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HomeMy WebLinkAboutItem 8.2 - 1316 Citywide Tree Report Page 1 of 4 STAFF REPORT CITY COUNCIL DATE: February 21, 2017 TO: Honorable Mayor and City Councilmembers FROM: Christopher L. Foss, City Manager SUBJECT: Citywide Tree Report Prepared by: Dan Stevenson, Public Works Manager EXECUTIVE SUMMARY: The City Council will receive a report on the status of City trees within public facilities, parks, and streets. STAFF RECOMMENDATION: Receive the report and provide direction, if any. FINANCIAL IMPACT: None. DESCRIPTION: Background The City of Dublin currently owns and maintains 12,700 trees of which approximately 4,100 trees are in parks and 8,600 trees are in public streets. Trees provide many benefits to the community and are an important asset to the City of Dublin. The City’s tree inventory is currently valued at approximately $20,000,000. Trees improve quality of life by improving air and water quality, lowering heating and cooling costs, cleaning the air, producing oxygen, reducing storm water runoff, reducing traffic speeds, providing shade, and providing wildlife habit. Trees also increase property values, enhance the economic vitality of business areas, and beautify the community. The City of Dublin is recognized as a Tree City USA community by the Arbor Day Foundation. To be a Tree City USA, the City must meet certain requirements that include having a tree ordinance, maintaining a tree board, spending at least two dollars per capita on urban forestry, and observing Arbor Day. Tree City USA recognition indicates that the City of Dublin emphasizes robust tree maintenance and urban forest management programs. The City’s current tree maintenance program includes trimming trees approximately every five years, depending on the tree species and growth cycles. The current tree Page 2 of 4 maintenance budget is approximately $185,000 per year. The budget allows for tree trimming and emergency response and removal for tree hazards, but has not necessarily focused on the replacement and replanting of trees. Trees are typically removed only if there are extenuating circumstances or concerns with them such as a tree is dead, a structural deficiency exists, the tree indicates signs of illness or disease, proximity to something that could render it a hazard, etc. The City uses the services of a certified arborist to evaluate trees proposed or requested for removal. The arborist provides recommendations based on a site evaluation of the tree. Recent City tree maintenance placed emphasis on tree trimming and tree removal as necessary. Tree replacement and planting is the next potential step, which will remedy a number of missing trees that have accumulated over time. The City tree inventory and maintenance history is currently maintained in a detailed GIS database. The GIS database includes: each tree site location, s pecies, age (if known), approximate height and trunk diameter, approximate value, and maintenance history. The database also identifies sites as ‘vacant’ if no tree exists at the site. The database currently indicates 646 sites as being vacant and another 103 trees have been recommended for removal and replacement. Staff estimates that approximately 100 additional sites are vacant due to storm damage, structural damage, vehicle accidents, vandalism, etc. These additional sites are not yet reflected in the d atabase because the database is updated after the maintenance visits, which occur on a five - year cycle. All totaled, Staff estimates 850 trees would be necessary to replace and/or replant at this time. Drought Three years of the worst drought in California’s history had a detrimental effect on trees throughout the State as well as in the City of Dublin. In some cases, trees have simply perished as a result of drought stress, while many others are in a state of decline and may eventually die off. The U.S. Forest Service published that at least 66 million trees died throughout the Sierra Nevada mountain range from drought conditions in California between 2013 and 2016. It is estimated that municipalities in California can expect to lose 10% to 20% of urban forest tree inventory as a direct result of the recent devastating drought. The exact number of trees that Dublin has lost or will lose due to the drought is difficult to ascertain as trees can often take several years to die off. Staff is estimating that the City might expect as many as 10% (approximately 1,300) of the City’s tree inventory to perish as a direct result of the drought over the next 10 years based on available data, but the City of Dublin should expect less loss due to the fact that we irrigate most of our public landscaping with recycled water. No matter the final number of tree casualties due to the recent drought, funding for these replacements will be proposed in a future operating budget or CIP. The drought has also caused trees to experience high levels of stress and many have become severely weakened. Trees in a weakened state become more susceptible to the effects of pests and diseases. For example, Bradford Pear species trees were preferred throughout the region and were planted extensively in Dublin. However, a tree disease known as “fire blight” has recently spread throughout the region and has caused extensive damage to Bradford Pear tree species. Fire blight is a bacteriological disease that attacks tree blossoms in early spring and then moves up the twigs and branches through the tree’s system. The name “fire blight” comes from the scorched appearance of the infected leaves, stems, and bark. These areas may appear black, Page 3 of 4 shrunken, and cracked. Blossoms will turn brown, wilt, an d die about 1-2 weeks after an infection occurs. In many cases in Dublin, Bradford Pear variety trees are in need of removal and replacement due to their current condition and extended vulnerability. For example, 38 Bradford Pear trees that were severely i nfested with fire blight and dying were removed from Emerald Glen Park last summer. Public Works is monitoring the remaining Bradford Pear trees for signs of disease. Recycled Water Recycled (reclaimed) water use has been gaining in popularity. Recycled water infrastructure has been extensively expanded in recent years and most of Dublin’s irrigation systems have been converted to recycled water. While treated to a high standard, the treated wastewater does contain some residual total dissolved solids (TDS) and salinity (salt). Some tree species do not perform well when irrigated with recycled water. For example, redwood trees are particularly sensitive to the trace amount of salt content in recycled water. Landscaped areas converted to recycled water in our community have seen redwood trees die off or show significant signs of decline. As a result, redwood trees are no longer selected for planting in areas of Dublin that have recycled water or are planned to be converted to recycled water in the future. Tree Species Selection The City considers several factors when selecting tree species to plant in public right -of- ways and parks for success in an urban forest environment. These factors include: Safety Heartiness Growth patterns Root impact Variation Drought tolerance Recycled water tolerance Consistency with adopted plans Urban forest planning and tree selection palettes have evolved as communities have learned how trees have responded in an urban setting. Dublin has learned from its experience, and the experiences of other Bay Area communities, that certain tree species do not perform as well as intended and thus are no longer used. For example, liquid ambar and camphor trees have aggressive roots that often have a damaging impact on infrastructure such as sidewalks and curbs. As a result, these types of trees are no longer included for planting in planter strips or other small areas in Dublin. The City Streetscape Master Plan adopted by the Dublin City Council in 2005, and amended in 2009, includes existing street tree pallets and includes recommendations for changes or additions when new trees are planted. The Plan designates East -West corridors to be planted with trees to achieve strong, fall colors, and a statuesque large canopy of foliage. North-south corridors were designated to include delicate, flowering trees displaying spring colors. Public Works communicates regularly with the Planning Division to incorporate updates to the City’s design guidelines when Staff has experienced or observed tree species that may not be performing as intended. Design guidelines that include a current list of approved trees are provided to developers to integrate during the design process. Submitted development project plans are also Page 4 of 4 thoroughly reviewed prior to acceptance by City Planning Division staff to assure compliance and adherence to the approved tree species list. It also important to keep a diversified palette of tree species to avoid developing a “mono-culture” of trees throughout the City. A mono-culture develops when similar tree species are planted in large numbers in one general area. In instances where a disease develops or a new pest type is introduced that effect one particular tree species, then the entire City tree inventory could suffer adverse consequences and large volumes of trees could be compromised. Safety is always a concern when selecting tree species. Tree species that have proven weak and prone to structural failure are excluded from planting. Species such as eucalyptus grow so quickly that the structural strength can be compromised and they can be brittle. For this reason, the City currently does not plant any eucalyptus trees. The City also does not include in the tree palette trees that shed objects such as large seed pods or fruit that can be hazardous. Tree Replacement As noted earlier, Staff has identified the need to replant and/or replace approximately 850 trees in City parks (475) and streets (375). While costs vary by tree size/box and level of removal/repair, the overall average cost to replace a tree is approximately $300 per tree, including labor. At this time, regular tree maintenance and removal is included in the City’s annual operating budget. The City Council may be interested in replacing the 850 trees identified in the City’s tree inventory either at one time or over a period of time. Staff will evaluate the better of two options; creating a Capital Improvement Program (CIP) project or managing replacement through the operating budget. Staff will either bring back a separate item at a future City Council meeting or the City Council will see a proposal as part of the upcoming budget process. NOTICING REQUIREMENTS/PUBLIC OUTREACH: None. ATTACHMENTS: None.