Street Tree Issues or Pavement Issues

Street trees serve many purposes in an urban environment. They improve the environmental quality; economic, physical and social health of the community and foster civic pride.
The City’s street system is a major engine in the local economy. Its service and performance can shape our local economic growth. For decades we have been in the cycle of build, rehabilitate and rebuild. With shrinking budgets and more demands from users, management must pay more attention to pavement preservation.
Street trees and street systems provide many benefits to the city and there are areas where they conflict with each other. This report discusses the issues and some of the options for improving pavement preservation and maintaining a vibrant urban forest. Realistically, conflicts will always be present to some degree. Tolerations of conflicts are necessary if street trees and vehicles are going to exist with us. The resolution of conflicts through management practices can enhance the benefits and reduce the negatives.
What Is a Street Tree Easement?
“Street tree easement" refers to the twelve (12) or eight (8) foot zone behind the sidewalk or curb if no sidewalk exists used for street trees. "Street tree" means any tree planted and/or maintained by the city, or recorded as a street tree, adjacent to a street or within a right-of-way or within the street tree easement.
Typically, street trees are located between the sidewalk and the curb. If a tree is located in an easement on the resident’s side of the sidewalk, a measurement is made by City staff to determine if it is within the City’s planting easement. If the tree is within the easement, the city would plant and maintain trees by scheduling an appointment with the property owner. If the tree is outside the City’s easement, it would be the property owner’s responsibility to maintain.
“Right-of-Way” refers to a public way dedicated to the public for the intended use.
“Public Utility” refers to a public utility (Investor Owned, Municipally Owned) that is generally a company or agency that provides and sells electricity, water, gas, telephone, cable TV, sewer or natural gas to homes and businesses.
ESTABLISHING CONTEXT
The primary purpose of road right-of-way is for public travel. The city that owns the right-of-way has some responsibility to see that utilities are installed in a way that minimizes traffic safety issues and does not unnecessarily hinder travel on the right-of-way. In addition these local governments own and maintain the street improvements such as pavement, curb, drainage structures and sidewalks. It is important that damage to these facilities is minimized and, when they are damaged, that they are repaired properly to obtain the maximum service life.
It is important to recognize the difference between utility easements and right-of-way. Wisconsin State Statutes gives the city authority over the right-of-way. The definition of right-of-way in this statute does not include “easements obtained by utilities or private easements in platted subdivisions or tracts.”
Most cities utility easements are dedicated when a subdivision plat is filed for a new development. The cities usually think of these utility easements as public utility easements, of which they have jurisdiction. However, the jurisdiction over the easement may be dependent on the exact wording on the subdivision plat.
Because Lake Mills’ utilities are under the street pavement, settlement can result in and around utility trenches causing uneven pavement surfaces, driver annoyance, and further maintenance. The utilities are located under the pavement because of design requirements and to avoid conflicts with street trees planted in the portion of the right of way between the sidewalk and curb. To reduce pavement maintenance costs and maintain a vibrant urban forest – many communities use street tree easements. This option allows utilities to locate on the terrace and the city can still provide an urban forest.
Utility construction under pavements and utility repair cuts made in completed pavement sections for electric, water and wastewater utilities, and drainage pipes under roadways are one of the main factors in pavement performance. Utility installations and repairs disturb the original base course and subgrade soils below the pavement. Once the utility is installed or repaired and in place, the utility trench is backfilled and surfaced with a pavement.
Utility installation and repairs under the pavement affect the performance of the existing pavement, as settlement and/or heave occurs in the backfill materials of the restoration. If the backfill materials used are not suitable for the site conditions and not properly installed, the materials will begin to settle relative to the original pavement. Utility installation and repairs have the greatest damaging impact on newly paved streets and therefore reduce roadway life considerably (Department of Public Works 1998). Longitudinal trenches made between the sidewalk and curb will reduce settlement and heaving issues. There will still be transverse trenches in the right of way – but they will be reduced by approximately fifty percent (50%).
Tree roots can also cause infrastructure damage such as sidewalk, sewer and pavement damage. Instances of pipes being broken by the growth of roots are rare, but blockage of damaged pipes is not uncommon. As roots enlarge, they may occasionally break the pipes and enter the cracks. More commonly, the pipes fail (especially at the joints) due to age or slight movement of the soil, allowing roots to invade. Moisture and nutrients released from ruptures can stimulate root growth toward the break in the pipe. Once a root enters a sewer pipe, the conditions of aeration, moisture, and nutrients are quite favorable for rapid growth. Species that are naturally found in wet areas such as poplars, willows, and silver maples, are commonly associated with clogged pipes. Blocked sewers usually must be cleared mechanically. Mechanical routing may be needed on an annual basis. Registered chemical treatments are available. The main advantage of these products is that they can be placed into the sewer as foam for more effective contact with roots; however, it is essential to follow label directions. The only permanent solution to the problem, however, is to replace ruptured pipes. Modern materials and joints should prevent most problems in the future.
If trees are too close to pavement, or if compacted soil forces large roots to grow very near the soil surface, roots can eventually lift pavement. When roots encounter a paved area, the only entry is often a gap between the soil and pavement. Future problems can be prevented at the time of planting by using smaller plants, providing a minimum distance of 4 feet between the tree and the pavement, or using mechanical barriers to prevent roots from growing under the pavement. Remedies for lifted pavements around mature trees often involve either moving the pavement away from the tree or pruning off the problem roots. Barriers are often installed after the roots are cut to prevent re-growth of the roots and recurrence of the pavement lifting. Cutting off the problem roots often causes stress and instability. Trees without sufficient root support can be blown over more easily in a storm.
Trees are also a large contributor to stormwater phosphate loading, flooding and yard waste materials. The most common and asked for solution to tree/infrastructure damage is the removal of a tree. Trees are a valuable community asset and provide many benefits, which include shading our streets and homes, blocking and screening winter winds thus lowering heating costs, raising property values, filtering pollutants and neighborhood beatification. Many tree benefits are taken for granted and their loss is often not felt until the tree has been removed.
The best approach to improving pavement preservation is preventing street tree/utility line conflicts from arising in the first place. Where practical, new utility lines should be constructed to avoid potential conflicts with pavement. Location and selection of appropriately sized trees prior to planting is critical to the trees’ successful co-existence with utility lines. This option is available to anyone involved with landscape design and installation - city planners, landscape designers and contractors, arborists, and private homeowners. Proper selection and planting of trees near utility lines can improve the appearance of the landscape, prevent safety hazards, improve utility service reliability, and reduce maintenance expenses for utility companies.
Taking the time to actually consider whether the community would be better served with one option or the other is a strong step forward. Obviously, costs aren’t the only issues that drive government decisions – but at least we have evaluated the options and intelligently set our standards.
ALTERNATIVES
Alternative 1 – No change. The City continue as it currently does with locating water, sewer and stormwater utilities under the pavement and electric utilities in rear yard easements.
Alternative 2 – Adopt a policy that requires the dedication of street tree easements and change city standard specifications to allow for the location of utilities in the terrace.
Alternative 3 – Adopt a policy that changes city standard specifications to allow for the location of utilities in backyard easements.
Alternative 4 – Adopt a policy that stops requiring the planting of street trees and change city standard specifications to allow for the location of utilities in the terrace.
Alternative 5 – Council develops their own procedure or utilizes combination of proposed alternatives.
Project the Outcomes
Alternative #1. No change. The City currently locates water, sewer and stormwater utilities under the pavement and electric utilities in rear yard easements.
The vast majority of Wisconsin communities locate their utilities under the pavement. The depth of facility placement required because of frost, narrow right of ways and the extensive use of asphalt pavement may be the reason for this standard.
Alternative #2. Adopt a policy that requires the dedication of street tree easements and change city standard specifications to allow for the location of longitudinal utilities in the terrace.
Today, we must consider better ways to manage our pavements that are cost effective and meet the increasing demands from the public. Placing the utilities in the terrace can provide longer lasting pavements, higher serviceability levels, and decreased maintenance costs.
The lifecycle difference between urban pavements and rural pavements can be attributed to the presence of buried utilities, the confined work space associated with installing and servicing utility appurtenances, pavement design (geometry) and traffic loading. Many utility cuts are made and many appurtenances (manholes, valve chambers and other “iron works”) are placed in urban and semi urban roads by utility companies.
Poor performance of pavements over and around utility trenches on local streets often causes unnecessary maintenance problems due to improper backfill placement (e.g., undercompacted, too wet, too dry). The cost of repairing pavements as a result of poorly performing utility installations and repairs can be reduced with an understanding of proper material selection and construction practices. Current utility installations and repairs practices vary widely across Wisconsin, which results in a range of maintenance problems.
A study in New York City showed that utility locations accounted for more than 85 percent of pavement defects. The result of this study was a recommendation to strictly enforced quality control requirements for pavement utility cuts and a first-class system for coordinating installation of underground utilities with roadway resurfacing programs. The latter will help prevent poor communication that can sometimes result in tearing up a road that one crew resurfaced in July for another crew to make utility improvements in August. A Canadian study indicates that road lifecycles are reduced by more than 30% by underground utilities.
The use of street tree easements allows for the selection of larger trees which is consistently preferred in surveys. Street trees are generally selected to fit into small terraces or under overhead utilities. Front yard tree easements generally have fewer restrictions based on roadway design, chemical tolerance and utility placement. Larger trees provide more shade to cool pavement and houses; they create a more enclosed feeling; have more visual impact; assist in traffic claming and increase property values.
Alternative #3. Adopt a policy that changes city standard specifications to allow for the location of utilities in backyard easements.
Today, we must consider better ways to manage our pavements in a cost effective manner and meet the increasing demands from the public. Placing the utilities in the terrace can provide longer lasting pavements, higher serviceability levels, and increase system performance.
This option eliminates issues with pavement and street trees. However, property owners have a tendency to clutter easements with personal facilities that significantly reduce ease of access; digging in backyards generates lots of mud and there is a bigger chance of utility damage from private digging with locates.
Alternative #4. Adopt a policy that stops requiring the planting of street trees and change city standard specifications to allow for the location of utilities in the terrace.
Although we must consider better ways to manage our pavements, it shouldn’t eliminate the option of having an urban forest. Again, tolerating the negative aspects of utilities and street trees allows us enjoy a larger range of benefits from these features of our community.
Street trees can be safety problems; damage pavement, sidewalks and curbs; interfere with overhead and underground utilities; and obscure signage.
Alternative #5. Council develops their own procedure or utilizes combination of proposed alternatives.
This memo was prepared in two days and was not the most significant issue that was being dealt with at the time. There are going to be issues that haven’t been researched and I’m sure that I haven’t even thought of all the possible outcomes at this time.
CONSEQUENCES
Ever since the first underground utilities were conceived the designers and planners of these facilities struggled with thought of where should we put these things. The simplest solution was the most direct route between point A and point B, a straight line. Our forefathers in utility planning had no idea what demands would be placed on public streets by growth in the underground utility industry.
The application of this change would have minimal and slow affect on the existing street trees and utilities of the city. The process would involve new subdivisions and site plans. There are currently no new subdivisions or site plans that this would affect. The process would not be applied to existing areas unless there were area restrictions based on facility design and right of way width.
Managing trees in an easement on private property sounds like a difficult proposition, however, most people consider the terrace their property and the forester works with the residents just like the tree was on there property. The end result is that there would be no substantial change to the method of managing street trees.
The cost of repairing utility lines would be reduced substantially. Leaking valve boxes, mains and corporations now require asphalt cuts, removal, careful backfill selection and compaction, and asphalt patching. Leaking, plugged or damaged sanitary sewers and storm sewers require the same type of costly repairs. The terrace only needs to meet landscaping requirements.
National, utilities are generally located as follows:
Mainline sewers were generally located in the center of the right-of-way.
High maintenance utilities such as gas mains and water mains were generally located outside the roadway pavements. If they need to be in the roadway area they are located in the curb lane. This is probably to limit the impact on vehicular traffic.
Transmission facilities that are not usually tapped and require a higher degree of protection and are therefore designed to be deeper than distribution facilities.
Street drainage intake structures are located in the roadway immediately adjoin the curb.
Street lighting and traffic control facilities are generally located in the sidewalk area immediately behind the road curb of improved streets. In unimproved streets they are generally further away from the road pavement.
Underground telephone, electric, and cable are generally located near the right-of-way line. If they need to be in the roadway area they are located in the curb lane.
This is probably to limit the impact on vehicular traffic.
A “clear zone” is defined by the American Association of State Highway and Transportation Officials’ (AASHTO) Roadside Design Guide as the total roadside border area, starting at the edge of the traveled way, available for safe use by errant vehicles. The clear zone aids designers of road or street projects so that rigid items within the clear zone, such as bridge rails, are required to have breakaway features or be protected by guardrail. The AASHTO A Policy on Geometric Design of Highways and Streets (Green Book) enumerates a clear zone value for two functional classes of highways. For local roads and streets, a minimum clear zone of 7 to 10 feet is considered desirable on sections without curb. A 10-foot minimum clear zone is recommended on collectors without curbs. The general discussion on Cross-Section Elements also indicates that a clear zone of 10 feet should be provided for low-speed rural collectors and rural local roads.
Errant vehicles routinely travel outside the clear zone, so it is always a good policy to locate rigid objects as far away from the road as possible. The Federal Highway Administration (FHWA) policy is that utility facilities should be located as close to the right-of-way line as feasible. The Green Book, AASHTO Highway Safety Design and Operations Guide, 1997 (Yellow Book) and the AASHTO A Guide for Accommodating
Utilities within Highway Right-of-way, state that utilities should be located as close to the right-of-way line as feasible. The Yellow Book, recognizing that crashes are over-represented on urban arterials and collectors, says this means as far as practical behind the face of outer curbs; and where feasible, behind the sidewalks. Local agencies should insist that utilities be placed as close as possible to the right-of-way line to enhance safety and to reduce conflicts with maintenance operations. Fire hydrants are a special feature that have a place in the clear zone and are discussed in a subsequent section.
CONCLUSION
In city streets the right-of-way is usually narrow and the utility corridor is effectively from the edge of the road to the right-of-way line. The city should consider establishing utility corridors where practical.
There is limited room within the right-of-way for all the utility companies, and no utility should occupy more room than necessary. On occasion a utility company will need to upgrade their line to increase capacity or replace an obsolete line. In this case the old line should be abandoned when the new line is placed into service. Some agencies have required the old line to be removed. This is an expensive process that should be discussed with the utility on a case-by-case basis.
The Board may want to propose that facilities should be located to the satisfaction of the City. This would mean that to enhance traffic safety the City would adopt the maximum clear zone available within the existing right-of-way, all utilities should be located as close as possible to the right-of-way line. On relocations for construction projects on the side of the road where a power pole line is planned, the parallel installation of buried utilities shall not be closer than 4 feet to the right-of-way line; at locations for above-ground facilities, the line would deflect to the right-of-way line so the above-ground facility could be placed at the right-of-way line. In subdivisions with platted utility easements, the facilities should be located in the utility easement if room is available. To allow room for all utilities, lines owned by the same utility company will not be allowed on both sides of the road, so if a line is upgraded the old line will have to be abandoned.