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7A Page 21 volumes. In response, City staff conducted a third party analysis. Costco's original estimate was 540,000 gallons/month (6.5 million gallons/year). The third party analysis results in a significantly higher volume of 750,000 gallons/month (9 million gallons/year). The appeal comment does not appear to dispute the new volume. The concern is that the trip generation rates were also not increased based on this new information about increased sales volumes. There are two reasons why this was not done: 1. Trip generation estimates in the Redwood City Costco traffic study are based on actual counts at other high volume Costeo locations that have added gas stations to an existing Costeo facility. 2. These actual counts of gas station trips are associated with stations that pump more than Costco's original estimate of 540,000 gallons/month. The original estimate for gas sales volume does not correspond with the trip generation estimate derived from real world observations of other Costco stores. Staff has conducted two analyses to provide further clarification. The following is an analysis using simple mathematical terms to explain the relationship between gas sales using two entirely different data sources (this analysis was presented by staff at the June 19, 2007 joint hearing). The first analysis (Table 1) starts with trip generation and converts it to an approximate gas sales volume. The trip generation estimate is for PM peak hour trips, which was used throughout the traffic study and was derived from actual field observations at 10 different high volume Costco stores. Table 1: Gas Sales Volume Derived from Trip Generation I i I Estimate Source: Traffic Studies 390 PM Peak Trips Factor PM peak hour trips are equivalent 390 PM Peak Trips/1 0% = to approximatelv 10% of dailv trips. Result 3,900 D~ilY Trips I Factor Each vehicle fill requires two trips, 3,900 Daily Trips /2 Trips per Fill = one into the station and one leaving I the station. Result ! 1,950 Fills/Day Factor . The average fill is about 13.5 1,950 Fills/Day * 13.5 Gallons/Fill = qallons. Result 26,32.!?_~allons/Dav Factor Multiply Gallons/Day by 30 to ! 26,325 Gallons/Day * 30 Days/Month =: determine Gallons/Month. I - I Result I 789,750 Gallons/Month The second analysis (Table 2) starts with the City's gasoline sales estimate of 750,000 gallons/month to determine a corresponding PM Peak Hour Trip estimate. Table 3 compares the input and outputs of each analysis: 3