160 tons of stone in the first and only 45 plus topdressing in the second is a huge difference. 45 tons isn't anywhere near enough. Even with the 160 ton, that will only give you about an average 8" depth. The 45 ton will hardly be enough as a top coat as it will only net about 2" average depth.
8" depth for a driveway seems skimpy to me but your native soil type could have a bearing on that. Something else to consider is laying geotextile fabric under the stone to keep it from mixing with the subsoil
Thanks for that info! This is where I have absolutely no experience. I am outside Richmond VA. I don't want to over engineer the driveway but also don't want to have to do it again in a couple years. As for soil this is what I found:
Here is a pic from websoilsurvey.nrcs.usda.gov website:
Definition of area 27C2:
27C2—Pacolet fine sandy loam, 7 to 15 percent slopes, eroded
Map Unit Setting
National map unit symbol: 3zv6
Elevation: 200 to 1,400 feet
Mean annual precipitation: 35 to 48 inches
Mean annual air temperature: 76 to 100 degrees F
Frost-free period: 153 to 205 days
Farmland classification: Farmland of statewide importance
Map Unit Composition
Pacolet and similar soils: 80 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Pacolet
Setting
Landform: Hillslopes
Landform position (two-dimensional): Shoulder
Landform position (three-dimensional): Interfluve
Down-slope shape: Convex
Across-slope shape: Convex
Parent material: Residuum weathered from granite and gneiss
Typical profile
H1 - 0 to 4 inches: fine sandy loam
H2 - 4 to 27 inches: clay
H3 - 27 to 42 inches: clay loam
H4 - 42 to 62 inches: loam
Properties and qualities
Slope: 7 to 15 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.57 to 1.98 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Moderate (about 7.6 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 3e
Hydrologic Soil Group: B
Definition of area 3B:
3B—Bolling soils, 2 to 7 percent slopes
Map Unit Setting
National map unit symbol: 3zw0
Mean annual precipitation: 35 to 48 inches
Mean annual air temperature: 76 to 100 degrees F
Frost-free period: 153 to 205 days
Farmland classification: All areas are prime farmland
Map Unit Composition
Bolling and similar soils: 90 percent
Estimates are based on observations, descriptions, and transects of the mapunit.
Description of Bolling
Setting
Landform: Stream terraces
Landform position (three-dimensional): Tread
Down-slope shape: Linear
Across-slope shape: Linear
Parent material: Alluvium
Typical profile
H1 - 0 to 11 inches: silt loam
H2 - 11 to 35 inches: clay loam
H3 - 35 to 63 inches: silty clay loam
Properties and qualities
Slope: 2 to 7 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Moderately well drained
Runoff class: Low
Capacity of the most limiting layer to transmit water (Ksat): Moderately high to high (0.57 to 1.98 in/hr)
Depth to water table: About 24 to 36 inches
Frequency of flooding: Occasional
Frequency of ponding: None
Available water storage in profile: High (about 9.2 inches)
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 2w
Hydrologic Soil Group: C