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P.P. Leahy

Publications and source records attributed to P.P. Leahy.

9 recordsLinked to original sources
USGS2008

Landslide hazard mitigation in North America

Active landslides throughout the states and territories of the United States result in extensive property loss and 25-50 deaths per year. The U.S. Geological Survey (USGS) has a long history of detailed examination of landslides since the work of Howe (1909) in the San Juan Mountains of Colorado. In the last four decades, landslide inventory maps and landslide hazard maps have depicted landslides of different ages, identified fresh landslide scarps, and indicated the direction of landslide movement for different regions of the states of Colorado, California, and Pennsylvania. Probability-based methods improve landslide hazards assessments. Rainstorms, earthquakes, wildfires, and volcanic eruptions can trigger landslides. Improvements in remote sensing of rainfall make it possible to issue landslide advisories and warnings for vulnerable areas. From 1986 to 1995, the USGS issued hazard warnings based on rainfall in the San Francisco Bay area. USGS workers also identified rainfall thresholds triggering landslides in Puerto Rico, Hawaii, Washington, and the Blue Ridge Mountains of central Virginia. Detailed onsite monitoring of landslides near highways in California and Colorado aided transportation officials. The USGS developed a comprehensive, multi-sector, and multi-agency strategy to mitigate landslide hazards nationwide. This study formed the foundation of the National Landslide Hazards Mitigation Strategy. The USGS, in partnership with the U.S. National Weather Service and the State of California, began to develop a real-time warning system for landslides from wildfires in Southern California as a pilot study in 2005.

Environmental & Engineering Geoscience↗
USGS1994

Overview of the National Water-Quality Assessment Program

The Nation's water resources are the basis for life and our economic vitality. These resources support a complex web of human activities and fishery and wildlife needs that depend upon clean water. Demands for good-quality water for drinking, recreation, farming, and industry are rising, and as a result, the American public is concerned about the condition and sustainability of our water resources. The American public is asking: Is it safe to swim in and drink water from our rivers or lakes? Can we eat the fish that come from them? Is our ground water polluted? Is water quality degrading with time, and if so, why? Has all the money we've spent to clean up our waters, done any good? The U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program was designed to provide information that will help answer these questions. NAWQA is designed to assess historical, current, and future water-quality conditions in representative river basins and aquifers nationwide. One of the primary objectives of the program is to describe relations between natural factors, human activities, and water-quality conditions and to define those factors that most affect water quality in different parts of the Nation. The linkage of water quality to environmental processes is of fundamental importance to water-resource managers, planners, and policy makers. It provides a strong and unbiased basis for better decisionmaking by those responsible for making decisions that affect our water resources, including the United States Congress, Federal, State, and local agencies, environmental groups, and industry. Information from the NAWQA Program also will be useful for guiding research, monitoring, and regulatory activities in cost effective ways.

Open-File Report↗
USGS1989

Well installation and documentation, and ground-water sampling protocols for the pilot National Water-Quality Assessment Program

Several pilot projects are being conducted as part of the National Water Quality Assessment (NAWQA) Program. The purpose of the pilot program is to test and refine concepts for a proposed full-scale program. Three of the pilot projects are specifically designed to assess groundwater. The purpose of this report is to describe the criteria that are being used in the NAWQA pilot projects for selecting and documenting wells, installing new wells, and sampling wells for different water quality constituents. Guidelines are presented for the selection of wells for sampling. Information needed to accurately document each well includes site characteristics related to the location of the well, land use near the well, and important well construction features. These guidelines ensure the consistency of the information collected and will provide comparable data for interpretive purposes. Guidelines for the installation of wells are presented and include procedures that need to be followed for preparations prior to drilling, the selection of the drilling technique and casing type, the grouting procedure, and the well-development technique. A major component of the protocols is related to water quality sampling. Tasks are identified that need to be completed prior to visiting the site for sampling. Guidelines are presented for purging the well prior t sampling, both in terms of the volume of water pumped and the chemical stability of field parameters. Guidelines are presented concerning sampler selection as related to both inorganic and organic constituents. Documentation needed to describe the measurements and observations related to sampling each well and treating and preserving the samples are also presented. Procedures are presented for the storage and shipping of water samples, equipment cleaning, and quality assurance. Quality assurance guidelines include the description of the general distribution of the various quality assurance samples (blanks, spikes, duplicates, and reference samples) that will be used in the pilot program. (Lantz-PTT)

Open-File Report↗
USGS1982

Test well DO-CE 88 at Cambridge, Dorchester County, Maryland

Test well DO-CE 88 at Cambridge, Maryland, penetrated 3,299 feet of unconsolidated Quaternary, Tertiary and Cretaceous sediments and bottomed in quartz-monzonite gneiss. The well was drilled to provide data for a study of the aquifer system of the northern Atlantic Coastal Plain. Twenty-one core samples were collected. Six sand zones were tested for aquifer properties and sampled for ground-water chemistry. Point-water heads were measured at seven depths. Environmental heads (which ranged from -18.33 to +44.16 feet relative to sea level) indicate an upward component of flow. A temperature log showed a maximum temperature of 41.9 degrees Celsius and a mean temperature gradient of 0.00838 degrees Celsius per foot. The water analyses delineated the freshwater-saltwater transition zone between 2,650 and 3,100 feet. The ground water changes progressively downward from a sodium bicarbonate to a sodium chloride character. Clays in the analyzed core samples belong to the montmorillonite and kaolinite groups, and mean cation exchange capacity ranged from 8.3 to 38.9 milliequivalents per 100 grams. Vertical and horizontal hydraulic conductivities measured in cores ranged from 1.5 x 10-s to 1.3 feet per day and from 7.3 x 10-6 to 1.3 feet per day, respectively, but the most permeable sands were not cored. Porosity was 1.5 percent in the quartz monzonite bedrock and ranged from 22.4 to 41 percent in the overlying sediments. Transmissivities from aquifer tests ranged from 25 to 850 feet squared per day, horizontal hydraulic conductivities ranged from 2.5 to 85 feet squared per day, and intrinsic permeabilities ranged from 0.8 to 23 micrometers squared. Fossils identified in core samples include palynomorphs, dinoflagellates, and foraminifers.

Maryland↗
USGS1982

A three-dimensional ground-water-flow model modified to reduce computer-memory requirements and better simulate confining-bed and aquifer pinchouts

The Trescott computer program for modeling groundwater flow in three dimensions has been modified to (1) treat aquifer and confining bed pinchouts more realistically and (2) reduce the computer memory requirements needed for the input data. Using the original program, simulation of aquifer systems with nonrectangular external boundaries may result in a large number of nodes that are not involved in the numerical solution of the problem, but require computer storage. (USGS)

Water-Resources Investigations Report↗