Have you wondered what those strange looking things are sticking up out of the water at Des Moines Beach Park?

Rest assured they're not the foundation for underwater condominiums-or a new city hall-with free-floating fish tanks. It's all about "sewer." Who would challenge that need?

Midway Sewer District's project, awarded to General Construction Co., is to complete the last 2,100 feet of a 48-inch diameter sewer outfall pipe that has been half finished for years.

This construction is vital to on-going housing and business growth within the district's six cities served-Des Moines, SeaTac, Normandy Park, Burien, Federal Way and Kent, plus Sea-Tac International Airport.

Midway Sewer District General Manager Ken Kase said, "The new outfall will prevent treated effluent from overflowing into Des Moines Creek during major storm events and accommodate increasing sewer demand. This water pollution control project will help serve communities well for 50 years or more."

Management and workers don't like disrupting beach and park use.

"The District has done a lot of construction recently placing a burden on the community we serve. It slowed traffic, kept people up after normal work hours and temporarily compromised public use of the beautiful Beach Park, Kase said.

"I noticed how understanding and cooperative people have been. It's a reflection on the people who make up this community and understand the work being done is important."

He explained the work plan this way.

There are five distinct construction zones in this project, each with specific challenges.

General Construction subcontracted the tunnel portion of pipeline work to Northwest Boring, who bored a tunnel underneath the bluff on the north side of the uphill pathway, terminating 290 feet away on the beach.

Tri-State was subcontracted to do the inter-tidal pipeline portion, burying the outfall in the beach from extreme low tide with four feet of cover-up. The inter-tidal operation ends at a length of about 575 feet at the beach seawall.

Working within a marine habitat, workers must operate within a narrow corridor minimizing impacts to the beach and eelgrass by using sheet piling and dewatering equipment.

The habitat zone with tidal constraints and handling eelgrass for sea life, including salmonids, is critical.

General Construction will work nighttime high tides, moving to deeper daytime water approaching eelgrass beds. Required temporary removal of a swath of eelgrass is under the direction of marine biologist Michael Kyte with Entrix and his team, employing state-of-the-art eelgrass harvesting and planting techniques ensuring eel-beds restoration.

Construction is slow in eelgrass zones, only 60-80 feet per week. Eelgrass will be replanted and monitored for five years or more.

Following the eelgrass zone, the next 180 feet of underwater trenching and pipe burial gets shallower until the pipe emerges onto the sea floor. The remainder of the outfall will be held in place with concrete anchors staring about 55 feet below the Sound's surface.

The 48-inch diameter outfall pipe and last 300 feet of telescoping diffuser pipe meet strict dilution criteria at both low and high flow conditions.

The outfall ends 1,800 feet offshore at a depth of about 170 feet below the surface of Puget Sound, north and beyond the fishing pier.

Even the old outfall pipe will see future use by the Des Moines Creek Basin Committee to help prevent flooding, erosion and damage to the streambed environment.

If you haven't talked to project inspector "Ole" Olson, you should. Single-handedly, he's a great public relations guy, savvy inspector, patient with public questions and likes pampered pups.

Ken Kase said, "We apologize for any inconvenience and will restore the park as good or better when finished."

Meantime, the attention-grabbing progress is fascinating!

Thought for the week: He who has all the answers hasn't heard all the questions.