Infrastructure Design & Public Art
RIVERSIDE COUNTY OAK TREE MANAGEMENT GUIDELINES
(Approved by the Board of Supervisors on March 2, 1993)
These guidelines are intended to address the treatment of oak woodlands in areas where zoning and/or general plan density restrictions will allow the effective use of clustering. Generally, these guidelines will be most effective where minimum lot sizes of 2.5 acres or larger are required or where oak woodlands are concentrated in a relatively small portion of a project site. While it is expected that most projects that follow these guidelines will reduce project impacts on oak trees to a level of insignificance, these guidelines in no way exempt a project from being reviewed pursuant to the California Environmental Quality Act (CEQA) and being evaluated for significant project impacts to oak trees.
- Biologist - individual qualified by the County of Riverside to perform a biological survey.
- Breast Height- 4.5 feet above ground level at the base of the tree.
- Clustering - the grouping together of homesites in a manner that maximizes the preservation of oak trees through the use of transfer of density, unless precluded by the general plan, unusual lot line configurations, placement of roads within lot boundaries, and other creative design techniques. Overall project density and minimum lot size requirements of the site's zoning or applicable general plan policies may not be varied pursuant to this policy, unless such variances are otherwise permitted by the applicable provisions of the general plan or project zoning.
- Conservation Agency- The Riverside County Regional Park and Open Space District, a land conservancy, or a County Service District or other agency with authorization to protect open space that can demonstrate that it possesses biological expertise in monitoring and maintaining open space.
- Construction Zone- area within which construction activity can occur with no impact to oak trees.
- DBH- Diameter at Breast Height. A standard of measurement for determining the size of a tree based on its trunk diameter.
- Dead Tree - an oak tree containing no living tissue (i.e. live limbs or green leaves).
- Drip Line the outermost edge of a tree's canopy. When depicted in plan view, the drip line will appear as an irregularly shaped circle defining the canopy perimeter. See Image Below
- Dying Tree- an oak tree unlikely to survive as determined with appropriate justification by a qualified biologist.
- Habitat Restoration - the establishment of a self-sufficient, self-renewing, permanent native vegetation consisting primarily of plant species native to the site. Such efforts may require temporary, monitored care.
- Homesite - the graded or altered area created for a home or other occupied structure and its incidental uses, including septic systems, wells, trenches, animal pasture and corrals, etc.
- Oak Tree- an individual plant of the genus Quercus, including in Riverside County the species Q. agrifolia, Q. chrysolepis, Q. engelmannii, Q. kelloggii, Q. morehus, and Q. wislezenii. Individual trees shall not be subject to these guidelines unless their trunks are larger than two inches in DBH for a single trunk or the sum of the diameters of multiple trunks at breast height.
- Oak Woodland - an area of natural vegetation that includes at least one oak tree and associated understory. An area of oak woodland can be many acres in extent or as small as a single tree.
- Protected Zone - a circle whose center is within the base of an oak tree, the radius of which is equal to an oak tree's height or 10 feet, whichever is greater. Where the outermost edge of an oak tree's drip line extends beyond this radius, that portion of the drip line shall also be included as part of that tree's protected zone. Protected zones do not apply to dead or dying oak trees, unless the tree's condition appears to be the result of human activity that indicates an intent to kill the tree.
- Understory - native shrubs, grasses, and other plants that are associated with trees in an oak woodland.
GUIDELINES FOR PROPERTIES WITH OAK TREE RESOURCES
- A biological study will be required for all applications on properties that contain oak trees.
- An inventory of on-site vegetation shall be required, which shall include:
- The location and size of individual oak trees that are two (2) inches DBH or larger within proposed roads, driveways, and homesites including their protected zones as identified by a biologist and mapped by a surveyor or engineer on a map that is the same scale as the project map.
- An accurate depiction of the distance and direction of all proposed grading.
- Identification of boundaries of plant communities.
- Dead or dying trees within proposed roads, driveways, or homesites shall be identified and evaluated for their value to cavity nesting birds.
- Impacts of the proposed development shall be identified and quantified.
- All possible options for mitigation measures shall be identified, including redesign/clustering, if impacts cannot be avoided by the project as proposed.
- The biological report shall include required mitigation, consistent with CEQA and applicable State or County codes and ordinances.
- The mitigation program shall be incorporated into the project's conditions of approval.
- Designs that cluster homesites together will be strongly encouraged when such a design would significantly reduce the impacts to oaks: however, such clustering shall not result in an increase in the density or reduction of the minimum lot size requirements of the Comprehensive General Plan absent a General Plan Amendment. Under these guidelines, clustering is not intended to be used in a manner that increases the overall impact on oak trees in order to avoid other constraints that could otherwise reduce project density. Clustering may only be permitted when it will significantly reduce the overall impact on oak trees, or where it will reduce impacts on other constrained areas while avoiding all impacts to oaks. When it would achieve the objectives of these guidelines, lot lines are strongly encouraged to be creatively placed to achieve such clustering. A variance for lot width, depth, and other standard design requirements may be required.
- The first objective of these guidelines is to design the placement of proposed homesites, driveways, and roads in locations that completely avoid any oak trees and their protected zones following existing ordinances and general plan policies. When this is possible and implemented on a project, oak trees and their protected zones will be identified and protected through an Environmental Constraints Sheet. No further mitigation for impacts to oak trees is required. Conditions which may render this approach infeasible include, but are not limited to, oak tree coverage patterns, steep slopes, drainage constraints, road and access locations, septic system limitations, and other significant hazards, resource or public facility constraints.
- When avoidance of oak trees and their protected zones is not feasible without some variance from existing ordinances or general plan policies, designs that would concentrate proposed homesites, driveways and roads into clusters of as many units as feasible into a single area and unusual lot line configurations shall be used to completely avoid impacts to oak trees and their protected zones, where possible. However, the minimum lot size requirements of any applicable zoning or general plan polices must be followed. If required to avoid stands of oak trees, proposed roads may be placed within a parcel rather than along a lot line. In consideration of such design variances, the applicant must have negotiated a conservation easement with a conservation agency that will at least cover the protected zones of the oak trees on the property. The negotiated, unexecuted easement document and a map of the area to be covered by the easement must accompany the development application as exhibits at the time of project approval. The project approval will be subject to a condition requiring that prior to or with the recordation of a final map or prior to the issuance of a grading permit the easement must be executed in substantial conformance with these exhibits. The easement shall be identified on an Environmental Constraints Sheet.
- When encroachment into an oak tree protected zone or oak tree removal is the only available means of creating a homesite or its required access, the maximum area unconstrained by oak trees shall be used, unless precluded by other significant constraints such as steep slopes. Clustering of homesites into the fewest number of areas possible which take advantage of the portions of the property which are the least constrained by oaks and other constraints is strongly encouraged to minimize the spread of impacts over a large portion of the property and to reduce the fragmentation of the remaining natural areas. However, the minimum lot size requirements of any applicable zoning or general plan policies must be followed. In no case will a homesite(s) be permitted to exceed 10,000 square feet if the creation of that homesite will result in the violation of one or more oak tree's protected zone(s). The homesite(s) should be less than 10,000 square feet, down to the minimum feasible size if necessary in order to avoid direct impacts to oak woodlands. The minimum mitigation of the loss of oak trees under these circumstances must include a conservation easement negotiated between the applicant and a conservation agency that will at least cover the undisturbed portion of the protected zone of any oak tree on the property whose drip line is not violated. The negotiated, unexecuted easement document and a map of the area to be covered by the easement must accompany the development application as exhibits at the time of project approval. The project approval will be subject to a condition requiring that prior to or with the recordation of a final map or prior to the issuance of a grading permit the easement must be executed in substantial conformance with these exhibits. The easement shall be identified on an Environmental Constraints Sheet.
- Application of any clustering provisions shall be permitted only when it is determined that these provisions provide a net environmental benefit. In the event that clustering will not provide a net environmental benefit and impacts to oak trees or their protected zones cannot be avoided, a design that least impacts oak trees without clustering shall be prepared. The minimum mitigation required under these circumstances must include limiting the homesite size to a maximum of 10,000 square feet (smaller if necessary to avoid direct impacts to oak woodlands) and a conservation easement negotiated between the applicant and a conservation agency that will at least cover the undisturbed portion of the protected zone of any oak tree on the property whose drip line has not been violated. The negotiated, unexecuted easement document and a map of the area to be covered by the easement must accompany the development application as exhibits at the time of project approval. The project approval will be subject to a condition requiring that prior to or with the recordation of a final map or prior to the issuance of a grading permit the easement must be executed in substantial conformance with these exhibits. The easement shall be identified on an Environmental Constraints Sheet.
- The determination that a project design will significantly reduce the overall impact to oak trees has to be judged relative to the initial state of the site. Additionally, a variety of factors must be considered. Those factors, listed in general order of importance, include, but are not limited to:
- a. The size and contiguity of the area covered by undisturbed oak tree protected zones
- b. The size and of the trees whose protected zones are left undisturbed
- c. The number of trees whose protected zones are left undisturbed
- d. The size and contiguity of the area covered by oak tree protected zones that are proposed to be disturbed outside of the tree's drip line
- e. The size of the trees in DBH whose protected zones re proposed to be disturbed outside of the tree's drip line
- f. The number of trees whose protected zones are proposed to disturbed outside of the tree's drip line. So long as a homesite violates an oak tree's drip line, the impacts on that tree cannot be regarded as significantly reduced.
- No construction activities or placement of structures shall occur within the protected zone of any oak tree or oak woodland except as provided for in these policies.
- Landscaping, trenching or irrigation systems shall not be installed within the existing protected zone of any oak tree or oak woodland, unless recommended by a biologist.
- Land uses that would cause excessive soil compaction within the protected zone of any individual oak tree shall be avoided. No recreational trails are permitted within the drip line of any individual oak tree.
- Manufactured cut slopes shall not begin their downward cut within the protected zone of any individual oak tree, except as provided in these guidelines.
- Manufactured fill slopes shall not extend within the protected zone, except as provided in these guidelines.
- On-slope retaining structures, if required, shall be designed to protect the root system of any individual oak tree by preserving the natural grade within the protected zone.
- Redirection of surface runoff which results in increased soil moisture for an extended period of time within the drip line area of any individual oak tree shall be avoided. If unavoidable, a drainage system shall be designed to maintain the previous amount of soil moisture.
- Sedimentation and siltation shall be controlled to avoid filling around bases of oak trees.
- Redirection of surface runoff which results in decreased soil moisture for an extended period of time within the drip line area shall be avoided. If unavoidable, an irrigation system shall be designed to maintain the previous amount of soil moisture.
- A construction zone at the interface with a protected zone shall be clearly delineated on the site in order to avoid impacts from construction operations and also to prevent the storage or parking of equipment outside the construction zone.
- Dead or dying oak trees are necessary for the excavation of nest cavities by woodpeckers. Twelve species of birds use nest cavities. It is important to the health of the habitat to retain dead and dying trees that are not a hazard to humans. Such oak trees shall be retained in place unless determined to pose a health or safety hazard, in which case they shall be discarded at an approved on-site location identified by the consulting biologist for habitat enhancement.
- On-site to on-site or off-site to off-site relocation of oak trees will not constitute mitigation and is considered the same as removal for the purposes of these guidelines.
- Replacement of oak trees with plantings of saplings or acorns is not required by these guidelines; however, replacement plantings may be used in addition to these guidelines when they are required by another agency or when it is determined to be biologically sound and appropriate to do so.
- Oak protection should be orientated toward protection of the life cycle of oak trees and oak woodland; i.e., young trees should be protected along with older trees.
Last Revised: September 1999