2024 Inspection Report 2497.pdf

DAM SAFETY INSPECTION REPORT

THREAD CREEK IMPOUNDMENT DAM – DAM ID NO. 2497

TRIB TO THREAD CREEK

OAKLAND COUNTY – NE 1/4 SECTION 7, T05N, R08E

OWNER(S)/OPERATOR(S): Department of Natural Resources Southeastern Management Unit Holly Field Office 8100 Grange Hall Road Holly, Michigan 48442

HAZARD POTENTIAL

CLASSIFICATION: Low

INSPECTION DATE: September 19, 2024

REPORT DATE: December 5, 2024

PREPARED AND INSPECTED BY:

Allyson Hartz Dam Safety Unit Water Resources Division Department of Environment, Great Lakes, and Energy P.O. Box 30458 Lansing, Michigan 48909-7958 517-331-5687

Lucas A. Trumble, P.E.

Registration Number: 58295 Dam Safety Unit Water Resources Division Department of Environment, Great Lakes, and Energy P.O. Box 30458 Lansing, Michigan 48909-7958 517-231-8594

INTRODUCTION

The purpose of this inspection was to evaluate the structural condition and hydraulic capacity of the Thread Creek Impoundment Dam, as required by Part 315, of the Natural Resources and Environmental Protection Act, 1994 PA 451, as amended. This inspection was conducted by the Department of Environment, Great Lakes, and Energy (EGLE) per the Memorandum of Understanding between the Michigan Department of Natural Resources (MDNR) and the Michigan Department of Environment, Great Lakes, and Energy [EGLE, formerly Michigan Department of Environmental Quality (MDEQ)], entitled “Inspection of MDNR-Owned Dams and Funding of MDEQ's Dam Safety Program”.

The report is limited to a discussion of observations based on a visual investigation and review of any available previous inspection reports, plans, and data. This report should not be considered an in-depth engineering investigation. All references to “right” and “left” in this report are based on the observer facing downstream.

CONCLUSIONS AND RECOMMENDATIONS

The Thread Creek Impoundment Dam is in unsatisfactory condition.

The following recommended actions are listed by priority:

1. Failing Material (Action: Engineer, Maintenance, Monitor): The CMP [corrugated metal pipe] Inlet Riser has deteriorated to the point of failure. The impoundment should be drawn down in spring of 2025 to prevent further deterioration of the inlet works. An EGLE permit will need to be obtained for drawdown. Consult with an engineer to remove and replace the failed inlet pipe. The pipe should be monitored weekly and after rain events until the rehabilitation is complete. Complete the repairs as soon as possible.

a. Principal Spillway - CMP Inlet Riser

2. Debris (Action: Maintenance): Remove cattail buildup from the inlet. Complete action as soon as possible.

a. Principal Spillway - CMP Inlet Riser

3. Trees and Brush (Action: Maintenance): Continue efforts to remove all trees and brush from the earthen embankments and auxiliary spillway. Flush cut and/or grind stumps and remove clearing debris from the embankment. The stumps should be cut a maximum of one-foot above ground. Establish appropriate vegetation if stump is to be ground. We do not recommend uprooting trees for removal. Tree roots can lead to piping failure by cultivating flow paths in the embankment especially when the tree dies.

Trees can also cause extensive damage and/or failure when they are uprooted from a storm. Complete action by December 31, 2026.

a. Embankment - Downstream Slope

b. Auxiliary Spillway - Chute

4. Deteriorating Material (Action: Monitor, Maintenance): Perform a televised inspection of the interior of the primary spillway structure including the inlet and outlet pipes before or by the time of the next inspection. Consider maintenance or rehabilitation of these components based on the results of the inspection.

a. Principal Spillway - CMP Inlet Riser

b. Principal Spillway - CMP Outlet Conduit

5. Erosion (Action: Monitor, Maintenance): Erosion was observed on both sides of the outlet pipe on the downstream embankment slope. Monitor the erosion for further loss of earth material. Consider reshaping and stabilizing the area with suitable fill material if erosion continues.

a. Principal Spillway - CMP Outlet Conduit

6. Create an operation and maintenance plan. A proper operation and maintenance plan will increase the dam’s service life and maintain the dam’s hydraulic and structural condition.

The dam’s current low hazard potential rating remains appropriate.

PROJECT INFORMATION

The Thread Creak Impoundment Dam was constructed in 1969 by the MDNR. Plans for the original construction are on file with the MDNR and the Dam Safety Unit.

Refurbishment of the original control structure and construction of an emergency spillway were performed in 1993, under the auspices of MDNR Permit No. 92-14-120.

The dam is located in the Holly Recreation Area and maintained by MDNR Wildlife Division staff. The dam consists of a 400-foot long earthen embankment with a structural height of 7 feet and a normal head of 3 feet, and creates a wildlife flooding with a surface area of approximately 40 acres. The primary spillway consists of a half section of 48-inch diameter CMP riser connected to a 40-foot long, 30-inch diameter CMP outlet pipe. Water levels are controlled by stoplogs located on the riser. A 65-foot wide riprap-lined auxiliary spillway is located on the embankment approximately 150 feet left of the principal spillway.

The dam was previously inspected by EGLE staff in 1989, 1992, 1997, 2002, 2007, 2012, and 2019. Copies of these inspection reports are on file with the Dam Safety Unit.

SITE INVESTIGATION

The following discussion of the dam’s physical condition and appurtenances is based on observations and photographs obtained on the inspection date.

In addition to the specific findings listed below, it is important to continue good maintenance practices. These practices include regular inspection of the dam embankments and hydraulic structures for any deficiencies. Some of the more common issues that are found include growth of trees and brush, development of erosion areas, and animal burrows.

The following data was collected on the date of the inspection and includes deficiencies observed during the inspection and necessary actions for remediation of the observed deficiencies.

Embankment

Upstream Slope

Issues Present None

Crest

Issues Present None

Downstream Slope

Issues Present Trees and Brush

Trees and Brush

Describe Issue Trees, brush, and woody vegetation were observed on the downstream embankment slope.

Photos 24, 25, 26, 27, 28

Action Required Maintenance

Describe Action Required

Continue efforts to remove all trees and brush from the earthen embankments. Trees should be removed to 10 feet beyond the downstream toe of slope. Once cleared, embankments should be mowed or treated with herbicide a minimum of two (2) times per year to prevent further establishment of woody vegetation and to facilitate visual inspection.

Principal Spillway

Issues Present Failing Material, Debris, Deteriorating Material, Erosion

Failing Material

Describe Issue The CMP inlet pipe has deteriorated to the point of failure. A large hole has developed in the pipe and the impoundment level is not being maintained.

Component CMP Inlet Riser

Photos 1, 2, 3, 5, 7

Action Required Engineer, Maintenance, Monitor

Describe Action Required

Obtain an EGLE permit for drawdown of the impoundment in spring of 2025. Consult with an engineer to remove and replace the inlet pipe and complete rehabilitation as soon as possible. Monitor the pipe weekly and after rain events to ensure stability.

Debris

Describe Issue Cattail vegetation has built up around the inlet pipe.

Component CMP Inlet Riser

Photo(s) 6

Action Required Maintenance

Describe Action Required Remove the cattails in this area as soon as possible.

Deteriorating Material

Describe Issue The inlet pipe is experiencing deterioration over time.

The outlet pipe is experiencing deterioration over time.

Component CMP Inlet Riser CMP Outlet Conduit

Photos 4 9

Material Metal Metal

Action Required Monitor

Describe Action Required A televised inspection of the interiors of the inlet and outlet pipes should be performed within five (5) years.

Erosion

Describe Issue Erosion of the downstream embankment slope was observed on both sides of the outlet pipe.

Component CMP Outlet Conduit

Photos 10

Action Required Monitor, Maintenance

Describe Action Required Monitor the eroded areas for additional loss of earth material and consider reshaping and stabilizing the area with suitable fill material if necessary.

Auxiliary Spillway

Issues Present Trees and Brush

Trees and Brush

Describe Issue Trees, brush, and woody vegetation were observed in the outlet of the auxiliary spillway channel.

Component Chute

Photos 14

Action Required Maintenance

Describe Action Required

Remove all trees and brush from the auxiliary spillway channel. Trees should be removed to 10 feet beyond the downstream toe of slope.

Once cleared, channel should be maintained along with the earthen embankments, mowed or treated with herbicide a minimum of two (2) times per year to prevent further establishment of woody vegetation and to facilitate visual inspection.

The above monitoring and maintenance items should be addressed in accordance with the Conclusions and Recommendations section of this report.

General notes about the issues observed are shown below:

Debris Debris reduces the hydraulic capacity of the dam and can cause damage to components.

Deteriorating Material All materials deteriorate over time, but proper maintenance can extend the service life of the material and reduce the life cycle cost of maintenance and operation of the dam.

Erosion Erosion is caused when the water has enough energy to dislodge and carry the surface material. Once the surface protective barriers (vegetation, rock, concrete, metal etc.) has been removed the remaining soil will much more easily be eroded by the water.

Trees, Brush, and Woody Vegetation If woody vegetation is allowed to mature, it could develop an extensive root system.

These root systems can lead to piping failure or if the brush and trees are uprooted in a storm, can cause extensive deterioration of the embankment. In addition, woody vegetation invites animal activity, impedes the visual inspection of the dam, and can kill other vegetation that helps stabilize the soil. Embankments should be clear of woody vegetation and mowed 10 feet past the toe of the embankment.

STRUCTURAL STABILITY

Due to the failure of the CMP inlet riser pipe, the structural stability of the dam is compromised. Water is flowing around the riser pipe and causing erosion of the upstream embankment and crest of the dam. Remedial action is required as soon as possible to prevent further erosion of the earthen embankment and deterioration of the inlet pipe. These components left in their current conditions could lead to dam failure.

HYDROLOGY AND HYDRAULICS

The contributing drainage area to the tributary to Thread Creek at the Thread Creek Impoundment Dam is approximately 8.9 square miles. The design discharge for this low hazard potential dam is the 1 percent annual chance (100-year) flood discharge which is estimated to be 170 cubic feet per second (cfs). The principal spillway and auxiliary spillways combined can pass 170 cfs with approximately 0.7 feet of freeboard at the earthen embankment. Therefore, the dam has adequate spillway capacity to convey the design flood inflow, but with less freeboard then typically recommended.

Given this apparent lack of spillway capacity, the design flood was routed through the system using the U.S. Army Corps of Engineers, Hydrologic Engineer Center’s Hydrologic Modeling Software (HEC-HMS). Flood routing takes into account available storage and attenuation of peak flows provided by the impoundment and dam. The HEC-HMS flood model predicts the dam can pass the design flood with a maximum discharge of approximately 160 cfs and a maximum rise in the impoundment of 2.9 feet.

This would result in approximately 0.8 feet of freeboard during the design flood. This is still less freeboard than desired, but HEC-HMS uses conservative estimates to perform the flood routing, and actual freeboard may be more than was determined through this modeling.

Hydraulic calculations used to make this determination are on file with the Dam Safety Unit. Estimated flood flows are shown in Appendix C.

OPERATION AND MAINTENANCE

Operation and maintenance (O&M) of the dam is performed by MDNR Wildlife Division staff. A written O&M Plan is not on record with the Dam Safety Unit. The Dam Safety Unit recommends creating an O&M Plan to ensure proper operation and maintenance of the dam. The Dam Safety Unit should be provided any future or current O&M Plans.

EMERGENCY ACTION PLAN

An Emergency Action Plan (EAP) is not required under Part 315 for a low hazard potential dam. Our records indicate that an EAP has not been developed for the dam.

APPENDICES

Appendix A - Location Map Appendix B - Inspection Photographs Appendix C - Hydraulic Data

THREAD CREEK IMPOUNDMENT DAM - OAKLAND COUNTY - DAM ID NO. 2497

APPENDIX A – LOCATION MAP

APPENDIX B – INSPECTION PHOTOS

Photos

Photo #1: Principal Spillway CMP Inlet Riser. The inlet pipe has deteriorated and failed.

Issue: Failing Material, Action: Engineer, Maintenance, Monitor

Photo #2: Principal Spillway CMP Inlet Riser. The inlet pipe has deteriorated and failed.

Photo #3: Principal Spillway CMP Inlet Riser. Embankment material around the inlet has eroded away.

Water is flowing around the upstream side of the half CMP pipe.

Photo #4: Principal Spillway CMP Inlet Riser.

Issue: Deteriorating Material, Action: Monitor

Photo #5: Principal Spillway CMP Inlet Riser. Embankment material around the inlet has eroded away.

Water is flowing around the upstream side of the half CMP pipe.

Photo #6: Principal Spillway CMP Inlet Riser. Note buildup of cattail vegetation around the inlet pipe.

Issue: Debris, Action: Maintenance

Photo #7: Principal Spillway CMP Inlet Riser. Water flowing around riser.

Photo #8: Principal Spillway CMP Inlet Riser. Stoplog weir inside of half CMP inlet riser.

Photo #9: Principal Spillway CMP Outlet Conduit.

Issue: Deteriorating Material, Action: Monitor

Photo #10: Principal Spillway CMP Outlet Conduit. Erosion on both sides of outlet pipe. Slopes are vegetated and appear stable but should be monitored after high flows.

Issue: Erosion, Action: Monitor

Photo #11: Principal Spillway CMP Outlet Conduit.

Photo #12: Principal Spillway CMP Outlet Conduit.

Photo #13: Auxiliary Spillway Inlet.

Photo #14: Auxiliary Spillway Chute.

Issue: Trees and Brush, Action: Maintenance

Photo #15: Embankment Upstream Slope.

Photo #16: Embankment Upstream Slope.

Photo #17: Embankment Upstream Slope.

Photo #18: Embankment Upstream Slope.

Photo #19: Embankment Upstream Slope.

Photo #20: Embankment Crest.

Photo #21: Embankment Crest.

Photo #22: Embankment Crest.

Photo #23: Embankment Crest.

Photo #24: Embankment Downstream Slope.

Photo #25: Embankment Downstream Slope.

Photo #26: Embankment Downstream Slope.

Photo #27: Embankment Downstream Slope.

Photo #28: Embankment Downstream Slope.

Photo #29 Impoundment.

APPENDIX C - HYDRAULIC DATA

-----Original Message----- From: EGLE-wrd-qreq <EGLE-wrd-qreq@michigan.gov> Sent: Monday, May 13, 2024 4:40 PM To: Hartz, Allyson (EGLE) <HartzA1@michigan.gov> Subject: RE: Flood or Low Flow Discharge Request

We have processed the discharge request submitted by email on April 5, 2024 (Process No.

20240224), as follows:

Thread Creek at Thread Creek Impoundment Dam, Dam ID 2497, Section 7, T5N, R8E, Groveland Township, Oakland County, has a total drainage area of 12.6 square miles and a contributing drainage area of 8.9 square miles. The design discharge for this dam is the 1% chance (100-year) flood. The 1% chance peak flow is estimated to be 170 cubic feet per second. (Watershed Basin No. 32B Flint).

These estimates should be confirmed by our office if an application is not submitted within one year. If you have any questions concerning the discharge estimates, please contact Ms.

Susan Greiner, Hydrologic Studies and Floodplain Management Unit, at 517-927-3838, or by email at: GreinerS@michigan.gov.

-----Original Message----- From: EGLE-Automated <EGLE-Automated@michigan.gov> Sent: Friday, April 5, 2024 1:21 PM To: EGLE-wrd-qreq <EGLE-wrd-qreq@michigan.gov> Subject: Flood or Low Flow Discharge Request

Requestor: Allyson Hartz Company: EGLE Address: SE MI City/State: Warren, MI ZIP Code: 00000 Phone: 5173315687 Date: 04/05/2024 1 percent Flood Discharge Request Type: Dam Other Description (if request type "Other" selected):

Dam Hazard Potential (if request type "Dam" selected): Low Dam ID (if request type "Dam" selected): 2497 Low Flow Project Description:

Contact Person:

Watercourse: Tributary to Thread Creek Local Name:

County: Oakland City/Township: ?

Section: 7 Town: 05N Range: 08E Location: Thread Creek Impoundment Dam Email: HartzA1@michigan.gov mailto:GreinerS@michigan.gov mailto:EGLE-Automated@michigan.gov mailto:EGLE-wrd-qreq@michigan.gov mailto:HartzA1@michigan.gov