Erik Severson, Research Associate and Interpretive Soil Scientist, - PowerPoint PPT Presentation

Erik Severson, Research Associate and Interpretive Soil Scientist, CSES department, Virginia Tech

Well Aerobic soil Groundwater

Trench Bottom Trench Bottom Trench Bottom Trench Bottom Clayton Site Clayton Site Left Side – Lateral 3 Left Side – Lateral 3 8/23/1999 8/23/1999 Coarse-Textured Coarse-Textured Coarse-Textured Coarse-Textured Clayey Horizon Clayey Horizon Clayey Horizon Clayey Horizon Source: Aziz Amoozegar, Lake Wheeler

Introduction

F

Flat Topography + Impermeable Layers = Perched Water Tables

1. Document morphology and monitor saturation in the Appomattox and Bentley Soil Series. 2. Calculate % wet season RMFs were saturated. 3. Confirm or deny epiaquic conditions.

4. Compare saturation differences of entirely residual soils versus transported soils.

Location 1: Bentley Soils Location 2: Residual Soil

Appomattox Bentley

Cap and vent hole Annulus Bentonite Solid pipe Restrictive Slotted Layer pipe gravel

0 10 20 30 Depth (cm) 30-day 40 50 Average 60 70 80 20-day 90 100 1/1 1/8 1/15 1/22 1/29 2/5 2/12 2/19 2/26 3/5 3/12 3/19 3/26 4/2 4/9 4/16 4/23 4/30 Date

0 10 20 Iron 30 5% Concentrations: Depth (cm) 40 50 60 70 80 Chroma 3 depleted ped 65% 90 faces 100 1/1 1/8 1/15 1/22 1/29 2/5 2/12 2/19 2/26 3/5 3/12 3/19 3/26 4/2 4/9 4/16 4/23 4/30 Date

1) Document Soil Morphology And 2) Monitor saturation for the Appomattox and Bentley Soils

Ap Bt1 Bt2 2BCt 3CBt 3Ct

0 200 180 -20 160 140 -40 Precipitation (mm) 120 Depth (cm) -60 100 80 -80 60 40 -100 20 -120 0 Oct-11 Mar-12 Aug-12 Jan-13 Jun-13 Nov-13 Apr-14 5YR 5/8 (c) 10YR 7/8 (d) 10YR 7/4 (d) N/8 (d) Precipitation

Depleted ped faces 41% n =36 Concentrations 23% n=11 ≥3 chroma depletions 41% n=20 ≤2 chroma depletions 65% n=12

0 -50 -100 -150 Depth (cm) -200 Perching confirmed at -250 6 out of 8 sites -300 -350 Sep-11 Apr-12 Oct-12 May-13 Nov-13 Jun-14 1.5M 3M Discontinuity

 Compare hydrology of entirely residual soils vs. transported soils at same depths (1 m).

0 -20 -40 Depth (cm) -60 -80 -100 -120 Nov-12 Mar-13 Jul-13 Nov-13 Mar-14 Residual Transported

Soils 30-day 20-day Avg. Water Table Transported 81 64 91 Residual 95 83 --

Conclusions Transported soils perch water for extended periods on impermeable layers.

Conclusions Redox Features with chroma ≥3 indicate a fluctuating water table.

Conclusions Residual soils underneath transported soils were not saturated.

Conclusions Entirely residual soils were “drier” than transported soils.

 Avoid use of transported soils with restriction and perched water table  Avoid 1 M below lithologic discontinuity