2 - 1992 Dam safety inspection report.pdf
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- Solicitation number
- RFP 171 260000002681 2
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- Michigan
About this file
This is a Dam Safety Inspection Report prepared by the Michigan Department of Natural Resources (DNR), Land and Water Management Division, for the Hancock Creek Dam located in Dickinson County. The inspection was conducted on June 12, 1991, by James T. Pawloski, P.E., Dam Safety Unit, with the report finalized on February 19, 1992. The Hancock Creek Dam is a 338-foot long earth fill embankment structure with a structural height of 12 feet, originally constructed in 1951 to control wildlife flooding created by a beaver dam. The facility creates a 7-foot head and impounds approximately 70 acres of water. The principal spillway consists of a concrete drop box inlet with a 7-foot wide stoplog section connected to a 40-foot long 60-inch diameter corrugated metal pipe outlet. The dam is operated by the Michigan DNR District 2 Wildlife Biologist and classified as Low Hazard Potential.
The inspection concluded that the Hancock Creek Dam is in good condition with no apparent deficiencies that may lead to failure. However, the report identified that the dam has insufficient spillway capacity. Six priority recommendations were provided, including adding one foot of compacted fill across the entire embankment with seeding and mulching, removing trees and brush from upstream and downstream slopes, removing a log from the spillway, replacing the walkway deck boards and stoplogs during 1992, adding a barrier at the south end to prevent off-road vehicle traffic, and developing a written Operation and Maintenance manual to be maintained at both the District Office and Dam Safety Unit. The current Low Hazard Potential classification was determined to be appropriate based on the inspection findings.
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Text version
DNR/Land 8 Water
No.517-373-9965 Fe 16:11 No.010 P.04 L,· 4.7
DAM SAFETY INSPECTION REPORT
HANCOCK CREEK DAM
HANCOCK CREEK
DAM ID NO. 00088
DICKINSON COUNTY
OWNER: Michigan Department of Natural Resources Wildlife Division
OPERATOR: Michigan Department of Natural Resources District 2 Wildlife Biologist P,O. Box 300
Crystal Falls, Michigan 49920 telephone: 906-875·6622
HAZARD POTENTIAL CLASSIACATION: Low
DiSPECTED BY: James T. Pawloski, P.E.
Dam Safety Unit Land and Water Management Division Michigan Department of Natural Resources
INSPECTION DATE: June 12, 1991
REPORT DATE: February 19, 1992
PREPARED BY: 77 RAL 1
Ja66 T. Pawloski, P.E.
Dam Safety Unit 1 Land and Water Management Division Michigan Department of Natural Resources P.O. Box 30028
Lansing, Michigan 48909 517-373-4786
DNR/Land & Water TEL No.517-373-9965 Fell.15,95 16:11 No.010 P.05
CUNCLUSIONS U U
The Hancock Creek Dam is in good condition. Based on the observations on the date of the inspection, there are no apparent deficiencies that may lead to failure of the dam. The dam has insufficient spillway capacity. Maintenance and operation recommendations follow.
The current low hazard potential classification is appropriate.
RECOMMENDATIONS
The following recommended actions are listed by priority. Thcse recommendations should be implemented as soon as possible.
1) Add 1 foot of compacted fill across entire embankment, seed and mulch to promote good grass growth.
2) Remove trees and brush from both upstream and downstream slopes of the dam embankment.
3) Remove log from spillway.
4) Replace walkway deck boards and stoplogs during 1992.
5) Add an additional post or large boulder at the south end of the dam between the gate post and the pond to pmvent off-road vehicle traffic from crossing the embankment.
6) Develop a written Operation & Maintenance (0 & M) manual and keep on file at the District Office and with the Dam Safety Unit.
PROJECT INFORMATION SECTION
The Hancock Creek Dam was constructed in 1951 to control a witdlife flooding created by a beaver dam. Reduced copies of construction plans are on file with the Dam Safety Unit.
The Hancock Creek Dam has a 338 foot long earth fill embankment with a structural height of 12 feet. Tile dam creates a head of about 7 feet and an impoundment with a surface area of approximately 70 acres.
The principal spillway consists of a concrete drop box inlet with a 7 foot wide stoplog section.
The concrete Wet structure is founded on 8 gauge steel sheet Filing. The drop inlet is connected to a 40 foot long 60 inch diameter corrugated metal pipe (CMP) outlet pipe. A wooden plank walkway and a pipe handmil provides access to the stoplogs.
DNR/Land & Water TEL No.517-373-9965 Feb-15,95 16:11 No.010 P.06
Hancock Creek Dam L.,· <vi Dam Safety Inspection Report Page Two
The embankment consists of unspecified earth fill with an upstream slope of 3 horizontal to 1 vertical, downstream slope of 2.5 horizontal to 1 vertical, and a top width of 10 feet. The embankment foundation consists of rock overlain by sands and gravels up to 5 feet thick, and covered with topsoil or muck varying up to 2 feet thick. Drawing notes indicate that unsuitable foundation material was to be excavated prior to placing embankment fill.
Previous inspection reports were completed in 1978, 1979 and 1988. Previous recommendations included adding 1 foot of fill on top of the embankment, replacement of stoplogs, brush removal, and repair of concrete cracks. These recommendations do not appear to have been implemented.
The concrete of the drop inlet structure is cracked and displaced in the headwall just to the left of the outlet pipe. The crack does not appear to be worse than noted in previous inspections.
Another crack in the headwall is located just to the right of the outlet pipe. The headwall is also cracked directly above the crown of the pipe. The cracks do not appear to be cause for concern at this time, but should be monitored in subsequent inspections.
The outlet pipe is in good condition. No leaking or deflected joints were observed.
EIELD INSPECTION
Field observations and photographs were obtained by James T. Pawloski, P.E., and Leon A.
Cook, P.E., of the Land and Water Management Division on June 12, 1991.
Following is a brief description of the physical condition of the dam and appurtenances on the date of inspection.
The embalikment is grass covered and in good condition. Both upstream and downstream slopes are covered with brush, which should be removed, There were no other indioations of deficiencies in the embankment. Off-road vehicle tmffic was noted at the south end of the embankment. Another post or large boulder could be placed between the end of the gate and tile water surface to prohibit traffic across the dam.
The concrete of the drop inlet structure is cracked and displaced in the headwalljust to the left of the outlet pipe, The crack does not appear to be worse than noted in previous inspections.
Another crack in the headwall is located just to the right of the outlet pipe. The headwall is also cracked directly above the crown of the pipe. The cracks do not appear to be cause for concern at this time, but should be monitored in subsequent inspections.
The outlet pipe is in good condition. No leaking or deflected joints Weit observed.
DNR/Land & Water 1-2 No.517-373-9965 Fe5,95 16:11 No.010 P.07 Hancock Creek Dam Lj Li Dam Safety Inspection Report Page Three
STRUCTURAL STABILITY
Based on the conditions observed during the field inspection, the embankment appears to be in stable condition. No further structural stability analysis is warranted at this time.
UYDROLOGY AND HIDRMJLICS
The contributing drainage area to the dam is approximately 6.4 square miles. The design discharge for this dam is the 1 % chance flood discharge of 360 cubic feet per second @fs). The existing Spillway capacity is 200 cfs, with 1. foot of freeboard.
Previous analyses has determined that the design flood event could be attenuated in the impoundment, with a maximum discharge of 210 cfs, with approximately 0.6 foot of freeboard.
It is recommended that 1.0 foot of fill be added to the top of the embankment to provide additional freeboard.
OPERATION AND MAINTENANCE
Operation and maintenance of the dam is by Mr. Jim Hammill, District 2 Wildlife Biologist.
No written operation and maintenance (0 & M) plan exists for the dam. An OAM plan should be established and kept on file at the District Office and with the Dam Safety Unit.
- Emergency Aclign-Rlan
No written emergency action plan (EAP) exists for this facility. Due to the low hazard potential rating for this dam, an RAP is not required.
APPENDICES
A. Photographs
B. Location Map
File details come from the government source that posted it. Updated .