U.S. Army Corps of Engineers New Orleans District: Chalmette Power Line

: Chalmette Power Line

NAVIGATION

Chalmette Power Line Mini-Inland Electronic Navigation Chart

The Chalmette Power Line Mini-IENC is a large-scale, specialized type of an Inland Electronic Navigation Chart (IENC). This Mini-IENC utilizes both real and virtual chart features to represent and display essential navigation information for a power line area that crosses the Mississippi River at Chalmette, LA. This electronic chart was created using standard navigation chart techniques but is also augmented by unique presentation of operating areas and virtual buoys that perform the same function as real buoys.

This project was initiated when the Carnival Cruise Lines' Conquest vessel needed assistance to pass safely under Entergy Corporation power lines crossing the river near Chalmette. Responding to a Crescent River Port Pilots Association recommendation, the New Orleans District provided a "total package solution" to include IENC development, pilot training, Navigation System, testing and deployment, and coordination between the river pilots, Carnival, and Entergy.

Mini-IENC Concepts

The Chalmette power line presented the main hazardous navigation obstruction for a very high airdraft vessel, such as the Conquest. The height of the wires (185 ft. at its lowest point - LWRP datum at high water, as surveyed) is not sufficient across the full width of the river to allow the Conquest, with a 209-foot airdraft, to pass without navigating precariously close to the east bank where the lines are higher.

The Mini-IENC provides new, accurately surveyed power line data, combined with computed areas identifying Safe-Passage and Non-Passage under the wire's extent. For the first time, the Conquest crew and pilots have a navigation tool to visualize the horizontal clearance for safe passage.

The Mini-IENC was compiled using the standard IHO S-57 data format, which allows easy distribution and use by any navigation system reading S-57 electronic charting data. The combination of real and virtual features and objects is, in our experience, the first practical application of virtual objects for this purpose in electronic charts.

Diamond Shaped Precautionary Area

Chalmette Mini-IENC - Click for full-size image.

The diamond-shaped precautionary area is represented by a magenta dashed line with an inner-rectangle shaped warning area. The precautionary area was computed for 3, 8, 11, 14 and 17 foot river stages, accounting for the power line's clearance at that stage for the Conquest's air draft. Passing outside the precautionary area ensures a safe passage with the required buffer clearance between the ship mast and power line. Passing inside the precautionary area, but outside the inner warning rectangle will allow for ship clearance, but will drastically reduce the required buffer clearance. Although no collision would result, no guarantee can be assured for power line arcing. Inside the diamond shape is a small, but critical area. It represents the "Obstruction Area of No-Passage," centered on the power line's extent. It defines the Conquest air draft for that stage. If this area is entered, the ship's mast and the power line will make contact. The Conquest needs to avoid this area at all times.

Virtual Buoys

A unique advantage of the Mini-IENC is its ability to use "virtual buoys" and several types are used in the chart:

SAFE-WATER buoys. The Safe-Water buoys are red and white vertical striped buoys that act as lead-in navigation aids to assist in either a west or east bank approach and transit under the power lines. These buoys were placed at 1000-foot intervals, both up and down river of the power line. Each 1000-foot interval is approximately one Conquest ship-length and aids in determining relative distances.
RED NUN AND GREEN CAN buoys. These buoys mark approach sides of the diamond-shaped precautionary area, to assist in proper routing. The buoys were placed at 300-foot intervals, both up and downriver of the power line, signifying approximately 1/3 ship length, which represents the critical ship pivot point. Additional Green Can buoys were placed along the river's east bank to mark the 30-foot depth curve.
ISOLATED DANGER buoys. The Isolated Danger buoys mark the innermost "Obstruction Area of No-Passage." Six buoys mark the four corners and middle of the rectangle-shaped no-passage area. This marked boundary should never be invaded, as the ship will make contact with the power lines.

Current Modeling

Chalmette Area Current Model - Click for full-size image.

The Corps developed river current models for the power line area to more realistically represent water velocities and directions. Models were computed for 3, 8, 11, 14 and 17 foot river stages.

These river flow model data can be utlitized by ship bridge simulators to operate with added realism for ship handling training. Realistic ship simulator training allows river pilots and ship crews to have prior experience using the Mini-IENC charts while training for various power line approach scenarios.

Since the February 2003 Mini-IENC development, Entergy announced a power line reconfiguration (4/30/03) to be completed in Fall 2003. This change necessitates release of updated Mini-IENC charts as well. Revised Mini-IENCs are scheduled to be released in March 2004. This project and product development demonstrated USACE and New Orleans District ability to rapidly respond to emerging navigation safety conditions and to provide an information and technology solution to help mitigate hazards as they ensue.

March 2004 Status

Revised Mini-IENCs were released to the USCG and local Pilots on March 22, 2004. The Mini-IENCs U35LMC12, U35LMC13, U35LMC14, U35LMC15, U35LMC16, and U35LMC17 have been updated to Edition 2 dated March 2004, for the Lower Mississippi River (Mile 89.2 AHP).

These new editions were produced for 12', 13', 14', 15', 16' and 17' river stages, as indicated by the Carrollton Gauge. A differing feature of the Edition 2 Mini-IENCs is no hazard area representing a contact area at the lowest point of the power lines. No wire contact is computed with existing power line heights and river stages up to 17' on the Carrollton Gauge.

Mini-IENCs U35LMC00, U35LMC01, U35LMC02, U35LMC03, U35LMC04, U35LMC05, U35LMC06, U35LMC07, U35LMC08, U35LMC09, U35LMC09, U35LMC10, U35LMC11, and U35LMC18 have been cancelled. New S-57 .001 update files supporting the cancelled charts have been produced for use as needed.

April 2006 Status

The Inland Electronic Navigational Charts for the Chalmette Powerline Crossing were cancelled on Apr 06, 2006 via NAVIGATION BULLETIN NO. MVN 06-14. The restricting power lines were removed from the towers, effective March 31, 2006.

The remaining USACE "Chalmette" IENCs are cancelled:

U35LMC12 Edition 2, March 2004
U35LMC13 Edition 2, March 2004
U35LMC14 Edition 2, March 2004
U35LMC15 Edition 2, March 2004
U35LMC16 Edition 2, March 2004
U35LMC17 Edition 2, March 2004