D. Environmentally Sensitive Lands Conservation System
1. Conservation System
ESL represents an interconnected system of resource conservation. The components of the system include seven (7) distinct categories for the purpose of conserving resources as open space. Key and essential biological resources are included in four (4) ESL categories:
a. Major wildlife linkage;
b. Critical resource;
c. Core resource; and
d. Resource management.
Environmentally sensitive resource categories that are nonbiologically based include:
f. Scenic resources; and
g. Hillside areas.
Each category includes distinct definitions and requirements that shall be applied independently when multiple categories occur on a site.
E. Open Space Requirements
1. Open Space ESOS Designation
a. Hillside resource area.
b. Scenic resource areas.
2. ESOS Tracts
ESOS shall be permanently protected by one (1) of the following methods:
a. Open space tract, or
c. A separate tract owned by a homeowners’ association.
3. General Requirements
a. Required ESOS must be configured in accordance with this section to conserve minimum percentages of identified resource categories as specified in Table 27.10-2.
b. Development can only occur in the nonopen space areas of the site. Required open space areas must be designated as ESOS in one (1) of the approved forms described in subsection E.2 of this section.
i. Minimum ESOS dimensions are maintained as specified in subsection E.4.e of this section.
i. ESOS areas of National, State, regional, or community-wide importance will be the responsibility of a public entity, land trust, or land conservation organization that is capable of satisfying the objectives specified herein. This level of dedication shall include ESOS areas with the following characteristics:
b) Regionally significant drainage.
d) Inclusion of identified major wildlife linkage areas.
ii. All other ESOS areas that contribute resource value primarily to adjacent neighborhoods and do not meet the criteria above shall be the responsibility of an HOA.
e. Permanent open space easements and/or deed restrictions must be provided for all ESOS tracts, unless dedicated to the public, prior to certifying that all conditions of rezoning, site plan or plat have been satisfied. Said easements or deed restrictions will be included on documents upon official recordation.
ii. Provisions to fund maintenance in perpetuity that may include:
a) Use of future homeowners’ association dues, or
c) Assurance from a third party caretaker such as a land trust, or
d) Other methods to assure maintenance as approved by the Planning and Zoning Administrator.
iii. The Town retains the authority to perform maintenance in ESOS tracts or common areas managed by an HOA or other property management association. A note will be included on the subdivision plat and/or site plan indicating the Town’s ability to enter the property and perform ESOS maintenance.
j. In no event shall the provisions of this section require greater area of ESOS than required by subsection D.3 of this section.
4. Criteria for ESOS Selection and Location
The following criteria must be used to select and locate ESOS providing the greatest degree of conservation for the most sensitive resource categories.
a. All resource areas identified on the ESL Planning Map enable limited encroachments as specified in Table 27.10-5.
Maximum Percentage Disturbance Permitted
Minimum Percentage ESOS Conservation
Major Wildlife Linkage
Critical Resource Area
Core Resource Area
Resource Management Area-1
Resource Management Area-2
Resource Management Area-3
b. The required percentage of ESOS is applied to total acreage of the identified resource area(s) and not a cumulative total of individual resources such as rock outcrops, boulders, and distinctive plant stands.
d. All mapped ESL resource areas meet required values specified in the category descriptions in subsection D.3 of this section. The following factors must be utilized to select priority areas for conservation within a resource category designation:
ii. Areas that exceed resource area density, size, and frequency specifications are a high priority.
iii. The value of different resources within a specific category will be balanced in a manner to achieve diversity of habitat.
v. Disturbance areas should be located in areas of least resource density, size, and frequency.
vi. Areas that include healthy and viable resources are a priority.
b) The rock outcrop or boulder is an isolated feature, located one thousand (1,000) feet or more from public preserves, major wildlife linkages or other rock outcrop or boulder features.
c) The rock outcrop or boulder feature provides connectivity between two (2) identified ESL areas, or is part of an identified linkage area including minor or major wildlife linkages and riparian areas.
d) The rock outcrop or boulder exhibits fractures, cracks and/or crevices.
e. Minimum ESOS Dimensions
The minimum contiguous area for ESOS is four thousand (4,000) square feet.
The minimum horizontal dimension for ESOS areas is thirty (30) feet.
ESOS dimensions do not apply to distinct native vegetation.
The Planning and Zoning Administrator may approve modifications to the minimum ESOS dimensions set forth above, subject to the following criteria:
a) The ESOS location criteria set forth in this subsection E.4 are met.
f. ESOS distribution within planned area developments (PADs)
If a master developer elects to provide ESOS in excess of the minimum requirements for a specific development site, the balance may be credited against ESOS requirements for other development sites within the Town, if approved by the Town Council. ESOS may be credited as follows:
ii. The Open Space Master Plan shall be included with the PAD application and must identify any excess ESOS by development project and allocate any excess ESOS to specific development locations elsewhere within the Open Space Master Plan.
iii. The excess ESOS must result in additional protection for the most sensitive resources in accordance with the hierarchy established in Table 27.10-5. Reductions in ESOS due to the application of credits cannot be applied to major wildlife linkage or critical resource areas.
g. Connectivity of ESOS areas is essential in maintaining ecosystem function. Conservation of identified areas that provide connectivity but are environmentally degraded is required.
i. Degraded areas that provide connectivity to the natural open space system, including identified minor wildlife linkages, must be protected from further disturbance. Restoration in accordance with ESL mitigation requirements, subsection G of this section, may be approved by the Planning and Zoning Administrator.
ii. Additional open space linkages that have not been identified on the ESL Planning Map may be recommended by the Planning and Zoning Administrator when the area:
a) Provides a unique and necessary connection to other ESOS areas.
b) Is not isolated from other open space areas.
c) Serves as a habitat corridor for movement of wildlife.
d) Newly identified linkages will be conserved in accordance with the following:
1) Restoration areas will be applied toward total ESOS requirements of the appropriate resource category as assigned by the Planning and Zoning Administrator.
Site-specific mitigation is required in order to restore biological functions and resource values of riparian areas, distinctive vegetation and rock outcrop features impacted by development activity or previous human disturbance.
a. Mitigation is required for disturbed areas of environmentally sensitive resources including restoration due to impacts from:
i. Essential services installation as described in subsection F.2.f.vi of this section;
ii. Degraded linkage areas as described in subsection E.4.g of this section; and
iii. Other instances of disturbance to environmentally sensitive resources.
b. This section applies to natural resources and does not apply to mitigation of a cultural resource.
3. General Requirements
Mitigation specific to each disturbed area is required for impacts to environmentally sensitive resources including:
a. Riparian areas;
b. Distinctive plant stands and communities; and
c. Rock outcrops and boulders.
a. Site Characterization
b. Sampling Riparian Areas and Distinctive Vegetation Stands
i. Sample Area(s)
a) Determine the sample areas within which plots or transects will be established in accordance with reference site requirements. The following qualities shall be included in the sample area:
1) Sample areas for distinctive vegetation stands should include stands of mature and healthy vegetation that meet the minimum cover or density definitions in the ESL for those resources being impacted.
2) Sample areas’ area shall be large enough to include all species belonging to the plant community.
a) Plots or transects shall be distributed throughout the sample area in a manner to capture all of the variability within that sample area. Plots or transects can be either located randomly within a sample area or according to an orderly sampling scheme (e.g., on a grid, at regular intervals, etc.) – as long as the result is that the sample area is accurately described by the plot number and arrangement.
b) The sampling locations must be approved as part of the mitigation plan review process, and must be representative of the area being sampled.
iii. Plot Sampling
a) Plot sampling, or quadrat sampling, can be used to describe a variety of plant community characteristics of an area that is too large for a complete vegetation inventory to be feasible.
b) The parameters to be addressed include: diversity (species present), cover, and density (number of species in a given area).
c) The number of plots or transects conducted within each sample area should be sufficient to characterize the range of vegetation conditions within it.
d) Size and Shape
1) Plot size and shape should fit the nature of the vegetation community to be sampled. Circular plots are generally recommended with these field mapping standards, as they are more efficient to accurately establish in the field.
2) Plot size should be large enough to include a significant number of individual plants, representing all dominant species, but small enough that plants can be counted without duplication or omission of individuals.
3) Suggested plot sizes that are typically appropriate for vegetation in the context of riparian habitat are listed below. Site characteristics may necessitate using a different plot size or shape (i.e., if the riparian vegetation entity is not wide enough). Plot shape and size should be consistent throughout.
4) Circular plots (preferred): ten (10) meter radius (314 m2 or 3,380 ft2).
5) Square plots: fifteen (15) to twenty (20) meters per side (225 m2 to 400 m2 or 2,422 ft2 to 4,306 ft2).
6) Rectangular plots: fifteen (15) meters by twenty (20) meters (300 m2 or 3,229 ft2).
iv. Transect Sampling
Transects may be conducted according to the point intercept and belt transect methods. The method is based on a fifty (50) meter point transect centered on a two (2) by fifty (50) meter plot (i.e., the belt transect). Using this method, vegetation is sampled by points at one-half (1/2) meter intervals along the fifty (50) meter transect to determine cover. The surveyor will note the species encountered at each interval. In addition, individuals of each perennial species rooted within the two (2) by fifty (50) meter plot will be counted to determine density and diversity. All annuals present in the two (2) by fifty (50) meter plot will also be noted.
c. Rock Outcrops and Boulders
If rock outcrops and/or boulders, as defined in Chapter 31, will be impacted beyond established thresholds, they must be addressed in the mitigation plan through salvage and relocation to re-create the original character as determined by an assessment of the following features:
i. The surface area and average height of the feature.
ii. Average size of boulders within the feature.
iii. General density and width of crevices or fractures across the outcrop.
iv. Aspect/orientation of the outcrop.
d. Reference Sites
i. When degraded areas do not permit site characterization in accordance with subsection G.4.b of this section, a reference site shall be selected and used as a proxy for desired conditions at the mitigation site.
iii. Reference sites shall be located in the same watershed and carefully chosen to reflect similar habitat resources including vegetation qualities and abiotic characteristics such as elevation, topography, stream characteristics, and substrate. Reference sites are informative and suggestive rather than prescriptive. Characterization of reference sites shall use the sample methodology outlined herein.
iv. Reference sites for riparian habitat impacts should include healthy, intact riparian habitat that is the same or higher riparian/xeroriparian classification and within the same watershed as that being impacted.
v. Each reference site may include several sampling areas.
vi. Number of Reference Sites
b) If the proposed impact area is between one-quarter (1/4) and five (5) acres in size and has been previously degraded or disturbed, at least two (2) reference sites shall be selected for characterization.
5. Mitigation Plan
a. Mitigation plans shall be prepared by a qualified habitat restoration specialist. The requirement to use a qualified habitat restoration specialist is waived for mitigation plans prepared for single residential parcels.
b. A mitigation plan shall include accurate information about resource elements present in the proposed impact area prior to such impacts and at any proposed mitigation area if different than impact area.
c. Mitigation Plan Contents
The following information must be included in a mitigation plan:
i. Aerial photograph at an appropriate scale with the following items clearly labeled:
a) Proposed project area, mitigation area, and reference area(s);
b) ESL resources;
c) Sampling entities;
d) Plot and/or transect locations, numerically labeled, to identify the plot relative to the data;
ii. Results summary table with all species listed;
iii. Evaluation of species diversity and vegetation cover;
iv. Representative photographs of each sample entity;
v. Planting plan, including specifications for the placement and relocation of rock and boulder features; and
vi. Other supporting data and evidence as appropriate.
d. Plant Density
i. For each area sampled, calculate the mean (average) number of individuals per species, based on the area of all plots or transects in that entity. For creating a planting plan, these values can be extrapolated to a meaningful area (e.g., one (1) acre or the size of the proposed disturbance) for each species as well as a total for shrubs and trees. The mean value will be used to calculate the mitigation required, using the following formula:
Total number of plants in all plots
X plants per area of interest
Total combined area of all plots
Area of interest
e. Plant Palette
i. The specific plant palette should include native species that are present in the proposed impact area or reference site(s), as determined by the sampling techniques described above.
ii. Historic flora may be consulted for additional species that may have occurred in the area in the past and that may be appropriate.
iii. Plant materials must be selected to create a diverse native vegetation community that will have the greatest habitat value possible. This should include (as appropriate) species of trees, large and mid-sized shrubs, bunchgrasses, sub-shrubs, vines, and annuals that will provide a structurally diverse vegetation community with ample cover for a variety of wildlife.
iv. Species selection must incorporate plant species that provide a variety of food resources for wildlife, including grains, berries, insects, pollen, and nectar.
f. Plant Size
Trees and shrub size shall reflect the average found in the transects. The following serve as minimum size requirements:
i. Trees: Fifty percent (50%) at twenty-four (24) inch boxed and fifty percent (50%) at fifteen (15) gallon.
ii. Shrubs: One hundred percent (100%) at five (5) gallon.
g. Planting, Rock and Boulder Design
i. Container plants must be installed in natural-looking patterns that mimic the surrounding and reference areas and not in rows or grids. Planting design shall be detailed on the planting plan.
ii. The placement of rock and boulder materials shall re-create the original character of the feature to the greatest practical extent. Rock and boulder placement shall be detailed on the planting plan.
h. Plant Material Quality
i. Emphasis on plant materials shall be for restoration quality stock that is native and as local to the project area as possible and preferably from within the same watershed.
ii. Plant materials may consist of salvaged plants or cuttings as well as container plants grown in traditional or tall pots from seed collected locally specifically for the project. Container plants will be grown at a nursery that specializes in producing high-quality native plant species for habitat restoration projects.
iii. Native soil shall be used in the plant containers if possible. If more native soil is needed than is available to fill plant containers, each container shall receive some native soil mixed with an appropriate commercial nursery soil mix.
iv. Container plants must be grown outdoors and in full sunlight. Prior to container plants being delivered to the project site, they shall be hardened off from water, so they may be able to sustain themselves under potential drought conditions once planted.
v. Deep-planting techniques for woody species are permitted in order to achieve maximum survival with minimal irrigation. This may include deep-planting of dormant pole cuttings as well as the use of container stock grown in tall pots.
vi. All plant materials shall be inspected by Town staff prior to installation to ensure they are healthy, disease free, and of proper species, quantities, and sizes.
i. Seed Types
ii. The seed mix palette must include only native species that occur in the vicinity of the restoration mitigation area and that are appropriate for the site, as determined by vegetation sampling.
iii. The mix should include as many species as possible, and, as with the container plants, a diverse mix of structural habits. It is important to include species that germinate at different times of the year as a contingency if precipitation is below average during the first wet season and to provide cover throughout the year.
j. Seed Application
Seeds can be applied through a variety of methods, including hand-broadcasting, pelletization, pitting, and hydroseeding. Timing of application shall be coordinated with precipitation for the greatest likelihood of germination success.
6. Off-Site Mitigation
i. Mitigation may be proposed on site or off site subject to Planning and Zoning Administrator approval. On-site mitigation is appropriate when impacts are temporary such as disturbance for a utility right-of-way. Off-site mitigation may be proposed if impacts will be permanent.
ii. Appropriate off-site mitigation locations include areas adjacent or in close proximity to the impacted area that contain similar resource elements such as areas upstream along the same riparian corridor where the impact occurred, or areas where resources have previously been degraded or disturbed.
iii. The location of the proposed mitigation area should consider the following items:
d) Zoning and long-term protection.
e) Access and logistical concerns.
f) Land use history.