Why Attorneys Hire an Arborist Expert Witness

Whether an attorney represents a plaintiff or defendant, they hire an expert who will provide compelling testimony to support their client.  Sometimes, multiple experts from a variety of disciplines may be required. When should an attorney consider hiring a certified or registered consulting arborist as an expert witness? 

  1. Trip, slip and fall accidents caused by tree roots damaging concrete sidewalks, asphalt streets, patios, and decks.
  2. Tree failures, forensic tree risk assessment to determine open and obvious?
  3. Appraisal(s) to establish the pre-casualty tree value prior loss due to fire, vandalism and trespass.
  4. Determine whether an owner, individual or company satisfied the arboriculture industry standard of care.

Living with trees implies accepting a certain amount of risk in exchange for the wonderful benefits trees provide.  While the risk of a tree limb or whole tree failure resulting in a fatal injury is low, hazards caused by trees that result in personal injury or property damage lawsuits are not uncommon.

Tree species and proximity to infrastructure may be a factor in accidents with personal injury or property damage.  Tree roots seek out moisture regardless of their location.  Structural roots emanate from the trunk to the edge of the crown, also known as the drip line, then small moisture absorbing root grow far beyond.  Tree root systems may grow 1.5 times the tree crown diameter.

Trip, Slip and Fall Accidents

In the urban environment, tree proximity to hardscape may result in roots growing beneath concrete sidewalks and paved streets while seeking moisture.  Roots will grow into adjacent water meters and sewer laterals, especially older leaking, permeable infrastructure.  Once established beneath a paved surface, a root continues growing, over time enlarging in diameter. 

Over time, these surfaces may begin to lift along the crack or expansion joint.  Adjacent sidewalk panels may lift several inches, resulting in a hazardous condition for pedestrians and bicyclists.

Uplifted sidewalk panels resulted in bicyclist personal injury lawsuit

After sidewalk was removed, large structural roots were observed beneath the sidewalk.
Multiple roots damaged the sidewalk, created the hazardous condition and resultant accident.

Eventually root enlargement lifts concrete infrastructure, including water meter boxes and sidewalks. Cracks may develop across a sidewalk panel, in my experience, most concrete sidewalk uplifts occur along an expansion joint.

In their pursuit of moisture, roots from neighboring trees ignore property lines.  They can grow beneath garage slabs and foundations, especially in situations where there has been a water or sewer leak beneath the slab. Moisture discharged beneath slabs, footing and foundations create an attractive environment for root development. 

Neighbor’s Ficus tree root grew beneath their garage slab, resulting in property damage lawsuit.
Roots suspected of lifting sidewalk panels and water meter box that resulted in personal injury lawsuit.
After sidewalk was removed, large roots observed growing around the water leaking water meter.

Installing street trees within small concrete confined planters is an invitation for root damaging infra-structure.  Leaking water meters, fittings and sewer connections increase soil moisture, an invitation for root growth.

A root penetrating a leaking sewer lateral or potable water meter pipe or fitting will quickly establish a mass of roots within and surrounding the pipe.  Root growth may continue from the sewer lateral into the public sewer main.  Over time, the root growth may block or cause a sewer back up to neighboring properties.

Roots deform a sewer lateral beneath garage slab.
Section of removed sewer lateral filled with roots.

Improperly designed, installed or maintained sprinkler systems may result in over-spraying paved pedestrian sidewalks. Regardless of cause, their is no reason to allow sprinklers to over-spray onto paved surfaces, it wastes a vital resource while creating an obvious slip and fall hazard.

Park sprinklers over-spraying a public sidewalk, resulted in a personal injury lawsuit.

Tree failures and forensic tree risk assessment

Tree limb and whole tree failures may result in personal injury and property damage lawsuits. Whole tree failures may occur due to loss of load bearing structural roots, whether due to root rot disease, construction impacts, mechanical root damage, or soil failure. Limb drops may occur for a variety of known reasons, typically the failure occurs during a weather event. Sometimes, a tree will drop a limb for unknown reasons, referred to as sudden or summer limb drop. Stems may contain defects such as cankers, decay, and cracks that may be predisposed to failure when enough force exceeds the wood carrying capacity. Forensic tree risk assessment may determine why the tree failed and whether the defects were open and obvious.

A root or soil failure.
Stem failure resulted in personal injury and property damage lawsuit.

Tree and landscape appraisal for fire damage, trespass and vandalism

The same holds true for tree loss or diminution in value due to trespass and vandalism.   You may love your tree, but your neighbor may not. Neighbors frequently engage in tree disputes, sometimes resulting in trespass and vandalized trees. You may love your tree, but your neighbor may not.

Avocado groove scorched from wildfire in Fallbrook. Appraisal performed for insurance and tax purposes.
Oak tree property damage claim due to Thomas fire.
Tree and landscape appraisal for property damage lawsuit caused by Thomas fire mudslide.
Palm tree nursery burned due to vandalism, appraised palm value for property damage lawsuit.
Bamboo hedge poisoned by neighbor, property damage lawsuit.
Tree loss due to neighbors pruning, resulting in property loss lawsuit.

Arboriculture standard of care

Tree service contractors may become involved in a lawsuit for failing to satisfy the industry standard of care. When a tree failure occurs, the landscape maintenance or tree care contractor may find themselves as defendants in a lawsuit. A plaintiff may contend the landscaper or tree care company should have known the tree had defects but was the contractor responsible for risk assessment?

A C-27 landscape contractor may not be a certified arborist or provide arboricultural tree care, certified arborist may not be a trained or knowledgeable of Tree Risk Assessor Qualified, (TRAQ).

To determine a contractor’s standard of care, I examine their membership in industry associations such as the California Landscape Contractor Association, (CLCA), the International Society of Arboriculture, (ISA), the American Society of Consulting Arborists, (ASCA), and Professional Tree Care Association. I determine whether the certified arborist and tree care professionals adhere to the American National Standards Institute, (ANSI) A300 arboriculture standard practices and Z133 safety requirements. I check their standing on the California State Licensing Board.

In summary, personal experience, education and training are essential qualifications an attorney looks when selecting an arborist expert witness. Having expertise in multiple disciplines is an added benefit. My qualifications as a professional horticulturist, a C-27 landscape contractor, a certified arborist, registered consulting arborist and tree risk assessor qualified and land development manager enable me to opine on a broad array of landscape, tree, plant and land development issues.

Trees for Tomorrow Start Today’ Workshop

Hello, this is Jeremy Rappoport, president of Rappoport Development Consulting Services LLC (RDCS). The workshop goal is to increase tree health and reduce impacts of urban heat islands by properly selecting and caring for trees today to ensure a greener tomorrow. The workshop is sponsored through the University of California Agriculture and Natural Resources.

As an experienced legal expert witness, I consult for defendant and plaintiff attorneys and insurers in the fields of arboriculture, horticulture, landscape and land development. My credentials as a certified arborist, registered consulting arborist, tree risk assessor qualified (TRAQ), C-27 landscape contractor, and B.S. in ornamental horticulture enable me to opine on relevant legal cases.

My presentation, ‘Are Your Trees Safe?’ focuses on legal cases involving roots lifting sidewalks creating trip and fall hazards, root, limb and trunk failures, and the forensic application of tree risk assessment. I will propose solutions to reduce tree potential tree risk during the design / development process for planners, landscape architects, civil engineers and government agencies and how to reduce current tree risk before the a defect results in a accident and resultant lawsuit.

The ‘Trees for Tomorrow Start Today’ Workshop also features ‘Working Together Across Professions ‘Success Stories’, presented by several distinguished speakers, followed by roundtable discussions. The workshop is scheduled on Tuesday, March 9, 2021 via Zoom. Click here for the registration link.

Tree Roots Lifting up Sidewalk?

Who is Better Qualified to Opine on Root Damage, Civil Engineer or Certified Arborist?

I was retained by a defendant attorney to determine whether her client’s tree was responsible for lifting the adjacent civil sidewalk that resulted in a plaintiff trip and fall lawsuit.  Based on the photographs and tree species, White mulberry (Morus alba), I was fairly certain her client’s tree was responsible for the sidewalk damage.

The attorney retained me and requested a site inspection and tree root assessment.  I trenched adjacent to the sidewalk and within a short time, encountered a three-inch diameter root growing under the sidewalk.  Further excavation revealed a network of two to four-inch diameter roots that had grown under the sidewalk, resulting in the tree roots lifting up the sidewalk panel, creating a hazardous condition resulting in a trip and fall accident.

I informed the attorney that tree roots lifting up the sidewalk, or root encroachment from her client’s tree resulted in the sidewalk damage, she said her civil engineer expert claimed it impossible for a tree root to lift a concrete sidewalk.  I questioned the engineers knowledge and experience with trees, was the civil engineer a certified arborist or horticulturist?

Although the answer was no, she felt his qualification as a civil engineer was superior to my qualifications as a certified arborist, tree risk assessor qualified, registered consulting arborist and a college educated horticulturist.  Her dilemma was having two experts who disagreed and she requested I alter my opinion.

I told the attorney altering my opinion to suit her needs was unethical, and I removed myself from the case.

What Causes Tree Roots To Lift up a Sidewalk?

The common myth is trees have tap roots that grow straight down into the soil.  While this may occur in very deep, loam soils, the reality is most containerized nursery grown trees lose their tap root in the container.  Once planted in our poor Southern California soils, when the tap root encounters physical soil obstructions, such as rock, clay or hardpan, the tap root divides and grows multiple roots around the obstacle, forming a fibrous root system.  Tap root grows into fibrous root system.

Trees require a spreading root system to maintain structural stability.  Trees dissipate energy generated during a storm or wind event by transmitting leaf, limb and trunk movement down to the roots.  A spreading root system anchors the tree movement and dissipates the energy far more effectively than a single tap root system.

Most tree roots grow within the top 24-inches of the soil horizon. Roots in top 24″ of soil.  Over time, structural tree roots (2-inch diameter and greater) growing within a shallow soil adjacent to sidewalks, footings, foundations, walls or othersub-surface infrastructure may cause damage.

Just as a twig grows into a branch, and then a limb, roots increase in length and circumference.  Irrigation water, sewer or water service leaks increase subsoil moisture beneath sidewalks or garage slabs, creating a perfect environment for root growth.

Cracked garage slab

As the root circumference increased, it exerts pressure on the concrete slab or footing above the root.  Depending on the species, root diameter might increase 1/8-1/4” annually.

Within five to eight years, a small feeder root may grow to one-inch in diameter or greater.

Ficus root cracked the garage slab

The root growth may be compared to the action of a hydraulic jack, as the circumference increases, the upward pressure on the sidewalk or slab may crack and or eventually cause tree roots to lift the sidewalk.  Concrete lifting may often occur at an expansion joint between concrete panels

Sidewalk lifted at expansion joint

Root network beneath sidewalk.

Roots seek out soil moisture, they can and will grow under walls, footings and garage slabs.  Roots are opportunistic, leaky plumbing, old cast iron sewer lateral or water services contribute to the soil moisture needed for roots to flourish. 

Sewer lateral root damage

Roots may infiltrate pvc, abs and cast-iron pipe through even the smallest of cracks or holes. 

Once inside, the roots expand in size and quantity, eventually completely clogging the utility.

If the tree crown has grown over a sidewalk or adjacent structure, it is a reasonable assumption structural roots (two-inch diameter and greater) have grown under the sidewalk, slab or footing.

Root growing under house footing

Planter areas confined by concrete pose one of the greatest risks for root damage.  City sidewalks often incorporate small, square planters within the sidewalk easement.

Roots lifting water meter and sidewalks

Confined planters quickly fill with structural roots, as well as damaging girdling root.  As the tree crown grows, so to do water absorbing feeder roots.  Over time, root mass and size increases, structural roots may begin to grow beneath concrete improvement while seeking out moisture.

Leaking water meter, high soil moisture, confined growing space.

The tree pictured above and to the right had a leaky water meter adjacent to the small sidewalk planter.  The leaky service provided idea soil moisture conditions for the roots to lift the water meter box, adjacent sidewalks and crack the curb and gutter.

Preventative measures to minimize root encroachment include a variety of root barrier methods.  All root barrier systems work best when the tree is installed.  Once roots have enlarged and matured, barrier mitigation is not successful.

In summary, our Southern California poor, shallow soils do not support deep tree tap root systems.  Most trees grow fibrous spreading root systems.  Structural roots emanating from the root collar extend to the edge of the tree crown, (drip line).  Most structural roots growing beneath sidewalks range from two to four inches in diameter, lifting sidewalk panels on average one-two inches. Trees growing in confined planters or adjacent to concrete, utilities or foundations may develop structural roots capable of lifting, cracking or damaging adjacent improvements.

Dealing with legal issues due to tree roots lifting up a sidewalk?

Attorneys should select an expert based on the case criteria, not simply a title, license or certificate. Choose an expert most appropriate to address the cause of the problem and develop opinions based on sound, industry practices.

Trip, Slip and Fall Hazard: Hidden Depressions in Grade

Successful landscapes require:

  • Proper grading, drainage and amended soil.
  • An automatic irrigation system achieving 100% head to head coverage.
  • Properly installed, high quality plant material.

Each of these functions may require a specific type component, installed at a specific height or location to reduce the potential of creating a site hazard that may result in an accident.  In commercial applications, landscape plans usually include details and specifications dictating type of product and how it should be installed.

Many common landscape products may be improperly installed including:

  • Pop up heads may be incorrectly set to grade against a sidewalk.
  • Valve or drainage boxes set too high or low relative to finish grade.
  • Shrub head installed on a riser adjacent to concrete improvement.
  • Hidden, obscured depressions in grade due to substandard compaction, settlement and subsidence.

    Drainage box set too low.

Improper product selection or substandard installation practices may appear obvious.  A pop up sprinkler head set above the top of  adjacent concrete sidewalk creates a trip hazard.  A drainage structure set well below the turf grade creates a trip slip and fall hazard.  Selecting and installing a spray head on a rigid riser next to a pedestrian sidewalk is a sub-standard industry practice that creates a trip and fall hazard.

Spray head on a riser next to a sidewalk creates a trip hazard.

Not all landscape hazards are visible.  Turf areas may have grade depressions or holes that are hidden by overgrown turf grass.  Depending on the cause and time period, turf grass may completely hide the depth, location and size of the depression or hole, creating a hidden hazard.

A depression, rut or hole may result from several factors.  Repeated mowing on saturated turf may  create ruts.  Overwatering may cause irrigation or utility trench settlement.  A dead tree removed from a turf area may result in a future depression if the grade is not properly backfilled and compacted.

A seven inch deep hole hidden by turf grass.

Bermuda grass is a fast horizontal spreading turf-grass used in parks and recreation facilities throughout the country.  Unless regularly aerated and de-thatched, Bermuda grass in known to grow a  thick layer of thatch.  Over time, the thatch layer can increase the turf grade several inches above adjacent sidewalk and curbs.

The backfill in utility trenches installed across pre-existing turf may settle, creating a depression in the sub-grade.  The photo depicts the edge of a trench cut across an asphalt driveway, across a turf area.  The trench backfill eventually settled, creating a trench sub-grade depression hidden by the Bermuda grass.

Thatch, hidden depression and sanded turf.

The depression resulted in a trip and fall accident.  After the accident, several hidden turf depressions were “sanded” to fill  depressions to proper grade.

Not all landscape hazards are open and obvious.  Even a perfectly installed landscape may develop hazardous conditions if not regularly inspected and maintained.

Irrigation systems should be monitored, inspected, tested and adjusted monthly.  Turf should be trimmed around utility boxes and vaults regularly, aerated and de-thatched annually to maintain optimum performance and minimize grade changes.  Drainage structures should be grade adjusted, repaired or replaced when damaged.  Valve, electrical and junction boxes should be monitored for grade changes and adjusted as required.  Bark mulch thickness should be monitored and supplemented annually to maintain proper coverage and grade.

In summary, a properly installed landscape is composed of several systems and components that require regular ongoing maintenance for optimum performance, efficiency and safety.  Pro-active landscape maintenance may reduce potential hazards, resultant accidents and lawsuits.  These actions demonstrates an Owner’s recognition of protecting the health and safety of the public, pedestrians, friends and family who may visit and use the site and may prove useful in a legal action.