Tree Protection Zones (TPZ) in Active Site Construction
Arboriculture November 15, 2025 • 1 min read

Tree Protection Zones (TPZ) in Active Site Construction

Tiffany Faulstich

California Licensed C-27 #1051100 | ISA Certified Arborist

Tree Protection Zones (TPZ) in Active Site Construction
Specimen Oak Protection

Summary

How proper fencing, root zone preservation, and arborist oversight safeguard specimen native oaks and mature trees during grading, trenching, and building operations.

01
Why Native Oaks Succumb to Construction Damage

Specimen native oaks (Quercus agrifolia and Quercus lobata) represent irreplaceable historical and environmental assets. However, over 80% of mature tree root systems reside in the upper 18 inches of soil. Heavy machinery compaction, grading cuts, and grade fills suffocate mycorrhizal fungi and sever primary feeder roots, often causing tree death 3 to 5 years after project completion.

02
Establishing an Uncompromising Tree Protection Zone

A proper Tree Protection Zone must extend at minimum to the tree’s dripline (or 1.25 feet per inch of trunk DBH). Rigid 6-foot chain-link fencing anchored with steel posts must be installed prior to any site mobilization, accompanied by bilingual warning signage.

03
Continuous Arborist Oversight & Trenching Protocols

Whenever utility lines must cross near root zones, pneumatic air-spading or directional boring must be mandated in place of mechanical trenchers. Regular trunk inspections and radial mulch applications maintain soil moisture and buffer subterranean root systems against stress.

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Tiffany Faulstich

Founder & Consultant

Tiffany is a California State Licensed Landscape Contractor (C-27 #1051100), ISA Certified Arborist (#WE-11753A), and LEED Green Associate with 30+ years of horticultural management experience across Central and Southern California.

California Licensed C-27 #1051100

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