2023.09_September_WQ_UpdateGeneral Updates
Monthly Water Quality Update
September 2023
•The Boulder Reservoir raw water pumping station (i.e., the device
that pumps water from the reservoir intake to the WTP) was tested
on 9/21. Since testing and after the transmission pipe was flushed,
63rd is treating Boulder Reservoir water.
•Water Treatment re-started routine taste and odor panels for staff at
the Boulder Reservoir WTP. These help staff anticipate potential
customer calls due to taste and odor events and were previously
discontinued during COVID.
•The annual Barker Gravity Line work is scheduled to begin Oct. 15th
through January 31st.
Remembering the 2013 Flood – Ten Years Ago This Month
• In September 2013, 18” of rain fell on Boulder County over an 8-day
period – more than a year’s worth of rain! September 12th set the all time
1-day record for 9.08” of rain.
•Estimates suggest that Boulder Creek reached an elevation of 7.78 feet
in town, flowing at a rate of 5,000 cubic feet per second.
• The full extent of the flood impact and damage is challenging to convey,
but Boulder County’s Storymap is a good start, providing details on the
loss of life, damage to infrastructure, lost homes, and washed-out roads.
• What most community members may not know, is just how close the
community was to not having potable drinking water. Due to a bit of luck
and hard-working staff, water treatment resumed but not without
difficulty.
• This update provides a summary of how the 2013 flood impacted
Boulder’s water utility.
Sources: City staff - Randy Bass, Kim Hutton, NOAA Physical Sciences Laboratory; Boulder County’s
Storymap
City of Boulder 5-min video on the 2013 flood
Photo of the
Boulder Reservoir
south dam
construction
Six Mile Reservoir overflowing
into Boulder Res.
BFC near Lyons
Boulder Creek at 287
Dry Creek flowing into Boulder Res.
Washed out Boulder Canyon Rd (photo – Randy Bass)
Washed out Boulder Canyon
Rd (photo – Randy Bass)
Photos of the Flood
2013 Flood – Impacts to Water Treatment
Betasso Water Treatment Plant
•Boulder Canyon Road partially washed out
on 9/12; closed to the public for weeks (if
not months). Only city vehicles allowed
through 9/25.
•WTP was only accessible to delivery trucks
from the top of Sugarloaf/north of
Nederland.
•Multi-day power outages at Betasso WTP,
Sunshine, Booton, 101 Pearl, Devils
Thumb, Silver Lake Hydro.
•Major concern of running out of diesel and
chemical. Only 6 days of chlorine available
at the WTP.
•City coordinated with the Office of Disaster
Management to allow for chemical delivery.
•A truck delivering alum to the WTP went
down Cold Springs Road off HWY 72,
nearly ending up in North Boulder Creek.
Rescuers and staff worked to transfer the
alum to an empty trailer.
•Increased coagulant demand on the
Lakewood source due to turbidity.
63rd Water Treatment Plant
•Major damage to Boulder Feeder Canal
(BFC); St. Vrain River flowing down BFC to
Boulder Reservoir.
•Upstream from Boulder Reservoir,
Fairways Metro WWTF discharging sewage
at a rate of 300 gal/min starting on 9/12.
•Boulder Reservoir was too turbid
(muddy/debris) to treat for several weeks
but luckily demand was low.
•63rd WTP brought back online at 4 MGD on
10/1 though turbidity was at 75 NTU in the
reservoir (typically 5-10 NTU).
•63rd WTP was able to begin treating BFC
on 5/15/2024.
Water Resources
•Staff carefully monitored the conditions
of dams but didn’t experience any
problems.
•Barker Reservoir and Silver Lake filled
and spilled – anomaly for two spills in
one year from each reservoir. Barker
gained 11 ft in elevation.
•Irrigation ditches in town experienced
overtopping and sedimentation.
Rainfall (inches) at the Boulder Jail from September 8 to 16, 2013.
2013 Flood – Impacts to Boulder Reservoir Raw Water Quality
•63rd went offline prior to the storm event due to low demand, but turbid water in Boulder
Reservoir and a breach in BFC, prevented the WTP from operating for several weeks.
•In just 48 hours (9/12-9/14), the reservoir gained 3,200 acre-feet of volume.
•Following the flood, Boulder Reservoir was laden with debris and sediment for days (see photo).
Debris-laden Boulder Res. at BFC inlet
•The flood caused immediate and multi-year changes in Boulder Reservoir water quality:
•Turbidity increased from 5 NTU before the flood to >580 NTU during the flood. Turbidity
remained above 10 NTU until January 2014.
•Total phosphorus increased 4-fold to 100 ug/L and nitrate (regulated in drinking water)
increased in raw water from non-detect to 145 ug/L.
•Boulder Reservoir alkalinity, hardness, total organic carbon, specific conductivity, UV
absorbance, uranium, and sulfate significantly (p<0.05) increased in the three years
post-flood.
•The figures below show the water quality changes in the months/years after the flood and
recovery in recent years.
•In the year following the flood, due gross alpha radiation levels in the water treatment
residuals, the city had to haul the residuals to the landfill instead of the typical A1
Organics. We do not have pre-flood radium, thorium, or uranium data for the residuals.
Red line indicates flood event
Chlorine Residual in the Distribution System
Location(s) with the lowest
chlorine residual reading.
Target Chlorine Residual Entering Distro: 1.1 mg/L.
Required Chlorine Residual in Distro: >0.2 mg/L
*Click here for definitions and goals related to distro characteristics
*EPA recommends >20% Tank Turnover
Average water residence
time was 46 hours this
month; 2% longer than
last month.
Water Distribution System Updates