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CITY OF ANAHEIM DRAINAGE MANUAL FOR PUBLIC AND PRIVATE DRAINAGE FACILITIES DIVISION I 3 AUGUST 2005 DIVISION I ORANGE COUNTY HYDROLOGY MANUAL REVISIONS, DELETIONS, AND ADDITIONS ---PAGE BREAK--- CITY OF ANAHEIM DRAINAGE MANUAL FOR PUBLIC AND PRIVATE DRAINAGE FACILITIES DIVISION I 4 AUGUST 2005 TABLE OF CONTENTS DIVISION I ORANGE COUNTY HYDROLOGY MANUAL REVISIONS, DELETIONS, AND ADDITIONS PAGE SECTION 1— REVISIONS, DELETIONS, AND ADDITIONS 5 SECTION A. INTRODUCTION 5 ---PAGE BREAK--- CITY OF ANAHEIM DRAINAGE MANUAL FOR PUBLIC AND PRIVATE DRAINAGE FACILITIES DIVISION I 5 AUGUST 2005 SECTION 1 – REVISIONS, DELETIONS, AND ADDITIONS As stated in the Introduction, the City of Anaheim has adopted the Orange County Hydrology Manual (OCHM, including addendums) as the governing manual for hydrologic analysis within the City of Anaheim except as modified below. An understanding of the criteria presented in the OCHM is necessary for the competent preparation of hydrologic studies in the City of Anaheim. In addition to the OCHM, revisions, deletions, and additions to the OCHM described in this section shall be incorporated into the hydrologic analysis and design of all storm drains in the City of Anaheim. SECTION A. INTRODUCTION Subsection A.2. HYDROLOGIC PROTECTION LEVELS, second paragraph, as shown on page A-1, shall be revised as follows: Additionally, it is the design objective of the City of Anaheim to afford specific design criteria for the more frequent flood events. That is, flood protection levels for 10-year and 25-year floods shall be required as outlined in Division II of this manual. The minimum recurrence intervals for the design of new local drainage facilities shall be: 1. Habitable structures shall have 100-year flood protection. 2. A 25-year storm event for all open and underground channels and storm drains with drainage areas less than 640 acres, and tributary to the Santa Ana River watershed. 3. A 10-year storm event for all open and underground channels and storm drains with drainage areas less than 640 acres, and tributary to all other watersheds. The above criteria are the minimum requirements for sizing a storm drainage system and that sizing shall be increased, as necessary, to address all requirements including those noted for the 100-year event. To Subsection A.2. HYDROLOGIC PROTECTION LEVELS, as shown on page A-1, add the following: For drainage systems in the City of Anaheim, the analysis of all storm events 10-, 25-, or 100-year) shall be based on the “high confidence level” storm frequency event.