HomeMy WebLinkAbout921276.tiff cupaa-
STATE_ cOLORADO
COLORADO DEPARTMENT OF HEALTH .of co19
Dedicated to protecting and improving the health and +', _,. n ss''
environment of the people of Colorado }5 �
4300 Cherry Creek Dr_S. aboratero liu Id nr 1 • y"
Denver, Colorado 8022?-1 v40 .1'1,)i 'irk A en e — 1876,
Phone(3031[9II-?0110 Ih:n.er ; ,1,44(l"An27n cn,
YY,,. •,1 -I J(i F.,v <'"mx
od,re
October 27, 1992 -
r.nrp,,.A..rw,L,,, nn u,n,rl I
Dave O'Sadnick
Golder Associates Inc.
200 Union Boulevard, Suite 100
Lakewood, Colorado 80228
Bill Hedberg
Waste Services Corporation
5660 Greenwood Flaza Bivd., Suite 400
Englewood, Colorado 80111
RE: Hydrogeological and Geotechnical Characterization for the Central Weld Sanitary Landfill, Weld
County, Colorado
Dear Mr. O'Sadnick and Mr. Hedberg:
The Hazardous Materials and Waste Management Division (the Division) of the Colorado Department of
Health has completed the review of the "Hydrogeologic and Geotechnical Characterization for the Central
Weld Sanitary landfill" located in Weld County. The review is made under the authority of the"Solid Waste
Disposal Sites and Facilities Act,"Title 30, Article 20, Part 1 of the Colorado Revised Statues, as amended
(the Statute), and the"Regulations Pertaining to Solid Waste Disposal Sites and Facilities." The Regulations
were adopted for the implementation of the Statute and are contained in the Colorado Code of Regulations,
6 CCR 1007-2 (the Regulations). The intent of the document was to provide the hydrologic, geologic and
geotechnical characterization of the Central Weld Sanitary Landfill.
The Division finds the document to be incomplete in some areas and asks for clarification in other areas.
The issues identified are as follows.
1. Please detail the tasks and schedule for completion of the tasks planned for the Central Weld
County Landfill. The submittal should include a narrative of the conceptual plans for the site,
inclusive of vertical or horizontal expansion, additional category of wastes, and the addition of
engineering features or structures.
2. Please provide specific information on the ground water wells within 1/4 mile of the site. The
information should include well logs, screen depth and well completion diagrams,the aquifer used,
and a cross-section relating the wells to the on-site hydrology and geology.
3. The report references geologic units, such as,the surficial unconsolidated unit,the upper weathered
bedrock unit, and the lower weathered bedrock unit. The names of the formations or the uppermost
aquifers have not been identified. Please provide additional explanation on the local geologic units
and their relationship to the regional geology and aquifers (both local and regional).
4. Section 4 states that the ground water flow is toward the south with a southwesterly component,
and then further on the same page (p.29), the ground water is said to have a south to southeast
component. This appears to be a discrepancy. Please explain in detail.
921276
t' l CLOCI Pwtv3 00 P_2
Mr. Hedberg and D. O'Sadnick
Central Weld County Landfill
October 27, 1992
Page 2/3
5. The report should state that the retention pond contains water and whether the pond is lined. Also
state the capacity of the pond, the rate and frequency at which water is entering the pond and
discharging to the pond. Specify, the usage of the water that is removed from the pond.
6. Page 33, section 4 states that 'A similar rise is not observed along the western wall of the trench,
since irrigation does not occur on the landfill.' It is presumed that you mean on the west side of
the landfill. The supposition is speculative, because not enough data has been gathered to
characterize the hydrogeology off site. Further, because of the numerous influences from off-site
to on-site,the Division requests that additional hydrogeological evaluations be performed to evaluate
off-site ground water contributions.
7. The report (Section 4, p.33) states that there is evidence of separation between the zones of
saturation. However, further in the text (p.34) it states that there are downward vertical gradients.
Please explain in detail this descrepancy.
8. Please provide north-south and east-west cross-sections through the landfill to show the relationship
of the landfill basegrade to the geology and saturated units.
9. Please provide an explanation for the ground water contamination identified in GWMW-2, an
upgradient well. What additional site investigation is planned for this area?
10. On figure 3-2 the stippling at SG-16 is incorrect. The left side is shown as sand and the right side
is shown as sandstone (near the top of the borehole).
11. Please provide an explanation for the ground water mounding on the east portion of the site.
12. Identify the uppermost aquifer beneath the site, within one mile of the site which is used for
domestic purposes.
13. Page 23, section 3 states that the site lies near the northern margin of the Laramie/Fox Hills
geologic units. As illustrated in figure 3-1,the base of the Laramie?Fox Hills aquifer subcrops some
distance southeast of the site. What is this distance? Where is the recharge area for the
Laramie/Fox Hills Aquifer? What are the geologic units beneath and within one mile of the site?
14. The text states that'The surface of the (upper weathered bedrock) unit appears to be erosional and
reflects the current topography of the site.' This is a misstatement. Since the current topography
is a significant alternation of the natural topography. Please provide a map showing the natural
topography, prior to landfill development and show the bedrock contours with respect to the natural
topography.
15. The Division notes that figures 3.3 and 3.4 are highly interpretive. The bedrock and isopach contour
map should be related to the site based on the natural topography. What data was used to
interpolate contours to the interior of the landfill.
16. Several of the GWMW wells, most of which were drilled to a depth of 60 feet, were not included on
Mr. Hedberg and D. O'Sadnick
Central Weld County Landfill
October 27, 1992
Page 3/3
figure 3.2. Since it appears, that these wells were used to generate the upper weathered/lower
weathered bedrock contact in figures 3.4 and 3.5. The wells should be shown on the cross-section.
17. During the recent site inspection, a shallow seep area was noted in the south central area of the
east section of the landfill. Please provide an explanation for its occurrence.
This concludes the Division's comments on the Hydrogeological and Geotechnical Characterization for the
Central Weld Sanitary Landfill. Please respond to the issues detailed above in a comprehensive document
within two weeks of this letters receipt. If you have any additional questions, you may contact either Roger
Doak or Austin Buckingham at this office.
Sincerely,
•
I c
6,/
Austin N. Buc ingha Roger Doak
Geologist Geologist
Hazardous Materials and Hazardous Materials and
Waste Management Division Waste Management Division
cc: J. Pickle, Weld County Health partment
A. Scheere, Waste Management of North America
L. Tagawa, Waste Management of rth America
Weld County Department of Pla ing
Weld County Commissioners
G. Mallory, CDH/HMWMD
P. Harley, CDH/HWMWD
file: SW/WLD/CEN correspondence
Hello