Development Plan for Atria Park of Lafayette Bridge & Culvert Retrofit, County File #CDDP20-03005

Development Plan for Atria Park of Lafayette Bridge & Culvert Retrofit, County File #CDDP20-03005

The applicant is requesting approval of a Development Plan modification of County File #CDDP88-03007 to allow construction of a retrofit of two existing retaining walls that form a bridge supporting the primary driveway to a congregate care facility currently operated as the Atria Park of Lafayette assisted living facility, and repairs to an existing culvert within the bridge structure on the subject property. The project consists of the following elements: 1. Injection of a “Uretek” polymer into the soils under the culvert footings, along the base of both retaining walls, and from the road surface extending approximately 30 feet into the existing engineered walls; 2. Bridge: • Excavation and grading (approximately 50 cubic yards, cut) at the base of the walls to set pads for scaffolding; • Installation of soil nails and tie rods throughout the surface and underlying soils of both retaining walls; • Application of shotcrete to cover the tie rods and soil nails; and, • Replacement of the existing roadway surface; 3. Culvert: • Excavation and grading (approximately 450 cubic yards, cut) within the culvert; • Construction of new footings, • Construction of a concrete apron the length of the culvert; • Placement of native gravels within the culvert to match the creek flowline; and, • Placement of up to 12 inches of rip rap upstream and downstream of the culvert for erosion control. The applicant estimates that the bridge will need to be closed to non-construction traffic for approximately 6 months due to crane and concrete pump equipment on the roadway during retrofitting work and repaving of the roadway. Thus, the project seeks approval to allow facility traffic to be detoured via Diablo View Road to an existing, gated, secondary driveway during construction activities on the bridge. Approximately 8,095 square feet of the approximately 16,945-square-foot project area is located within a restricted development area (Grant Deed of Development Rights, 13693OR414, recorded June 8, 1987), therefore, the applicant seeks approval of the County to perform work within the restricted development area. (On December 11, 2024, the County Board of Supervisor’s granted approval to perform the work within the restricted development area.) The applicant also requests approval of a tree permit to allow removal of up to ten (10) code-protected trees (two coast live oak and one valley oak, three coast redwood, one walnut, two blue gum eucalyptus, and one deodar cedar) due to grading and construction activities or poor health and condition, and to allow work within the driplines of approximately seven (7) code-protected trees (three coast live oak, two blue gum eucalyptus, one white alder, and one salix) for required grading and construction activities. The retrofitted retaining walls will allow the driveway continued to be used for safe access to the facility and the repaired and retrofitted culvert bed will prevent further erosion of the existing culvert walls and scouring of the culvert apron. No changes to the buildings or congregate care use of the facility are proposed.

Lafayette

Contra Costa

Citywide, Countywide, San Francisco Bay Area

Contra Costa