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Frequently Asked Questior. 2 2 June 2010 Waste Management Plans General Order No. R5-2007-0035 For Existing Milk Cow Dairies also be referred to as the 20-year ARI (annual recurrence interval) design flood. Similarly, under the Title 27 regulations, facilities or portions thereof which began operation after 27 November 1984 must be protected from inundation or washout during 100-year peak stream flows. Additional language regarding flood protection requirements is contained in the Tulare Lake Basin Plan and in the General Order; please see page 12, General Specifications No. 2 and 3, of the General Order for more information. Unfortunately, there are few sources for a determination as to whether a facility is in a 20- year ARI design flood area, as the Federal Emergency Management Agency (FEMA) flood maps are drawn for the 100-year ARI design flood. In the absence of a 20-year ARI flood map, first determine if the production area is outside the boundaries (outside the shaded areas) of the 100-year ARI design flood. If an area is outside the 100-year ARI, it will be outside the 20-year ARI. Zones B, C, and X are outside the 100-year ARI. This link describes all the FEMA flood zone classifications: http://www.msc.fema.gov/webapp/wcs/stores/servlet/info?storeld=10001&cataloqld=10001 &langld=-1&content=floodZones&title=FEMA%20FIood%20Zone%20Designations . At this point, determination of the elevation of a specific flood is typically performed by modeling of a natural river or other channel by an engineer. The model most commonly used was developed by the Hydrologic Engineering Center called the River Analysis System. These modeling runs are commonly referred to as HEC-RAS studies. However, these analyses are frequently expensive to run. An alternative to modeling the 20-year ARI could be to have an engineer determine the depth of flooding on the property should the 100-year ARI flood occur. Based on discussions with engineers, it appears that in most cases there will be little difference in height between the 20-year ARI and the 100-year ARI flood. 3. What if there is no depth of flooding defined for my production area, such as areas labeled "Zone A" and "Zone D" on the FEMA maps? Sometimes areas that are actually above the 100-year flood level are inadvertently shown as within the boundaries of the 100-year ARI design flood because of limits of scale or topographic definition of the source maps used to prepare inundation maps. Sometimes no depth of flooding is shown on the map. To resolve either of these issues, you can request a Letter of Map Addendum (LOMA) from FEMA. To request a LOMA, go to the FEMA website at http://www.fema.gov/plan/prevent/fhm/dl mt-1.shtm . Complete the MT-1 form and mail it, following the instructions at the link above. FEMA staff will review the site information and render a determination in 4 to 6 weeks. If you need to request a LOMA determination, submit the balance of your WMP according to the schedule in the General Order, and include a copy of the MT-1 form that you submitted. When you receive the information from FEMA and the engineering review of the flood information has been completed, submit the flood information to the appropriate Regional Water Board office.