Mill Valley planning commission approves 316 West Blythedale with conditions to protect redwoods

The Mill Valley Planning Commission approved a design for a new single-family home with an accessory dwelling unit at 316 West Blythedale, conditioning the decision on measures intended to protect several mature redwoods on and near the lot.

Planning staff summarized the project as "a proposed new single family dwelling and accessory dwelling unit," and said the resubmittal responds to commission direction from an October study session by reducing visible massing, eliminating a proposed parking stall in the public right-of-way and changing materials to darker, earth-toned finishes. Staff recommended the commission find the project categorically exempt under CEQA guidelines section 15303 and to approve the application subject to revised conditions, including tree-protection measures.

The commission’s discussion centered on tree impacts and construction logistics. Staff flagged one heritage redwood identified as Tree 14 that the applicant proposed to remove because of its proximity to the proposed living-room wall; staff also identified Trees 12, 6 and 7 as at risk from excavation and retaining walls. "We do recommend that you consider ... the heritage tree removal that's proposed and the potential impacts to those additional trees," staff said during the presentation.

Applicant Kevin described changes made since the study session—raising the garage floor and driveway slope to reduce earthwork, pulling a second-story element back seven feet to break up massing, revising materials and adding landscaping—and said the project had reduced off-haul to "under 300 yards" after revisions. On tree protection he told the commission, "that's our commitment is to make whatever changes we have to to the patio and the walls in this area, to preserve the health of this tree." The applicant also described neighbor outreach conducted in person and by phone.

Commissioners pressed staff and the applicant on tree-replacement rules and fire-department restrictions on plantings in the wildland-urban interface. Staff and a technical speaker explained the city's heritage-tree replacement formula is based on trunk diameter and that site conditions and fire-safety guidance sometimes limit the practicality of large on-site replacements. Commissioner questions also covered driveway slope, pervious paver feasibility, ADU access, and the logistics of off-haul truck trips on the roadway.

One neighbor, Carolyn Perot, spoke in favor of the revised plan and raised a drainage question: "My main question is drainage because we are below," she said, noting support for a permeable driveway and asking whether the site drains to the street system. Staff noted required bio‑swales and said drainage details will be addressed in plan check.

After deliberation the commission agreed on conditions intended to preserve Trees 12, 6 and 7, allow removal of the proposed heritage Tree 14 as part of the approved tree-removal permit, require the applicant to provide one additional 24-inch-box specimen in the front setback, and to implement tree-protection measures and arborist inspections during construction. Commissioners instructed staff to draft condition language that would require the applicant to pursue patio and retaining-wall alternatives (including stepping up patios and use of piers) where feasible to avoid critical-root-zone impacts; removal of a tree would be allowed only if the arborist demonstrates unavoidable impacts to long‑term health.

Commissioner Ioannis moved to approve the project with those conditions; Commissioner Macros seconded. The motion carried by voice vote. The planning commission chair noted that the project decision may be appealed to the city council by filing a letter with the planning and building department within 10 calendar days and paying the $1,057 appeal fee.

The commission also reviewed upcoming items (parking ordinance update, inclusionary-housing ratio discussion and a commercial-code overhaul) before adjourning.