The basic wind speed V in the ACI 307-98 standard was revised from fastest-mile to a 3-second gust speed to reflect the changes published in ASCE 7-02. Equation (4-1) was modified accordingly. In Eq. (4-1), 1.47 converts wind speed from mph to ft/s, and 0.65 converts the 3-second gust speed to a mean hourly speed. The revised power law coefficient 0.154 (as an approximation of 1/6.5) came from Table 6.2 of ASCE 7-02 for Exposure C and for flexible or dynamically sensitive structures; the increase in the exponent increases the calculated pressures over the chimney height for the same speed.