Semester

Fall

Date of Graduation

2010

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Horticulture

Committee Chair

Eugenia Pena-Yewtukhiw.

Abstract

The hydrologic soil group refers to the infiltration potential of the soil after prolonged wetting. This classification system separates soils into four hydrologic groups (A, B, C, and D), based upon the intake and transmission of water under conditions of maximum yearly wetness. Group A has the lowest runoff potential and D the highest. Several soil properties are used to determine the hydrologic soil groupings. In the study of the hydrologic soil nature, soil properties that affect infiltration, such as bulk density, porosity and texture, should be considered. Associated factors that affect infiltration in the field are slope and vegetation. Surface coal mining is a common practice for extracting coal in West Virginia. This practice destroys soil where mining takes place unless it is saved for later use. Surface grading for stability during minesoil reclamation often causes high compaction and, as a consequence, high bulk density and low porosity. Therefore, it has been assumed that minesoils are somewhat poorly drained with low infiltration rates and high runoff potential. This assumption results in minesoils being classified in hydrologic soil group C. The objectives of this study were to determine the true hydrologic soil grouping of a minesoil and the minesoils hydrologic behavior, as affected by slope and cover. Two study areas were selected on a reclaimed surface mine in Webster County, WV. Site #1 was selected to study the effect of vegetative cover and slope on surface hydrology while Site #2 was selected to study the hydraulic properties of the most compacted layer present in the profile of reclaimed minesoils, the compacted backfill. The properties measured to determine the minesoils true hydrologic grouping included organic carbon, texture, bulk density, and saturated hydraulic conductivity. Site #1 exhibited high infiltration and low surface runoff and erosion. Results obtained in Site #1 showed that, although minimal, the effect of slope on hydraulic properties was greater than that of vegetative cover. The organic carbon in Site #1 was 46.1 +/- 3.2 g/kg while that in Site #2 was 21.3 +/- 2.8 g/kg. Site #1 had a higher fraction of rocks, more silt and more clay, while Site #2 had fewer rocks and a greater amount of sand. Bulk density values were higher in Site #2, with uncorrected bulk density values averaging 2.10 +/- 0.18 Mg/m 3, as compared to 1.54 +/- 0.24 Mg/m3 in Site #1. Corrected bulk density values for Site #2 were 1.80 +/- 0.24 Mg/m 3 while Site #1 exhibited corrected bulk density values of 0.91 +/- 0.17 Mg/m3. The saturated hydraulic conductivity values for Site #1 averaged 47.3 +/- 26.2 microm/s, while Site #2 had a much lower average of 3.0 +/- 2.7 microm/s. Higher bulk density values and lower Ks values confirm that the compacted backfill found in Site #2 was the most limiting layer in the minesoil profile. The study findings lead to the conclusion that the hydrologic soil grouping for this minesoil should be hydrologic soil group A. In order to ensure that other minesoils are placed into the correct hydrologic soil grouping, future work should be done on more mine sites to determine whether similar hydrologic behavior may change an assumed hydrologic soil grouping. Such work should also be conducted over a longer period of time to study how soil hydrologic properties may change as minesoils become more developed.

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