WSP10284 - Laserfiche WebLink

Home Browse Search

0228 Table 13. Results of Wilcoxon rank-sum test (Hailed) of pre-treatment (April 199o-March 1992) and post-treatment (April 1992--March 1993) instantaneous streamflow and lead concentrations at selected sites in the upper Arkansas River Basin [fillS, cubic feel per second; J.lglL. micrograms per liter; n. test could not be perfonned; NA. not applicable; <, less than; S. less than or equal to] Streamflow DI.solved lead Total-recoverable lead Site name Pre-/post- Pre-/post- Pr.../pos,- (S88 lIble 1) treatment p-value treatment p-value treatment I>-value median 1 median 1 median 1 (ft3/s) ("giLl ("g/L) Leadville Mine Drainage Tunnel 2.312.4 0.38 -_!. NA .71<1.' <0.0\ California Gulch 1.8/1.8 .50 -- 2 NA 1041135 .42 leadville 70/58 .50 -- 2 NA 3/1 .13 Malta 99/134 .35 -- 2 NA \1/8 .42 Granite 277/470 .45 -- , NA 7.5/7 .44 Buena Vista 400/462 .45 -- 2 NA 7/2 .18 Nathrop 563/717 .45 -- 2 NA .9/3 .04 Wellsville 524/742 .38 -- 2 NA 4.5/2 .20 Parkdale 582/843 .41 -- 2 NA 3.5/3 .41 Portland 512/800 .18 - 2 NA 4/6 .22 1 Significant differences (p:5:0.0S) are shaded. 2 Test nol performed because more than 50 percent oflhe data were less than the reponing level. Water-quality standards for lead were exceeded in a se,all number of samples at five sites in tbe upper basin (table 14). The acute standard was exceeded in only one sample tbat was collected at Nathrop during tbe snowmelt-runoff regime in 1990. The chronic stan- dard for lead was exceeded in a few samples that were collected at Leadville, Malta, Granite, Buena Vista, .. and Natbrop. The largest number of chronic exceedances (four) occurred at Natbrop (table 14). Ninety-two percent of 1he chronic exceedances occurred during the mine-drainage pre-treatment period. Eighty-three percent of the chronic exceedances occurred during the snowmelt-runoff regime. Table 14. Number of samples that exceeded acute and chronic lead water-quality standards in the upper Arkansas River, April 199o-March 1993 SUe name {see table 1l Leadville Malta Granite Buena Vista Nathrop Wellsville Park dale Portland Number of samples analyzed 27 26 27 27 27 27 27 26 Number of samples that exceeded standard I Acull Chronic standard2 standard3 o 2 o I o 3 o 2 I 4 o 0 o 0 o 0 I Acute and chronic lead standards are based on dissolved-lead concentration (Colorado Department of Health, 1994). 2 Acute standard = e( 1.6418[ln(hardneSll)j.2.8736). 3 Chronic standard = eO 4] 7[ln(hardnessl].~.167). WATER QUALITY 29