HomeMy WebLinkAboutSTERLING SPECIAL REVIEW - COUNTY REFERRAL - 40-88 - SUBMITTAL DOCUMENTS - ROUND 2 - SUPPLEMENTAL INFORMATIONWater
Engineering &
Technology, Int
Poftw
419 Canyon, Suite 225
Fort Collins, Colorado 80521 U.S.A.
1-303-482-8201 May 13, 1988
March and Myatt
110 East Oak, Suite 200
Fort Collins, Colorado
Attention: Ms. Lucia A. Liley
Subject: Resource Consultants, Inc.
Groundwater Evaluation Report
Dear Lucia:
Mike Harvey and I have reviewed a report by Resource Consultants,
Inc. of Fort Collins entitled: "Evaluation of the Ground -water
Resources in the Vicinity of Gravel Mining by Sterling Companies, Fort
Collins, Colorado". The report was included as a portion of Sterling's
most recent permit application to mine the area west of Taft Hill Road
and immediately north of the existing Seaworth Pit. The intent of the
report is to demonstrate whether or not dewatering of the new pit will
have an impact on local groundwater levels and to propose mitigation
measures for any detrimental effects due to mining.
On page one the report states that groundwater is sustained by
leakage from irrigation canals to the north and percolation from
irrigation of agricultural lands. The report does not provide estimates
of the rate of seepage from the irrigation canals. It may be that many
of the local canals have relatively low seepate rates due to sealing by
fine material. Diverted flow can contain concentrations of fine
material which will be deposited in low gradient irrigation ditches.
The contention that groundwater is sustained by canal seepage ignores
the fact that groundwater levels are also related to percolation of
local precipitation and to the water level in the Cache la Poudre River.
The river can be considered as the largest ditch within the valley and
because it has a gravel bed it is reasonable to assume that the river is
hydraulically connected to the groundwater within adjacent alluvial
deposits.
Water depths from two test -boring programs are discussed beginning
on page two of the report. These data are presented to demonstrate that
water levels declined approximately 2 feet between 1985 and 1988. For
A
Ms. Lucia A. Liley
March and Myatt
May 13, 1988
Page 2
several reasons any comparison between the 1985 and 1988 data is
essentially meaningless. First, there are no elevations for any of the
test borings. Groundwater elevations are not correlated to depth
because the surface elevation of individual test holes can vary
considerably. The valley surface adjacent to the Poudre River is
relatively flat; however, undulations of 2 to 3 feet commonly occur.
Road surfaces, where some drilling may have been performed, are often
several feet above the surrounding topography.
Second, the two drilling programs are located in different areas.
The 1985 drilling program is approximately located in the NE! of the SE!
of Section 33 and the 1988 test borings are located in the4 SE1 of the
NE-! 4 of Section 33 and the SW! of the NW! of Section 34. Two4borings
from each program are within several hundred feet of each other;
however, the distance between the most distant holes is approximately
0.8 miles with an elevation difference (estimated from 1:24,000 scale
topographic map) of about 20 feet. Apparently, no water level
observations were made in the same well in 1985 and in 1988. Comparison
of the two data sets to demonstrate a 2 foot change in water depth is
meaningless if the ground elevation at each boring is not known.
Runoff volumes for the Poudre River at the mouth of Poudre Canyon
are presented on page six of the report to demonstrate the availability
of water for diversion into irrigation ditches for the years 1983 to
1987. The runoff for 1987 is the lowest for the 5 years of data which
are presented. The data indicate that less water was available for
diversion in 1987 but they do not indicate how much was actually
diverted. Some landowners have occupied the buildings across Taft Hill
Road from the proposed pit for 12 years or more during which time they
have only observed a decline in pond levels in 1987. Precipitation data
(see our letter of March 21, 1988) indicate that several years between
1975 and 1983 experienced lower precipitation than 1987 and these years
would presumably cause a decline in pond and groundwater levels.
However, no such decline was observed. It is more reasonable to assume
that dewatering at the Seaworth Pit is responsible for recent declines
in groundwater levels.
Irrigation ditches are not located on a map to indicate their
proximity to ponds and wells adjacent to the proposed pit expansion. In
addition no discussion is provided to indicate how far from an
irrigation ditch one might expect to see an influence of seepage on
groundwater levels.
On page ten, second paragraph, the 1985 and 1988 data are presented
to show the effect of dewatering at the Seaworth Pit on the surrounding
Ms. Lucia A. Liley
March and Myatt
May 13, 1988
Page 3
groundwater levels. Again, because of a lack of elevations for
individual borings the data are meaningless for demonstrating changes in
groundwater levels. Changes in water depth could be caused by
differences in the ground surface elevation at each boring.
A discussion on the first half of page eight concludes from the
boring data that subirrigation conditions do not occur in or around the
project area. The boring data may not represent conditions on the
landowners' property and the assumption of a 2 to 3 foot water depth to
maintain subirrigation may not be appropriate for the crops grown by
landowners.
The second complete paragraph on page nine states that two wells
just over 100 feet from the proposed pit may experience excessive water
level declines during mining. No data or analysis are presented in the
report to demonstrate why only these two wells may be affected, how much
water -level decline may occur, or how great a response time can be
expected between initiation of pumping and the occurrence of a
measurable decline in groundwater. In addition, no data or analyses are
provided to demonstrate why the wells may be impacted for only 45 months
(or approximately 4 years).
The conclusion that there are no negative impacts on existing
groundwater users in the area is not supported by the 1985 and 1988
boring data. In fact, these data are meaningless for determining a
change in groundwater levels through time. The groundwater levels in
the area are dependent upon percolation of local precipitation and the
water level of the Poudre River in addition to seepage from irrigation
ditches. It may be that seepage losses from ditches have declined with
time as the bottoms of the ditches become sealed with fine material.
The monitoring program proposed by RCI includes a recommendation for
additional observation wells; however, no locations for additional wells
are suggested. Monthly monitoring of observation wells is suggested;
however, if the alluvial deposits of the Poudre River have a high
hydraulic conductivity, which is reasonable to assume because the
material is predominantly sand and gravel, then changes in groundwater
levels due to pit dewatering may be very rapid and monthly monitoring
may not detect these fluctuations in water levels. A number of
mitigation techniques are suggested at the end of the report. Until the
impacts of mining have been quantitatively determined, however, it is
irrelevant to discuss mitigation.
The report by RCI does not present any new or meaningful data or
analyses which demonstrate quantitatively the effects of gravel mining
Ms. Lucia A. Liley
March and Myatt
May 13, 1988
Page 4
on local groundwater levels. The suggestion that additional observation
wells may be constructed is welcomed, however, no suggestions were made
as to location of these wells. We suggest that monitoring be enhanced
through a coordinated pump test which would provide a quantitative
measure of the hydraulic conductivity of the water -bearing alluvium.
This number will enable prediction of possible impacts to local water
wells and ponds and the determination of appropriate mitigation
measures.
Please give us a call if we can be of service during further
discussions with Larimer County and/or Sterling Sand and Gravel.
Very truly yours,
Water Engineering and Technology, Inc.
By: Daniel I. Gregor✓ V
Geomorphologist/Project Manager
DIG:sp
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FORII5I,
SFI&fiCE
O Foothills Campus
r Itatc Univcrsity
Colorado 80523
_ ire (303) 491-8660
June 10, 1988 Wry 2® � ,
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S rling S&G
March & Myatt
Attorneys and Counselors at Law
110 East Oak Street
Fort Collins CO 80524-2880
Attn: Christine Wood
RE: Sterling Sand and Gravel
I have reviewed the undated modified windbreak Planting Plan
(tree screening plan) submitted by Sterling to Frank Lancaster,
Larimer County Forester. My comments follow:
--I assume that the "Type A" species row closest to the pond as
shown on the plat, should be Type C or shrubs. My feeling is
that a shrub row would not be as valuable for a sound barrier
as a tree row. This row should be eliminated.
--For information, golden willow and Russian olive are not shrubs.
They grow to 35' and 25' respectively.
--The 25' screening area is inadequate. A 100' barrier is recom-
mended to obtain a 6-8 decibel reduction of sound intensity.
A 50' barrier should be minimum.
--Spacing between the two rows of Type Q species is so narrow that
it would create serious competition between adjoining trees.
In row spacing is adequate for the desired effects.
--Species in Type Q are satisfactory.
--The suggested spacing of 15-20' is too far to obtain the desired
effect. I feel that spacing of 8-10' should be used for deciduous
trees. This will allow for quicker crown closure. Thinning of
this row at a later date is suggested when the trees get closer
to maturity.
March & Myatt
page 2
June 10, 1988
--Honeylocust-isnot a satisfactory species for the Type A row.
Burr oak is questionable due to its slow growth rate.
--Is it possible to use any of the 50' ROW set -back for tree planting?
I feel the submitted plan is inadequate and recommend against
approval.
Sincerely,
Raymond L. Mehaffey
District Forester
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Io: Lucia H. Liley
(larch & Hyatt
11U E. Oak
Ft. Collins, CD
From: H. Steven Ackley, Ph.D.
Department of Audiology
Colorado State University
Re: Sterling Sand & Gravel
Date: ('larch 20, 1988
Background. Noise in the community and at the workplace are
managed Federally by the EPA, OSHA, and MSHH. Generally
speaking, there is no overlap in Federal regulations which
protect workers (OSHA, MSHA) and protection of property/citizens
(EPA) from annoying/hazardous levels of noise.
Noise is hazardous to the peripheral auditory system
(cochlea and vestibule) at 75 - 85 dBA, according to numerous
studies. Nonethless, OSHA has adopted an BS - 90 dBA noise Floor
as a compromise to industry. twenty per cent of all workers
exposed to 90 dBA for an eight hour work shift for a career w.ili
still incur signiricant noise induced hearing loss, so the
standard is at best 60% effective. Aside from physiological
damage to the ear, extra -auditory effects of noise are also well
documented. These effects include stress and general mental
health disturbances, blood Flow problems, disequilibrium, cardio-
vascular disease, elevated serum corticostercid levels, increased
respiration rate, difficulty with concentration and task
completion, sleep disorder, anxiety, and non-speciFic annoyance.
While OSHA and MSHA do not regulate extra -auditory effects of
noise, the EPA and other agencies including the National Safety
Council are concerned with Factors other than auditory
physiological damage in the protection of citizens on their
private property.
The Following Table (Table 1) compares nonoccupational and
occupation noise exposures, as recommended by the National Safety
Council and OSHA:
Table 1. Noise limits For nonoccupational vs. occupational
noise exposures.
---------------------------------------------- -------
Daily exposure limit For dBA Daily exposure limit For
nonoccupational noise occupational noise
< 2 minutes
115
< `t minutes
110
< B minutes
105
15 minutes
100
30 minutes
95
1 hour
90
2 hours
65
`t hours
BO
B hours
75
16-21 hours
70
15 minutes
30 minutes
1 hour
2 hours
`t hours
B hours
B hours
07,, - (' P "P, = e/ A u_- s
That is, although OSHA does not regulate noise exposure below an
intensity of BS dBA, other agencies are concerned with levels of
environmental noise occuring at between 70 and 85 dB. ReFerence
levels For Familiar sounds are given in Table 1.1.
Sand _and _Grav_el_Ogerations. Although actual data has not been
obtained relative to Sterling_Sand_and_Gravel -Co., a body of data
---------------
reporting sound level measurements is available on equipment used
in gravel and mining operations. Diesel and electric rock and
gravel crushers manuFactured by Cedar Rapids and Humboldt-Wedag
produce 101 - 109 dBA at 10 - 20 Feet during use. Applying the
inverse -square law formula to noise and distance, the Following
Table (Table 1.0) can be used to calculate noise From a single
crusher at various distances. However, this table reFlects only
noise From a single machine, and does not take into account
screeners, diesel generators, Front-end loaders and diesel trucks
also necessarily operating as part of a gravel works. This
additional machinery can increase noise output by 10 - 30 dB.
•
f@j�j@ 1,0. Noise at various distances produced by a gravel
crusher of the type used at Sterling -Sand -and Gravel.
-----------------
Calculations were made for least possible (101 dB at 10 feet) and
greatest possible C109 dB at 20 feet) noise levels.
101 dBA at 10 Feet
95 dBA at 20 Feet
89........ `i0
B3........80
77.......160
71.......320
65....... 6`i0
109 dBA at 20 Feet
103 dBA at `tU feet
97........60
91.......160
65.......320
78....... 6`0
72......1280
As is evident in Table 1.0, the most conservative calculation
using 101 dBA at 10 Feet For a single machine still produces
sufficient noise at 320 feet to be of concern by the National
Safety Council. The more liberal calculation using 109 dBA at 20
feet would Fall under National Safety Council scrutiny at 1260
Feet, or about 100 Feet shy of a quarter mile. Adding other
machinery normally in use in this type of operation will
significantly alter the results.
In sum, the Findings indicate that while actual
physiological damage is not likely to be incurred by residents
beyond BO - 320 Feet of the operation, according to Table 1.0,
extra -auditory effects most deFinitely will be incurred by these
residents at a substantially greater distance. Furthermore,
because of the low Frequency (125 - 750 Hz) nature of the noise
generated by these types of machinery, landscaping barriers are
less effective in attenuating the noise than more costly and less
attractive wood or cement block barriers.
Table 1.1 Reference Levels of Familiar Sounds (dBA).
Sound Level Industrial (and Military)
Community (Outdoor)
Home (Indoor)
U — Threshold of
audibility
(Brownian noise)
to — Barely detectable
Very faint whisper (20)
20 —
Audible whisper (30)
30 —
Quiet office (40)
40 —
Quiet residence (45)
50 —
Light traffic (50)
Average office (50)
Large transformer (53)
60—
Air conditioner (60)
Conversation (60)
Near freeway (64)
— Annoying (65)
Fairly loud speech (70)
70—
Television audio (70)
Noisy restaurant (70)
Vacuum cleaner (74)
Dishwasher (75)
Inside auto at 65 mph (77)
Living room muwic (76)
Clothes washer (78)
80 — intolerable for
Tabulator (80)
Loud singing (80)
telephone use
Lathe (81)
Garbage disposal (80)
Cotton spinning (83)
Diesel train (83)
Ear damage
possible (85)
Milling (85)
Cockpit, prop (88)
Diesel truck (84)
Prop Flyover at 1,000 ft. (88)
Food blender (88)
90 — Speech
Motorcycle at 25 ft. (90)
Loud shout (90)
interference
Subway (90)
Cockpit, light plane (90)
Rock drill (92)
Compressor (94)
Power mower (96)
Loud subway (95)
Newspaper press (97)
Farm tractor (98)
l00 — Very loud
Heat furnace (100)
Police siren at 100 ft. (10U)
Air hammer (100)
Snowmobile (100)
Loud outboard (102)
)et flyover at 1,000 ft. (103'
Loud motorcycle (105)
Loud mower (105)
Textile loom (106)
Loom room (108)
110 —
Riveter (110)
Diesel truck accelerating (114)
— Maximum under
federal law
Compacter (116)
(115)
Scraper -loader (117)
Chain saw (118)