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| | {{alert|This page is an edit and testing page use by the wiki authors. It is not a content page for the Manual. Information on this page may not be accurate and should not be used as guidance in managing stormwater.|alert-danger}} | | {{alert|This page is an edit and testing page use by the wiki authors. It is not a content page for the Manual. Information on this page may not be accurate and should not be used as guidance in managing stormwater.|alert-danger}} |
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| − | [[Operation and maintenance (O&M) of tree trenches and tree boxes]] | + | [[Operation and maintenance (O&M) of green roofs]] |
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| − | [[File:Central corridor cross section B.jpg|thumb|300px|alt=schematic cross-section of Central Corridor Light Rail tree system|<font size=3>Cross section of the tree system installed for the Central Corridor Light Rail Transit project in St. Paul, MN. Image courtesy of the [http://www.capitolregionwd.org/ Capitol Region Watershed District].</font size>]]
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| − | [[File:Marquette avenue 5.jpg|thumb|300px|alt=photo of completed project, Marquette Avenue, Minneapolis|<font size=3>Completed tree system, Marquette and 2nd Avenue Busways project, Minneapolis, MN. Image Courtesy of The Kestrel Design Group.</font size>]]
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| − | {{alert|Trees can be an important tool for retention and detention of stormwater runoff. Trees provide additional benefits, including cleaner air, reduction of heat island effects, carbon sequestration, reduced noise pollution, reduced pavement maintenance needs, and cooler cars in shaded parking lots.|alert-success}}
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| − | This page provides guidance for operation and maintenance (O&M) of tree trenches and tree boxes. A tree trench is a <span title="Bioretention is a terrestrial-based (up-land as opposed to wetland) water quality and water quantity control process. Bioretention employs a simplistic, site-integrated design that provides opportunity for runoff infiltration, filtration, storage, and water uptake by vegetation. Bioretention areas are suitable stormwater treatment practices for all land uses, as long as the contributing drainage area is appropriate for the size of the facility. Common bioretention opportunities include landscaping islands, cul-de-sacs, parking lot margins, commercial setbacks, open space, rooftop drainage and street-scapes (i.e., between the curb and sidewalk). Bioretention, when designed with an underdrain and liner, is also a good design option for treating Potential stormwater hotspots. Bioretention is extremely versatile because of its ability to be incorporated into landscaped areas. The versatility of the practice also allows for bioretention areas to be frequently employed as stormwater retrofits."> '''bioretention practice'''</span> that contains one or more trees. Tree trenches and boxes may be designed as <span title="Infiltration Best Management Practices (BMPs) treat urban stormwater runoff as it flows through a filtering medium and into underlying soil, where it may eventually percolate into groundwater. The filtering media is typically coarse-textured and may contain organic material, as in the case of bioinfiltration BMPs."> [https://stormwater.pca.state.mn.us/index.php?title=Stormwater_infiltration_Best_Management_Practices '''infiltration''']</span> or <span title="Filtration Best Management Practices (BMPs) treat urban stormwater runoff as it flows through a filtering medium, such as sand or an organic material. They are generally used on small drainage areas (5 acres or less) and are primarily designed for pollutant removal. They are effective at removing total suspended solids (TSS), particulate phosphorus, metals, and most organics. They are less effective for soluble pollutants such as dissolved phosphorus, chloride, and nitrate."> [https://stormwater.pca.state.mn.us/index.php?title=Filtration '''filtration''']</span> (<span title="An underground drain or trench with openings through which the water may percolate from the soil or ground above">'''underdrained'''</span>) systems.
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| − | Supplemental information can be found on the page called [[Operation and maintenance of tree trenches and tree boxes - supplemental information]]. Supplemental information includes the following.
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| − | *Supplemental watering
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| − | *Pruning
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| − | *Staking and straightening
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| − | *Protecting the trunk
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| − | *Mulching
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| − | *Fertilizers
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| − | *Check tree safety
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| − | *Tree health troubleshooting guidelines
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| − | *References
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| − | ==Overview of typical O&M Issues==
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| − | In addition to runoff reduction and stormwater treatment, street trees and tree boxes provide a range of community benefits. Trees contribute to air pollution reduction, <span title="The process of capturing and storing atmospheric carbon dioxide.> '''carbon sequestration'''</span>, reduction in <span title="an urban area having higher average temperature than its rural surroundings owing to the greater absorption, retention, and generation of heat by its buildings, pavements, and human activities."> '''heat island'''</span> effect, habitat creation for wildlife, and can be used as tools for <span title="Adjustments in ecological, social, or economic systems in response to actual or expected climatic stimuli and their effects or impacts."> '''climate adaptation'''</span>. <span title="Green stormwater infrastructure (GSI) describes practices that use natural systems (or engineered systems that mimic or use natural processes) to capture, clean, and infiltrate stormwater; shade and cool surfaces and buildings; reduce flooding, create wildlife habitat; and provide other services that improve environmental quality and communities’ quality of life. (City of Tucson)"> '''Green stormwater infrastructure'''</span> (GSI) trees are often planted in highly visible areas and are subject to public interaction, vandalism, and winter <span title="Deicing typically refers to removal of salt from impervious surfaces, such as roads, driveways, parking lots, and sidewalks. Chemicals, most commonly sodium chloride, are often used for deicing."> '''deicing'''</span>, but trees typically remain resilient with proper maintenance.
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| − | O&M of tree trenches and boxes generally requires a low level of effort and expertise, and street trees can have life spans of up to 60 years ([https://www.chesapeakebay.net/documents/Urban_Tree_Canopy_EP_Report_WQGIT_approved_final.pdf Cappiella et al.], 2016). <span title="Green stormwater infrastructure is designed to mimic nature and capture rainwater where it falls. Green infrastructure reduces and treats stormwater at its source while while also providing multiple community benefits such as improvements in water quality, reduced flooding, habitat, carbon capture, etc."> '''Green infrastructure'''</span> managers do share common issues and concerns related to trees. The most common O&M concerns for tree trenches and tree boxes include
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| − | *general poor health,
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| − | *insufficient water for growth,
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| − | *accumulation of litter and debris in the inlet, and
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| − | *spent and lost mulch.
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| − | The sections below describe best practices to prevent or minimize these common problems.
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| − | ==Design phase O&M considerations==
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| − | Tree trenches and tree boxes have a small footprint and should be designed to treat a relatively small drainage area (0.25 acres or less per tree). Surface area of the tree trench or box and surface area to drainage area ratio are key design characteristics. Design specifications vary based on the selected filter <span title="Engineered media is a mixture of sand, fines (silt, clay), and organic matter utilized in stormwater practices, most frequently in bioretention practices. The media is typically designed to have a rapid infiltration rate, attenuate pollutants, and allow for plant growth."> [https://stormwater.pca.state.mn.us/index.php?title=Design_criteria_for_bioretention#Materials_specifications_-_filter_media '''media''']</span> and filter box manufacturer (most tree trench and box systems are proprietary practices). Properly <span title="Sizing refers to the physical dimensions of a stormwater treatment practice or device needed to meet a water quality or quantity goal. For example, stormwater BMPs may be sized to treat a volume of runoff, a flow rate, or to meet a pollutant removal target."> '''sizing'''</span> and designing the tree box will help prevent O&M issues. Designers should consider
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| − | *minimizing the surface area to drainage area ratio, based on the manufacturer guidelines;
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| − | *properly sizing the tree box or tree trench to manage an appropriate surface area based on local precipitation patterns;
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| − | *selecting regionally appropriately species that are tolerant to the soil and growth media (see [https://stormwater.pca.state.mn.us/index.php?title=Design_guidelines_for_tree_quality_and_planting_-_tree_trenches_and_tree_boxes Design Guidelines for Tree Quality and Planting]); and
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| − | *selecting species that will grow in the limited space provided by the filter box see ([https://stormwater.pca.state.mn.us/index.php?title=Design_guidelines_for_tree_quality_and_planting_-_tree_trenches_and_tree_boxes Design Guidelines for Tree Quality and Planting]).
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| − | Designers should also consider the maintenance schedules and tasks when locating tree trenches or tree boxes on their site. The small surface area of tree boxes makes them versatile. However, they should be placed within areas that are easily accessible to ensure proper maintenance. Maintenance of tree trenches and tree boxes does not require large or heavy equipment, but routine maintenance should be expected once or twice a year. Designers can incorporate solutions to facilitate the following maintenance activities.
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| − | *Incorporating multiple and easy access points
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| − | *Placement near supportive companion plants to prevent diseases
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| − | *Installing <span title="A well used to observe changes in groundwater levels or groundwater quality over a period of time."> '''observation wells'''</span>
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| − | *Specifying the optimized soil <span title="Engineered media is a mixture of sand, fines (silt, clay), and organic matter utilized in stormwater practices, most frequently in bioretention practices. The media is typically designed to have a rapid infiltration rate, attenuate pollutants, and allow for plant growth."> [https://stormwater.pca.state.mn.us/index.php?title=Design_criteria_for_bioretention#Materials_specifications_-_filter_media '''media''']</span> composition and depth to effectively trap or <span title="to remove or withdraw"> '''sequester'''</span> nutrients (phosphorus in particular), and that can also support the desired species
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| − | *Site-specific species selections that take into account sun exposure, shade, proximity to traffic corners (visibility issues), salt-tolerance, etc.
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| − | *Providing educational signage to increase public awareness.
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| − | *Installing measures like low fencing to prevent damage from pedestrian foot traffic
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| − | Designers should consult and include any local requirements regarding green infrastructure. O&M considerations often depend on whether the practice is located on public land, private land, or in the public right of way. For example, plantings in the public right of way that conflict with any traffic safety considerations could require increased O&M, such as pruning or complete removal.
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| − | The designer should also provide a site-specific O&M plan that includes the following.
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| − | *Construction inspection schedule and checklists
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| − | *Post-construction routine maintenance schedule and checklists
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| − | *Operating instructions for the practice (if applicable)
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| − | Additional information that should be included in O&M plans is described in the “Post-Construction Phase O&M Considerations” section. Example O&M plans are also provided further down.
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| − |
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| − | ==Construction Phase O&M Considerations==
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| − | Proper construction methods and sequencing play a significant role in reducing O&M problems. Some key items during the construction phase include:
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| − | #Before construction begins:
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| − | ##Ensure that the contributing drainage area is fully stabilized with vegetation prior to the beginning of construction. Also make sure that impervious areas in the contributing drainage area are clean. If this is not possible, use barriers or diversions to direct stormwater flows from the contributing drainage area away from the practice.
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| − | ##Install any needed erosion and sediment controls in your construction site and prepare a storm water pollution prevention plan (SWPPP).
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| − | ##Designate a stormwater supervisor to make sure someone is responsible for erosion and sediment control.
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| − | ##Hold a pre-construction meeting to review the construction plans and the sequencing of construction.Other agenda items could include discussing the status of the pre-construction drainage, erosion, and sediment controls; and reviewing or assign points of contacts for the stormwater and/or green infrastructure key personnel.
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| − | #During construction:
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| − | ##Construct any pre-treatment devices before installing any tree boxes or trenches. Depending on the site design and drainage pattern, this may not be necessary, but stormwater should be directed away from the boxes during the construction phase.
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| − | ##Ensure heavy equipment does not enter the footprint of the practice to avoid compaction of the infiltration medium.
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| − | ##Store any soil, mulch, or gravel media away from the practice footprint to avoid clogging the infiltration medium.
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| − | ##Inspect the practice during construction to ensure that the tree trenches or tree boxes are built in accordance with the approved design and standards and specifications. Use a detailed inspection checklists that include sign-offs by qualified individuals at critical stages of construction, to ensure that the contractor’s interpretation of the plan is acceptable to the professional designer. An example construction phase inspection checklist is provided below.
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| − | #After construction:
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| − | ##Verify that the tree trenches or tree boxes were built in accordance with the approved design and standards and specifications.
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| − | ##Verify that tree is staked and supported with guy wires to promote stable growth, if necessary.
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| − | ##Verify that the contributing drainage area is fully stabilized with vegetation prior to removing any barriers, diversions, or erosion and sediment control measures.
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| − | ##Verify that the practice actually captures and infiltrates runoff. Conduct a full inundation test to inspect the underdrain and outflow function.
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| − | ##Use a detailed inspection checklists that include sign-offs by qualified individuals at the completion of construction, to ensure that the contractor’s interpretation of the plan is acceptable to the professional designer. An example construction phase inspection checklist is provided below.
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| − | ==Post-Construction Phase O&M==
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| − | Post-construction maintenance is performed on tree trenches and tree boxes to maintain proper infiltration, filtration, and to promote healthy vegetation. Immediately after construction, short-term maintenance goals include efforts to establish and keep the tree healthy. Not all trees are guaranteed to survive the establishment phase, so care should be taken to inspect the health following construction. Important post-construction considerations are provided below.
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| − | *A site-specific Operations and Maintenance Plan should be prepared by the designer prior to putting the stormwater practice into operation. This plan should provide any operating procedures related to the practices. The plan should also provide clear maintenance expectations, activities, and schedules. Include photos if possible. Be clear about who is responsible for the maintenance and the type of expertise that will be needed for distinct O&M activities. The O&M plan should include an anticipated budget for O&M activities. The O&M plan should also include an example O&M inspection checklist and an example maintenance report. Example O&M plans are provided here.
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| − | *A legally binding and enforceable maintenance agreement should be executed between the practice owner and the local review authority. Example maintenance agreements are provided here.
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| − | *Inspection and maintenance activities are distinct and can be done as separate activities or together. Inspection will typically assess the practice for any O&M issues, whereas maintenance will address the O&M issues identified by the inspection. A dedicated inspection effort on a large number of BMPs can help prioritize maintenance activities.
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| − | *Maintenance activities should be careful not to cause compaction. No vehicles or stockpiling should be allowed within the footprint of the practice. Foot traffic should be kept to a minimum.
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| − | *BMP areas generally should not be used as dedicated snow storage areas.
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| − | {{:Overview and schedule of general maintenance activities for tree trenches and tree boxes}}
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| − | {{:Common problems and how to troubleshoot them for tree trenches and tree boxes}}
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| − |
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| − | ==Maintenance Costs==
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| − | Maintenance costs will vary on a number of factors, including but not limited to:
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| − | *Size of the practice and its contributing drainage area
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| − | *Type of plantings used
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| − | *Site visit frequency
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| − | *Level of maintenance needed
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| − | *Local weather conditions
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| − | *Staffing needs (number of staff, external vs. internal staff, etc)
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| − | *Travel time between sites
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| − | *Efficiencies of scale (single GI vs. a cluster of GI)
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| − | *Equipment needed
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| − | Maintenance costs for trees and tree boxes should be relatively low compared to other green infrastructure practices, partially due to its size. Routine maintenance can take as little as 30 minutes per unit and does not require any special training, tools, or machinery. Because routine maintenance does not require any specialized training, the range of annual maintenance cost is around $100-$500 (CRWA). A study published in 2017 by ASCE describes the annual maintenance cost for a tree planter to be $260 per year, based on 2015 data from Fort Collins, CO (Clary, 2017).
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| − | ==Useful Resources==
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| − | Additional Detailed O&M Information
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| − | *More detailed information regarding specific maintenance activities are provided here: https://docs.google.com/document/d/1nIz8g947JdefxTxUPv_JKAP-_tecrUUPeuv5p1XXhZA/edit?usp=sharing. Topics discussed include:
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| − | **Supplemental Watering
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| − | **Pruning
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| − | **Staking and Straightening
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| − | **Protecting the Trunk
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| − | **Mulching
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| − | **Fertilizers
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| − | **Checking Tree Safety
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| − | **Tree Health and Troubleshooting Guidelines
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| − | **References
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| − | ==Case Studies==
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| − | *Application of Stormwater Tree Trenches in the City of Vancouver, 2018 – https://sustain.ubc.ca/sites/default/files/2018-52%20Application%20of%20Stormwater%20Tree%20Trenches%20in%20the%20City%20of%20Vancouver_Vega.pdf
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| − | *https://stormwater.pca.state.mn.us/index.php?title=Case_studies_for_tree_trenches_and_tree_boxes
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| − | ==Maintenance Training Documents and Videos==
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| − | *International Society of Arboriculture – Tree Risk Assessment Qualification: https://www.isa-arbor.com/Credentials/ISA-Tree-Risk-Assessment-Qualification
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| − | *Tree Care Industry Association (TCIA) – ANSI A300 Tree Care Standards: https://www.tcia.org/TCIA/Build_Your_Business/A300_Standards/A300_Standards.aspx
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| − | *Shade Tree Maintenance: https://youtu.be/8emNNf3QyWA
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| − | *Tree planting aftercare: https://extension.psu.edu/planting-aftercare-webinar-essential-to-tree-establishment-and-survival
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| − | [[Example O&M Plans, Checklists, Reports, and Maintenance Agreements for tree trenches and tree boxes]]
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| − |
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| − | ==References==
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| − | *Cappiella, Karen, Sally Claggett, Keith Cline, Michael Galving, Peter MacDonagh, Jessica Sanders, Thomas Whitlow, and Qingfu Xiao. 2016. [https://www.chesapeakebay.net/documents/Urban_Tree_Canopy_EP_Report_WQGIT_approved_final.pdf Recommendation of the Expert Panel to Define BMP Effectiveness for Urban Tree Canopy Expansion].
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| − | *Charles River Watershed Association (CRWA). 2008. [https://www.crwa.org/uploads/1/2/6/7/126781580/crwa_tree_pit.pdf Stormwater Tree Pit Low Impact Best Management Practice (BMP) Information Sheet].
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| − | *Clary, J., Piza, H. 2017. [https://owl.cwp.org/mdocs-posts/cost-of-maintaining-green-infrastructure/ Cost of Maintaining Green Infrastructure]. American Society of Civil Engineers (ASCE), Reston, VA.
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| − | <!--
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| − | '''Street sweeping quiz'''
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| − | #In areas with high tree canopy cover (e.g. 30% or more), which sweeping regime is likely to work best for reducing phosphorus loads?
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| − | ##Monthly
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| − | ##Bi-weekly
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| − | ##Bi-weekly to monthly in summer, weekly in fall
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| − | ##Weekly in fall
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| − | #Which of these is not a concern with mechanical broom sweepers?
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| − | ##They grind up organic material, thus increasing the surface area of the material, which leads to increased phosphorus loss
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| − | ##They cannot remove material from cracks
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| − | ##They are ineffective at capturing fine sediment
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| − | ##They are ineffective at capturing coarse sediment
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| − | #True or false: Street sweeping debris must be landfilled
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| − | #If you were planning a street sweeping program for your city, which of these would be least important?
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| − | ##Mapping areas that do not have curbs
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| − | ##Ensuring my drivers are trained and certified
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| − | ##Identifying watersheds with phosphorus or sediment impairments
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| − | ##Implementing parking restrictions when streets are swept
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| − | #True or false: For a medium to large city with mechanical broom sweepers and multiple impaired waters, it is cost effective to upgrade to regenerative air sweepers
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| − | #True or false: Very few cities sweep in late winter or early spring because there is little water quality benefit.
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| − | Answers
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| − | #(c)
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| − | #(d) [https://stormwater.pca.state.mn.us/index.php?title=Recommended_street_sweeping_practices_for_water_quality_purposes#Street_sweeping_equipment Read more here]
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| − | #False. It can be reused in areas where human contact is limited (e.g. don't use in residential areas, playgrounds, athletic fields, etc.)
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| − | #(a) While the presence or absence of curbs is important, if drivers are properly trained they will know how to sweep correctly in uncurbed areas, thus eliminating the need to map these areas
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| − | #True [https://stormwater.pca.state.mn.us/index.php?title=Recommended_street_sweeping_practices_for_water_quality_purposes#Cost_considerations Read more here]
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| − | #False. Late winter runoff contributes significant amounts of sediment, phosphorus, and salt. Winter sweeping is generally avoided for logistical reasons. Newer, regenerative sweepers can be used year-round.
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| − | <!--[[Operation and Maintenance of Bioretention and Other Stormwater Infiltration Practices-->
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