2016_Memo_Potential_WQ_Impacts July 14, 2016
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Cold Springs Wildfire- Potential Water
Quality Impacts
Cold Springs Wildfire
The Cold Springs wildfire began on 7/9/2016 in the afternoon, immediately southeast of the Peak to
Peak Highway and Lakewood reservoir. By 7/14/2016, the wildfire is considered to be 100% contained
(Figure 1). Throughout the wildfire, winds moved west to east, as did the fire. Over 169,000 gallons of
ammonia-based slurry was applied to the wildfire,1 but not near Lakewood Reservoir.
Figure 1. Cold Springs wildfire burn area as of 7/14/2016 (red shaded area). Lakewood Reservoir is on the upper left; Barker
Reservoir is on the lower left. Yellow shading = evacuation area; red dotted roads = road closures; orange dotted roads = lim ited
access roads.
Potential Water Quality Impacts
Barker and Lakewood Reservoirs
Given that the wildfire was primarily located outside of the Lakewood and Barker Reservoir watersheds,
and that the winds and wildfire moved west to east, there will unlikely be noticeable water quality
impacts to the City of Boulder’s source water. However, results from the post-wildfire water quality
samples will be analyzed for potential increases in hardness, conductivity, pH, turbidity, nutrients, total
and dissolved organic carbon, and metals.
1 https://www.cpr.org/news/story/whats-red-slurry-crews-are-dumping-colorado-wildfires
July 14, 2016
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North Boulder Creek and Boulder Creek
Any water quality impacts are likely to be observed following runoff from the first post-fire precipitation
event in the burned area. Depending on the severity of the wildfire, runoff from the burned area may be
a source of water quality contaminants for an extended period of time. Based on impacts from other
wildfires in the region, it may be of interest for the downstream ditch companies to monitor for the
following:
Constituent Description Source and Sampling Rationale
Conductivity, hardness, and pH
Conductivity is an index of
dissolved ionic solids; hardness
is an index of total calcium and
magnesium in the water. Both
parameters track closely with
pH, which measures the acidity
or basicity of the water
These will likely be elevated due to
increased concentrations of calcium
and magnesium in the surface ash
and in sediments from runoff.
Total dissolved solids and turbidity
Turbidity measures the ability
for light to penetrate the
water column and is
influenced by the amount of
suspended material in the
water
These will likely be elevated during
and immediately following a runoff
event.
Total organic carbon
Dissolved and particulate
carbon originating from
watershed soils and biological
material
This will likely be elevated following a
runoff event.
Nutrients Nitrogen and phosphorus
Levels of ammonia, total Kjeldahl
nitrogen, ortho phosphorus, and total
phosphorus will likely remain
elevated post-wildfire for a period.
Nitrate is quite mobile so it may not
stay elevated. Overland runoff and
slurry are the primary sources. The
active ingredient in the slurry used on
the Cold Springs wildfire is ammonia.
Metals Aluminum, manganese,
arsenic, etc.
Runoff may contribute to slightly
elevated levels of metals.
Dioxins and polycyclic aromatic
hydrocarbons (PAH)
Organic compounds naturally
produced during combustion.
They are carcinogens.
Dioxins and PAHs are released during
wildfires. Few laboratories analyze for
these parameters and analysis is
costly.
Boulder Reservoir
It may take ~10-12 hours for burn area runoff to flow the roughly 20+ miles through North Boulder
Creek and Boulder Creek, to Farmers Ditch, and ultimately into Boulder Reservoir. Most likely, there will
be minimal water quality impacts due to dilution. However, to ensure that the wildfire does not impact
Boulder Reservoir water quality, Farmers Ditch should be diverted away from the reservoir during and
immediately following the first post-wildfire precipitation event that produces runoff. Kate Dunlap has
discussed this with Joanna Bloom and Doug Dunn. d