[5] A later U.S. Army Corps of Engineers (USACE) inspection report said, "In 1985, the jetties at the mouth of the Siuslaw River were again extended seaward.

[5] The decline in Siuslaw presence in the watershed brought the start of white settlement, and the expectation the river would be used by larger commercial craft to transport resources and goods.

The report concluded, "The people living on the river... think that no improvement is required; all they ask is that an accurate survey be made and the depth on the bar be officially declared.

When this is done and the entrance buoyed, it is thought small steamers and schooners can be induced to run into the river, and reasonable insurance can be obtained on their cargoes.

[7] The USACE began constructing a tramway in late 1892, spending approximately $70,000 in the first two years to transport rock that had been brought down river by barge from a quarry in Mapleton.

[9] By 1900, the jetties were still under construction, slowed by inadequate funding and the inherent difficulties of building underwater with active river and ocean currents.

When the 1910 Rivers and Harbors Act required local interests to pay half the costs of federal construction projects,[12] the Port Commission sold $324,000 in retirement bonds.

[5] In December 1982, Congress approved $4 million to finance the first stage of a proposed $34-million extension of both jetties at the mouth of the Siuslaw River.

[19] In 1983 the USACE contracted with Kiewit Pacific Company of Vancouver, Washington to lengthen the jetties "to keep sand from drifting into the estuary and clogging the port's boat channel".

"[23] The report made specific design recommendations on the number of layers, shapes of armor stones, and placement of the rock to repair and construct different areas of the jetty's trunk and head section.

[24] Lizarraga Arciniega described the drift: In general, accretion of the shoreline took place adjacent to the jetties following their construction, both to the north and south.

[24]Between 1981 and 1991 the Coastal Engineering Research Center of the USACE conducted studies on "the impact of the jetty design on the entire area, including sediment shoaling in the channel and beach erosion or build-up".

[25][26] The World of Coos Bay described the study: The work is part of an ongoing process of monitoring the effectiveness of the unique Siuslaw jetty design.

These spurs are designed to trap sand and sediment moving along the shoreline, to keep it from entering the navigation channel and thus reduce the need for dredging... Beach profiles and dye studies have been used twice a year since 1981 to monitor the jetty area.

[27] The study concluded, "...the 1985 jetty improvements are a success... Navigability has been improved, construction cost of the spur system was estimated to be approximately $5 million less than the original design cost estimate for jetty extension... and annual maintenance dredging requirements have been reduced to approximately 100,000 cu yd".