Northeastern Section - 42nd Annual Meeting (12–14 March 2007)

Paper No. 4
Presentation Time: 9:20 AM


MABEE, Stephen B. and NATHAN, Stephen A., Office of the Massachusetts State Geologist, Geosciences Department, University of Massachusetts, 611 North Pleasant Street, Amherst, MA 01003,

In response to the growing concerns over the availability of groundwater resources statewide, the Office of the Massachusetts State Geologist has implemented a wide range of initiatives specifically targeted for groundwater issues. Here we present two examples of activities that help address these concerns. In the first example, the Office, in collaboration with MassGIS and the Massachusetts Department of Conservation and Recreation, initiated a program to improve the quality and consistency of subsurface data reported by well drillers on state-mandated well completion reports. We developed a standardized coding system for soil and rock descriptions for Massachusetts and now require GPS locations for all new wells. We trained over 340 well drillers to use the new standardized coding system and GPS technology in a series of 7 workshops held across the state. In addition, paper well log submissions have been eliminated; all well log information is now submitted electronically over the Internet so that the data are readily accessible to all for use in the evaluation of water assets and contamination problems.

In a second example, borehole data was integrated with surficial mapping to produce a true 3-D model of the geology within the Marlborough quadrangle, Massachusetts. Layers representing each of six major stratigraphic units were isolated in Adobe Illustrator and converted to six grid files in RockWorks2004. Nodes within each grid file were assigned thicknesses using 190 borehole logs as a guide, effectively creating an isopach for each unit. Subtracting the uppermost isopach from a 25-meter DEM created a base grid for that unit. Repeatedly subtracting each isopach from the overlying grid produced a series of base grids that RockWorks2004 could model as a block diagram with the area and volume of each unit. This effort provided three benefits: 1) a more realistic estimate of the volume of sand and gravel; 2) an estimate of the volume of water stored in the permeable units; and 3) the grids were successfully imported into MODFLOW-2000 to model steady-state groundwater flow within a sub-region of the quadrangle. The first-order agreement between measured and observed hydraulic heads suggests that the 3-D geologic model is a useful tool for groundwater modelers looking to expedite the modeling and calibration process.