Lake Manassas is a 706-acre public water supply reservoir for the City of Manassas, formed by the impoundment of Broad Run. It is located in western Prince William County at the periphery of the metropolitan Washington, D. c. area. Its watershed drains approximately 46,500 acres of rural land that is expected to undergo rapid development in the next 25 years. The objective of this study was to provide a comprehensive report of the quality of water in Lake Manassas and its tributary streams, analyzing data that had been collected from October, 1984 through April, 1986, as part of a monitoring program funded by the City of Manassas. The capacity of Lake Manassas at full pool was determined to be 4.2 billion gallons (15.8 million cubic meters) and its mean depth 25 feet (7.7 meters). The calculated volume was considerably less than had been previously thought. Trophic state indices indicated that Lake Manassas is eutrophic, and water column chemistry suggested phosphorus to be the limiting nutrient. The Vollenweider model was applied to illucidate the relative impacts of South Run and Broad Run on the lake. While Broad Run contributed the vast majority of flow to the reservoir, higher concentrations of algal nutrients, nitrogen and phosphorus, were transported to the lake by South Run, which receives effluent from the treatment plant at Vint Hill Station, a U.S. Army reservation. Phosphorus loadings from South Run were higher than from Broad Run under baseflow conditions. On an annual basis, stormflow runoff contributed as much as twelve times the tributary baseflow loading of phosphorus. / M.S.

The Manassas oil field was discovered in 1986 in Lincoln County, Colorado (Township 14S, Range 56W) by Petro Lewis Corporation and it completed production from the Pennsylvanian Atoka Sandstone within 24 years. It is located on the theoretical NW extension of the Haswell-Salt Lake Morrow sandstone producing trend and Morrow sandstones have found in some of the available wells in the area. The productive Morrow sandstones are fluvial channel deposits that are encased by marine shales. The distribution of the Morrow channel system is difficult to define from either data obtained from sparsely located wells alone, or directly from seismic data due to low acoustic contrast between fluvial sandstones and marine shale. Therefore, this study has used a correlation of well log data to understand regional stratigraphy of the selected study area and seismic attributes were used to develop a workflow to define the Morrow sandstone channel system in the Manassas prospect. Well logs from forty wells were used to define the early Pennsylvanian strata (Marmaton, Cherokee, upper and lower Atoka, upper and lower Morrow) and underlying Mississippian unit (St. Louis). The formation data were used to visualize the regional stratigraphy using isopach maps and stratigraphic cross sections. The acoustic and density logs from the Lockwood 27-22 well located in the Manassas field, were used to generate the synthetic seismogram for the purpose of seismic horizons interpretation. The upper Morrow isochron thick was defined using upper and lower Morrow time structure maps. The channel infill system was first detected using the Chaos attribute that identifies reflectors associated with channel infills that are normally chaotic signals with low consistency. The observation was confirmed using, Variance attribute that analyzes signal coherency, and estimates trace to trace variance. The amplitude attributes (RMS Amplitude – iterative attribute, and Envelope) highlight both channel infills and bright spots. The Genetic Inversion identifies relative variations of rock properties. The Generalized Spectral Decomposition attribute was used to visualize the detailed channel morphology through generating a RGB blending model as the final step. This study shows that the Morrow channel sandstones are present across the Manassas prospect and are interpreted as a composite meandered and anastomosed channel system. The observed high amplitude variations are interpreted as tuning effects of thin beds and relative lithological changes caused by variations of rock properties such as density and porosity.

Lake Manassas is a man-made impoundment in the Northern Virginia suburbs of Washington, D.C. The lake currently supplies drinking water at a rate of 6.7 million gallons per day to the City of Manassas, Virginia. The lake discharges, via the stream Broad Run, to the Occoquan Reservoir. The Occoquan Reservoir supplies potable water to over 750,000 people in the Northern Virginia area. As the population of Washington, D.C., continues to increase, the development of the surrounding suburbs changes the quality of surface runoff water into existing reservoirs. These reservoirs can become enriched with both toxic and biomass inducing nutrient pollutants. The result can be less desirable and less dependable supplies of drinking water. A State of Virginia mandated Environmental Monitoring Program is in force in this area to ensure the Occoquan Watershed remains a dependable supply of potable water. A computerized database, containing the results of the environmental monitoring program, allows for a quantitative estimate of the overall water quality of the reservoirs to be made. This thesis presents the results of a limnological analysis of Lake Manassas. The analysis techniques used are established limnological techniques to arrive at a profile which can be compared to accepted scales of ranking. One conclusion from the analysis is that Lake Manassas is eutrophic, which means that the production of biomass in the lake is at a higher than desired rate. The result of this eutrophic condition is that the water quality of the lake will decline rather rapidly. Another conclusion is that Broad Run is the major supplier of nutrients into Lake Manassas, but that conditions are also affected by a point source discharge from a sewage treatment plant. These conclusions are consistent with previous studies done on Lake Manassas. In summary, Lake Manassas is an important water resource in the Northern Virginia area, and it is important to continue to closely monitor and manage runoff practices in the watershed to ensure the lake does not degrade to unacceptable conditions. / Master of Science

Three rain events were sampled from a storm drain at Manassas Mall in Manassas, Virginia. The urban runoff samples obtained were placed into lab-scale Plexiglas~ settling columns to monitor removal of total hydrocarbons (THC) by extended quiescent settling. Samples were collected from the columns at specific depths and times over the 48-hour settling period. The samples were analyzed for total hydrocarbon content on a Horiba oil content analyzer. Hydrocarbon values were averaged at each column depth in order to construct average THC concentration and average THC percent removal profiles over settling time. Maximum average THC removals were 77.8%,32.5%, and 73.6%, respectively, for Storms #1, 2, and 3 after 48 hours of quiescent settling. These average removals corresponded to depths of -2 feet, -1 foot, and -3 feet in the 5-foot tall columns. According to traditional sedimentation theory, pollutants settle out of water to the bottom of the container of interest. This did not appear to be solely the case in this hydrocarbon sedimentation study. It appeared that sedimentation was not the sole removal mechanism at work. Some fractions of oil and grease seemed to reorganize into low-density sub-groups and float to upper regions of the column. Also, the majority of THe removal occurred within the first 18 hours of settling for two of the three storms sampled. / Master of Science

The examination of size distribution, composition and elemental concentration of the aerosol species in the Shenandoah National Park and Manassas, Virginia regions was investigated during a three month summertime period. The relationships between the above mentioned parameters along with prevalent meteorological patterns, emission sources and associated topography were used to determine the geographical origin, aerosol age, and numerous other chemical and physical characteristics of the ambient aerosol. Data for the study were obtained by ground based sampling of particulates and from in situ sampling from an airborne sampling platform. The need for continued surveillance along with improved methods of characterization of the ambient aerosol species is discussed. / Master of Science