Field Evaluation of Phytostabilization Actions, Kerber Creek
Field Evaluation of Phytostabilization
Actions, Kerber Creek Watershed
Karl Ford, Ph.D
November 12, 2012
Deposits of acidic mine tailings high in metals have degraded the environmental quality of the
Kerber Creek watershed. These conditions have resulted in denuded areas along the creek
(“slickens”) and have served as reservoirs of pollutants affecting Kerber Creek, contributing to
poor water quality.
At the request of some members of the Bonanza Stakeholders’ Group, a field evaluation of the
phytostabilization work was conducted by Karl Ford in the Kerber Creek floodplain near Villa
Grove, Colorado. Dr. Ford is a retired BLM environmental scientist who assisted in site
characterization and developed the phytostabilization amendment recipes. Karl Ford and Jeff
Dragos conducted a preliminary site reconnaissance on July 23, 2012 to decide which parcels to
evaluate. Not counting control areas, six parcels were identified: KC18, KC17 (2 sites), KC08,
KC04, KC20. The actual evaluation work was performed August 13-15, 2012.
1.1 Floodplain Contamination, Kerber Creek
Tailings along Kerber Creek are associated with tailings impoundments from the historic Rawley
Mine complex upstream. These tailings dams failed over time releasing tailings and mine waste
downstream during flood events. Remedial activities were conducted in the 1990s by ASARCO
to contain the remaining tailings in an engineered repository; however, this remedy did not
address downstream tailings deposits. The tailings are characterized as low pH with
concentrations of heavy metals in the thousands of parts per million, especially lead and zinc,
with lesser concentrations of arsenic, cadmium and copper. These conditions are toxic to plant
growth as indicated by the lack of vegetation in some floodplain areas called “slickens” (Photos
9-13). These tailings are discontinuous and quite extensive, covering an estimated 122 acres.
1.2 Phytostabilization Methods, Locations
Phytostabilization relies on use of lime products to correct immediate soil acidity and limestone
to neutralize future acidity from remaining sulfide weathering. Compost and fertilizer were
added to aid soil moisture and nutrients. Most plants cannot survive below pH 3.0 and reduced
vigor is found up to neutral pH (7.0). In addition, acidity mobilizes metals that are toxic to
plants. Phytostabilization work was performed initially in 2008 by BLM at several BLM
managed locations. These locations were not requested to be evaluated. Records show treatments
on private lands were conducted in 2008-2011. Table 1 shows some of the locations and
Phytostabilzation was completed on sites KC04 (0.79 acres), KC07 (1.22 acres), KC08
(1.08 acres), KC13-14 (1.63 acres), KC19 (0.50 acres), and KC17 (15.1 acres). Sites are
privately owned. Equipment utilized to complete the phytostabilzation process included a
Kobleco 210 excavator, a John Deere 650J bulldozer with ripper teeth, a John Deere 544J
wheel loader, a Land Pride spreader, a Goosen straw blower, and a Land Pride disc
crimper. All materials were delivered and staged at the requested locations and quantities
prior to implementation of the phytostabilzation process. A summary of the delivered
quantities are provided in the attached figures.
Phytostabilzation at the six locations was completed by first preparing the individual sites
for application of the lime and limestone. All impacted areas were graded to relatively
flat slopes (not to exceed 3:1) and all dead vegetation was incorporated into the
subsurface. Second, both the lime and limestone were spread onto the impacted tailings
areas at the specified application rate, followed by incorporation into the subsurface using
the ripper teeth on the bulldozer. The ripper teeth were extended to a maximum depth of
16-inches, and multiple passes were made to ensure the most efficient mixing of the lime,
limestone, and tailings. Once incorporation of the lime and limestone was completed, the
potato compost was applied at the prescribed rates and subsequently ripped in to the
subsurface to a depth of approximately four inches. All disturbed areas were then tracked
with the bulldozer to obtain a relatively flat area. Fertilizer and seed were then applied at
the requested rate for most 2010 sites using a mechanical broadcast spreader and
immediately chain dragged to achieve a thin layer of soil cover. A drill seeder was
utilized for seed application at sites KC18 and KC17 rather than a mechanical broadcast
seeder. Weed free straw mulch was applied at a rate of two tons per acre utilizing a
Goosen straw blower capable of applying 2-3 bales per minute. The final step of the
process involved disc crimping of mulched areas to make certain the wind did not
actively strip the mulch from the surface. All staging areas and stream crossings were
then reclaimed and vegetated to attain previously undisturbed conditions.
Site KC17 included the purchase of materials for treatment of 15.1 acres of
impacted mine tailings; however, work under this contract included the treatment of 12.1
acres associated with the eastern portion of the property in 2009. The remaining work
was completed in 2010.
The only work performed in 2011 was for sites KC20 (2.14 acres), KC18 (14 acres), and
KC21 (1.5 acres, not evaluated).
2.0 Evaluation Methods
The purpose of the evaluation was to assess the success of the phytostabilization work in
returning the rangeland to a healthy condition. To conduct the assessment, BLM uses a
qualitative assessment procedure, Interpreting Indicators of Rangeland Health, (BLM Technical
Reference 1734-6, 2000).
2.1 Interpreting Indicators of Rangeland Health
This procedure uses 17 indicators (worksheets available upon request) to assess rangeland health.
The indicators span categories of soil/site stability, hydrologic function, and biotic integrity.
Together, they are used to assess rangeland health. One soil indicator not listed that was
measured is field pH because of the soil acidity associated with the floodplain tailings. Field pH
was measured using a Control Wizard Products pH meter $64.95
(http://www.controlwizardproducts.com/products.php?cat=168, and Photo 8). Other products,
vendors and methods can be used to assess soil pH, but this tool is easy and inexpensive to use.
Typical pH before restoration was 3.0. Targeted pH after restoration was 7.0.
2.1.1 Positive control
The methodology calls for using either an Ecological Site Description to describe site
potential soil and vegetation conditions in the absence of human disturbance, OR using
an ecological reference area (ERA). An ERA is a positive control: an untreated,
uncontaminated soil with natural pH and metals concentrations. The area selected for this
work is located on Little Kerber Creek on site KC16 (Photos 6 and 7) within the same
watershed and soil type. Upon assessment, this site was found to be heavily grazed, had
high litter accumulations, and is not in ideal condition. For the purpose of this report, a
negative control was also used.
2.1.2 Negative control
Because the stakeholders are more interested in comparing phytostabilization
improvement results to untreated contaminated rangelands, a negative control was
selected on site KC16 immediately upstream of site KC17. A negative control is an
untreated, contaminated area along the Kerber Creek floodplain with low pH and high
metals concentration (Photos 16-18).
This section summarizes the evaluation results for each of the six parcels in comparison to the
positive and negative controls (reference areas).
3.1 KC16 ERA, uncontaminated reference area An uncontaminated reference area was selected
on Little Kerber Creek (see section 2.1.1). The site was composed of purple asters, sedges, iris
and Canada thistle. No riparian shrubs were present, although they probably should have been. It
had extensive cow-pies, high litter accumulations (31-50%) and 6-15% bare ground. Vegetation
cover was 51-75% and was short, indicative of heavy grazing, (Photos 6 and 7).
3.2 KC16 ERA, contaminated reference area
A contaminated, untreated reference area was selected on site KC16 immediately west of the
KC17 west property line. The site is covered with fine brown tailings and is dissected by Kerber
Creek and gullies draining into the creek. A few willow copses occur along with sedges,
gooseberries (acid loving), wild rose and iris. The site was approximately 51-75% bare ground
This area was treated in 2011 and is shown on Figure 1 and Photos 1 and 3. This area had been
grazed. Vegetation on the evaluated site was composed of western wheatgrass, wild rye,
equisetum, beeplant, and the noxious weeds Canada thistle and Russian thistle. From 16-30%
was bare ground. Some portions had thick grass cover and others did not, indicating either
inadequate amounts or mixing of amendments, or drought conditions. Average pH was 5.4 with
range of 4.0 to 6.8. The departure (improvement) from the contaminated area was rated as
moderate for all three attributes: soil/site stability, hydrologic function and biotic integrity.
3.4 KC17 (1)
This area was treated in 2009 and is shown on Figure 4 and Photo 2. Vegetation on the site was
composed of willow, kochia, western wheatgrass, wild rye, squirreltail, equisetum, and timothy.
From 16-30% was bare ground. Average pH was 6.8 with range from 6.0 to 7.0. The departure
(improvement) from the contaminated area was rated as moderate for all three attributes: soil/site
stability, hydrologic function and biotic integrity.
3.5 KC17 (2)
This area was treated in 2009 and is located on Figure 4 and Photo 15. Vegetation on the site was
composed of pre-existing willow, western wheatgrass, wild rye, kochia, tufted hairgrass, and a
small patch of the noxious weed Canada thistle. From 16-30% was bare ground. Some portions
had willow recruitment occurring. Average pH was 6.4 with range from 5.1 to 6.8. The departure
(improvement) from the contaminated area was rated as moderate to extreme for soil/site
stability, and biotic integrity and moderate for hydrologic function.
This area was treated in 2009 and is located on Figure 5 and Photo 5. Vegetation on the site was
composed of slender or western wheatgrass, wild rye, kochia, fringed sage, gooseberry,
ticklegrass, and a few existing lodgepole pine. From 16-30% was bare ground. Average pH was
5.7 with range from 5.1 to 6.1. The departure (improvement) from the contaminated area was
rated as moderate to extreme for all three attributes: soil/site stability, hydrologic function and
This area was treated in 2009 and is located on Figure 3 and Photo 14. Vegetation on the site was
composed of western wheatgrass and kochia. Elk droppings were prevalent. From 16-30% was
bare ground. Some portions had grass cover and others did not, indicating either inadequate
amounts or mixing of amendments or drought conditions. Average pH was 5.2 with range from
3.0 to 6.2, probably due to poor soil mixing (tilling of amendments). The departure
(improvement) from the contaminated area was rated as moderate to extreme for soil/site
stability and hydrologic function and moderate for biotic integrity.
This area was treated in 2011. Vegetation on the site was composed of western wheatgrass, wild
rye, nodding brome, smooth brome, foxtail barley, and beeplant. From 16-30% was bare ground.
Most areas had tall grass cover and fewer areas had little cover. As with other sites, areas of less
cover indicate either inadequate amounts or mixing of amendments, improper timing of seeding,
drought conditions, or not enough time since treatment (only one year). Average pH was 4.2 with
range from <3.0 to 5.5, indicating inadequate amount of amendment may have been used. The
departure (improvement) from the contaminated area was rated as moderate for soil/site stability
and hydrologic function and moderate to extreme for biotic integrity.
4.0 Conclusions and Recommendations
All of the six treated sites that were evaluated had bare ground in the 16-30% range, litter was
minimal and vegetation cover was therefore in the 70-84% range indicating good success
considering: (1) only 1-3 years of elapsed time since treatment, (2) extreme multi-year drought in
the area, and (3) livestock or wildlife grazing. Comparison of treated sites with the negative
control (contaminated) indicated moderate to extreme departure (from contaminated).
Comparison of treated sites with the positive uncontaminated control was ultimately not used in
the worksheets because it did not reflect improvement from the contaminated condition. All of
the three categories--soil/site stability, hydrologic function and biotic integrity--showed moderate
to moderate to extreme improvement in condition compared to the negative control. Areas with
less cover indicate either inadequate amounts or mixing of amendments, improper timing of
seeding, drought conditions, or not enough time since treatment (only one year).
Recommendations are as follows:
Some of the sites may have had inadequate amounts of amendment applied or had
inadequate mixing. A landowner can do his own monitoring by taking field pH
measurements randomly throughout a treated (or untreated) area. Spot treatment of
residual low pH areas can be applied by tilling in 1 lb lime and 2 lbs limestone per square
foot as deeply as possible followed by a mellowing period (see below) followed by
Amendments to untreated parcels can be applied following the general prescription of 25
tons per acre lime, 41 tons per acre limestone and 83 tons per acre compost, tilling in at
least to 16 inches. Thinner tailings accumulations require proportionately less. Unless it is
a fall treatment, a mellowing period of three months should be observed after treatment to
allow the pH neutralization reactions to occur, followed by drill seeding. These quantities
are conservative averages used at these sites based on site characterization to attain short
term neutral pH (lime) and to ensure long term neutral pH (limestone) due to future
sulfide weathering. Site characterization is encouraged to fine tune or potentially reduce
these amendment quantities. Laboratory samples should be collected for SMP buffer and
Livestock must be excluded for several years for the re-vegetation to be successful,
especially in drought years.
Although considerable progress has been made with phytostabilization, slickens are still
fairly prevalent in the watershed, see Photos 9-15. Further work in these areas will help
restore the watershed to a more productive land and water condition.
Annual monitoring should consist of pH measurements and photo points (not available
for this project). Use of the rangeland indicators used in this report would be
recommended on a2-3 year basis.
Weed management should be observed as weeds will follow disturbance unless managed.
Appendix: Tables, Figures,
Table 1. Sites and pertinent information regarding composition and time of phytostabilization treatment.
Plot (UTM N)
Plot (UTM E)
Figure 1. KC 18 Tailings
Figure 2. KC07 Tailings
Figure 3. KC04 Tailings
Figure 4. KC17 Tailings
KC17 Tailings Piles
Note corrections (1) to compost
quantity should be 1275 tons, (2) blue
shaded area was also completed and
channel not moved.
Figure 5. KC08 Tailings
Photo 1. KC18: Note thick grass area to the right, bare ground area to the
Photo 2. KC17 (1)
Photo 3. KC18
Photo 4. KC18: Not evaluated.
Photo 5: KC08
Photo 6. KC16 Ecological Reference Area (ERA), uncontaminated,
positive control. Note high litter accumulation.
Photo 7. KC16 Ecological Reference Area (ERA), uncontaminated,
positive control. Looking west.
Photo 8. Field pH meter
Photo 9. Slickens, likely on western KC16
Photo 10. Slickens near turnoff to Ute Pass
Photo 11. Slickens near USGS gaging station
Photo 12. Other slickens in lower watershed
Photo 13. Slickens west of Bonanza Bed and Breakfast, lower watershed
Photo 14. KC04
Photo 15. KC17 (2)
Photo 16. KC16 Ecological Reference Area, contaminated, negative
control. Note pedicels and standing dead willow skeletons.
Photo 17. KC16 Ecological Reference Area, contaminated, negative
control. Note gully at bottom and dead shrubs.
Photo 18. KC16 Ecological Reference Area, contaminated, negative
control. Note bare ground.