2016_07_July_WQ_Update
Acronyms: CB-T=Colorado Big Thompson, TCR=Total Coliform Rule, TOC=total organic carbon
Monthly Water Quality Update July 2016
Source Water Updates
• On 7/17 issues with the Carter Lake
flow control gates reduced BFC flow
from 50 to 7.2 cfs by 3pm. 63rd was
able to maintain treatment at 8 MGD
(i.e., 12.4 cfs).
• The wetter winter/spring caused Lake
Granby to start spilling on 6/23 at a
rate of 1,065 cfs (see photo). Overall,
CB-T reservoir levels are in good
shape.
Cold Springs Wildfire
• The wildfire began on 7/9 and burned ~527 acres northeast of Nederland before reaching 100% containment
on 7/14.
• More than 169,000 gallons of slurry were applied (active ingredient: ammonium polyphosphate).
• Boulder’s source waters were spared from wildfire impacts
because the fire was outside of our watersheds, moved east (away from
Lakewood and Barker), and slurry was only applied on the eastern portion
of the fire perimeter.
• The first runoff-producing rainstorm is when downstream water
quality impacts would be observed. Typical wildfire water quality impacts
include: elevated conductivity, pH, turbidity, and TOC. Nutrients and
metals may also be mobilized depending on burn severity (and slurry
application).
• Water quality samples were collected from Boulder Creek
upstream from the Farmers Ditch diversion, before and after the first
post-wildfire rainstorm. Water quality data showed changes that would likely result from any typical runoff
event. Specifically, alkalinity and conductivity remained similar, ammonia and nitrate were not detected, pH
slightly increased (7.37.7) and turbidity slightly increased (2.44.5 NTU). Metals and phosphorus data are not
yet available.
• Because water quality impacts were not observed, the city continued to divert into Farmers Ditch (out of
Boulder Creek and ultimately to Boulder Reservoir).
Betasso Post-Runoff Water Quality
• Boulder Creek watershed snowpack
was higher than average, though
runoff came and ended quickly,
dropping to below the historical
average by mid-June (see Figure on
right).
• In mid- June, peak levels for
Lakewood were: TOC=6.4 mg/L;
UV254=0.25 cm-1; color=47 units.
Barker peak levels were TOC=3.7
mg/L; UV254=1.25 cm-1; color=28 units. Monthly medians shown in figures below.
• DOC mirrors TOC since ~ >90% of the Lakewood and Barker natural organic matter is in the dissolved form.
• Alkalinity has decreased at Barker and Lakewood since runoff began, due to dilution. Alkalinity will likely start
to level out soon.
Acronyms: CB-T=Colorado Big Thompson, TCR=Total Coliform Rule, TOC=total organic carbon
Monthly Water Quality Update July 2016
Distribution System –Tank Levels
EPA recommends 20-30% daily tank
turnover for ~3-5 day water age.
The thee tanks with the lowest %
volume turnover during July were
Chautauqua, Kohler and Maxwell.
Distribution System – Residence Time
Optimal system wide water age varies by system and season.
Overall water age in the system from total storage (including
clearwells and distribution pipe volume) and total demand
averaged 1-2 days.
o Comparison to the month of June provided in plot on
the right.
28
47
0
5
10
15
20
25
30
35
40
45
50
Color UnitsBarker Intake
Lakewood Intake
0.00
0.05
0.10
0.15
0.20
1 2 3 4 5 6 7 8 9 10 11 12Median UV254 (cm-1)Month
Barker (Historic)Lakewood (Historic)
Barker (2016)Lakewood (2016)
Acronyms: CB-T=Colorado Big Thompson, TCR=Total Coliform Rule, TOC=total organic carbon
Monthly Water Quality Update July 2016
Total Coliform Rule (TCR): Chlorine
121 TCR samples were collected in July from 39 sites (schools are not sampled during the summer months).