62 NAUTICAL CHART MANUAL 



TINTS IN WATER AREAS (R) 



On an increasing number of printed charts, a blue tint is shown in water areas to the curve 

 which is considered the danger curve for that particular chart. In general, the 6-foot curve 

 shall be considered the danger curve for small-craft and Intracoastal Waterway charts, the 12- 

 or 18-foot curve for harbor charts, and the 30-foot curve for coast and general charts. The 

 blue tint should be omitted within the dashed Unes used to indicate the side limits of dredged 

 channels when they connect with the untinted deeper water areas, regardless of depth of dredged 

 channel. 



As a blue tint enhances the value of a chart for navigation, it should be added to all charts 

 not now tinted which have curves complete enough to define the limits of the tinted areas. 



IV 

 Improved Channels 



CORPS OF ENGINEERS (D-De) 



The Corps of Engineers is the administrator of the Federal laws enacted for the protection 

 and preservation of navigable waters of the United States. They are authorized to establish 

 regidations for navigation therein, approve plans for structures of any kind, estabhsh anchorage 

 grounds and harbor hues, remove sunken vessels obstructing or endangering navigation and 

 grant permits for the installation of cables and pipehnes. They are also charged with the 

 improvement of rivers and harbors and the Intracoastal Waterways. Copies of surveys made 

 by the Corps of Engineers are furnished this Bureau for apphcation to the charts. 



IMPROVED CHANNELS (Figs. 1, 21) (Q-5, -6) 



The side limits of the improved channels are shown on the charts by dashed Unes. Except 

 when tabidated, the controlling depth with width and date ascertained are given within or 

 adjacent to the channel. Surveys, Monthly Reports, Annual Reports, and letters of the Corps 

 of Engineers are the principal sources of information for charting available depths. 



In addition to the surveys, detailed information regarding depths in the important dredged 

 channels is furnished, usually monthly, by the Corps of Engineers, on tabular forms. These 

 give the project dimensions, controlling depth in each quarter, and date of survey for channels 

 400 feet wide and greater, and the same information is given for channels from 100 feet to 400 

 feet wide except that the controlling depth is given for the middle half and for each outside 

 quarter. This information is disseminated by placing a similar tabulation on the charts, 

 usually in the form of a sticker and by pubhcation in the weekly Notice to Mariners. 



In general, tabular forms are not submitted by the Corps of Engineers for channels less 

 than 100 feet in width, or for channels having a project depth less than 10 feet, except coastal 

 inlets and harbors of refuge. Controlling depths reported for these channels are based on at 

 least 80 percent of the project width. 



Tabulated values should not be published in the Notice to Mariners unless a similar 

 tabulation is shown on the charts. 



