Our Permeable Class 2 Base Rock is a crushed gravel blend engineered to provide excellent drainage while offering load-bearing stability. Commonly used in permeable pavement systems, bioswales, French drains, and stormwater retention features, this eco-friendly base material meets Caltrans-like gradation specs while allowing water infiltration—making it a preferred option for sustainable landscape and construction projects.
 
Ideal for projects in Alameda, Napa, Sonoma, Marin, Solano, and Contra Costa counties, especially where stormwater mitigation or LEED credits are required.
 
Common Usage & Applications:
Permeable Paver Systems – Base layer for driveways, patios, walkways, and parking lots designed for stormwater infiltration.
Drainage Layers – Installed beneath synthetic turf, planter beds, and retaining walls to ensure proper subgrade drainage.
Bioswales & Rain Gardens – Promotes groundwater recharge while providing structural stability for sustainable landscape design.
Road & Driveway Subbases – Provides a firm, stable foundation while preventing water buildup in low-lying areas.
Erosion Control & Utility Trenches – Used around pipelines, conduits, and utility trenches to prevent settling and water pooling.
 
Typical Material Specifications:
Gradation Range: 3/4x1/4" (little to no fines)
Aggregate Type: Crushed rock — angular, fractured faces for strong interlock
Fines Content: < 2% passing No. 200 sieve
Moisture Content: Typically 2–6% (varies by source and weather)
Compaction: 92% relative compaction achievable with open-graded aggregate methods
Permeability Rate: 100–250 inches/hour (depending on compaction and gradation)
Specific Gravity: Approx. 2.65
Weight per Cubic Yard: ~1.4 tons (2,900 lbs.)
Color: Light gray to blue-gray (varies by quarry source)
 
Technical Notes:
Meets or exceeds Caltrans Section 68 for permeable base rock and ASTM D448 #57 coarse aggregate gradation.
Free-draining structure reduces hydrostatic pressure and supports efficient stormwater management.
Recommended for use with geotextile separation fabric in soft or expansive subgrades to prevent migration of fines.
Compact in thin lifts using vibratory rollers or plate compactors for uniform density and stability.
Avoid mixing with fine or non-draining materials to maintain permeability.
 
Delivery Method
North Bay Materials offers fast, reliable dump-truck delivery of Permeable Class 2 Base Rock directly to job sites across Napa, Solano, Marin, Sonoma, Alameda, and Contra Costa counties.
 
Delivery Details:
Truck Type: Small Dump to Transfer Truck
Capacity: from 5 tons up to 24 tons (varies by access)
Service Type: Curbside or on-site delivery (where access allows)
Minimum Order: Typically 3 tons or 2 cubic yards
Delivery Scheduling: Same-day or next-day service available in some areas
Placement: Material is dumped in a single pile; tailgate spreading available upon request for accessible sites and truck type being used.
Volume discounts are available upon request for large volume orders.
 
Material Coverage Per Ton
~ 100 sq ft 2" depth
~ 55 sq ft 4" depth
~ 30 sq ft 6" depth
 
Section 5 — Frequently Asked Questions (FAQs)
Q1: What size is Permeable Class 2 Base Rock?
A: It’s an open-graded crushed rock mix typically ranging from ¾″ to 1½″ in size, with minimal fines to promote maximum water infiltration.
 
Q2: Is this material Caltrans-approved?
A: Yes. Our Permeable Class 2 Base Rock meets Caltrans Section 68 specifications for permeable base applications commonly used under permeable pavements and drainage systems.
 
Q3: Can it be used under concrete or asphalt?
A: It’s best suited for permeable paving systems. For standard concrete or asphalt bases, use Class 2 Aggregate Base (with fines) for better compaction and density.
 
Q4: Does this rock compact well?
A: Yes—while open-graded, it achieves strong interlock through angular particle geometry. Compact with a vibratory plate or roller in thin lifts to achieve uniform support without crushing the aggregate.
 
Q5: How should it be installed for permeable applications?
A: Install over a geotextile fabric layer, compact in thin lifts, and avoid mixing with fines or soil. Always verify slope and subgrade preparation for proper infiltration.