2016-09-02_HYDROLOGY - M1992069

• Permit No: M1992069
• IBM Index Class Name: Hydrology
• Doc Date: 9/2/2016
• Doc Name: Correspondence
• From: City of Greeley
• To: DRMS
• Email Name: PSH
• Media Type: D
• Archive: No

WWE
Wright Water Engineers, Inc.
2490 West 26th Ave.,Suite 100A www.wrightwater.com
Denver,Colorado 80211 e-mail:[e-mail]
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September 2, 2016
Via U.S.Mail
Mr. Roger Schmidt
President,Boyd Irrigation Company
1100 loth Street, Suite 300
Greeley, Colorado 80631
Re: Engineering Evaluation of Nature and Causes of Erosion in Agricultural Field Adjacent to
Boyd Irrigation Company Pipeline and Damage to Pipeline
Dear Mr. Schmidt:
Wright Water Engineers, Inc. (WWE) has prepared this letter report to present our analysis and
findings from an engineering evaluation regarding the nature and causes of erosion in an
agricultural field owned by the City of Greeley (City) and the related cause of damage to a
pipeline owned by the Boyd Irrigation Company (BIC). The field is located adjacent to a
pipeline owned by the BIC that conveys water in the Boyd-Freeman Ditch. The erosion damage
to the field and damage to the pipeline occurred in June 2014 when the water level in the Cache
La Poudre River overtopped its banks, resulting in flow across the field, causing a breach in the
pipeline and its embankment and formation of an erosional headcut in the field. Damage to the
ditch and pipeline also occurred in the same vicinity in 2010 and 2013,respectively.
The subject agricultural property, referred to in this report as the F Street agricultural field, is
bounded on the south by F Street and miscellaneous properties; on the north by the Great
Western Railroad; on the east by a gravel pit on property owned by 83`d Joint Venture and
constructed by Aggregate Industries (Al) (herein referred to jointly as Al); and on the west by a
concrete bike path owned by the City. Further west, beyond the bike path, is the Cache La
Poudre River and its associated floodplain (Figure 1). (Note: The north/south ditch alignment is
on the parcel owned by Carl Hill. The only portion of the ditch that is located on the City-owned
F Street property is the siphon that was newly constructed in 2016).
The primary question addressed by this evaluation is to identify the cause(s) of the large
erosional headcut feature that formed on the F Street agricultural field and damaged the BIC
pipeline east of the field during a major runoff event that peaked on June 2, 2014. Based on the
evaluation conducted to date by WWE, the following are our major findings which are made
with a reasonable degree of engineering probability:
• The erosional feature on the F Street agricultural field was formed when water
overflowing the east bank of the Cache La Poudre River crossed the field as sheet flow
and then cascaded down into the Al gravel pit. The velocity of the cascading flow down
the pit's western bank was sufficiently high enough to erode the soils on top of and along
GLENWOOD SPRINGS DURANGO
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