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San Diego County Water Authority

Vic Bianes, PE - Engineering Manager

Tad Brierton, SR/WA - Right of Way Supervisor

APWA National Congress 2013

Chicago, IL

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• Background - San Diego County Water Authority

• ROW Encroachments

• Management of Trees• Policy Challenges

• Easement Language

• Tree species investigation

• Tree Root Study Findings

• Design and Construction Recommendations

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• Public Agency serving SD Region

• Whole Sale Provider of Water

• Provide service to 24 Member Agencies

• Own & Operate Pipelines up to 9 ft in Dia (2.7 Meters) & 6 to 8 Ft (1.8-2.4 Meters) in cover

• 5 major pipelines totaling approx. 300 miles

• Import 80% of our water4

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• Wholesale water agency created by State Legislature in 1944• 24 member water agencies• 36-member board of directors• Serves 3.1 million people and

region’s $186 billion economy

• Mission is to provide safe and reliable water supply to member agencies

• Service area• 950,000 acres • 97% of county’s population

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• Benign neglect toward new encroachmentsThree-fold result:1. Trespass of property rights

purchased and additional cost to resolve the encroachment

2. Interference with our ability to access our facilities and pipelines

3. Potential damage to pipelines and facilities

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• Progressively more proactive on prevention of new encroachments

• Adopted prioritization of old encroachments in ROW

• More interaction with Legal Department and governing board to resolve encroachments

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• Homes

• Pool and Spas

• Room Additions

• Retaining Walls

• Various structures

• Fences

• Trees

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K. Schroder

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• Landscaping with trees increase property value

• Trees reduce home heating and cooling costs

• Improve water quality resulting in less runoff and erosion. Recharge groundwater supply.

• Provide food and shelter for wildlife

• Absorb carbon dioxide and produce oxygen

• Add beauty and reduce stress10

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• Being a good neighbor and balancing the demands of the mission and the property owner

• Social/Political pressure to retain trees

• Limiting Risk & Liability to the agency

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• SDCWA Easement restrictions

• Excavation delays in the event of urgent repair

• Potential damage to the pipeline

• Costs to remove

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• Pipeline Easements - Prohibit use

• Excavation delays in the event of urgent repair impacting service restoration

• Potential damage to the pipeline

• Cost to remove

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Grantor CannotGrow Trees

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• Avocado, citrus and other similar fruit trees, so long as the trunks are no closer than five (5’) feet from the centerline of any authority pipeline.

• Shallow-rooted trees that grow no higher than twenty-five feet (25’) and have a mature root spread of no more than twenty feet (20’) may be permitted provided the trees are planted no closer than twenty-five (25’) from the closest edge of any of the authority’s pipelines.

• Deep-rooted trees are prohibited.

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PIPELINE

Source: California Polytechnic State University, Urban Forest Ecosystems Institute, NRES Department

• Easement language - Prohibit use

• Excavation delays in the event of urgent repair

• Potential damage to the pipeline

• Costs to remove

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• Pipeline Easements - Prohibit use

• Excavation delays in the event of urgent repair

• Potential damage to the pipeline

• Cost to remove

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• Search to find data on tree roots impacting water pipelines

• Internet research – IKT

• Collaboration with IKT and WA staff

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Since 1998:IKT-Research on Root Growth and Underground Pipes

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• Consulted an Arborist to understand tree roots

• Identified locations of various tree species over pipeline joints

• Initiated Tree Root Study

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Examples of Trees in the ROW

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Examples of Trees in the ROW

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Examples of Trees in the ROW

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Removal of Tree by Conventional Felling Methods

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Air Spading of Roots

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Water Blasting and Vacuum Excavation

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Excavator and Backhoe Excavation

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Pipeline Internal Inspection

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• Pine Tree

• Laurel Sumac Bush

• Eucalyptus Tree

• Pepper Tree

• Citrus Tree

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Pine Tree

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Laurel Sumac Bush

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Eucalyptus Tree

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Excavation Around Pipe

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Excavation Around Pipe

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Pepper Tree

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Excavation of Pipe

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Citrus Tree

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Excavation of Tree

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• WA Pipelines have minimum cover of 5 to 7-Feet

• Disturbed Soil of a pipe trench does act as a French Drain

• Majority of Trees Excavated have shallow roots around pipelines

• Trees do appear to go deeper when no surface irrigation and water draining into pipe trench

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• Pipelines under pressure with corrosion protected joints are not water sources

• Pipe Joints exposed did not show any sign of leakage or damage to coatings by tree roots

• Tree roots still pose a challenge during emergency repairs

• WA will continue to implement the tree management policy

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• Install slurry plugs at expansion joints to reduce migration of water in pipe zone

• Install filter fabric in pipe zone to stop migration of fines into gravel backfill, which removes the source of nutrients for tree roots

• Install subsoil drains to daylight at low points near blow offs and pump wells to remove excess water from pipe zone

• Use liquid soil (Slurry Cement Mix) $57

• SDCWA Easement restrictions

• Excavation delays in the event of urgent repair

• Potential damage to the pipeline

• Costs to remove

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• Time: Up to a day to remove large trees located near roads, structures, or utilities.

• Dollars: $500 to $3,500 per tree.

• Environmental Restrictions: Bird nesting season January through August. Nesting survey for removal during this period.

• Notification to owner and nearby residents.

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• Inventory

• Pipeline condition

• Tree factors

• Rank and Prioritize

• Implement Policy

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• Highest risk pipe

• Largest trees that are within a 25-foot distance from the edge of pipe and are a threat to fall onto homes, power lines, or other improvements if they are not removed with time consuming care.

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• Highest risk pipe +

• Other large trees within 25 feet of the edge of pipe that are holding up execution of an encroachment permit involving more serious encroachments than trees, and the owner agrees to cost-share in removal.

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• 2nd Lower Risk Pipe

• Largest trees that are within a 25-foot distance from the edge of pipe and are a threat to fall onto homes, power lines, or other improvements if they are not removed with time consuming care.

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Questions?

Reducing the Risk of Root-Intrusion into the Trench

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Bedding Material with a Minimized Pore Volume (Liquid Soil)