Sloat Restoration through Managed Retreat

Sloat Restoration through Managed Retreat
This is our original vision for Sloat Restoration - graphic courtesy of PSA and Associates and the Ocean Beach Task Force

Our Vision of Beach Restoration and Preservation

We advocate a managed retreat strategy to restore both Ocean Beach south of Sloat and Sharp Park. At Sloat, our vision involves:

A long-term plan to relocate threatened infrastructure
(including the south of Sloat Great Highway, the two oceanside parking lots and the sewer lines underneath them).

The cleanup of all the rock and rubble littering the beach.

The use of sand dunes as the primary tool to slow erosion.

For Sharp Park, we advocate the decommissioning of the golf course, the removal of the rip-rap berm, and a full restoration of the wetland.

Tuesday, January 26, 2010

2005 Storm Damage Protection Project Report

So I went through the 2005 Storm Damage Protection Project Report for the USACE and SF DPW (thanks to DPW for the posting it) and it gives a better overview of the shore protection problem up to 2005. I summarized a few of my favorite points: points that may shed light on 2010’s problem, but I encourage you to download the report and skim it yourself.

My Favorites Points:

The description of the different interests involved: pulling apart the road, from the lots, from the outfall pipe, from the Merced Transport pipe, from the bluffs. An outline of the interests on page 2-26 was originally by the SF Parks and Recreation Dept in 2002. The public discussion in 2010 often lumps all the interests together so it becomes difficult to weigh the cost/benefit and scope of different solutions.

Figure 3-3 on page 53 of the *.pdf shows a diagram of the most recent rip rap placement (referred to as Emergency Quarrystone Revetment) between first and second lots.

Moffatt and Nichol’s 1995 description of the coastal morphology starting on page 3-13. It indicates the the south lot area’s sand source is derived largely from the bluffs, and goes over seasonal reversals based on the wave climate.

Just like today: USACE (and other by CH2M Hill) 1996 study included the scenario where the lots were eroded and the Merced Transport box was threatened. The summary of this report is brief, but the area of the 1996 study appears to be further north in way of the lots, rather than just south of the outfall pipe where is 2010’s problem is. It gives a 22% chance of damage to the Merced Transport box, but it’s unclear if that is on a “per year” or “per storm” or what the relevant time scale is once the roadside has been reached. See page 3-16.

CH2M Hill reports that the southern reaches show large fluctuations in the area of the shoreline on page 3-25, and subsequent plots by Moffatt and Nichol show very large fluctuations of the shoreline of up to 100 to 150 feet.

Comic relief: When discussing constraints of different alternatives on 4-15, it notes that gorillas displays aggressive behavior during noisy earthwork. It’s tough to imagine a project with more exotic constraints.

Preferred alternatives are identified by each stakeholder on page 5-6. In 2005, as in 2010, the DPW prefers a hard structure over other alternatives for its lower maintenance cost.

Quoting from the discussion of acceptable alternatives on page 5-8, “SFPUC could not support any of the options that would result in the loss of the traffic lanes and possible exposure or loss of cover to the Lake Merced Transport facilities. The north bound traffic lane is important to the SFPUC as a means of access to the Oceanside WPCP. The northbound lane is also important in case of emergency in order to have two means of egress out of the WPCP facility. There is also concern that if the cover on the Lake Merced Transport is reduced there could be issues with structural stability or buoyancy effects.” The 2010 discussion has focused on the DPW’s interests; I’m curious as to why the PUC did not bring their interests to the public debate when the northbound lanes first closed. (Perhaps PUC is satified with the alternate routes onto Harding Rd and Armory Way and no longer considers Great Highway critical.) In 2005, DPW needed anything besides “no action.”

A stakeholder agency workshop held in 2005 gave all the agencies a chance to look at various alternatives. The DPW’s acceptable solutions listed on 5-12 include nearshore sand placement (which was the strategy adopted) and hard structures on the existing (then existing?) shoreline, presumablely for their lower maintenance cost. The SFPUC was willing to try anything that did not involve facilitated retreat or doing nothing. Each agency’s conclusions are summarized in a chart on 5-15.

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