Other Sponsored Research: NOAA

GWUDI Study

WERI is currently engaged in an ongoing collaborative study with representatives from the United States Environmental Protection Agency (USEPA), Guam Environmental Protection Agency, (GEPA), Guam Waterworks Authority (GWA), the military and the private sector; to determine whether Guam’s aquifer should be designated as groundwater under the direct influence (GWUDI) of surface water and, as such, fall under the USEPA Surface Water Treatment Rule (SWTR) of 1989 and subsequent amendments.

Background

The SWTR requires all raw water sources be evaluated to determine if they are surface water or groundwater. The definition of surface water includes groundwater under the direct influence (GWUDI) of surface water (i.e., groundwater in aquifers that rapidly recharge). The purpose of the rule is to remove waterborne, disease-causing microbes from drinking water, specifically the viruses, Legionella (a bacterium), Giardia and Cryptosporidium (microscopic parasites). These organisms, while not normally found in groundwater, may occur under GWUDI conditions.

The aquifer encompassing the northern half of Guam consists primarily of uplifted fractured limestone. Such aquifers are highly porous and recharge rapidly during storm events. They are also generally regarded as sensitive to surface water contamination and there are many sources of such contamination in northern Guam. Raw sewage overflows from inadequate wastewater facilities, particularly during wet weather conditions, can run directly into recharge basins, as can urban runoff and animal wastes from the many small-scale animal husbandry operations that currently exist. In fact, there is a long history of microbial contamination in Guam’s groundwater. As a result, mandatory chlorination is currently required for all the islands drinking water production wells.

It has been suggested that the entire aquifer be designated as groundwater under the direct influence of surface water (GWUDI), because of this contamination, and because groundwater contamination can rapidly follow major rain events. However, current USEPA guidance for the determination of GWUDI does not adequately address this hydrogeological setting. This guidance was developed primarily for aquifers in unconsolidated soils and for water flowing from surface water bodies such as lakes and rivers. The purpose was to identify situations where inadequate barriers, natural filtration, or time for pathogen inactivation existed between these surface waters and the groundwater reaching a well. In these cases, additional treatment in the form of filtration and enhanced disinfection might be required. The guidance was not designed for rainfall-induced transport of contaminants, nor for deep aquifers.

In addition, specific data normally used for this determination are limited or lacking. These include water quality information to quantitatively demonstrate relatedness, and microscopic particulate analysis results that can indicate the presence of materials not normally associated with true groundwater. Additionally, while some wells show frequent and/or persistent contamination, many have no history of contamination. The depth to groundwater is generally large (300′ is common), allowing for some physical and temporal barriers in some cases. This means that, while concern for direct influence is warranted, whether all or the majority of the ~150 public water supply wells should be so designated is unclear. Because of these reasons, classification of the wells and/or aquifer remains controversial.

The ongoing study was designed to provide the necessary information to make the GWUDI determination and to help select appropriate water treatment. It essentially involves correlating measurable changes in aquifer turbidity, temperature, conductivity, hardness, microscopic particle characteristics, and coliform bacteria detections with significant storm events. To this end, automated water quality monitoring devices and data loggers have been fitted to 25 drinking water production wells selected in high and low-risk areas. Rainfall data is also being recorded from a network of rain gauges set up across the northern half of the island. WERI’s primary roles in the study are to gather the precipitation data, coordinate the sampling activities of all other collaborative entities, and evaluate and statistically examine the overall data. Further details are available from WERI Meteorologist, Dr. Mark Lander, at mlander@uguam.uog.edu.

Guam Septic Tank Survey

The Guam Septic Tank Survey project was assigned to WERI under the USEPA Revolving Fund in 2001. Guam law requires that unconnected buildings within 200 feet of existing sewer mains, or sewered buildings, be connected to the sewer system. The objective of this project was to identify buildings that were not connected to the existing sewer mains in order to implement the law. Over 13,000 buildings were manually surveyed over the entire island.

Background

The Northern Guam Lens Aquifer (NGLA) supplies about 80% of Guam’s population with potable water. Protecting this vital resource from contaminants associated with domestic wastewater (e.g., nitrates and fecal coliform) is crucially important both from a public health and sustainable development perspective. Septic tanks and pit toilets are major sources of these contaminants, and several thousands of these are located right above the NGLA. It is estimated that septic tanks alone discharge around 5 million gallons of wastewater into the Guam environment each day. To what extent these facilities have impacted the chemical and biological integrity of the NGLA is currently unknown.

In completing this work, we gratefully acknowledge access to the Bureau of Statistics and Plans GIS data of Guam buildings with house tags, and GWA’s customer database. We are also indebted to GWA’s field personnel for technical assistance during the gathering of crucial GPS data that allowed us to join the data-bases.

Natural Resources of Southern Guam

A common problem in Guam, as well as every other place in the Western Pacific is the lack of accessibility to local natural resources data. This includes vegetation, soil types, river miles, badlands, roads, location of stream gage, and maps. In Guam, this information is scattered among government agencies.

In 2005, WERI researchers, Drs. Shahram Khosrowpanah and Yuming Wen, and their collaborator, Dr. Danko Taborosi of Island Research & Education Initiative, Pohnpei, began constructing a digital atlas of the natural resources of southern Guam’s watersheds using GIS technology to centralize these scattered data sets. The project was partially funded by the National Oceanic and Atmospheric Administration (NOAA) through the Guam Bureau of Statistics and Plans Office.

The finished product, aptly named the ‘Natural Resources Atlas of Southern Guam’ was designed as a reference and educational tool that provides a comprehensive picture of the natural resources found within the fourteen watersheds of southern Guam. It was designed as a comprehensive and user-friendly web-based information server and is freely accessible on the Internet at http://www.hydroguam.net.

The website offers a wide range of textual, graphical, statistical, and geographic information to any interested user, and allows advanced operations, such as viewing and manipulation of GIS data using standard web browsing software. It is the foundation of a planned series of products dedicated to disseminating information and raising public awareness of the diversity, current state, sustainable use, and critical threats to natural features of southern Guam, and is being widely used by Guam’s agencies, researchers, developers, students, and the community at large. For further information about the website or the natural resources of southern Guam watersheds, contact D. Shahram Khosrowpanah at khosrow@uguam.uog.edu

Constitutive Modeling of Glacial Till

Interdisciplinary study of the potential role of subglacial sediment in ice sheet movement.

• J.W. Jenson
  Water & Environmental Research Institute of the Western Pacific, University of Guam
• C.S. Desai
  Department of Civil Engineering & Engineering & Engineering Mechanics, University of Arizona
• A.E. Carlson
  Department of Geosciences, University of Wisconsin-Madison
• P.U. Clark
  Department of Geosciences, Oregon State University

Background

Exposure of glacial till layers in bluffs above the Nelson River, northern Manitoba, from which specimens of the Sky Pilot Till, deposited by the Laurentide Ice Sheet, were obtained.

We have recently completed a set of geotechnical experiments (Sane et al., 2008) using the Disturbed State Concept (DSC) model (Desai, 2001) to evaluate the rheology of two regionally significant North American Pleistocene tills (Carlson et al., 2004). The results suggest that soft beds could, at certain stages of deformation–assuming sufficiently strong coupling at the ice-till interface–support shear stresses of about 20 kPa, substantially greater than the residual strengths measured in other tills by Kamb (1991) and Iverson et al (1997; Iverson et al., 1998) (<3 kPa). Having thus developed the DSC model for the fully-coupled case (in which there is assumed to be no “sliding” or “slippage” between the basal ice and the underlying bed of “soft” (i.e., water-saturated) till, the research team proposes now to extend the application of the DSC model to the mechanics of relative motion at the interface between the basal ice and underlying till. The proposed work will utilize the specialized Cyclic Multi-Degree-of-Freedom (CYMDOF) shear device at the University of Arizona´s Constitutive Modeling Laboratory, which has been developed and proven in previous advanced geotechnical research applications. The CYMDOF test box will be modified to accommodate ice-till interface specimens with controlled configurations guided by insights gained from continued field study by the research team and from previous observations published by others. The model will be validated by independent tests and then implemented in numerical simulations to predict the motion resulting from the combined effects of interface motion and deformation in the till and ice. The proposed work will take advantage of previously proven methodology and the mathematical and numerical models developed and tested in the previous project.

Applications of the research

Ice sheet modelers have long sought a reliable model for soft-bedded ice sheet movement. Despite the important role of slip in ice movement,however, no truly predictive models have yet been developed for slip of ice over a till surface. The results of this project will be an important contribution toward the ultimate development of sophisticated ice sheet models that could provide reliable predictions of growth, decay, and stability of glaciers and ice sheets–both Pleistocene and modern–and their interaction with climate. Such models may also yield new insights into landscape evolution in glacial terrains, such as whether soft-bed deformation could have mobilized sufficient sediment flux to account for the large volumes of till in the Midwestern United States or the large deposits of glacigenic material in the Barents Sea. Answers to such questions have applications to important economic activities in glaciated regions, including water resource management and mineral prospecting and mining.

References

• Carlson, A. E., J. W. Jenson, and P. U. Clark, 2004, Field observations from the Tiskilwa Till, IL, and Sky Pilot Till, MB of the Laurentide Ice Sheet: Geographie Physique et Quaternaire, v. 58, p. 229-239.
• Desai, C. S., 2001, Mechanics of Materials and Interfaces: The Disturbed State Concept: Boca Raton, Florida, CRC Press.
• Iverson, N. R., R. W. Baker, and T.S. Hooyer, 1997, A ring shear device for the study of till deformation: Tests on tills with contrasting clay contents: Quaternary Science Reviews, v. 16, p. 1057-1066.
• Iverson, N. R., T. S. Hooyer, and R. W. Baker, 1998, Ring-shear studies of till deformation: Coulomb-plastic behavior and distributed strain in glacier beds: Journal of Glaciology, v. 44, p. 634-642.
• Kamb, B., 1991, Rheological nonlinearity and flow instability in the deforming bed mechanism of ice stream motion: Journal of Geophysical Research, v. 96, p. 585-16,595.
• Sane, S. M., C. S. Desai, J. W. Jenson, D. S. Contractor, A. E. Carlson, and P. U. Clark, 2008, Disturbed state constitutive modeling of two Pleistocene tills: Quaternary Science Reviews, v. 27, p. 267-283

Climate History of Guam Study

A stalagmite collected by WERI researcher, Dr. Jenson and his students, in April 2005 from a cave on northern Guam is providing clues as to how the climate of Guam and the surrounding region evolved over the past 28,000 years. Stable isotope (18O and 13C) and trace element (Mg/Ca and Sr/Ca) analysis on the stalagmite layers are being conducted by collaborators at the University of Texas-Austin School of Geosciences and provide chemical clues about climate history. The initial results from the stalagmite are consistent with results from other islands in the Pacific and suggest, among other things, that the regional climate was much drier some 5000-6000 years ago. The western Pacific Ocean plays an important, but still poorly understood, role in global climate.