annually in Colorado's forests. This increase in recreational activity creates direct and indirect wildlife interactions. Motorized winter recreation in the backcountry compacts the snow possibly influencing the physical and mechanical properties of the snowpack. Snow depth, density, stratigraphy and grain characteristics control to the insulating properties of the snowpack and create habitat for small non-hibernating mammals. Changes to these physical properties and compaction of the subnivean space may be detrimental to these species. Two hypotheses were formulated: (1) a snowpack compacted by motorized winter recreation will result in changes to physical and mechanical properties of the snowpack; and (2) the amount of motorized winter recreation and the depth of snow when motorized winter recreation begins affects the physical properties of the snowpack. During the 2009-2010 winter season snow compaction plots near Rabbit Ears Pass and Fraser Experimental Forest, Colorado were manipulated with varying use of motorized winter recreation (low, medium and heavy use) beginning on different snow depths, shallow (30 cm) and deep (120 cm). Physical and mechanical properties of the snowpack, including snow density, temperature, snow depth, snow water equivalent, stratigraphy, hardness and ram resistance were measured and used to examine the statistical difference between no use and varying degrees of motorized winter recreation (low, medium and heavy use). The results were used to infer implications on changes to the insulative value of the subnivean space and the potential for movement by subnivean mammals. The largest differences in snowpack properties were associated with motorized winter recreation beginning on a shallow snowpack. Compaction from motorized winter recreation that began on a shallow snowpack increased both mean and subnivean density, hardness, and ram resistance, which resulted in significant differences (p<0.10) between varying use of motorized winter recreation and no use. Snow depth and basal temperatures (ground/snow interface) decreased as a result of motorized winter recreation beginning on a shallow snowpack (p<0.10), while temperature gradients were unaffected throughout the duration of the winter season. Implications to changes in these snowpack properties could decrease the insulative value of the snowpack and make movement by small mammals that utilize the subnivean space more difficult. On the contrary, motorized winter recreation that began on a deep snowpack showed no significant difference suggesting later initiation of use minimizes changes to snowpack properties from compaction.
Open Access
Produced water quality characterization and prediction for Wattenberg field
(Colorado State University. Libraries, 2013) Li, Huishu, author; Carlson, Kenneth H., advisor; Sharvelle, Sybil, committee member; Stednick, John, committee member
Produced water is the major Exploration & Production waste in oil and gas production operations on most onshore and offshore platforms. There are some concerns about the environmental impacts of produced water, because of the potential danger of large volume of water disposal by shale plays. It is a complex mixture of dissolved and particulate inorganic and organic matters ranging from near freshwater quality to concentrated saline brine. The most abundant inorganic chemicals are calcium, magnesium, sodium and chloride. Other inorganic components, such as barium, strontium, boron, sulfate, carbonate and bicarbonate are also present in the produced water but at high concentrations. The dominant organic chemicals in most produced water are soluble low molecular weight organic acids and some aromatic hydrocarbons. Constituents of produced water vary a lot depending on a number of factors, including geographic locations, characteristics of formations (i.e. the depth of formation, porosity and permeability of formation rocks/sands, water content) and injected fracturing fluid. Since water is becoming a big issue in some arid areas and as regulations become more restrictive for disposal and reinjection, produced water reuse/recycle will be a solution to reduce the wastewater production and alleviate environmental effects. The main objective of this study was to statistically evaluate the produced water quality and to provide an assessment on the spatial distribution of specific groundwater quality parameters. Produced water samples were collected at 80 sample points (producing oil and gas wells) from May to August in 2012. pH, conductivity, alkalinity, turbidity, total organic carbon, total nitrogen, and barium were tested at Colorado State University's Environmental Engineering lab; total dissolved solids (TDS), calcium, magnesium, sodium, potassium, strontium, boron, chloride and sulfate were measured in ACZ Laboratories Inc., Colorado. All the produced water samples were acidic with pH ranging from 5.1-6.8. TDS, cations, anions and organic carbons tested in our study varied a lot. Maps showing the spatial distributions of these parameters were made using ArcGIS. Linear correlations between chloride, conductivity/TDS, and cations (log) were shown, which made it possible to estimate unknown parameters. Spatial and temporal trends of pH, TDS and total organics together with inner relationships of ion concentrations could allow us to make predictions of produced water qualities. This project was the first phase of the development of a GIS application that will provide a tool that can benefit industry when making decisions regarding produced water recycling.
Open Access
Restoration of a small, shallow, eutrophic lake by submerged aeration and comparison with a similar lake
(Colorado State University. Libraries, 2013) Zhang, Xiaoju, author; Roesner, Larry, advisor; Sharvelle, Sybil, committee member; Carlson, Kenneth, committee member; Catton, Kimberly, committee member; Stednick, John, committee member
A submerged aeration system was introduced to Fossil Creek Lake, a small scale, shallow, eutrophic, very hard water lake, to increase hypolimnetic dissolved oxygen levels, prevent thermal stratification and improve water quality. There has been a long-standing concentration of research effort on aeration systems in deep water lakes, but very little attention has been paid to urban shallow lakes. This research describes the investigation of physical, chemical and biological parameters of the lake before and after aeration. The aeration system gradually and permanently improved the water quality of the entire lake and eliminated many undesirable lake conditions. With the destratification caused by the aeration system, the bottom water dissolved oxygen concentrations increased significantly (p<0.05) from less than 1 mg L-1 to above 4 mg L-1. Furthermore, the vertical variations of many water quality parameters have been significantly reduced with the complete mixing of the entire lake, which are: pH, specific conductance, nutrients, chlorophyll a, alkalinity, total suspended solids, sulfate, and hardness. However, limiting nutrient, trophic status and water clarity of the lake were barely affected by the aeration system. Multiple years of continuous aeration on this lake may be necessary to achieve a lower trophic condition. In addition, this research also discusses sources of extremely high sulfate and sulfide levels of Fossil Creek Lake and provides aeration startup recommendations for lakes with high sulfide concentrations. In this study, the water quality parameters, trophic status and nutrient mass balance of Fossil Creek Lake were compared with Sheldon Lake from April to December in 2010 and 2011, a turbid, phytoplankton-dominated lake, which is restored by submerged aeration after bottom sediment removal. Monthly mean values of temperature and dissolved oxygen, as well as monthly mean total alkalinity, total inorganic carbon, total organic carbon, orthophosphate and total nitrogen concentrations showed similar distributions in the two lakes. However, the total suspended solids and chlorophyll a concentrations were significantly (p<0.05) higher in Sheldon Lake than those in Fossil Creek Lake. In addition, the Secchi disk transparency of Sheldon Lake rarely exceeded 0.5 m, which was lower than Fossil Creek Lake (>1m). Models relating water clarity to monitored water quality parameters over a period of 2 years are developed in both lakes. In Fossil Creek Lake, the water clarity is not only significantly related with inorganic carbon, nitrogen and orthophosphate, but also hardness, alkalinity, total suspended solids and chlorophyll a concentrations. But in Sheldon Lake, the lake clarity is only significantly related to two parameters, which are total suspended solids and chlorophyll a concentrations.
Open Access
Soil weathering under mountain pine beetle killed trees, Grand County, Colorado
(Colorado State University. Libraries, 2013) Denison, Christopher W., author; Sutton, Sally, advisor; Ridley, John, committee member; Stednick, John, committee member
The objective of this study is to assess differences in soil weathering processes under mountain pine beetle killed trees, as compared to soil weathering under living trees. As pine beetle (Dendroctonus pondersoae) infected trees die, pine needles are shed and accumulate on the forest floor, which may lead to changes in soil pH and soil temperature as the organic horizon thickens and insulates the soils below. Additionally, decomposition of the dropped needles may cause chemical changes in the substrate. These changes in soil pH, temperature, and chemistry are likely to affect weathering of soil minerals. Two hypotheses related to soil weathering processes under beetle infected trees are evaluated: (1) the death of pine trees and accompanying increased pine needle decomposition has increased chemical weathering of the substrate, and (2) an increase in soil weathering under dead pine stands has increased downslope physical migration of weathered material. This study was conducted in the Kauffman Creek watershed in the mountain pine beetle infected Arapahoe National Forest of Grand County, Colorado. Soil samples were collected from a south facing hillslope and from elevations of approximately 9100 to 9400 feet, thus minimizing differences in weathering processes related to hillslope aspect or elevation. Kauffman Creek incises mountainous terrain and the study area is hosted by Paleocene - Eocene sedimentary rocks of the Coalmont Formation. Soils of Kauffman Creek are predominately inceptisols and entisols. The field site was chosen to show a range in pine beetle infestation and health conditions of pine trees on the hillside. On the hillslope there are stands of healthy (green) or recently attacked (brown) pine trees and there are other areas where the pines are in the final stages (gray) of beetle infestation (4+ years post attack) and have dropped most of their needles. A study of soil characteristics (i.e. grain size, inorganic geochemistry, mineralogy, pH, and saturated paste electric conductivity) was conducted to evaluate soil weathering processes. Analytical results indicate that the mean grain size is approximately 1.3 times coarser beneath the gray stands than beneath the healthy-appearing, green pine stands. Major element geochemistry shows average concentrations of Na and K are greater, and average concentrations of Mn and Mg are smaller, in soils beneath the gray pine stands than from those under green stands. The differences in soil chemistry within the soils beneath the gray stands, compared to the soils beneath the green pine stands, suggest increased chemical weathering of soil under the gray stands. Chemical results for soils under the brown stands suggest they also have experienced increased weathering, compared to the green stands. Petrographic results show that the modal percentage of quartz is approximately 1.2 to 1.4 times greater in the soils beneath the gray stands than in the soils under the green stands, while the modal percentages of soil aggregates and micas decrease from the soils under the green stands to the soils under gray trees. The average topsoil pH is lower in the soils beneath the brown and gray trees than in the soils beneath the healthy pines. Soil conductivity data suggests an increase in soil moisture under the brown and gray pine stands. Overall, increased pine needle litter and its decomposition appear to have increased soil weathering. Downslope migration of weathered material was not evident in the results of this study.