[Federal Register Volume 78, Number 242 (Tuesday, December 17, 2013)]
[Pages 76288-76289]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2013-29984]



Department of the Army; Corps of Engineers

Notice of Intent To Prepare a Draft Environmental Impact 
Statement and Dam Safety Modification Study Report for the Cherry Creek 
Project, Arapahoe County, Colorado

AGENCY: Department of the Army, U.S. Army Corps of Engineers; DoD.

ACTION: Notice of intent.


SUMMARY: Pursuant to the National Environmental Policy Act of 1969, as 
amended, the U.S. Army Corps of Engineers, Omaha District (Corps) 
intends to prepare a draft Environmental Impact Statement (EIS) for the 
federal action to remediate dam safety concerns at Cherry Creek Dam. 
The dam safety concerns are primarily related to a hydrologic 
deficiency resulting from an extreme precipitation event and the large 
population that could be affected by such an event. Cherry Creek Dam 
and Lake is located on Cherry Creek, 11.4 miles upstream of its 
confluence with the South Platte River, in Aurora, Colorado (southeast 
Denver metropolitan area). The remediation actions will be identified 
through a Dam Safety Modification Study (DSMS) being conducted in 
accordance with Corps policy as described in Engineering Regulation 
1110-2-1156 ``Safety of Dams--Policy and Procedures.''

ADDRESSES: Omaha District Corps of Engineers, 1616 Capitol Ave, Omaha, 
NE 68102-4926 (Attn: Margaret Oldham CENWO-PAO).

FOR FURTHER INFORMATION CONTACT: Current and archival information 
regarding Cherry Creek Dam may be obtained by contacting the Omaha 
District. The point of contact is Margaret Oldham, Phone: (402) 995-
2416; email: [email protected]. Questions or comments 
regarding the upcoming studies at Cherry Creek Dam should also be 
directed to Ms. Oldham.

    1. Background Information. The Cherry Creek Dam project was 
authorized in the 1940s for the primary purpose of protecting the city 
of Denver against floods from Cherry Creek. The dam is located in a 
densely populated area and provides flood protection to over 200,000 
people. Starting in 2005, the Corps sought to better categorize the 
risk at all of its dams. Risk considers both the probability and 
consequences of a dam failure. Cherry Creek Dam received an elevated 
risk rating primarily because of the hydraulic deficiency resulting 
from an extreme precipitation event and the large population which is 
protected by the dam. Estimation of extreme precipitation events is 
based on the Probable Maximum Precipitation (PMP) for a given location. 
A PMP is an extremely rare event and is defined as the maximum amount 
of precipitation that could occur if all meteorological elements were 
optimal to allow a perfect environment for forming precipitation. The 
resulting stream flow from a PMP is a flood defined as the Probable 
Maximum Flood (PMF).
    Multiple past studies have indicated that Cherry Creek may not be 
able to adequately pass a PMF event. Hydrologic deficiency issues 
associated with Cherry Creek Dam were initially brought to light in 
1970 after the National Weather Service (NWS) completed a site-specific 
PMP study of the upper South Platte River basin for the design of 
Chatfield Dam (a nearby dam on the South Platte River). Applying the 
1970 PMP criteria to the Cherry Creek basin resulted in a larger stream 
flow than used in the project's original design and indicated the dam 
had a potential hydrologic deficiency. Since 1970, the NWS and the 
Corps have completed several PMP and PMF estimates including a Cherry 
Creek basin, site-specific PMP study completed by the NWS in 1995. 
Applying the current estimate of the PMF, which is also based on the 
1995 PMP study, Cherry Creek Dam has a hydrologic deficiency even if 
the pool elevation at the start of the PMF was at normal operating 
    Because of the risk rating, Omaha District completed an Issue 
Evaluation Study (IES) in 2011 to further evaluate Cherry Creek Dam's 
safety issues and corresponding risk. The IES findings were presented 
to a Senior Oversight Group (SOG) appointed by the Corps' Headquarters. 
The SOG reviewed the IES and confirmed the risk rating for the dam. 
Omaha District was directed to proceed into a DSMS, which is currently 
under way, with the task of defining in detail the risk associated with 
the Cherry Creek Dam's safety issues and assessing possible options for 
mitigating the risk. Those options may include federal actions which 
will be the subject of the EIS.
    2. Remediation Alternatives. The draft EIS will address an array of 
remediation alternatives that could reduce the risk of life loss, 
extensive downstream damage, functional loss of the project, and the 
loss of all project benefits. The nature and extent of the remediation 
alternatives will be determined based on the results of on-going 
engineering studies, public and agency input during the scoping period, 
and preparation of the draft EIS.
    3. Issues To Be Addressed. The draft EIS will address environmental 
issues concerning the remediation alternatives proposed. Issues will be 
identified based on public input during the scoping process and during 
preparation of the draft EIS. Environmental issues initially identified 
as potentially significant include, but are not limited to: hydrology 
and water quality, noise and vibration, air quality, socioeconomics, 
water supply, land use, recreation, visual and aesthetic resources, 
traffic and transportation, historical and cultural resources, 
vegetation and wildlife, special status species, and fisheries.
    4. Public Involvement. Public scoping meetings will be held in 2014 
at specific locations to be announced within the local Cherry Creek Dam 
project area. The purpose of the public scoping meetings will be to 
present information to the public regarding the array of remediation 
alternatives that may be addressed in the draft EIS, receive public 
comments, and solicit input regarding dam safety issues, remediation 
alternatives to consider, and environmental issues of concern to the 
public. These meetings are intended to initiate the process to involve 
concerned individuals, and local, state, and federal agencies. The 
public scoping meeting place, date, and time will be advertised in 
advance in local newspapers, and meeting announcement letters will be 
sent to interested parties.

[[Page 76289]]

    5. Availability of the Draft EIS. The Corps intends to issue the 
draft EIS in the 2015/2016 time frame. The Corps will announce 
availability of the draft EIS in the Federal Register and other media, 
and will provide the public, organizations, and agencies with an 
opportunity to submit comments to be addressed in the final EIS.

    Dated: December 4, 2013.
John Palensky,
Project Manager, U.S. Army Corps of Engineers.
[FR Doc. 2013-29984 Filed 12-16-13; 8:45 am]