1. REGULATION 43 GEOLOGY AND SOILS
Ed Church, P.E.
SCG Enterprises, Inc.
CPOW 2014

2. GEOLOGY AND SOILS FOR REGULATION 43 – 0WTS
Has the geology changed?
Has the soil changed?
Has the groundwater changed?
WHAT HAS CHANGED?
CPOW 2014

3. How we observe subsurface conditions, classify the soils and evaluate moisture conditions? Attempt to provide guides to getting the Soil Types of Table 10.1 A major consideration is STRUCTURE
CPOW 2014

4. What classifications system?
Unified Soils Classification* – Civil Engineers
AASHTO – Highway Engineers
Another for runways
Percolation Tests with Unified Classification
Geologic*
Agricultural soil morphology – SCS, which is where CO is joining most other states
*Well sorted means exact opposite in Geologic and Engineering Classifications. Geologic, all one size, Engr., a variety of sizes, SW
CPOW 2014

5. BUT FIRST GEOLOGY – BASIC ROCK TYPES
IGNEOUS – everything starts here
SEDIMENTARY – weathering and erosion of other rock or soil
METAMORPHIC – igneous, sedimentary or metamorphic material that has been reconstructed under heat and pressure.
CPOW 2014

6. CPOW 2014

7. IGNEOUS Granite - Quartz Monzonite - Granodiorite volcanic Basalt lava
CPOW 2014

8. VOLCANIC LAVA / BASALT
CPOW 2014

9. GRANITE
CPOW 2014

10. SEDIMENTARY Sandstone Shale / claystone Mudstone Arkose Limestone
CPOW 2014

11. SEDIMENTARY
DAWSON
DAKOTA
CPOW 2014

12. METAMORPHIC Quartzite – Sandstone with heat and pressure
Schist – Shale with heat and pressure
Gneiss – mix of sandstone, shale and other metamorphic
Shale – Claystone with heat and pressure
Marble – Limestone with heat and pressure
CPOW 2014

13. METAMORPHIC
CPOW 2014

14. GEOMORPHOLOGY How landforms develop: Mountains with valleys – HIGH
Plateaus
Terraces
Basins
Great Plain
Lakes and offshore - LOW
CPOW 2014

15. WHAT DOES THIS MEAN TO REG 43
USDA SOIL PERC RATE STRUCTURE REG 43 Sandy Clay 40 Massive 3 Sandy Clay 70 Massive 3A Sandy Clay 100 Massive 4A What is the difference – USDA Structure-Shape None, Prismatic, Block, Granular or Platy AND - USDA Structure Grade 0-Single Grain, 1-Weak, 2-Moderate, 3-Moderate or Massive
CPOW 2014

16. What is the difference?
To get to the various Soil Treatment capabilities, the soil has gone thru a geologic/geomorphic history, which results in the soil’s ability to treat effluent. This history includes: weathering, transportation, compaction and moisture conditions resulting in a Soil Structure.
CPOW 2014

17. GRANULAR - Sand
With granular materials, there is a general improvement in treatment capability as the material is weather and erodes from granite and other “hard rocks” to smaller sand sizes capable of treatment. The exception is Dawson Arkose which contains clay minerals in sand sizes which do not treat effluent at granular rates.
CPOW 2014

18. COHESIVE, CLAY
Cohesive soils are fine grained and generally have poorer treatment capabilities.
Percolation rates are much slower and larger treatment areas (drainfields) are required.
Structure is very important and includes:
Prismatic, Blocky, Massive and Platy
In between is silt, which may have a combination of properties.
CPOW 2014

19. RESIDUAL SOILS
These are derived from weathering inplace of underlying bedrock. Sand/decomposed granite from granite. What is the difference between decomposed and weathered granite? Clay from weathering of shale and claystone
CPOW 2014

20. TRANSPORTED SOILS
Soils moved by gravity and most frequently by water. The movement sorts material by size, so that the further it has been transported, the more uniform the size of material and the better the treatment capability. Colluvium, alluvium and glacial till and moraines.
CPOW 2014

21. USDA /CO SOIL PROFILE
COLORADO
TYPICAL
CPOW 2014

22. 3 DIFFICULT SOIL/BEDROCK CONDITIONS OF COLORADO
GRANITE / GRANODIORITE / DECOMPOSED GRANITE / DAWSON AKROSE
PIERRE SHALE / MANCOS SHALE
CLAYSTONE
CPOW 2014

23. GRANITE / GRANODIORITE / DECOMPOSED GRANITE / DAWSON AKROSE
All similar chemically, but vary due to state of weathering and transport. What is the difference between weathering and decomposition? Arkose is defined as having 25% clay forming minerals.
CPOW 2014

24. Granite
CPOW 2014

25. Decomposed Granite
CPOW 2014

26. Granite as Soil
CPOW 2014

27. WEATHERED FRACTURE GRANITE
CPOW 2014

28. SEDIMENTARY Fountain Formation, Jefferson County
CPOW 2014

29. Dawson Arkose as Bedrock
CPOW 2014

30. DAWSON ARKOSE SLOPE
CPOW 2014

31. Dawson Arkose as Soil
CPOW 2014

32. Pierre / Mancos Shale
Being shale: The Pierre & Mancos can occur as hard fractured rock with permeability through fractures similar to igneous or metamorphic materials – requiring Treatment Level 2 or greater or As a claystone or clay with no fractures and little permeability as a sedimentary material – requiring design as 3, 4 or 5 Soil Type
CPOW 2014

33. Pierre Shale overlain by gravel terrace material, Roaring Fork Valley
CPOW 2014

34. Claystone / Clay
CPOW 2014

35. QUESTONS?
Ed Church, P.E. SCG Enterprises, Inc
CPOW 2014