Detailed Report on Ashepoo-Coosaw Alternate, AICW Statute Mile 517
Once again we are indebted to Captains Mark and Diana Doyle for this excellent report from the alternative route to Ashepoo-Coosaw Cut-off which is a perennial shoaling spot. As the Ashepoo-Coosaw Cut-off has silted in further, we have had several reports of the use of an alternate route to by-pass the shoaling, see /?p=145074. For a chart of Ashepoo-Coosaw Cut-off, scroll northwest on the chartview and don’t forget to check Argus from the top bar to see the shoaling.
Diana and I ran the alternative route out into St. Helena Sound and around the Ashepoo Coosaw Cut-Off the other day … and found deep water all of the way.
For those interested in evaluating the option to avoid this ICW Trouble Spot [Ashepoo-Coosaw Cut-off], here’s a depth-annotated track and survey report:
Ashepoo Coosaw Cut-Off Alternative: St. Helena Sound Route
Diana and I transited the Ashepoo Coosaw Cut-Off Alternative on November 22nd, 2014 with about two-thirds tide and falling. (Small-scale overview, screenshot at upper right.)
The (northern) relevant tide station, Seabrook, has a Spring Tidal Range (STR) of 7.3 feet and our height of tide was 4.5 above MLLW.
Our plan was to run a southerly course, along the deeper charted waters west of Fenwick Island, through the marshes west of the Otter Islands, and into St. Helena Sound to round Combahee Bank and then proceed northwesterly up the Coosaw River to rejoin the ICW near R186 and STM 519.
A few observations on this alternative route:
1. The alternative route is longer than the preferred ICW Magenta Line route but avoids the Ashepoo Coosaw Cut-Off ICW Trouble Spot. At lower water stages, some cruisers may wish to evaluate this option.
2. There are few significant navaids to follow for this alternative route. The route is fairly well charted, but unaided.
3. St. Helena Sound can often be `boisterous’ and busy with shrimping traffic.
4. We experienced water depths of no less than 16 feet (11.5 feet adjusted for MLLW) on the transit. The lowest water was along Fenwick Island, then deepening into the 20s and 30s, and even 40s, 50s, and 60s for the St. Helena Sound and Coosaw River portions.
5. Note that we chose to move farther easterly of the extending shoals at Combahee Bank than some other reports have advised. There are varying reports of success, although also noting substantially less water, by splitting the charted dayboard on Combahee Bank and the charted 15-foot shoal. Shrimpers and other locals have reported substantially more water eastward of the 15-foot pocket, which we experienced during our depth survey (see primary screenshot to right).
Again, no recommendation being made here. Just sharing data. Captains are responsible for their decisions and outcome.
Captains Mark & Diana Doyle