HomeMy WebLinkAbout981762.tiff MEMORANDUM
TO: Julie Chester, Current Planner DATE: August 19, 1998
C� FROM: Donald Carroll, Engineering Administrator iOP
COLORADO
SUBJECT: USR-1192; Little Thompson Water District
In my memo dated June 29, 1998, I had requested the applicant address Item #2E of the Land Use Application
Summary Sheet. The Engineering Company from Fort Collins has provided a storm water drainage plan,
calculations, and narrative. I have reviewed these items and have no conflict with the proposal. This addresses
Item #2 E in the summary sheet.
cc: RE-2299
Weld County Planning Dept.
plan29 •
AUG 1 9 1998
RECEIVED
EXHIBIT
981762
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EXHIBIT
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09/01/98 06:57 FAX 3073275385 SAULCY LAND CO Q01
FAX
DATE 9-1-98
TO Board of County
Commissioners—Weld County
FAX# 970-352-0242
FROM Bill Saulcy and Judy Saulcy
PAGES this page
INC THIS PAGE
Messaae
Re: Docket No. 98-48
Please accept our objection to the placing of any structure whatsoever
on this site other than a treated water storage tank.
During the negotiation to purchase the site, Little Thompson Water Dist.
has made no mention of anything other than one additional water tank in
the area.
We object to further change in the aesthetics of the area.
William R. "Bill" Saulcy
Judy Saulcy
P. O. Box 127
Encampment WY 82325
307-327-5543
EXHIBIT
S91762 asc r//92
STORM WATER DRAINAGE PLAN
TWIN MOUNDS 5.0-MG TREATED WATER STORAGE
TANK
Prepared for:
Little Thompson Water District
835 E Highway 56, Drawer G
Berthoud, CO 80513
(970) 532-2096
Prepared by:
The Engineering Co.
2310 East Prospect Road
Fort Collins, CO 80525
(970) 484-7477
August 18, 1998
11 EXHIBIT
A. GENERAL LOCATION AND DESCRIPTION
Little Thompson Water District is proposing the construction of a 5.0 million-gallon ground level,
steel, water storage tank to be located adjacent to an existing 2.0 million-gallon water storage
tank on the Twin Mounds site. The proposed tank measures 185 feet in diameter and 32 feet tall
(same height as existing tank). At the time that the original tank was approved, the plan also
showed a future 2.0 million-gallon tank just to the south. Because of rapidly increasing demands
on the distribution system,the District now requires a 5.0 million-gallon tank on the site.
The site is approximately 3.1 acres and is located in the NE quarter of Section 4, Township 4N,
Range 68 in Weld County. Access to the site is off of Weld County Road #7 approximately 'A
mile south of State Highway 60.
In general the objectives of storm water improvements are to convey minor storm runoff out of
streets and to protect life and property from major storm events. Because this project does not
include permanent residence or paved streets, the objectives are different. The purpose of the
drainage improvements on this site are as follows: (1) to reduce maintenance requirements on
site, (2) to adequately drain the soils surrounding the tank foundation, and (3) to protect
downstream properties and drainage facilities.
The purpose of this report is to provide a description of the existing(historic)drainage conditions
and to predict the effect of development on future drainage. The site under consideration is a
relatively small site and the proposed development will have only a minor effect on the storm
water. Therefore, this report will identify appropriate, cost-effective measures to ensure that
storm water leaving the site does not adversely impact neighboring properties or downstream
drainage facilities.
B. DRAINAGE BASINS AND SUB-BASINS
A 2.0-MG concrete treated water storage tank is currently located on the site. A gravel road is in
place to access the existing tank. The remainder of the site is covered in native grasses. The site
is surrounded on all sides by irrigated agricultural land. There is no evidence of erosion or other
adverse effects from storm water runoff from the existing tank site.
The site is located on the top of a hill and therefore, no drainage from offsite basins enters the
site. At least some flow from the site drains in all directions. However, the site is graded so that
increased flows from the tank and surrounding access road are all conveyed to the south. The
flows then enter a roadside ditch along the access easement and flow into the roadside ditch along
County Road 7.
Soil borings taken on the site indicate that the site has a thin layer of topsoil, approximately 2 V2'
to 6 %' of clay,and approximately 25' of shale. Slopes on the site range from near zero at the top
of the hill to approximately 10%along the hillside.
C. HYDROLOGY AND HYDRAULICS
A simplistic hydrologic analysis was done on the site to evaluate the increase in volume and peak
discharge of storm water from the site caused by the proposed improvements. The site's peak
flows were determined for the existing site under 5-year and 100-year storm conditions and for
the proposed site under 100-year storm conditions. The Rational Method was used to estimate
these peak flows. The required storage volume was calculated based on the difference in volume
between the 100-year developed condition and the 5-year historic allowable release rate. The
results of this analysis are summarized below.
Condition Discharge(cfs)
Existing 5-year 1.5
Existing 100-year 3.8
Proposed 100-year 7.0
Required Storage: 0.16 ac-ft
D. DRAINAGE DESIGN
The drainage design for the site includes the following elements:
(I) The access road surrounding the tank will slope to the outside. Storm water will
be conveyed along the outside of the road in an earthen ditch and directed to the
south side of the site.
(2) The tank will have an overflow and drain line. The overflow is used only in the
case of a malfunction of the tank filling system. The drain will be used to drain
the bottom 6" of the tank (less than 2% of the total volume) when the tank is
emptied for routine maintenance. These lines discharge at Weld County Road 7
into the roadside ditch.
(3) An underdrain system will collect a small amount of water from underneath the
tank. This pipe will discharge along the south slope.
(4) The access road will be crowned to drain. The drainage from the road will be
collected along side the road and conveyed to the south.
(5) A combination of a berming and excavation along the southern property edge
will provide the required 0.16 ac-ft of storage. An outlet pipe will be provided
under the access road to slowly discharge the water to the east.
E. SUMMARY
The addition of the proposed tank will increase the volume and intensity of the storm water
discharge from the site. However, this increase is relatively minor considering that the site is
small, no pavement is proposed, and the site is surrounded by undeveloped farmland. Every
attempt has been made to provide cost-effective measures to adequately mitigate the storm water
effects of the proposed construction.
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LANDSCAPING PLAN
TWIN MOUNDS 5.0-MG TREATED WATER STORAGE
TANK
Prepared for:
Little Thompson Water District
835 E Highway 56, Drawer G
Berthoud, CO 80513
(970) 532-2096
Prepared by:
The Engineering Co.
2310 East Prospect Road
Fort Collins, CO 80525
(970) 484-7477
August 27, 1998
A, GENERAL LOCATION AND DESCRIPTION
Little Thompson Water District is proposing the construction of a 5.0 million-gallon ground level,
steel, water storage tank to be located adjacent to an existing 2.0 million-gallon water storage
tank on the Twin Mounds site. The proposed tank measures 185 feet in diameter and 32 feet tall
(same height as existing tank). At the time that the original tank was approved, the plan also
showed a future 2.0 million-gallon tank just to the south. Because of rapidly increasing demands
on the distribution system, the District now requires a 5.0 million-gallon tank on the site.
The site is approximately 3.1 acres and is located in the NE quarter of Section 4, Township 4N,
Range 68 in Weld County. Access to the site is off of Weld County Road #7 approximately %3
mile south of State Highway 60.
The purpose of this report is to provide a description of the proposed landscaping improvements.
B. PROPOSED LANDSCAPING
The intent of the proposed landscaping is to provide low-maintenance vegetation that will serve
to soften the visual impact of the tank and prevent erosion on the site. The landscaping includes
the following elements:
1. Reseeding. Areas disturbed by construction will be reseeded with a native grass
seed.
2. Trees. A mix of deciduous and evergreen trees will be planted on the site to provide
visual relief and some buffering of the tank from the surrounding areas.
3. Irrigation. An irrigation system is currently in place at the site to serve existing
landscaping. This system will be expanded to serve the additional plantings.
The owner(Little Thompson Water District)will install the landscaping following the completion
of the construction. The landscaping is designed to be low-maintenance. The maintenance that is
required will be provided by the owner. The proposed landscaping plan is delineated on the
enclosed drawing.
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