How To Preserve Trees

Transcription

1 San Diego County Water Authority Vic Bianes, PE - Engineering Manager Tad Brierton, SR/WA - Right of Way Supervisor APWA National Congress 2013 Chicago, IL 2 1

2 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 3 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 ( Meters) in cover 5 major pipelines totaling approx. 300 miles Import 80% of our water 4 2

3 Wholesale water agency created by State Legislature in 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 5 Benign neglect toward new encroachments Three-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 6 3

4 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 7 Homes Pool and Spas Room Additions Retaining Walls Various structures Fences Trees 8 4

5 K. Schroder 9 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 stress 10 5

6 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 11 SDCWA Easement restrictions Excavation delays in the event of urgent repair Potential damage to the pipeline Costs to remove 12 6

7 Pipeline Easements - Prohibit use Excavation delays in the event of urgent repair impacting service restoration Potential damage to the pipeline Cost to remove 13 Grantor Cannot Grow Trees 14 7

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9 17 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. 18 9

10 PIPELINE Source: California Polytechnic State University, Urban Forest Ecosystems Institute, NRES Department 19 Easement language - Prohibit use Excavation delays in the event of urgent repair Potential damage to the pipeline Costs to remove 20 10

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12 Pipeline Easements - Prohibit use Excavation delays in the event of urgent repair Potential damage to the pipeline Cost to remove

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16 Search to find data on tree roots impacting water pipelines Internet research IKT Collaboration with IKT and WA staff

17 Since 1998: IKT-Research on Root Growth and Underground Pipes 33 Consulted an Arborist to understand tree roots Identified locations of various tree species over pipeline joints Initiated Tree Root Study 34 17

18 Examples of Trees in the ROW 35 Examples of Trees in the ROW 36 18

19 Examples of Trees in the ROW

20 39 Removal of Tree by Conventional Felling Methods 40 20

21 Air Spading of Roots 41 Water Blasting and Vacuum Excavation 42 21

22 Excavator and Backhoe Excavation 43 Pipeline Internal Inspection 44 22

23 Pine Tree Laurel Sumac Bush Eucalyptus Tree Pepper Tree Citrus Tree 45 Pine Tree 46 23

24 Laurel Sumac Bush 47 Eucalyptus Tree 48 24

25 Excavation Around Pipe 49 Excavation Around Pipe 50 25

26 Pepper Tree 51 Excavation of Pipe 52 26

27 Citrus Tree 53 Excavation of Tree 54 27

28 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 55 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 56 28

29 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 58 29

30 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. 59 Inventory Pipeline condition Tree factors Rank and Prioritize Implement Policy 60 30

31 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. 61 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

32 2 nd 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

33 Questions? 65 Reducing the Risk of Root- Intrusion into the Trench 66 33

34 Bedding Material with a Minimized Pore Volume (Liquid Soil) 67 34