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<br />TABLE 6 <br /> <br />Comparison of BOD5 from Combined Overflows, and Separate <br />Storm Discharges, and Snow Melt; Des Moines, :owa <br />(Lager and Smith, 1974) <br /> <br />; <br /> <br />Type of Discharge <br /> <br />Mean of the <br />Test Areas, <br />mg/~ <br /> <br />80 <br /> <br />Range of the <br />Test Area Means, <br />mg/~ <br /> <br />53-117 <br /> <br />Combined overflows <br />(5 areas) <br /> <br />Storm sewer discharge <br />(rain induced - <br />4 areas) <br /> <br />Storm sewer discharge <br />(snow melt - 4 areas) <br /> <br />32 <br /> <br />23-46 <br /> <br />75 <br /> <br />67-85 <br /> <br />It is interesting to note the high concentrations associated <br /> <br />with urban snowmelt. In this case, the mean values are more <br /> <br />than twice as high for snowmelt as for rain. <br /> <br />In 1969, during the spring, a study was conducted in the <br /> <br />southern part of Stockholm, Sweden (Soderlund, Lehtinen and <br /> <br />Finberg, 1970), in a newly developed area with separate drainage <br /> <br />systems. The area is mostly residential and commercial, but <br /> <br />includes some industrial sites. European Highway No.4 passes <br /> <br />the area with an average of 55,000 vehicles every 24 hours. The <br /> <br />stormwater is collected in a discharge tunnel 2.2 m (7.22 ft) <br /> <br />in diameter which dewaters 1,000 hectares (2,470 acres) of the <br /> <br />sampling area. <br /> <br />The sampling was started in February after a heavy snowfall. <br /> <br />Since most of the snow was later removed and dumped into a lake, <br /> <br />snow samples from different streets were collected about four <br /> <br />13 <br />