WSP10010

• File Number: 8449.700
• Description: Cherry Creek
• State: CO
• Basin: South Platte
• Date: 9/1/1995
• Author: Halepaska & Assoc.
• Title: Phase 1 Baseline Water Quality Data Collection Study for the Upper Cherry Creek Basin - Final Report
• Water Supply Pro - Doc Type: Publication

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leHA

f1naI R_ft. PIwe I R....... Water OuoIitv Om CoDoctioa Stadv

Seut...ber 1995

Based on the flow and concentration data presented in Figure 6, loadings for nitrate-nitrogen,
total phosphorus and SRP were calculated at each of the surface water sampling locations (Figure
7). The 12-month average loading rate plots for each of these constituents is very similar, in
that the loading observed at Castlewood Canyon is essentially the same, or greater than, the
loadings observed at Cherry Creek Reservoir (CC-9), even though there are fluxes of higher
loadings in the intermittent reach. This is true even for nitrate-nitrogen, which showed higher
concentrations entering the reservoir than at Castlewood, but the loads are similar due to the
higher flow at Castlewood (Figure 7).

The nitrate-nitrogen loading averaged approximately 5.8 pounds per day (lbsJday) at Castlewood
and 6.6lbs/day at the reservoir, while SRP loading averaged 4.9lbsJday at Castlewood and 3.7
lbs/day at tlte reservoir (Figure 7). Total phosphorus loading at Castlewood averaged 7.3
lbs/day, compared to 4.7lbs/day at tlte reservoir (Figure 7)(Appendix E).

Samples obtained from tlte Pinery advance-treated wastewater discharge have indicated a few
instances of detectable levels of ammonia-nitrogen concentrations (February and March 1995),
while generally ammonia-nitrogen concentrations have been below tlte detection limit for the
remainder of tlte study period. Nitrate-nitrogen concentrations have been observed to range
from less titan 0.05 mg/L to a maximum of 9.8 mg/L in November 1994 (Appendix A). Total
phosphorus, total dissolved phosphorus and SRP concentrations have been very low tltroughout
tlte study period (less titan 0.02 mg/L to 0.10 mg/L).

Even tltough extremely high flows were recorded in tlte Spring of 1995, total suspended solids
concentrations in tlte surface channels remained at relatively low levels (maximum total
suspended solids concentration of 50 mg/L at CC-8 in July 1995). In addition, tlte total volatile
suspended solids have remained near, or below, detection limits, indicating tltat tlte suspended
solids are generally inorganic in nature. However, based on differences in tlte total phosphorus

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