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1. Purpose And Intent: The purpose of this section is to establish requirements for the design, installation and maintenance of landscapes that contribute ecologically and aesthetically to the growth and economic prosperity of the City; that achieve healthy, attractive and safe environments according to recognized design and urban forestry principles; that encourage water conservation; storm water integration; and that conserve, protect and promote the natural identity and environment of the City.
2. Landscaping:
A. Landscaping Plan:
(1) Landscape Plan Preparation: All landscape plans shall be prepared by an architect, landscape architect, landscape designer working as a professional in this field or qualified nurseryman.
(2) Applicability: A landscape plan is required for all commercial, industrial, office, substandard lot, and multi- family developments, alterations and additions to buildings or parking lots, or changes in use. The landscape plan may be required as part of an application for a Design Review, Conditional Use, Variance, Zoning Certificate or Certificate of Appropriateness.
(3) Adopted Streetscape Plans: Where streetscape standards have been adopted by the City of Boise for the streets bordering a project site, and there is a difference between the adopted streetscape standards and the requirements of this section, the adopted streetscape standards shall govern the streetscape elements of the project.
(4) Uses/Buildings:
(a) New Development: All new developments shall provide landscaping in accordance with the requirements of this section.
(b) Expansions And Alterations To Existing Buildings: The requirements of this section shall apply to the expansion and alteration of existing buildings when the project increases 50 percent or more in gross square footage.
(c) Change Of Use: The requirements of this section shall not be imposed unless one or more of the following circumstances apply:
i. An expansion or alteration to the building/lot is being proposed as per Subsection (b) or (c) above; or
ii. The property never complied (or no longer complies) with the ordinance requirements in existence at the time of approval or conditions of approval at the time of construction.
(5) Existing Parking Lots:
(a) Re-striping or Re-surfacing: Replace and repair the existing landscaping to previous approval standards.
(b) 0 - 25 Percent Expansion or Replacement of the Parking Lot: Replace and repair the existing landscaping to previous approval standards.
(c) 26 - 50 Percent Expansion or Replacement of the Parking Lot: Replace and repair the existing landscaping to previous approval standards and provide perimeter landscaping.
(d) 51 - 100 Percent Expansion or Replacement of the Parking Lot: Comply with all requirements of this section.
(6) Waivers: If the location of existing buildings or other structures prevents conformance with the requirements of Sections 11-07-05.2.A(4) and/or 11-07-05.2.A(5), or its implementation would create non-conformity of parking standards or other special circumstances, the Planning Director may grant a waiver based on the following findings:
(b) That granting a waiver will not have a detrimental effect on adjacent properties; and
(c) That granting a waiver will not be in conflict with past approvals that required landscape improvements. A letter requesting a waiver and reasons therefore, shall be submitted at the time of application. Decisions of the Planning Director may be appealed to the Planning and Zoning Commission within 10 calendar days from the date of the decision in accordance with Chapter 3 of this Code.
(7) Alternative Compliance:
(a) Purpose: To provide for alternative means to meet the intended purposes of the landscape requirements when explicit compliance is not feasible or the alternative means are superior to what is required.
(b) Process:
i. General: The applicant shall request alternative compliance in conjunction with the submittal of a Conditional Use Permit or Design Review application or upon the determination that the development does not comply with the specific provisions of this title. The request will be considered by the same approval body as the base application. The request shall specify:
A. The specific requirements that are proposed to be modified;
B. The reasons for the modification; and
C. A demonstration of how the alternative means for compliance meets the requirements' intended purpose.
ii. Stormwater Swales: Stormwater swales within front setbacks can be approved at staff level provided that the landscape plans approved by the applicable approval body are not changed substantially and comply with Section 11-07-05.2.G(2). A landscape plan with swale construction details which incorporate the landscape design shall be submitted for the staff level review.
(c) Standard: The proposed alternative means for compliance with the specific requirements shall demonstrate that the alternative provides an equal or superior means of meeting the intent and purpose of the regulation.
(d) Required Findings: In order to grant approval for an alternative compliance, the director shall determine the following:
i. Strict adherence or application of the requirements is not feasible because one of the following conditions exist:
A. Topography, soil, vegetation, or other site conditions are such that full compliance is impossible or impractical;
B. The site involves space limitations or an unusually shaped lot;
C. Safety considerations;
D. Other regulatory agencies or departments having jurisdiction are requiring design standards that conflict with the requirements of this section;
E. The proposed design includes innovative design features based on "new urbanism," "neotraditional design," or other site designs that promote walkable and mixed use neighborhoods; or
F. Environmental quality benefits;
ii. The alternative compliance provides an equal or superior means for meeting the requirements; and
iii. The alternative means will not be detrimental to the public welfare or adversely affect the uses and character of surrounding properties.
B. Minimum Design Standards And Requirements:
(1) Approved Plant Material:
(a) The publication titled Tree Selection Guide by the Community Forestry Unit of the Boise Parks & Recreation Department (latest edition) is hereby adopted as the list of approved and recommended trees for on-site planting.
(b) The Stormwater Plant Materials Resource Guide published by the Boise City Public Works Department is recommended for plant selection, establishment and maintenance for storm water facilities.
(c) New plant varieties are being produced every year and other species not listed in the above publications or species which are more disease resistant, pest resistant, or drought tolerant may also be considered.
(2) Prohibited Plant Material: The plants listed under "Trees not permitted for Rights-of-Way Property Planting" in the Tree Selection Guide are prohibited from being planted along any street or within any parking lot regulated by this section.
(3) Minimum Plant Sizes:
(4) Tree Species Mix: When five or more trees are to be planted to meet the requirements of any portion of this section, a mix of species shall be provided as per the table below:
(5) Tree Spacing: For design flexibility, trees may be grouped together or spaced evenly as desired. However, trees shall be spaced no closer than 80 percent of the average mature width of the trees, as demonstrated in the following examples:
(6) Mulch: Organic mulch such as bark or soil aid shall be applied to all planting areas, except that rock mulch may be permitted as part of the approved landscape plan. Planting areas utilizing rock mulch shall have 50 percent of the ground surface covered by vegetation at plant maturity. Natural colors shall be used and patterning of the materials is prohibited. Use of mulch as the only ground cover in required planting areas is prohibited. Impermeable plastic weed barrier under the mulch is prohibited.
(7) Curbing: All planting areas that border driveways, parking lots and other vehicle use areas shall be protected by curbing, wheel stops or other protective devices. Such devices shall be a minimum of 30 inches from all tree trunks to prevent cars from damaging tree trunks.
(8) Utilities: The following standards apply to the planting of trees near existing utilities and to trenching for new utilities near existing trees:
(a) Overhead Utilities: Only approved Class I trees in the Tree Selection Guide may be planted under or within ten lateral feet of any overhead utility wires.
(b) Underground Utilities: All trees shall be planted outside of any utility easement, unless written approval is obtained from the applicable agency. All trees shall be planted outside of any easement that contains a City sewer main, unless written approval is obtained from the City Engineer. If any utility easement precludes trees required by this section, the width of the required buffer shall be increased to accommodate the required trees.
(c) Trenching: New underground utilities shall be located outside of the dripline of existing trees if trenched, or be tunneled a minimum of three feet below existing grade within the tree's dripline. The guiding principle is that no root two inches or larger shall be cut. Note: This requirement is for placement of new utilities and does not affect the City's or the Utility's ability to access existing utilities for repair, replacement and maintenance.
(9) Berms: Berm slopes shall not exceed 3:1 (horizontal:vertical). Slopes shall not exceed 4:1 on areas which require mowing.
(10) Water Efficiency: The landscape plan shall provide for water efficient landscaping as follows:
(a) Lawn Areas: Where appropriate and on sites where other landscape options can be incorporated, large expanses of mown lawn, such as Kentucky Bluegrass, are discouraged due to its high water consumption. Lawn should not be treated as a fill-in material but rather as a functional or aesthetic element of the landscape. Mown lawn should not be used in median strips, parking strips, or other difficult areas to irrigate less than six feet in width. Areas of lawn larger than 15,000 square feet shall have soil moisture sensors that are properly installed and adjusted.
(b) Plant Selection And Location: Plants should be placed based on adaptability to regional and micro climatic conditions, i.e., shade, sun, wind, etc. Plants having similar water needs should be grouped together in distinct hydrazones, and spaced to minimize watering needs while maximizing growth and spread of plants. The use of native and other low-water-use plants is encouraged.
C. Irrigation:
(1) Irrigation Required: All landscape areas requiring irrigation shall be served with an automatic underground irrigation system. Areas of landscaping which will not require supplemental watering after initial establishment are not required to have permanent irrigation.
(2) Irrigation Water: Use of non-potable irrigation water is required when determined to be available and adequate. Year round water availability is also required by connecting to potable water or an on-site well as a secondary source.
D. Perimeter Buffers:
(1) Street Buffers:
(a) Applicability: Landscape street buffers shall be required for all multi-family residential, office, commercial and industrial developments. Street buffers shall not be required in the C-5 (Central Business) zone in circumstances where a landscape buffer would prevent the placement of a proposed building at the allowed zero foot front or street side setbacks. For single family subdivisions, buffers shall be as required by Chapter 11-09, Subdivision Standards.
(b) Size And Location: Landscape buffer widths along streets shall be based on the required setbacks of the underlying zone. All required buffers shall be located outside any street right-of-way and shall be maintained by the property owner. All street buffers shall be measured from the property line (after dedication of any right-of-way) and not from the sidewalk or curb. Subdivisions shall comply with Chapter 11-09, Subdivision Standards.
(c) Street Trees: All required landscape street buffers shall be planted with trees and shrubs, lawn or other vegetative groundcover, with a minimum density of one tree per 40 lineal feet. If this calculation results in a fraction of .5 or greater, round up to an additional tree. Class I trees are discouraged within street buffers except where justified. Clustering is allowed, however, trees shall be spaced no closer than 80 percent of the average mature width of the trees.
(d) Conifers Along Streets: Coniferous trees are allowed along streets only within planting areas 20 feet or greater in width.
(e) Tree Wells: Tree wells shall be a minimum of 36 square feet in size.
(f) Parkways & Detached Sidewalks: Parkway widths shall be six feet for Class II trees with ACHD approved root barriers, eight feet for Class II trees without root barriers, and ten feet for Class I and III trees as measured from the inside of the sidewalk to the inside of the curb.
(2) Side And Rear Perimeter Buffers:
(a) Applicability: Side and rear landscape buffers shall be required for all residential, office, commercial and industrial developments. For single family subdivisions, buffers shall be as required by Chapter 11-09, Subdivision Standards.
(b) Size And Location: Landscape buffer widths shall be based on the required setbacks of the underlying zone. Single family residential subdivisions shall comply with Chapter 11-09, Subdivision Standards. All required side and rear buffers shall be located within the property and shall be maintained by the property owner.
(c) Parking Lot/Vehicular Use Area Buffers: If an interior side or rear lot line is adjacent to a parking lot or other vehicular use area, such as, but not limited to, vehicle sales areas, truck and bus parking areas and driveways the following standards shall apply.
i. Landscaping: The perimeter landscape strip shall be planted with one tree per 40 lineal feet. If this calculation results in a fraction of .5 or greater, round up to an additional tree. Species shall be selected from the Boise City Tree Selection Guide. Clustering is allowed, however, trees shall be spaced no closer than 80 percent of the average mature width of the trees.
ii. Exceptions: Where two properties have a shared access and parking agreement that has been approved by the city, the above requirements may be waived.
(3) Buffers Between Different Land Uses:
(a) Applicability: Land use buffers shall be required along contiguous property lines between residential uses and dissimilar uses such as industrial, commercial, and office. The buffers are required along the entire contiguous property line. This section shall not apply to mixed use projects on contiguous properties.
(b) Size: The minimum buffer width between land uses is based on the required setbacks of the underlying zone.
(c) Buffer Materials: The materials within the required buffer between incompatible land uses are regulated as follows:
i. Mix Of Materials: All buffer areas shall be comprised of, but not limited to, a mix of evergreen and deciduous trees, shrubs, lawn, or other vegetative groundcover. Fences, walls and berms may also be incorporated into the buffer area.
ii. Barrier Effectiveness: The required buffer area shall result in an effective barrier within five years of installation and be maintained such that 60 percent or more of the vertical surface is closed and prevents the passage of vision through it. Clustering is allowed, however, trees shall be spaced no closer than 80 percent of the average mature width of the trees.
iii. Buffer Walls: Where existing or proposed adjacent land uses cannot be adequately buffered with plant material(s), the City may require inclusion of a wall, fence, or other type of screen that mitigates noise and/or unsightly uses. If a wall or fence at least six feet tall is provided, the planting requirement may be reduced to at least one tree per 40 lineal feet, plus shrubs, lawn, or other vegetative groundcover, in lieu of the requirements of subsection (b). Clustering is allowed, however, trees shall be spaced no closer than 80 percent of the average mature width of the trees.
iv. Chain-Link Fencing: Chain-link fencing does not qualify as a screening material; therefore the buffer must still be landscaped as per subsection (b), even if a chain-link fence is provided.
v. Pedestrian Access: Landscaping and screens shall not eliminate pedestrian access between commercial and residential districts.
E. Parking Lots (Interior): Interior parking lot landscaping shall be required in any parking lot with 12 spaces or more, including vehicle sales lots.
(1) Planter Size: Landscape planters shall be a minimum of 8 feet in width for Class I & II trees and ten feet in width for Class III trees. Required parking lot planters shall be the length of the adjacent parking space. Dimensions are measured inside curbs.
(2) Parking Lot Layout: No linear grouping of parking spaces shall exceed ten in a row, without an internal planter island. Interior landscaping shall be used to delineate and guide major traffic movement within the parking area. Terminal planters shall be provided at the ends of rows of parking to protect parked vehicles and confine moving traffic to aisles and driveways. Interior landscape planters shall be spaced as evenly as feasible to reduce the visual impact of long rows of parked cars.
(3) Trees Required: Each interior planter that serves a single row of parking spaces shall be landscaped with at least one tree and shall be covered with low shrubs or other vegetative groundcover. Each interior planter that serves a double row of parking spaces shall have at least two trees and shall be covered with low shrubs or other vegetative groundcover. Deciduous shade trees must be pruned to a minimum height of eight feet above the adjacent parking areas. Evergreen trees are prohibited in interior planters.
(4) Lights Prohibited: Light poles and fixtures shall be located outside of landscape planters which contain trees as required by this section.
(5) Industrial Exclusion: Industrial parking, storage, and loading areas are specifically excluded from the interior landscape requirements, but shall meet all perimeter and right of way landscape and screening requirements.
F. Preservation Of Existing Trees:
(1) Landscape Plan: All existing trees four inch caliper and greater shall be shown on the landscape plan. Indicate whether each tree is to be retained or removed and include an assessment by an approved Arborist of the health of the trees. Include on the plan a description of how existing trees to be retained are to be protected during construction.
(2) Protection During Construction: Existing trees that are retained shall be protected from damage to bark, branches, and roots during construction. Protection fences around existing trees are required for the duration of construction.
(3) Construction Within The Dripline Of Existing Trees: Specific requirements for construction within the dripline of existing trees are as follows:
(a) Paving: Impervious surfaces may be allowed at a distance from the trunk of a retained tree equal to the diameter of the tree trunk plus five feet.
(b) Grade Changes: Grade changes are discouraged within the dripline of existing trees and are subject to recommendation by the City Forester or an approved Arborist.
(c) Utilities: New underground utilities to be placed within the dripline of existing trees shall be installed as per Subsection 11-07-05.2.B(8)(c) of this section.
(4) Mitigation Trees: Healthy desirable trees four inch caliper or greater that are removed shall be replaced with an equal replacement of the total caliper inches lost either on site or off-site per recommendation of the City Forester. Example: two 10-inch caliper trees removed may be mitigated with four 5-inch caliper trees, five 4-inch caliper trees, or seven 3-inch caliper trees.
(5) Required Landscaping: Existing trees that are retained or relocated on site may count toward the required landscaping.
(6) Incentives: The Planning Director may allow up to a ten percent reduction of the required parking spaces to save healthy desirable trees.
G. Stormwater Integration:
(1) Purpose: The City encourages the incorporation of vegetated, well-designed stormwater filtration swales into landscape areas where topography and hydrologic features allow. Such integrated site designs can improve water quality and provide a natural, effective form of flood and water pollution control. Landscape areas which incorporate stormwater swales shall generally be above and beyond the landscaping required by this section.
(2) Design Guidelines: Below are requirements for designing a landscape area that integrate stormwater facilities. The Planning & Zoning and Public Works Departments should be involved in the initial design and determining the appropriateness of any site. Additional information regarding stormwater system design is provided in the publications titled Boise Stormwater Design Manual and Stormwater Plant Materials Resource Guide, which are available from Boise City Public Works.
(a) Street Buffers: Except in industrial areas, swales shall not be located in required landscape buffers along streets. However, swales located along streets within required landscape buffers may be approved through the Alternative Compliance process at staff level provided that the landscape plans are not changed substantially from the previous approval and comply with this section. Swales located within street buffers shall meet the following standards:
i. Swales shall not exceed twelve inches in storage depth;
ii. Swales shall be separated from back of sidewalk by a minimum of two feet;
iii. Street trees shall be provided as required by this section;
iv. Rapid sand infiltration windows shall be integrated for timely drainage of stormwater; and
v. No infiltration basins are allowed.
(b) Perimeter Buffers: Swales located within required buffers in side and rear yards shall meet the following standards:
i. Swales shall not exceed 18 inches in storage depth;
ii. Trees shall be provided as required by this section; and
iii. Rapid sand infiltration windows shall be integrated for timely drainage of stormwater.
(c) Gravel, rock, or cobble on the surface of swales shall not exceed 20 percent of the surface area of the bottom of the swale. Cobble may be incorporated into required landscape areas if designed as a dry creek bed or other design feature.
(d) Stormwater swales shall be vegetated with appropriate plant materials. Plant materials shall be a species that are able to withstand the anticipated changes in soil wetness and moisture levels. Examples of appropriate plants materials include, but are not limited to:
i. Trees: River Birch (Betula nigra), American Hornbeam (Carpinus caroliniana), Green Ash (Fraxinus pennsylvanica), Sweetgum (Liquidambar styraciflua), Sycamore (Platanus occidentalis) and Mountain Alder (Alnus tenuifolia).
ii. Shrubs: Red Osier Dogwood (Cornus sericea), Serviceberry (Amelanchier alnifolia), Rhododendrons (Rhododendron sp.), American Cranberry Bush (Viburnum trilobum), Golden Currant (Ribes aureum) and Drummond Willow (Salix drummondiana).
iii. Groundcovers: Sedges (Carex sp.), Spike Rush (Eleocharus acicularis), Maiden Grass (Miscanthus sp.), and Fountain Grass (Pennisetum sp.).
(e) Organic mulch shall not be used adjacent to the flow path. Plant material shall be installed adjacent to the flow path and infiltration area to aid in capturing sediment and reducing clogging.
(f) Open water ponds and holding areas with a permanent water level are not permitted in required landscape or buffer areas, except along Interstate-84. However, ponds that are aesthetically designed with special grading and vegetative features may be approved as provided for through Alternative Compliance.
(g) Slopes shall not exceed 3:1 (horizontal:vertical).
H. Arterial And Collector Street Buffering: Landscaped buffer areas shall be provided where single family residential lots are adjacent to collector or arterial streets.
(1) Perimeter Landscape Buffer:
(a) The buffer shall be located outside of any planned future right-of-way.
(b) The width of the buffer along arterial streets shall be a minimum of 30 feet. Along collector streets it shall be a minimum of 20 feet.
(c) The buffer area may be located within the lot provided that:
i. The depth of the lot is a minimum of 130 feet; and
ii. In cases where the side lot line runs along an arterial or collector, the width of the lot is a minimum of 80 feet.
(d) Fences and walls shall not be placed in buffer areas.
(2) Frontage Road:
(a) Frontage roads, as permitted by the ACHD, and separated from a collector or arterial street by a ten foot wide landscaped median, may be permitted.
(b) The landscaped median shall be planted with trees and shrubs that at maturity will form a solid screen at least six feet high and a continuous tree canopy.
I. Installation:
(1) Certificate Of Completion: Before issuance of the final certificate of occupancy, the author of the landscape plan shall submit to the City certification that the landscaping has been installed in compliance with the approved plans.
(2) Installation Schedule: All required landscaping, irrigation systems and site features shall be installed according to the approved landscape plan prior to issuance of a final certificate of occupancy.
(3) Extension Of Time For Installation: Upon recommendation of the director, a temporary certificate of occupancy may be issued for a specified time period, not to exceed 180 days when:
(a) Due to weather or other circumstances, the landscaping or other required site amenities cannot be completed; and
(b) The applicant has provided surety to the City for the required improvements.
J. Landscape Maintenance:
(1) Applicability: The requirement for landscape maintenance applies in all districts where landscaping has been required.
(2) Standards:
(a) The property owner is responsible for the maintenance of all landscaping and screening devices required by this section.
(b) Topping any street tree required by this section is prohibited. For trees not within street right-of-way, alternative pruning techniques to achieve specific horticultural or aesthetic effects may be used if approved by Boise City Forestry. Examples include pleached allee, pleached bosque, espalier, and pollarded canopy.
(c) Tree grates shall be widened to accommodate the growing tree trunk and prevent girdling of any trees planted in tree wells within sidewalks or other public right of way.
(d) Plant materials that exhibit evidence of insect pests, disease, and/or damage shall be appropriately treated to correct the problem. Dead plant materials shall be replaced.
(e) All landscaping required by this subsection may be subject to periodic inspections by City officials to determine compliance or to investigate.
3. Fences:
A. General Provisions:
(1) In historic districts, a Certificate of Appropriateness is required for fences made with any material other than dog-eared cedar.
(2) Electric fences are prohibited.
(3) Barbed wire is permitted in commercial and industrial zones only as the top section of a security fence. Barbed wire must be located at least 72 inches above grade.
(4) Walls, lattices, and screens shall be considered to be fences.
(5) Boxes, sheet metal, old or decayed wood, broken masonry blocks, or other unsightly materials may not be used for fencing.
B. Allowed Fences:
(1) In residential and office districts maximum fence heights are as follows:
(a) Solid fences to a height of 36 inches or open- vision fences to height of 48 inches may be built within the front yard setback. Fences to a height of 72 inches may be built outside the front yard setback and along the rear and side property lines.
(b) Fences, walls, or plantings on or within the clear vision triangle shall be limited to 36 inches in height.
(c) Multiple fences, railings, and/or privacy screens within setbacks must be separated by a minimum distance of five-feet in order to be considered separate.
(2) Any variance from the above requirements shall be considered per Section 11-03-04.14, Variance.
(3) If a fence is to be erected upon and within public right-of-way, approval must also be obtained from the ACHD.
(4) In commercial districts, concrete and masonry walls of any height and fences over seven feet tall must also be approved by the Building Department.
(5) The property owner installing the fence must locate the fence entirely on their property or within an easement unless agreements are made with the adjoining property owners.
(6) All fences shall be maintained and kept structurally sound so as to not endanger life, property or become a nuisance.
(7) One ornamental gate/entryway in a front or street side setback may be allowed to exceed the fence height limits, provided the gate/entryway and does not exceed eight feet in height by six feet in width, and is not located within a clear vision triangle.
(8) Fences adjacent to micro-paths shall comply with Section 11-07-04.5.D(3).
4. Retaining Walls: The following shall apply to retaining walls located within setbacks:
(1) Individual retaining walls may not exceed three feet in height when located within a front setback or clear vision triangle. Individual retaining walls may not exceed six feet in height when located within any other setback. The height of retaining walls shall be measured from the finished grade adjacent to the exterior wall. (See Section 11-012-03/Definition of Grade). Attached fences, retaining walls, railings and privacy screens shall also be included in the total height.
(2) Walls must be separated by a minimum distance of five feet in order to be considered as separate walls.
(3) Multiple walls with a combined height that exceeds the height allowed in the setback may be approved through the Category II Hillside permit process when in compliance with the following conditions:
(a) The additional height is necessary and appropriate because of the size, configuration, topography, or other unique characteristics of the property;
(b) The Director and City Engineer have jointly determined that the height, location, and grading for the walls are the minimum necessary for reasonable development of the property;
(c) The additional height will not have any substantial detrimental effect on adjacent or nearby properties;
(d) Terraces between the walls are of sufficient width and depth to accommodate landscaping or other techniques designed to reduce the visual impact. Conditions requiring such techniques shall be incorporated into the permit; and
(e) Clear vision triangles are free of obstructions that exceed three feet in height.
5. Screening: All parking and storage areas (except those in conjunction with single family residences) including vehicle sales areas, truck parking areas, bus parking areas, and service drives shall meet the following standards: A solid screen with a height not less than five and one-half feet shall be provided when a parking lot is adjacent to residential land uses. This screen may include fencing, walls, or landscape combinations that will provide a dense barrier.