8.3 Demolition Plans & Tree Protection Requirements

Core Focus: Site demolition and vegetation preservation plans establish the baseline physical boundaries of site transformation. Errors in delineating removals, protecting existing specimens, or stripping topsoil result in severe contractor claims, legal liability, structural pavement settlement, and irreversible ecological damage. The LARE rigorously tests candidate mastery of Tree Protection Zones (TPZ), Critical Root Zone (CRZ) mathematics, clearing versus grubbing specifications, topsoil stockpile biology, and utility abandonment procedures.

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1. Demolition Plans & Material Disposition

The Demolition Plan (typically L-100 series) provides the legal and physical instructions for dismantling, clearing, and reconfiguring existing site features. A complete demolition plan must unambiguously categorize every existing object into one of three distinct categories:

1. Items to Be Removed: Pavements, foundations, fences, light poles, utilities, or vegetation scheduled for complete extraction and off-site disposal.
2. Items to Remain and Be Protected: Existing trees, historic structures, utility mains, boundary monuments, or adjacent pavements that must be safeguarded throughout construction.
3. Items to Be Salvaged or Relocated: High-value or historic components to be carefully disassembled, cleaned, indexed, and stored for reinstallation (e.g., historic granite curbing, cobblestones, decorative iron gates, architectural light fixtures, or existing mature specimen palms).

+-----------------------------------------------------------------------------+
|                        DEMOLITION PLAN DRAFTING SYMBOLOGY                   |
|                                                                             |
|   FEATURE                    EXISTING TO REMAIN          SCHEDULED REMOVAL  |
|   -------                    ------------------          -----------------  |
|   Asphalt Pavement           Light Gray Screen / Solid   Heavy Strikethrough|
|   Concrete Walk              Dashed Line (Hidden)        Cross-Hatched X's  |
|   Deciduous Tree             Existing Canopy Outline     Canopy with 'X'    |
|   Underground Pipe           Dashed Layer (Screened)     Dashed with 'R'    |
|   Pavement Boundary Cut      N/A                         Full-Depth Sawcut  |
+-----------------------------------------------------------------------------+

Full-Depth Sawcutting Requirements

Where existing concrete or asphalt pavement is to be partially removed while an adjacent section remains, the drawing must explicitly specify a clean, full-depth vertical sawcut along the exact removal boundary line:

• The Failure Risk: Using a hydraulic jackhammer, excavator bucket, or hoe-ram without a preliminary sawcut creates micro-fractures, ragged edges, subbase disturbance, and spalling along the retained slab. This creates an unmaintainable, raveling joint that fails rapidly under freeze-thaw cycles and vehicular loads.
• Detailing Standard: The demolition plan must call out: "Provide clean, full-depth sawcut prior to pavement demolition. Match joint alignment cleanly and seal exposed edges per Detail X/L-701."

Salvage and Sustainability Tracking

Under sustainable rating systems (SITES and LEED), demolition plans must incorporate a Materials Salvage and Diversion Schedule:

• Existing concrete slabs crushed on-site for use as recycled aggregate base course (typically saving significant trucking costs and embodied carbon).
• Existing asphalt milled for reclaimed asphalt pavement (RAP).
• Salvageable topsoil stripped and amended rather than imported from virgin quarries.

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2. Tree and Vegetation Protection Plans: CRZ and TPZ

Preserving mature trees requires understanding the physiological reality of root systems. Contrary to the common myth of a deep "taproot mirroring the canopy," over 80% to 90% of a tree's absorbing root system lies within the top 12 to 18 inches of soil, extending horizontally two to three times beyond the visual canopy dripline.

                                  TREE CANOPY
                               (Visible Dripline)
                                      |  |
                                      V  V
                              +------------------+
                              |    TREE TRUNK    |
                              |    (DBH at 4.5') |
                              +--------+---------+
                                       |
=======================================|=======================================
                  ROOT SYSTEM (Top 12" to 18" of Soil)
<- - - - - - - - - - - - - - - - - - - | - - - - - - - - - - - - - - - - - - ->
  DRIPLINE: Inadequate Boundary        |   CRZ / TPZ RADIUS:
                                       |   1.0' to 1.5' per 1" DBH
                                       |   (Extends beyond dripline!)

Calculating the Critical Root Zone (CRZ) and Tree Protection Zone (TPZ)

On the LARE, candidates must calculate the minimum required radial boundary for root preservation:

• Diameter at Breast Height (DBH): The trunk diameter measured at 4.5 feet (1.37 meters) above the natural ground elevation.
• The DBH-to-Radius Rule of Thumb: For mature, sensitive, or high-value specimen trees, the radial distance from the trunk to the perimeter of the Tree Protection Zone (TPZ) is calculated at 1.0 to 1.5 feet of radius for every 1 inch of DBH:

$\text{TPZ Radius (feet)} = \text{DBH (inches)} \times (1.0\text{ to }1.5)$

$\text{TPZ Total Diameter (feet)} = 2 \times \text{TPZ Radius}$

Mathematical Calculation Example

Scenario: A historic white oak (Quercus alba) measures 28 inches DBH.

• Conservative / High Sensitivity TPZ Radius: $28\text{ inches} \times 1.5\text{ ft/inch} = 42\text{ feet radial distance}$ from the trunk center.
• Total Protection Diameter: $42\text{ ft} \times 2 = 84\text{ feet clear circular diameter}$.
• The Dripline Fallacy: If the tree's physical foliage dripline extends only 25 feet from the trunk, placing fencing at the dripline would destroy over 40% of the tree's vital absorbing root network, likely leading to crown decline, vascular wilt, or death within 2 to 5 years.

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3. Root Pruning, Trunk Protection & Soil Compaction Mitigation

Tree Protection Fencing Specifications

The physical barrier delineating the TPZ is the single most critical line on the demolition plan. Fencing specifications must withstand aggressive construction environments:

• Mandatory Heavy-Duty Standard: 4- to 6-foot-high galvanized steel chain-link fabric, mounted rigidly on 2-inch diameter steel posts driven a minimum of 24 inches directly into the ground at 8- to 10-foot intervals. Post-driven chain link cannot be easily moved by construction laborers or pushed back by bulldozer blades.
• The Orange Snow Fence Failure: Flexible orange polyethylene snow fencing mounted on lightweight steel T-posts is universally recognized as inadequate for high-risk urban or institutional sites. Subcontractors routinely unclip, crush, or shift snow fences to park pickup trucks, stage gravel, or dump concrete wash water.
• Signage: Durable weatherproof aluminum signs must be mounted every 50 feet along the fence reading: "TREE PROTECTION ZONE – DO NOT ENTER – NO STORAGE, PARKING, EXCAVATION, OR CLEANING OF EQUIPMENT. VIOLATORS SUBJECT TO LIQUIDATED DAMAGES."

       RIGID CHAIN-LINK FENCE                       TEMPORARY CRANE MATTING
   +---+---+---+---+---+---+---+                 ==============================
   |   |   |   |   |   |   |   | 6' Height       [Heavy Timber / Composite Mat]
   |   | [TPZ WARNING] |   |   |                 ------------------------------
   |   |   |   |   |   |   |   |                 [6" to 12" Wood Chip Mulch   ]
   +---+---+---+---+---+---+---+                 ==============================
     |       |       |       |                     Undisturbed Native Soil
    ===     ===     ===     === (Grade)           (Compaction prevented below)
     |       |       |       | 24" Driven Depth

Root Pruning Standards (ANSI A300 Part 8)

When trenching or excavation is unavoidable near the perimeter of the CRZ:

• No Excavator Tearing: Excavator teeth, backhoe buckets, and bulldozers must never be permitted to rip through root systems. Ripping shatters roots lengthwise, tearing the vascular cambium back toward the trunk and introducing fungal root rot pathogens.
• Mechanical Trenching / Rock Saw: Trenching along the outer limit of disturbance must be pre-cut using a specialized vibrating rock saw, mechanical trenching blade, or supersonic air-spade (pneumatic soil excavation).
• Manual Clean Cuts: Roots larger than 1.5 to 2 inches in diameter must be cleanly severed at right angles using sharp bypass loppers, a hand pruning saw, or a clean diamond-bladed saw, leaving a smooth, unfrayed cut edge that forms wound periderm rapidly.
• Moisture Maintenance: Exposed severed root faces must be covered immediately with damp burlap, unamended native topsoil, or geotextile and kept continuously moist until backfilling occurs.

Mitigating Soil Compaction from Temporary Vehicular Traffic

Where construction equipment must cross the root zone of a preserved tree:

1. Mulch Cushion: Lay a minimum of 6 to 12 inches of coarse, uncompacted organic wood chip mulch directly over the root zone surface.
2. Load Distribution Mats: Place heavy timber crane mats, interlocking structural composite mats, or 3/4-inch exterior-grade plywood sheets directly over the mulch layer.
3. Mechanics: The rigid mats distribute the concentrated dynamic wheel loads of heavy machinery across a broad surface area, while the thick mulch layer absorbs shear deformation, preventing the compression of macro-pore soil spaces and preserving root oxygenation.

Trunk Armor (Boxing)

Where equipment must operate in close proximity to mature tree trunks:

• Wrap the trunk in a protective layer of heavy closed-cell foam or layered burlap.
• Strapping vertical 2" x 4" or 2" x 6" dimensional lumber around the circumference of the trunk using adjustable steel strapping bands (never driving nails, screws, or staples into the tree bark).

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