Urban Forestry Associates July 21, 2026
8100 Valentine Avenue Development Tree Review
Summary
The 8100 Valentine Avenue site supports a mix of native and ornamental trees in generally fair to good condition, including a stand of mature coast redwoods (Sequoia sempervirens) in the northeast corner and several protected native oaks. The materials submitted for the development function as a basic tree inventory, but they do not yet meet the tree protection plan requirements that this project triggers under the Sebastopol Municipal Code. The inventory does not include a protection plan sheet a contractor can follow, the field tagging could not be verified, at least one protected tree is misidentified, and replacement and protection measures are described only in general terms. The inventory also applies the protected-tree threshold for single-family and duplex properties, which understates the number of protected trees on this parcel and the mitigation their removal requires.
Before a meaningful protection review can be completed, the applicant must correct these items and submit a tree protection plan, including a plan sheet, prepared by the project arborist. I also recommend that Tree 52 be reclassified as a removal or that the site plan be modified to give it a survivable growing space.
Assignment
John Jay, contract associate planner with the City of Sebastopol Community Development Department, asked me to review the tree-related materials submitted for the proposed residential development at 8100 Valentine Avenue and to provide comments for the City's conditions of approval. The materials I reviewed are the Tree Inventory Report prepared by John C. Meserve of Horticultural Associates dated December 5, 2025, the applicant's written project description dated December 18, 2025 and updated May 21, 2026, and the tentative map. The project is a 20-lot, 39-home residential subdivision on the former Church of Jesus Christ of Latterday Saints parcel, Assessor's Parcel Number 008-510-054.
I inspected the site on July 21, 2026 and walked the tree locations. I did not conduct an independent tree-bytree inventory or a formal tree risk assessment, and my comments rely on Meserve's inventory data except where my field observations differ. This review is limited to the adequacy of the submitted tree materials and to the tree protection and removal issues raised by the proposed development.
Observations
The site is the former church property. Trees are concentrated along the perimeter and in the northeast corner, and the inventory documents 46 trees. The dominant trees are the coast redwoods in the northeast corner and a group of protected native oaks, including coast live oak (Quercus agrifolia), Oregon oak (Quercus garryana), and valley oak (Quercus lobata). The remaining trees are ornamental species, including flowering pear (Pyrus calleryana), crape myrtle (Lagerstroemia indica), London plane (Platanus x acerifolia), Chinese pistache (Pistacia chinensis), European birch (Betula sp.), flowering cherry (Prunus serrulata), Pacific wax myrtle (Morella californica), and Eastern redbud (Cercis canadensis).
The Tree Inventory Report states that each tree was identified in the field with a numbered aluminum tag placed at approximately eye level. During my inspection most of the trees did not have tags. Without reliable tags, or another unambiguous way to locate each numbered tree, a contractor cannot connect the report's recommendations to the trees on the ground.
Tree 52 is identified in the inventory as a valley oak. Based on my field inspection it is an Oregon oak. Its canopy is asymmetric and weighted over the footprint of Building 22.
Client: City of Sebastopol, Community Development Department Project Location: 8100 Valentine Avenue, Sebastopol, CA Inspection Date: July 21, 2026
Arborist: Ben Anderson
Agenda Item Number 7
Agenda Item Number 7
City Council Meeting Packet for October 20, 2026
Urban Forestry Associates July 21, 2026
8100 Valentine Avenue Development Tree Review
The coast redwoods in the northeast corner, including Tree 32, are close to proposed grading and structures and will experience significant root zone impacts during construction.
Several additional trees grow just outside the property lines on neighboring parcels. Their trunks are off site, but their root systems, and in some cases their canopies, extend onto the project site.
Discussion
Because this is a development project with work proposed within the driplines of protected trees, a tree protection plan prepared by an International Society of Arboriculture certified arborist is required as part of the application under Sebastopol Municipal Code 8.12.050. The code lists the information a tree protection plan must contain. It calls for the size, species, health, crown diameter, and trunk location of all trees whose dripline is within the development area, whether on the subject property or an adjoining property. It also calls for the measures proposed to ensure the survival of the trees to remain, the size, species, and location of replacement trees, the maintenance and irrigation program for those trees, the existing and proposed grading and drainage characteristics as they relate to trees, and the protective fencing, tree protection zones, and contractor responsibility notes to be shown on the plan sheets.
The submitted Tree Inventory Report provides tree size, species, health, structure, and a location plan, which partly satisfies the first requirement. It does not provide the survival measures, the tree protection zones and fencing locations, the grading and drainage detail, the replacement tree specifications and maintenance program, or the plan sheet notes that the remaining subsections require. The report is a basic inventory, not the tree protection plan the code calls for.
The applicable threshold for a protected native tree depends on the property type. Sebastopol Municipal Code
8.12.040 defines a protected native tree as a listed native species with a trunk diameter of at least 10 inches on all properties other than single-family or duplex residential properties, and at least 20 inches on singlefamily or duplex residential properties. Sebastopol Municipal Code 8.12.060(A) makes the same distinction for when a tree removal permit is required.
The Tree Inventory Report applies the 20-inch single-family and duplex threshold and identifies 18 protected native trees on that basis. This parcel is zoned R-4, Medium Density Residential, and currently houses a church, so it is not a single-family or duplex residential property. The 10-inch threshold applies, which brings additional native trees into the protected category and increases the mitigation associated with their removal.
Sebastopol Municipal Code 8.12.060(E) provides that any tree removal permit shall include a condition requiring replacement trees, an in-lieu fee, or an approved alternative, and that the mitigation must be related to the significance, meaning the size and age, of the trees proposed for removal.
The submittal defers replacement to construction drawings and does not specify replacement species, sizes, locations, or in-lieu fees.
Oregon oak is a protected native tree under the ordinance. Oregon oak and valley oak are among the native oaks susceptible to the Mediterranean oak borer (Xyleborus monographus), an invasive ambrosia beetle that carries pathogenic fungi. The beetle is established in Sonoma, Napa, and Lake counties, where it has killed native oaks, and trees weakened by construction stress are more vulnerable to attack. Coast redwood is a large, long-lived species with shallow, wide-spreading roots that are sensitive to grade changes, soil compaction, and altered drainage, and it depends on consistent soil moisture.
ANSI A300-2023 Tree Care Standards and the ISA Best Management Practices: Managing Trees During Site Development and Construction, third edition, establish the accepted methods for tree protection zones, protective fencing, root pruning, mulching, and construction monitoring. A tree protection zone is generally set at or beyond the dripline and adjusted for species tolerance by the project arborist.
Conclusions
The submitted materials are adequate as a basic tree inventory, but they do not meet the tree protection plan Agenda Item Number 7
Agenda Item Number 7
City Council Meeting Packet for October 20, 2026
Urban Forestry Associates July 21, 2026
8100 Valentine Avenue Development Tree Review
requirements of Sebastopol Municipal Code 8.12.050. Before the City can condition this project effectively, and before I can complete a protection review, the applicant should prepare and submit a tree protection plan, including a plan sheet, prepared by the project arborist. I recommend that the City require the applicant to clarify or provide the following.
1. A tree protection plan sheet, drawn over the civil site plan, that shows in plan view each tree to be removed, each tree to be retained and protected, and the tree protection zone and fencing location for each retained tree. The plan sheet shall translate the report's numeric recommendation codes into plain protection notes a contractor can follow.
2. Field re-tagging of the inventoried trees, or another unambiguous method of identifying each numbered tree on the ground, because most tags were missing at the time of my inspection.
3. Correction of the species identification for Tree 52 from valley oak to Oregon oak, with a corresponding review of its retention, replacement, and pest-risk implications.
4. Application of the correct protected-tree threshold. The property is currently developed with a former church and is not an existing single-family or duplex residential property. Therefore, under Sebastopol Municipal Code 8.12.040, the protected-native-tree threshold is a 10-inch trunk diameter rather than 20 inches.
Applying the correct threshold adds Trees 12, 13, 14, 27, and 42 to the protected-tree count. Based on the dispositions presently shown on the tentative map, the site contains 23 protected native trees, of which 12 are proposed for retention and 11 are proposed for removal. The protected-tree schedule and required mitigation shall be recalculated accordingly.
5. Reconciliation of the tree inventory, numbering, and disposition schedules. The inventory report states that 46 trees were evaluated, but its inventory chart contains 47 entries, numbered 10 through 56. Tree 54 is identified as an off-site tree and is not included in the tentative map’s on-site disposition lists. The inventory location plan also labels Tree 57, but no corresponding Tree 57 entry appears in the inventory chart. In addition, the inventory report states that there are 18 protected trees, while the tentative map identifies 19 and the written project description refers to 15 “heritage trees.” The applicant shall provide one definitive schedule identifying the location, species, diameter, protection status, and proposed disposition of every numbered tree.
6. Tree protection zones and measures specified for each retained tree, including fencing distances, grading and trenching restrictions, mulch, and required arborist monitoring, consistent with ANSI A300-2023 Tree Care Standards and the ISA Best Management Practices: Managing Trees During Site Development and Construction, third edition. Protection notes shall use the words shall and must.
7. A replacement and mitigation plan under Sebastopol Municipal Code 8.12.060(E) that specifies replacement species, sizes, locations, and any in-lieu fees, rather than deferring these to construction drawings.
8. Inventory and protection of the neighboring trees whose driplines extend onto the site. Under Sebastopol Municipal Code 8.12.050, the tree protection plan must include trees on adjoining property whose dripline is within the development area, so these trees shall be added to the inventory. The plan shall require protective fencing and arborist oversight for any work within their root zones.
9. A construction-phase protection and monitoring program for the coast redwoods in the northeast corner, including Tree 32. The final landscape and irrigation plan shall maintain soil moisture within the redwood root zones and shall not introduce planting or irrigation that is incompatible with the retained trees.
For Tree 52, I recommend that it be reclassified as a removal, or that the site plan be modified to provide it a survivable growing space. The canopy is asymmetric and weighted over Building 22, and Oregon oak is susceptible to the Mediterranean oak borer, so the construction stress expected at this location makes longterm retention unlikely.
Agenda Item Number 7
Agenda Item Number 7
City Council Meeting Packet for October 20, 2026
Urban Forestry Associates July 21, 2026
8100 Valentine Avenue Development Tree Review
Works Cited
Adobe Associates, Inc. 8100 Valentine Avenue Development: Vesting Tentative Map Package. July 2026.
City of Sebastopol. Sebastopol Municipal Code, Chapter 8.12, Tree Protection. Current through Ordinance No. 1164, passed March 3, 2026.
Fordyce, Lauren. “Mediterranean Oak Borer: Questions & Answers.” Pests in the Urban Landscape, University of California Agriculture and Natural Resources, May 28, 2025.
Grupe Investment Company, Inc. Project Description: For-Sale Missing Middle Single-Family Home Development at Sebastopol, 8100 Valentine Avenue. December 18, 2025; updated May 21, 2026.
Matheny, Nelda, E. Thomas Smiley, Ryan Gilpin, and Richard Hauer. Best Management Practices: Managing Trees During Site Development and Construction. 3rd ed., International Society of Arboriculture, 2023.
Meserve, John C. Tree Inventory Report, 8100 Valentine Avenue, Sebastopol, California. Horticultural Associates, December 5, 2025.
Oregon Department of Forestry. Mediterranean Oak Borer. May 2026.
Tree Care Industry Association. ANSI A300-2023 Tree Care Standards. 2023.
University of California Statewide Integrated Pest Management Program. “Coast Redwood.” UC IPM.
University of California Statewide Integrated Pest Management Program. “Protecting Trees During Construction.” UC IPM.
Scope of Work and Limitations
Urban Forestry Associates has no personal or monetary interest in the outcome of this investigation. All observations regarding trees in this report were made by UFA, independently, based on our education and experience. This review was limited to a visual site inspection and evaluation of the submitted plans and treerelated materials. I did not perform a complete independent tree inventory, subsurface root investigation, or tree risk assessment. Internal and belowground conditions were not investigated, and these conclusions may require revision if the project plans or observed site conditions change.
Benjamin Anderson, Urban Forester
ISA Board Certified Master Arborist & TRAQ
RCA #686, WE #10160B
(415) 454-4212
Agenda Item Number 7
Agenda Item Number 7
City Council Meeting Packet for October 20, 2026