Exhibit 16.1 Office of the Chief Accountant Securities and Exchange Commission 450 Fifth Street, N.W. Washington, DC 20549 April 5, 2002 Dear Sir/Madam: We have read the paragraphs 1 through 4 of Item 4 included in the Form 8-K dated April 5, 2002 of Colonial Gas Company filed with the Securities and Exchange Commission and are in agreement with the statements contained therein. Very truly yours, ARTHUR ANDERSEN LLP cc: Dennis Carroll, Vice President and Controller, Colonial Gas Company