Rock Slope Protection / Rip Rap

Slope Protection consists of rock, concrete, or concreted rock or slope paving

Rock Slope Protection Rock Should Demonstrate

  • Stability: Angular shapes may be used on any planed slope
  • Durability: Resist degradation and have a durability of 52 minimum (Caltrans)
  • Consistency: Product is the same load after load.
  • Meets Specification: No rejections due to inferior material, complies with all project specific specifications, or to Caltrans or Army Corps specifications.
  • Availability: Product is locally available when needed.

Angular vs. Rounded or Cobbles

Angular or crushed rock is used in most applications due to its interlocking qualities. Rounded or cobble rock is not specified by Caltrans for projects with a slope greater than 1:2 (vertical: horizontal)


Most Public Agencies in Central California specify that Stone Protection (Rip Rap) meet Section 72 of the Caltrans Standard Specifications. Caltrans standards set limits for Gradation or Size, Apparent Specific Gravity, Absorption, and Durability Index. Suitable Slope Protection (Rip Rap) materials demonstrate test results that consistently meet these standards.

Caltrans identifies eleven different sizes and two placement methods. The sizes as specified by Caltrans are: 8 ton, 4 ton, 2 ton, 1 ton, ½ ton, ¼ ton, Light, and No. 1, No. 2 or No. 3 Backing.

The placement methods designated by Caltrans

  • Method A Placement
  • Method B Placement

The principal differences in the two placement methods are the size range of the rock specified and actual placement mechanism. Method A requires placement of individual stones, while Method B allows placement by dumping or dozing. Refer to the project special provisions for Placement Method and additional direction.

Both private and public work projects can use either the Caltrans Standard Specifications or specify by average size of Rip Rap i.e. 2 foot or 3 foot rock, additionally a size range can be specified, such as 15 to 24 . Please keep in mind that material specifications can be modified in the Project Special Provisions Documents.

Considerations worth noting

  • Make certain of the Product Required
    • Project Service Requirements
    • Product Name
    • Product Maximum / Minimum Size
    • Specifying Agency (Caltrans, Green Book, Army Corp or Other)
    • Special Provisions addressing additional specifications
  • Certification Required (Submittals) Caltrans, Army Corps, other agency or engineer
  • Quantity Required (Specific Gravity—Conversion Tons to Cubic Yards)
  • Product Availability (Available when required, can handle Daily Shipping Requirements)
  • Technical Support Required (Lab Work)
  • The Reputation of your Supplier and their Products & Services

Advantages of using Rip Rap or Stone Protection from Wilson Quarry (Aromas)

  • 100% Crushed Granite (Provides Superior Stability and Durability)
  • Many different Rip Rap types available:
    • All Caltrans Classes and Sizes
    • Custom Sizes and Ranges available
    • Gabion Sized 4 to 10
  • High Daily Production and Shipping Capacity (Can Handle Large & Small Jobs)
  • Graniterock can provide delivery to your jobsite if desired. (One call ordering and delivery)
  • Technical Support available for assistance.
  • Proven Product Track Record (Aggregate is widely accepted and approved)
    • Wilson Quarry Products are recognized as the Industry Standard in the Monterey Bay Area
    • Product meets and is Certified for Army Corp Projects
    • Graniterock has a 101-year history of providing high quality products and service.

Please call the Sales Office for pricing and scheduling information Office 831.768.2380 Fax 831.768.2401 or e-mail to: Don Barrett.