Introduction: Wells developed in local valley floor aquifers in southern Madison and northern Chenango County generally have relatively high sustainable yields in the 100’s of gallons per minute range. Wells developed in thick glacial outwash and ice contact drift may yield rather hard water (>150 mg/l CaCO₃) although the levels of iron and sulfur are low (Fe<0.05 mg/l; SO₄<20 mg/l). Wells developed in upland shallow till and bedrock commonly have much lower yields and may have deleterious levels of iron and sulfate.

In this lab we will examine the hydrogeology of a site near Sherburne, New York that was proposed as the location of an 80-megawatt wood-fired electric generation station in the mid-1990’s. A key issue for the plant is the availability of a sufficient supply of cooling water for the condensing cycle. The operators propose using groundwater in a single-cycle cooling system, and this method requires 860 gallons per minute for a plant of this sort. In addition, the water should be of relatively good quality, although the quality requirements were not established. Surface water from the nearby streams (e.g. Pleasant Brook and Handsome Brook) cannot be used because these streams are protected as brook trout habitat by the NYSDEC.

To become familiar with the site, open ArcView and examine the coverages that include:

Sherburne 7.5 minute quad (.tif)

Sherburne NW Tile0 (Mr. Sid image)

Plant (shapefile illustrating plant location)

Colinewells (shapefile showing nearby wells and proposed wellsite)

Bdrkexp (shapefile showing occurrence of surface bedrock exposures)

Note that the shapefiles for the wells, plant and bedrock exposure are referenced to the Sherburne NW Tile0 base, and that there is not exact correspondence between the orthophoto and the 7.5 minute quad .tif file. If you want to use the 7.5 minute quad as a basemap for your final presentation, you will need to re-register the image using the align tool with corresponding points selected from the orthophoto. Also note that the lab folder includes the bedrock and surficial geology coverages for the area (these are the Hudson Valley region coverage). We will briefly review the dominant bedrock and surficial units in the area in lab.

Well Data: The Excel Spreadsheet file Cowells contains hydrologic information regarding yield, aquifer thickness, and chemical composition. Please open this file and examine the data. You may wish to make appropriate files to join to the colinewlls.shp file in ArcView. Additional information regarding well yields and water quality in the area immediately to the south of the site is found in Reynolds and Brown (1984) Hydrogeologic Appraisal of a Stratified-Drift Aquifer Near Smyrna, Chenango County, New York; USGS Water Resources Investigation Report 84-4029. Copies of this document will be available in 305 Lathrop.

Other Hydrogeologic Information: During the investigation of the hydrogeology of the Countyline site, a number of slug tests were performed on wells in the area. The aquifer transmissivity at the tested wells is noted in the Excel Spreadsheet. Remember that transmissivity (T) is equal to Kb. Discharge (Q), transmissivity (T) and drawdown (s) are related as follow:

______ T___________ x s

Q = 264 log ____t______ - 65.5

(2693 r_w²S)

where Q = discharge in gallons per minute

s = drawdown

T = transmissivity in gallons per day per foot

S = storage coefficient

r_w = nominal radius of the well in feet

t = time after pumping started in minutes

The Problem: Your analysis of the site and surrounding area should address:

1. What is the predicted drawdown of the potential surface aquifer that will result from a sustained pumping rate of 860 gallons per minute? Is this drawdown acceptable? What consequences might be expected on nearby wells and surface water bodies?

2. What water quality problems may be anticipated based on the chemical characteristics of nearby groundwater? How could these qualitative factors be addressed? What ancillary impacts of the extraction of groundwater could be expected?

3. Prepare a map that illustrates the groundwater quantity and quality factors that are important to the use of this site. This map should clearly demonstrate those factors that determine the suitability (or unsuitability) of this site for the planned wood-fired plant.

4. An assessment of the overall suitability of the site.