Damaged Goods

Demolition is scheduled to start today on the problem-plagued Aliso Pier, which was declared unsafe in September. Poor design and construction--not wave damage--are the primary reasons it crumbled. It may never be rebuilt, due to lack of funds.

WHY PIER CRUMBLED

Deck and pile caps:

* Made of lightweight concrete too porous to withstand prolonged exposure to ocean water and salt air

Pilings:

Made from normal-weight, pre-stressed concrete. Theories explaining failure:

* Use of improperly mixed, inferior concrete

* Microscopic cracks occurred while piles were driven into ocean floor

* Concrete layer surrounding steel-reinforcement rods too thin

* No lateral-support bracing

Ocean water and salty air seep through concrete, causing steel-reinforcement rods to rust and swell. Swelling causes concrete to fall off in chunks and rods to break

Leapfrogging the Crane

Workers use a leapfrogging technique to move the demolition crane along the length of the pier. The process is reversed for the return trip.

1. Crane rolls to next section of platform

2. Crane turns, lifts vacated section in level position, using guide wires

3. Lifted section placed on next set of pilings; crane returns to work

WHY REPAIR FAILED

The pier underwent an unsuccessful repair effort in 1988-89:

How Repair Was Done

Cracks in deck, pile caps and piles injected with epoxy cement; most severely damaged areas of seven pilings jacketed in steel above water and coated with epoxy cement; entire pier coated with waterproof epoxy paint.

Why It Didn’t Help

* Most severe piling damage existed underwater and was never addressed

* Concrete so corroded by ocean moisture that deterioration continued beneath jacketing and waterproof coating

* Jackets added stress points, making pilings more vulnerable to wave damage

* Sealants do nothing to replace lost structural strength

DEMOLITION PROCESS

Preparation: Pier deck is pressure-washed; railings, light standards, benches and sinks removed. Steel piles are driven every 50 feet along pier to support crane platform, two 25-foot platform segments are positioned

First pass: Debris carts, running on pre-constructed track, haul sections of pier deck ashore to be trucked away. Sections have been sawed into thirds length-wise, leaving the closest section as a walkway.

Return trip: Pile caps, pilings and remaining deck slabs removed.

Piling Removal

1. Pipe fitted over piling.2. Pressurized ocean water jetted into pipe to clear away sand and rock

3. Freed piling removed by crane and dumped into debris cart

Price Tag

* 1971 original construction: $672,426

* 1988-89 repair: $1.2 million

* Cost to demolish: $1 million

* Estimated cost to rebuild: $5 million-$7 million

Sources: Orange County Public Facility and Resource Dept., Traylor Pacific, Moffat & Nichol Engineers, Times reports

Graphics reporting by JANICE JONES DODDS / LOS ANGELES TIMES