Cape May Engineers Present Beach Safety Study

CAPE MAY – In an effort to deal with a history of injuries to beach goers occurring in the Cape May City surf, city officials tasked municipal engineering firm, Hatch Mott MacDonald, to evaluate the surf zone conditions and recommend potential actions which the city might undertake to increase beach safety. The firm reported results at the Dec. 15 city council meeting.
Cape May’s beaches are largely the result of design by the Army Corp of Engineers. Critical to the resort’s economy, beaches have been replenished on a regular basis with the first beach fill occurring in 1989.
The city has a 50-year arrangement with the Army Corp of Engineers and has never itself taken on the task to directly modify beaches. Potential liability arising from city intervention has been one of the debating points in the discussions about the present feasibility study by Hatch Mott MacDonald and the representative who serves as city engineer, Thomas Thornton.
The feasibility study’s objective was to identify possible actions where city intervention would be likely to have a positive impact on safety and to identify potential costs involved.
In a less than two month period, the firm approached the study by reviewing existing data extending back to the first federal beach fill projects, analyzing sand grain size, conducting a wave analysis along the beaches, and modeling projected waves under different criteria for beach slope.
In the presentation, the firm outlined potential alternative projects, but largely discounted all but one for a variety of reasons. The alternatives focused on mechanically altering beach slope, lowering crest height while also shortening length of selected groins, and altering the grain size in future beach fill projects.
The problem with any process, as outlined, is that analysis showed “beach fill projects have not resulted in steeper beach slopes in the surf zone.”
The slope problem is caused by natural rather than man-made activity. Altering grain size was evaluated but deemed “unlikely to have any effect.”
Alternatives requiring additional sand on the beaches were also seen as “unfeasible from a performance perspective” given that the added sand would be quickly vulnerable to wave action.
At issue is the fact that the seemingly natural slope of the beaches produces plunging wave action which compromises beach-goer safety even in relatively low levels of water. Changing wave patterns so as to eliminate or curtail the plunging wave type requires dealing with beach slope.
What the engineers recommended was a mechanical alteration of the foreshore slope. Essentially it involves using a bulldozer to change the slope. This would be a pre-summer activity that would have to be repeated whenever nature works to return beaches to their more natural slope.
The effort would join beach replenishment and back bay dredging as normal, expensive, periodic activities.
Engineers recommended that beach slope be adjusted from Queen Street to Grant Street. This would involve mechanically moving sand from down drift sides of groins back to the surf zone and into the dunes. This would result in a more uniform slope designated by the engineers as 1V:25H, meaning one foot vertical for every 25 feet horizontal.
With this slope, the intent is to alter the plunging wave action currently experienced. It would have the added benefit of providing increased resiliency to dunes in areas flooded by Sandy.
The firm recommended further study on how altering groins might result in gentler slopes. This option would, the engineers said, be more expensive and could result in less beach width.
The study also provided council with what Thornton called “rough estimates of cost.”
To accomplish the recommendation for the base project area, Queen to Grant streets, would cost $850,000. It would not be permanent and it would require on-going maintenance. To expand the project 375 feet west of Grant and east of Queen would require an additional $1 million.
Council will review the recommendation and make a decision on any future actions at its Jan. 5, 2016 meeting.
According to City Clerk Louise Cummiskey, an “Internet problem” caused the presentation to go unrecorded.
City’s council meetings are normally streamed live and then posted for future viewing. It is possible for the public to get a PDF version of the Hatch Mott MacDonald power point presentation from the city’s website under the category “Announcements.”
To contact Vince Conti, email vconti@cmcherald.com.