Attached, as 2 jpg files, is the Corps of Engineers Letter regarding the
lack of need for dredging as well as their chart of the
Occoquan showing the channel. Please read the language carefully and
look at their chart. Commodores, you are encouraged to pass this
information to your members.
Some interesting observations:
1. At their own
admission, the Corps has paid no attention to the silting in the Occoquan
Channel for nearly 40 years!
2. The outer channel
(from along Conrad Island all the way to the Potomac) is supposed to be
wider than we thought (150 x 6 ft) - it isn't, especially near
Conrad Island. I don't believe that the navigational markers even
appear to be 150 ft apart there - this needs to be checked.
3. The Corps is
measuring depths at Mean Low Water. All normal NOAA Navigational
Charts are marked in depths of Mean Lower Low Water - which could
make an adverse difference of a foot or more to mariners.
(There are two low tides in each tidal cycle -usually two low tides in
each day. These two low tides are not quite the same height because one
tide is generated by the gravitational interaction with the sun (which is
small), and the other is generated by the gravitational interaction with
the moon (which is not so small). Since the two low tides (or water
levels) are different levels of low, one is naturally the higher low
water (higher low tide) and the other is the lower low water (lower low
tide). So Mean Lower Low Water is the average of the lower low water
height of each tidal day (ie average of the lowest low tide from each
day).
4. The boxes on their
chart must be where they dredged before. The annotation on the chart
indicates that the channel(s) encompass the entire river
("creek") all the way to the upstream side of the Town Jetty,
but not in front of the town any further than the town park.
5. The Corps' 1985
chart is so out of date that it doesn't even show the current Route 123
Bridge. It shows the old Occoquan Bridge which was washed out in
1972.
