Active and Passive Anchor Systems in Long Beach — Design That Holds When Soft Ground Won't

We have seen too many shoring failures in Long Beach that trace back to one assumption: that a single row of passive anchors will hold in saturated sand behind a tidally influenced bulkhead. The harbor area and downtown zones sit on young Holocene deposits where groundwater fluctuates with the San Gabriel River level and harbor tides — a condition that makes anchor creep a real risk if the bonded length is not designed beyond the active failure wedge plus a safety buffer for pore pressure variation. For deep excavations along Ocean Boulevard or retention structures near the Port of Long Beach, the difference between a working system and a costly remedial job often lies in how the unbonded length is calculated under ASCE 7 seismic load combinations. We integrate the site-specific SPT data from our SPT drilling program directly into the anchor load-transfer analysis, ensuring that the grout-to-ground bond stress values reflect the actual fine-grained sand layers present at the project depth, not a generic textbook range.

In Long Beach, anchor bond length is not just about pullout — it is about keeping the unbonded zone clear through layers that want to collapse.

How we work

The physical installation of an active anchor in Long Beach typically involves a rotary duplex drill rig that can case through the loose recent alluvium and weathered sandstone of the Palos Verdes formation without collapsing the hole. Because the city sits atop the Newport-Inglewood fault zone and much of the downtown is underlain by liquefiable silty sand from the Los Angeles River floodplain, the rig must be capable of maintaining hole stability while installing the tendon through zones where the standard penetration resistance can drop below N60=8 between depths of 15 and 30 feet. The tendon itself is usually a 150-ksi Grade 270 strand assembly, with the unbonded length sheathed in smooth PVC to prevent grout adhesion within the free-stressing zone. At the bond length, the corrugated sheathing transitions to a textured profile that enhances mechanical interlock with the neat cement grout, injected under pressure through a tremie line that withdraws as the column fills from the bottom up — a method that is non-negotiable when working within 500 feet of the mean high tide line because it prevents saltwater intrusion from contaminating the grout column during curing.

Local geotechnical context

The risk profile for an anchor system shifts dramatically between two areas of Long Beach: the Belmont Shore/Peninsula neighborhood versus the inland Signal Hill area. At Belmont Shore, anchors are typically installed through loose beach sand with the water table less than 8 feet below grade; the bond zone is frequently submerged, and the risk of hydrofracture during grout injection is high enough that we limit injection pressure to less than 0.5 psi per foot of overburden and monitor for daylighting continuously. By contrast, a project near Signal Hill encounters stiff Pleistocene-age clays and cemented sands that provide excellent bond capacity but introduce a different failure mode: the tendon can kink at the interface between the stiff clay and the softer alluvium if the borehole deviates more than 2 degrees from the design inclination. In both cases, the common thread is that a proof test to 133% of the design lock-off load — held for a minimum of 10 minutes with creep not exceeding 0.04 inches — is the only reliable way to confirm that the anchor will perform under the long-term sustained load of a tied-back retaining wall or a deep basement excavation.

Technical data

Parameter	Typical value
Tendon type	Grade 270 (270 ksi) 7-wire strand per ASTM A416
Typical anchor capacity (working)	100 to 350 kips per anchor
Bond length range	15 to 45 ft, dependent on soil type and N-value
Unbonded length minimum	15 ft or 120% of excavation depth, whichever is greater per PTI DC35.1
Design standard	ASCE 7-22, IBC 2024, PTI Recommendations for Prestressed Rock and Soil Anchors
Grout compressive strength (28-day)	5,000 psi minimum, neat cement, w/c ratio ≤ 0.45
Corrosion protection class	Class I (double corrosion protection) within 1,500 ft of shoreline

Related services

Active Tieback Anchor Design and Proof Testing Protocol

Full design package including bond length calculations based on load-transfer curves derived from site-specific SPT data, unbonded length verification per the excavation depth and soil wedge geometry, lock-off load specification, and a detailed step-by-step proof and performance test procedure aligned with PTI DC35.1. We specify the drilling method, grout mix, and corrosion protection class per the site's distance from the shoreline.

Passive Anchor and Soil Nail Wall Design

Design of passive bar anchors and soil nail arrays for cut slopes and excavations where prestressing is not required. This includes pullout resistance verification along the grouted length using the effective stress method with beta-coefficients calibrated to the local fine-grained sands, and a facing design that accounts for the moderate seismic demands of the Long Beach area under ASCE 7.

Relevant standards

ASCE 7-22 (Minimum Design Loads and Associated Criteria for Buildings and Other Structures), IBC 2024 (International Building Code, Chapter 18 — Soils and Foundations), PTI DC35.1-20 (Recommendations for Prestressed Rock and Soil Anchors), ASTM A416/A416M (Standard Specification for Low-Relaxation, Seven-Wire Steel Strand for Prestressed Concrete)

Common questions

How much does an active/passive anchor design cost for a project in Long Beach?

For a single-family lot or small commercial excavation with three to five tieback rows, the anchor design package typically ranges between US$950 and US$3,420, depending on the number of test anchors required, the complexity of the subsurface profile, and whether the project is within the Coastal Zone requiring additional corrosion protection analysis.

What is the difference between active and passive anchors in a shoring wall?

An active anchor is prestressed — we apply a lock-off load after the grout reaches strength, which immediately engages the anchor and limits wall deflection. Passive anchors are not prestressed; they only develop resistance when the wall moves and the ground strains. In Long Beach, we specify active anchors for nearly all tieback walls deeper than 12 feet because the allowable lateral deflection under adjacent structures along streets like Pine Avenue or Atlantic Boulevard is typically under 1 inch.

How close to the shoreline can you install grouted anchors without corrosion concerns?

Within 1,500 feet of the mean high tide line, we follow PTI Class I corrosion protection requirements, which means each strand has a corrugated plastic duct filled with grout over the full length, plus an outer encapsulating duct over the bond length. We also use epoxy-coated bearing plates and trumpets at the anchorage head. This double-corrosion-protection system is designed to meet the 75-year service life requirement in an aggressive marine environment.

Do you perform the load testing, or just the anchor design?

We provide the design and the complete proof testing protocol, including the acceptance criteria for creep, the load-hold schedule, and the dial gauge monitoring frequency. The actual pulling is usually performed by the specialty anchor contractor, but we are on-site during the first two proof tests to verify that the load-displacement curve does not indicate a bond failure or an undersized unbonded length — a situation we have caught more than once in the layered soils near the Long Beach Convention Center.