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31 BMPs to Conserve Wooded Areas at the Subdivision Level BMPs TO CONSERVE WOODED AREAS AT THE SUBDIVISION LEVEL Audience This section is primarily directed toward: •local units of government, •landowners and developers, •builders and utility companies, and •community and citizen organizations. Overview The development of a subdivision is always affected by state and federal laws, local comprehensive plans and regulations, zoning and subdivision ordinances, codes and policies, and housing market demand. All people involved in subdivision development should recognize the need and reasons to protect wooded areas and other natural areas, while complying with regulations. City planners, landown- ers, developers, and builders play a major role in subdivi- sion development by planning and creating development plans in conformance with municipal, township, and county zoning and subdivision ordinances and by oversee- ing development. However, landowners, developers, builders, local units of government, and homeowners may have different agendas (Figure 10, page 32).

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Page 1: Conserving Wooded Areas in Developing Communties · Obtain aerial photography Aerial photography can provide fast knowledge of existing resources and adjacent areas. Agencies that

31BMPs to Conserve Wooded Areasat the Subdivision Level

BMPs TO CONSERVE WOODEDAREAS AT THE SUBDIVISION LEVEL

AudienceThis section is primarily directed toward:

•local units of government,•landowners and developers,•builders and utility companies, and•community and citizen organizations.

OverviewThe development of a subdivision is always affected bystate and federal laws, local comprehensive plans andregulations, zoning and subdivision ordinances, codes andpolicies, and housing market demand. All people involvedin subdivision development should recognize the need andreasons to protect wooded areas and other natural areas,while complying with regulations. City planners, landown-ers, developers, and builders play a major role in subdivi-sion development by planning and creating developmentplans in conformance with municipal, township, andcounty zoning and subdivision ordinances and by oversee-ing development. However, landowners, developers,builders, local units of government, and homeowners mayhave different agendas (Figure 10, page 32).

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32 BMPs to Conserve Wooded Areasat the Subdivision Level

Recommended practicesProtecting wooded areas and other plant communitiesmust begin with a plan. “A planning process begins whenthe decision to develop the land is made and finishes whenthe completed development is occupied” (Watson andNeely, 1995).

■ Define goals

Defining goals is the first step to consider in land devel-opment. The goals should include:

•conservation of green corridors,

•conservation of wooded areas as natural open space orconservancy area, and

•protection of individual trees.

Neighborhoods, homeowners• affordable price• attractive and pleasant place

to live and work• maintain biological diversity

Landowners,developers, builders

• observe zoning codes• meet market demand• maintain desirable appearance

Local units of government• fulfill development needs• control lot density• provide tax revenue• protect the environment

Figure 10. People involved in subdivision development may havedifferent priorities.

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33BMPs to Conserve Wooded Areasat the Subdivision Level

■ Inventory and assess resource

Resource inventory and assessment is an important stepin protecting wooded areas and meeting the goals. Theobjective is to create a comprehensive resource map forthe subdivision. This map will be the main document touse when making decisions.

A resource inventory and assessment for a subdivisioncan be achieved in three steps:

•evaluate existing resource information,

•conduct site review and survey trees, and

•create a comprehensive resource map for the subdivi-sion.

◆Evaluate existing resource information

A number of local and regional units of governmentcollect information on the status of natural resources.This information is useful in planning at the subdivi-sion level. Landowners and developers may takeadvantage of this information including topographicmaps, aerial photography, and information on water-sheds, wetlands, historic land uses, proposedgreenways, soils, septic system suitability, areas occu-pied by rare plant and animal species, conservationeasements, and protected wooded areas (see Appendix1, page 91). Local zoning and tree preservation ordi-nances may also provide some information andguidelines.

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34 BMPs to Conserve Wooded Areasat the Subdivision Level

◆Conduct site review and survey trees

A site review and tree survey are the physical examina-tion of the resources within the subdivision andadjacent land. They include:

• identification and location of wooded areas andother natural resources, and

• delineation of potential wooded areas to protect.

A site review and tree survey must be perfo rmed by anatural re so urce pro fe s s io nal such as a fo rester, arbo ris t,o r landscape architect.

✴Obtain aerial photography

Aerial photography can provide fast knowledge ofexisting resources and adjacent areas. Agencies thatprovide aerial photography (prints or services)include the Metropolitan Council, U.S. GeologicalSurvey, or DNR (see Appendix 1, page 91).

✴Identify and locate wooded areas and other landtypes

After identifying wooded areas using aerial photogra-phy, it is necessary to physically locate the woodedareas, measure them, profile trees by species and sizedistribution, determine cover types, and draw cover-type boundaries on the subdivision map using anappropriate scale. For definitions of specific cover

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35BMPs to Conserve Wooded Areasat the Subdivision Level

types use references such as Tester, J., 1995; Wovcha,D. S., B. C. Delaney, and G. E. Nordquist, 1995;Minnesota Department of Natural Resources, 1993.

Sampling techniques can be used to profile trees onwooded areas larger than 10 acres and a completeinventory of trees on wooded areas of less than 10acres. When profiling trees, highlight wooded areasand trees with historical, cultural, or biologicalsignificance. Identify wooded areas that have beenlocated or designated for protection by units ofgovernment, landowners, and/or community organi-zations, and record them on the subdivision map.Pay particular attention to younger stands of treesand trees that are suited to the site condition. Con-tact the Minnesota DNR’s Division of Fish andWildlife, Section of Ecological Services (CountyBiological Survey) to obtain information on thestatus and distribution of flora, fauna, and naturalcommunities, and the State Historic PreservationOffice to obtain other information.

Other land types, including wetlands, farmlands, andland classified as potential natural areas for rareplant and animal species, should be located, identi-fied, and recorded on the comprehensive resourcemap.

✴Delineate potential wooded areas to protect

The initial evaluation of natural resources shouldnote areas of priority for protection and conserva-tion. These areas may include:

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36 BMPs to Conserve Wooded Areasat the Subdivision Level

•wooded areas protected or identified by local, state,and federal laws; policies and/or regulations, suchas wetlands, and designated greenways and naturalareas,

•wooded flood plains, wooded stream corridors,steep wooded slopes, and buffer zones. These areashave important ecological functions for waterquality and wildlife habitat, and

•remnant tracts of wooded areas at least one acre insize with healthy trees.

Remnant tracts of wooded areas may have aestheticvalues and provide recreation for surroundingneighborhoods. They may offer ecological benefits,including carbon sequestration; screening andprivacy; wildlife attraction for resting, nesting,feeding, and breeding; and energy conservation andprotection against drifting snow. All of these func-tions may have direct impact on property values andquality of life.

A site review and tree survey may have significant financialcost. The DNR provides a number of financial assistanceprograms to organizations and individuals to do resourceinventory and assessment and to reach their conservationand natural resource stewardship goals. Landowners anddevelopers may be able to receive assistance for sometypes of projects. A directory of financial assistance isavailable to identify existing financial assistance programsadministered by the DNR (see Appendix 2, page 97).

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37BMPs to Conserve Wooded Areasat the Subdivision Level

◆Create a comprehensive resource mapof the subdivision

The ultimate purpose of the resource assessment andinventory is to create a comprehensive resource mapfor the subdivision. This map constitutes the basic toolfrom which to make all decisions related to the devel-opment, including the type of the development design,location of permanent structures (buildings, roads, andutilities), and location of temporary facilities such asoffices, parking lots, equipment maintenance space,and rights of way. Record on the map pertinent infor-mation including location of wooded areas and treesby outlining their canopy or tree line, wetlands andother type of land cover, planned unit development(roads and buildings), and preserved areas. A develop-ment map from North Oaks is a good example of asubdivision resource map (Figure 11, page 38). Anotherexample from Robert Engstrom Companies shows aseries of five comprehensive steps or maps to developthe final development plan for a subdivision. The stepsor maps include site analysis, existing vegetation/woodlands, planned unit development/housing area,first development plan, and final development plan(Appendix 4 d, page 109).

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38 BMPs to Conserve Wooded Areasat the Subdivision Level

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39BMPs to Conserve Wooded Areasat the Subdivision Level

■ Create a wooded area protection plan

Develop a protection plan for wooded areas based on informa-tion provided on the subdivision comprehensive resource map.The protection plan should include:

•selection and delineation of the wooded areas to be protected,and

•selection of the protection method.

A succes s ful pro tectio n plan to co nserve wo o ded areas ina sub divis io n wo uld set aside at least 50 percent to 70percent o f the to tal wo o ded area in fo rm o f natural o penspace , green co rrido rs , o r co nservancy area. A number o flo cal develo pe rs and b uilders have achieved thes e go als(e .g., develo pment plans fro m No rth Oaks and SettlerRidge). If the subdivis io n is no t co vered with wo o dedareas, an alternative plan, including refo restatio n, may beinitiated. Other techniques , including tree transplanting,can be used to save tree s .

◆Select and delineate wooded areas to protect

To achieve a successful wooded area protection plan,consider the following steps:

✴Record location of wooded areas to be protected

Select wooded areas to be protected based on thegoals and information provided on the comprehen-sive resource map. Record these areas on the com-prehensive resource map with a distinctive pattern.

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40 BMPs to Conserve Wooded Areasat the Subdivision Level

✴Record all areas likely to be adversely im-pacted during construction

Wooded areas located on potentially sensitive sites such aswetlands and steep slopes may need additional protection.Identify and mark these areas as natural amenities to thedevelopment plan.

✴Record areas that can be used for reforesta-t ionand/or restoration

These areas may be located on natural drainage orsensitive sites.

✴Locate and delineate developable and buildable sites

Locate areas for development to meet subdivisiondensity requirements, road sites, and other ease-ments (sewer, water, communication and electricallines, septic system, storm water, etc.). It is necessaryto draw a few alternative sketches of concept plansbefore making a final decision. Alternative conceptplans (Figure 12) may include the lot size, location,and distribution; road and transportation systems; utilitysystems, designs, and location; and location of areas to begraded (also see Appendix 4 d, page 109).

◆Submit the development plan for approval

When submitting the final development plan, the developerand the county, city, or township planner should review theplan together.

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41BMPs to Conserve Wooded Areasat the Subdivision Level

Figure 12. Drawing different alternative development plansfor the subdivision provides the opportunity to look at allpossible options and optimize the land use and conservationeffort.

Conservation or Open-space Development (c, d,e )

Conservation Village

Limited Development

(c)

(e)

(b)

(a)

fpo

fpo

Farmstead/Subdivision

fpo

ConventionalDevelopment(Cookie-cutter Approach)

Mixed ResidentialDevelop-ment (d)fpo

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42 BMPs to Conserve Wooded Areasat the Subdivision Level

■ Select a protection method

Once the development plan is approved, the developer and/orbuilder should select the protection method that consists ofseveral steps:

•Determine the protected root zone.

•Mark the protected root zone.

•Identify the grading area and method.

•Create the reforestation plan and method.

•Identify trees to be transplanted.

◆Determine the protected root zone

The protected root zone (PRZ) is defined as optimumspace needed for a group of trees or an individual tree toretain good health and vigor. The larger or wider thiszone is the better for the trees’ health and vigor. Thiszone should be protected and off limits to all constructionactivities, including driving and parking vehicles, storingmaterials, and soil excavation, to minimize site disturbanceand physical damage to trees during construction. Itshould be determined and protected before constructionbegins. A number of methods including the dripline,minimum area, site occupancy, and trunk diametermethods have been developed to determine the protectedroot zone. These methods are described in the lot-levelsection of this guidebook (see page 51). Each method has

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43BMPs to Conserve Wooded Areasat the Subdivision Level

its own merit to provide adequate protection area. How-ever, the dripline m ethod is widely recommended andused to protect mature individual trees, groups of trees, orwooded areas. The minimum area method can be usedto protect small mature individual trees, groups of trees,or wooded areas. The m inim um area m ethod can besed to protect small and young trees. On larger develop-ment sites, a construction danger zone up to 30 feetwide between the construction area and the protectedroot zone is necessary to minimize construction damageto trees (Figure13).

Figure 13. Determining the construction danger zone betweenthe protective fence and the building site assists with final siteand building design and selection of equipment to be used.Note that the tree protective fence is placed in front to preventaccess and disturbance to the protected root zone.

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44 BMPs to Conserve Wooded Areasat the Subdivision Level

◆Mark the protected root zone

Once the protected root zone has been determined, theprotection method becomes a straightforward process.It consists of marking the protected area and puttingup highly visible ribbon or fencing and signs to enclosethe entire area (Figure 14). This area should be off limitsto all construction activities including parking vehicles,storing materials, and soil excavation.

If the protected areas are located on a down slope of theconstruction site or near wetlands, it is important to install acombination fence—a silt fence to prevent runoff andsediment, and a visual fence for enclosure (Figure 15).

Figure 14. Highly visible ribbon identifies protectedwooded areas and trees.

FPO

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45BMPs to Conserve Wooded Areasat the Subdivision Level

◆Determine the grading area and method

Before construction begins, evaluate the site to determinethe area that needs grading and also the percentage ofgrading needed. When filling or cutting grades near theprotected root zone, build the retaining walls beforegrading begins to prevent runoff into the protected rootzone, stabilize the slope, and prevent soil erosion. Customgrading is recommended and encouraged because itimpacts a smaller area and saves more trees than massgrading (see individual lot level, page 51).

Figure 15. A combination of visual fences and silt fencesprevent access to the protected root zone and constructiondamage to trees as well as runoff.

FPO

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46 BMPs to Conserve Wooded Areasat the Subdivision Level

◆Define reforestation plan and method

On a site with few or no trees, a reforestation plan may beinitiated with well-defined goals. Goals for reforestation mayinclude the establishment of energy conservation trees, aliving snow fence, a wildlife planting, windbreaks, orboulevard trees. A reforestation plan consists of selecting themost suitable tree species and planting design to meet theintended goals. Since the timing and design of the planting areimportant, the reforestation plan should be done by a naturalresource professional.

◆Record trees to be transplanted and the site

Some trees in the construction zone and on building sites canbe transplanted to a different location. This conservationmethod can be cost effective and provide immediate func-tional and aesthetic benefits. However, tree transplanting is ahighly specialized activity that needs to be done by a knowl-edgeable and experienced person. A number of tools isavailable to transplant trees. These tools may include abackhoe, tree spade, and crane. Understanding the biologicallimitations of each tree species to tolerate disturbance and thetiming are critical for a successful transplantation. A system-atic tree care program, including irrigation and fertilization, isnecessary after transplanting. When possible, transplant treestwo to four years before construction begins.

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47BMPs to Conserve Wooded Areasat the Subdivision Level

■ Monitor and evaluate the conservation plan

A successful conservation plan requires the participation andcommitment of all parties involved in the development project.Before the project begins, communicate the tree conservationgoals and methods to all participants, including landowners,developers, builders, contractors, and utility companies. Theplan monitoring and evaluation should include education, siteinspection, and financial penalties.

◆Educate

Plan implementation should begin with education about thegoals and tree protection measures. All people involved in theproject should know about the tree protection goal andmethod. They should be informed about the protected rootzone and the purpose of protective fences and signs. Contracts(including those with subcontractors) should explicitly statethat any disturbance in the protected root zone (includinghuman or machine activity, storage of material, and soilexcavation) violates the contract and that specified penaltieswill be applied. A provision binding the contractor to thesurvival of protected trees up to five years from the datethe construction was completed should be written into thecontract.

◆Site inspection

Monitor the program as the project proceeds. Themonitoring program may include frequent visits to the siteby the landowner, local unit of government, or citizenorganization to check for violations of the tree protection

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48 BMPs to Conserve Wooded Areasat the Subdivision Level

plan. Project managers, including the supervisor, superin-tendent, crew leader, or an outside consultant may beassigned this task.

◆Financial penalty

The penalty may be monetary or replacement of trees. TheMinneso ta Supplement to the Guide fo r Plant Appraisalwith Regio nal Tree Appraisal Facto rs can be used as aguide defining the financial penalty (Minnesota Society ofArboriculture, 1996).

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49BMPs to Conserve Wooded Areasat the Subdivision Level

Check list� Define goals

� Inventory and assess resource (subdivision scale)

� Evaluate existing resource information

� Conduct site review and survey trees

� Obtain aerial photography

� Identify and locate wooded areas and other landtypes

� Delineate potential wooded areas to protect

� Create a comprehensive resource map of the subdivision

� Create a wooded area protection plan

� Select and delineate wooded areas to protect

� Record location of wooded areas to be protected

� Record all areas likely to be adversely impactedduring construction

� Record areas that can be used for reforestationand/or restoration

� Locate and delineate developable and buildablesites

� Submit the development plan for approval

� Select a protection method

� Determine the protected root zone

� Mark the protected root zone

� Determine the grading area and method

� Define reforestation plan and method

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50 BMPs to Conserve Wooded Areasat the Subdivision Level

� Record trees to be transplanted and site

� Monitor and evaluate the conservation plan

� Educate

� Site inspection

� Financial penalty