Engineering Disciplines


Services

Bulkheads & Retaining Walls

Sausalito Yacht Harbor Bulkhead Repair, Sausalito, CA.

NCI performed the engineering design for replacement of a 500-foot timber pile bulkhead. Services included a site and geotechnical investigation; topographic and boundary survey; feasibility analysis of alternative construction materials and methodologies; final design; and preparation of plans, specifications, contract documents and construction cost estimate. The improvements included a tied-back concrete sheet pile bulkhead, public promenade, landscaping, drainage and repavement of the parking lot.

Bolinas Lagoon Bulkhead Design and Construction-Phase 1 & 2, Stinson Beach, CA

This project consisted of replacing a failing bulkhead with a new bulkhead along 670 lineal feet of Bolinas Lagoon, fronting ten properties from 331 Seadrift Road through 349 Seadrift Road at the western end of Seadrift Road within Seadrift Estates. NCI provided all required engineering services consisting of the initial assessment/feasibility of bulkhead repair alternatives; processing and securing all required regulatory permits; performing engineering design of the selected bulkhead alternative; preparation of construction drawings, specifications and contract documents; contractor bidding and award/negotiation of contract; and full time construction management and inspection during construction. The selected bulkhead alternative consisted of installing epoxy coated interlocking steel sheet piling anchored by Chance helical anchors/tie-rods which attached to the sheet piles by use of a double steel channel waler system spanning the length of the bulkhead and that was encased within a reinforced concrete bulkhead cap. The new bulkhead system was installed during 1988 directly behind the failing bulkhead with the failing bulkhead then removed after installation of the new bulkhead sheet piles.  The initial site inspection for this project was performed during early 1997.

In 1998 NCI performed the same services described for the Phase 1 project in order to extend this new bulkhead 230 lineal feet to the west to replace the failed portion of existing timber bulkhead fronting the Seadrift Tennis Club (Phase 2).  The only difference in this Phase 2 bulkhead design was that a conventional continuous buried concrete deadman with tie-rods secured to the bulkhead’s steel waler system as the bulkhead’s anchor system was used instead of the chance helical anchors since there was sufficient open space directly behind the bulkhead for the concrete deadman anchor system.

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Newport Harbor Patrol Headquarters Bulkhead, Newport Beach, CA.

NCI initially evaluated alternative replacement bulkhead designs, and then performed the final engineering design and preparation of construction drawings and specifications for the selected alternative. This replacement bulkhead consisted of a coal tar epoxy coated steel sheet pile bulkhead driven into a very hard bottom. The bulkhead was anchored by use of a double corrosion protected Dywidag tie-rod system secured to the sheet piles by use of a double steel channel waler, and anchored on the landward side by an anchor system consisting of tension and compression steel H-piles with a reinforced concrete cap per each tie-rod. The tension piles also incorporated drilled/grouted Dywidag rock anchors for additional tension capacity. A reinforced concrete cap encased the steel channel waler and top of sheet piles. This new bulkhead was installed directly outboard of the 50-year old existing bulkhead prior to construction of the new County harbor patrol headquarters building and other site improvements. NCI also provided construction support services throughout the bulkhead's construction.

Coronado Cays Waterfront Development, San Diego, CA.

NCI provided planning and engineering design services for the marine aspects of this $100-million waterfront development, which included over five miles of reinforced concrete sheet pile bulkheading, riprap slope protection, floating breakwater protection, dredging, and marking of navigational channels. Work included the preparation of plans, specifications and construction cost estimates, along with onsite construction inspection.

Plum Island Bulkhead Replacement, Foster City, CA.

NCI provided all waterside engineering for the development of Ventura Keys, a residential waterfront community, which is located adjacent to and north of Ventura Harbor, and shares the Ventura Harbor entrance channel to the ocean. The residential waterfront channels and slope protection were excavated and constructed in the dry prior to final excavation of the earth plug separating the development from the ocean waters. Engineering planning and design services included excavation/dredging of the channels/side slopes; stone riprap slope protection; and floating docks, piling and gangways for the entire development. Construction support services were also provided during construction of this waterfront community.

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Dredging, Bulkhead & Fender Improvements Berth D-46 Port of Long Beach Facility, CA.

Noble Consultants performed a preliminary engineering and construction cost assessment for the repair and rehabilitation requirements for G-P Gypsum’s Berth D-46 Port of Long Beach facility.  The purpose of NCI’s services was to provide recommendations regarding the most economical approach to maintain the plant’s bulkhead protection, rehabilitate the deteriorated wharf fender system, and restore project depths within the bulk carrier berth.

The G-P Gypsum Berth 46 plant receives deliveries of gypsum ore by bulk carrier on a monthly basis.  The existing berth is 640 feet long with an existing depth of -31 to -33 feet MLLW that requires dredging in order to deepen to a projected depth of -38 to -40 feet MLLW.  NCI evaluated dredging methods, disposal alternatives, dredged channel stabilization retention structures, permit requirements, and opinion of construction costs.   In addition, NCI evaluated alternative designs and construction methods including opinion of construction costs to replace the wharf’s deteriorated fender system and to rehabilitate and replace its deteriorating bulkhead system.

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Bolinas Lagoon Bulkhead Design and Construction-Phase 3, Stinson Beach, CA

During 2007/2008 NCI performed the final engineering design; regulatory permit processing; preparation of construction drawings, specifications & contract documents; contractor bidding; award of construction contract; and the construction management & resident engineering inspection during construction for the Phase 3 Bolinas Lagoon bulkhead project. NCI had previously performed the inspection of the existing bulkhead, assessment of repair alternatives, design investigations and conceptual design for the proposed new bulkhead during 2006/2007.  This project consisted of the easterly extension to a replacement bulkhead project that was permitted and constructed in 1998 (Phase 1).  The design and construction of this project was similar to the earlier project and included bulkhead replacement for the ten properties from 307 to 329 Seadrift Road, approximately 750 lineal feet of new bulkhead in the same location as the existing failing bulkhead, except this bulkhead was constructed using 26-feet long steel sheets versus the 35-feet long steel sheets used in the bulkhead to the west, and had anchored tie-backs placed at twelve feet on-centers versus the eight feet on-centers used in the bulkhead to the west.  The reason for using the shorter steel sheet pile lengths and wider anchor tie-back spacing for this bulkhead was that the design scour depth fronting the bulkhead was less than the design scour depth used for the existing replacement bulkhead to the west, and therefore resulted in lower design lateral loading.

The new steel sheet pile bulkhead was driven in-place by use of an overhead crane with a vibratory hammer.  All construction and construction equipment was performed from the landside with no construction activity performed from the Bolinas Lagoon.  Chance helical anchors (tie rod and helices) were installed at twelve feet on-centers through the steel sheet piles by use of a small bobcat from landside in order to anchor the top of wall.  The tie rods were 43 feet in length and placed at a 30 degree angle from horizontal in order to penetrate the denser sandy materials.  A double steel channel and wide flange beam wale system secured the tie rods to the steel sheet piles at elevation +8.5 feet NAVD (top of wall at +10.0 feet) with a reinforced concrete cap formed and cast in-place.  This Phase 3 bulkhead replacement resulted in a total of 1,650 lineal feet of bulkhead being replaced since Phase 1 included 670 lineal feet in 1998, and Phase 2 included 230 lineal feet in 1999.

 

 

 

 

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Seadrift Lagoon Bulkhead Design and Construction, Stinson Beach, CA

From 2002 through 2005 NCI performed the following scope of services for the replacement of over 12,000 lineal feet of existing deteriorating timber bulkhead fronting 127 properties on the Seadrift Lagoon with a new bulkhead; initial site inspection and assessment of existing timber bulkhead; preparation of detailed site base map after performing aerial photography/mapping and hydrographical/bathymetric survey; preparation of conceptual new bulkhead layout and plan including detailed report of alternative bulkhead comparisons; participating in numerous stake holder’s meetings to address findings and recommendations; processing and securing all required local, state and federal regulatory permits; preparation of final design, construction drawings, specifications and contract documents; contractor bidding and award of construction contract; and full time construction management and resident engineer inspection.

The new constructed bulkhead consisted of a cantilever coated steel sheet pile bulkhead with a timber waler/cap.  The new bulkhead was installed in the same location as the existing bulkhead as it was being removed.  All construction work involving the removal of the existing bulkhead and installation of the new bulkhead was performed from the water side utilizing low draft flexi pontoon floats (barges).

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Dana Headlands Pedestrian Walkway, Retaining Wall and Stairway, Dana Point, CA.

As part of the Dana Headlands development, a walkway and associated retaining wall was built atop the shore protective revetment to promote public use and enhance the aesthetic scenic view. To construct the walkway, following installation of the center footing and stem wall, forms were set on the graded surface along each edge of the walkway.  The walkway was cast against grade and temporary support from the riprap along the beach side of the structure.  The cantilevered slab concept did increase thickness and reinforcement in the section; however, those additional costs were made up in reduced labor and materials costs eliminating the down-slope supports for the structure.

Beach access, through the riprap revetment, is provided by an ADA compliant stairway and an emergency-vehicle access ramp.   The stairway is oriented diagonal to the alongshore alignment to minimize wave uprush, with the stairs accommodating a sand elevation range of over 10-feet. The cast-in-place concrete structure is founded on spread footings keyed into bedrock at the base and bearing on competent soil near the top.

To thoroughly understand behavior of the structure under loading and settlement scenarios, a finite element model was used in the structural analysis. Stress levels in the structure, when subjected to lateral earth or seismic forces depend largely on the soil characteristics that support it. By modeling the soil as springs in the finite element analysis, and altering spring constants to cover a safe range of soil characteristics, stress envelopes reflecting the worst-case scenario for all loading and soil combinations were clearly defined. Using this approach produced a design that reliably meets its service requirements.

 

 

 

 

 

 

 

 

 

 

 

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