Neptune Avenue, Encinitas
Project: Drilled Pier Upper Bluff Retention System, Lower Coastal Bluff Seawall
Client: Homeowner
Location: Encinitas, CA
Design Engineer, Geotechnical Consultant and Contractor:
Soil Engineering Construction, Inc.
Government Permit Agent:
The Trettin Company
Project Description:
In the mid-1990's, SEC constructed a below-grade caisson retention system in the rear yard of the coastal bluff property. Due to caving bluff materials, the work included the injection of micro fine cement grout to facilitate drilling of the piers. The upper bluff retention system utilized 30-inch diameter drilled reinforced concrete piers with associated grade beam along the top of the piers. The drilled piers were laterally supported by drilled tiebacks, placed approximately 10' on center and extending into the bluff +/- 50 feet. The benefits of this buried system include delaying the need for full retention wall construction and reducing the scope of construction at such time as the caissons become exposed due to ongoing coastal bluff erosion. Permitting agencies also favor the system because of its limited visual impact. At the base of the 95-foot high coastal bluff, SEC constructed a 15-foot high poured-in-place color-treated concrete seawall. The concrete forms used for the wall were pre-sculpted by a local artisan to allow the finished product to mimic natural bluff appearance. The wall's construction included epoxy-coated steel and tiebacks placed approximately 10-feet on center.
As ongoing erosion of the mid- to upper coastal bluff finally exposed the rear-yard caissons, SEC recently completed the design and construction of an additional two rows of lower tiebacks and completed the surfacing of the upper bluff retention wall. After steel and concrete were placed, drilled tiebacks were placed approximately 50 feet into the bluff, under the bluff top residence. The project was completed with a hand-sculpted, color-treated shotcrete finish designed to complement adjacent natural bluff materials. The finished project received accolades from city and coastal staff for its enhanced aesthetic appearance.
The initial project was permitted as an emergency with the City of Encinitas and received both emergency and regular permits from the California Coastal Commission. This recent, final project phase received all permits from the City of Encinitas, in consultation with the Coastal Commission.
Coastal Bluff Stabilization (50' upper; 50' lower)
Coverage of Retention Walls: 2,000 Sq. Ft.
31 Drilled Tiebacks (Upper and Lower Walls)
Hand-Sculpted / Color Treated Shotcrete Finish (Upper Retention Wall)
Poured-In-Place (in Hand-Sculpted Concrete Forms) Lower Bluff Seawall
