Geological Research at the IGS

Field evaluation of on-site sewage disposal systems (OSDS) and broad-scale mapping of suitable and unsuitable areas for OSDS, Morgan County, Indiana

Status Start Date End Date Locations
completed Oct 1, 2003 Sep 30, 2005 Morgan
Director: Sally Letsinger
Other Researchers: Jack Haddan, Greg Olyphant,
Funding: Indiana State Department of Health (ISDH)
Issue: More than 800,000 on-site sewage disposal systems exist in Indiana; evaulating nitrogen loading of aquifers is important so the state can make informed management decisions concerning the suitability of on-site sewage disposal systems in different landform and soil settings. Many citizens of Morgan County use on-site sewage disposal systems (OSDS) as their primary method of wastewater treatment. These systems can be cost-effective and efficient methods of treating wastewater if they are properly designed and installed. However, some areas of Morgan County may not be suitable for these systems. Potential water-quality degradation is a public health concern because of the increased possibility for transmission of waterborne diseases in contaminated drinking water.
Objective: The objective of this project was to collect data concerning the subsurface groundwater characteristics that exist in and adjacent to on-site sewage disposal systems throughout the entire year.
Approach: As a pilot effort in addressing this issue, Morgan County, Indiana, with its wide range of soils and topographic settings, was selected for intensive site-specific investigations and geographic information system (GIS) analysis. We monitored in and beneath septic distribution fields at each of four field sites. The sites selected were different from one another in setting and soil texture, and were representative of a broad range of soil types within Morgan County. Each site was monitored for 10 months.
Products: The results of the monitoring were used to calculate rates at which nitrogen was recharging into groundwater. These loading rates and their relationship to topographic and geologic factors were subsequently used to guide a GIS analysis of Morgan County and to derive a preliminary map showing various degrees of OSDS suitability.
Benefits: Research-based recommendations were provided to the Indiana State Department of Health regarding the suitability of on-site sewage disposal systems in Morgan County. The methodology developed for assessing the suitability of OSDS can be applied to other areas of the state.

Field Evaluation of On-Site Sewage Disposal Systems and Broad-Scale Suitability Mapping, Morgan County, Indiana
Olyphant, G.A., and Letsinger, S.L., 2010, Field Evaluation of On-Site Sewage Disposal Systems and Broad-Scale Suitability Mapping, Morgan County, Indiana: Indiana Geological Survey Open File Study 09-04, 21 p.

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