WSP03001

• File Number: 8449.850
• Description: Metro Water Supply Investigation - MWSI
• State: CO
• Basin: South Platte
• Date: 8/1/1995
• Author: Hydrosphere, HRS
• Title: Phase II Conjunctive Use Summary Report - Draft
• Water Supply Pro - Doc Type: Publication

MWSI Project
Phase II Conjunctive Use Summary Report - DRAFT

August 22, 1995

operation, Centennial Arapahoe Well A-3 was equipped for injection and recovery in 1994. The
first water will be injected at Well A-3 in 1995, The volumes of surface water injected at A-6 are
shown on Table 4.

Table 4

Volumes of Treated Surface Water Injected at A-6

Year
1993
1994

1995

Month
July
March
April
May
June
April
May
June

Volume (af)
5.3
24.6
20,9
17,]
0,7
1.5
61.7
60'
192.1

Total

· Estimated value

Project Conclusions

Both the Centennial and Willows projects have successfully injected and stored treated
surface water into the Arapahoe aquifer. Current average injection rates are in the range of 400
to more than 900 gpm, Centennial has pumped its injection well for a period up to 41 days,
Work performed in these projects has evaluated the effect injection has on Arapahoe well and
aquifer characteristic.. These evaluations address the concern that the physical and chemical
processes related to injection and pumping could adversely effect the injection well's short and
long-term performance.

Both studies have stressed the importance of injecting high quality treated surface water
which is chemically compatible with the native groundwater, Neither study has experienced
serious water quality related problems which threaten the success of the injection/recovery
programs. The water quality issues addressed by these studies have focused on variations in
inorganic vs, biologic solids in pumped water and the chemistry of the "mixed" injected surface
water and native groundwaters, There are varied results with respect to well hydraulic issues.
To date, Centennial has not experienced adverse well hydraulic concerns. Willows has
experienced some problems which were not significantly improved by well rehabilitation efforts.
The following results are based on geochemical, water quality and well hydraulic analyses,

The Willows has concluded the following:

. Pumped water quality data indicate varying concentrations of iron and
manganese, The Arapahoe aquifer at A-S does not have the oxidation-reduction

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