Lake Whetstone Dam Toe Drain Project Update

by Patrick Herron

Lake Whetstone Dam Toe Drain Project Update

In June 2021, the Montgomery County Department of Environmental Protection (DEP) started its Lake Whetstone Dam Toe Drain Repair project, which is located on the downstream side of the dam, just west of Montgomery Village Avenue, which runs along the top of the dam.

As outlined on the County website: “During DEP’s routine maintenance inspection of the Lake Whetstone dam and outfall it was discovered that the toe drain is corroded and in need of replacement. The purpose of the toe drain is to collect water seepage in the earthen dam and safely convey it to the pond outfall.  Toe drains perform an important function in maintaining a safe and secure dam. If not replaced the toe drain pipe would eventually collapse and fail to convey water seepage safely through the dam. The repair work will involve abandonment of the existing toe drain pipe, excavating a new trench and placement of two new 8” slotted, double walled, corrugated HDPE (plastic) pipes that terminate at the concrete outfall wall.”

Due to the excavation of the dam and repair of the toe drain, the Lake Whetstone water level is required to be 4’ lower than normal levels. Due to the lowered water level, temporary safety fencing was installed around the perimeter of the lake. The lowering of the lake is a continual task as the lake water level will continue to rise. Earlier this month, on Tuesday, July 6, the lake level was noticeably lower than the 4’ level. MVF staff contacted DEP staff who wrote the following: “DEP agrees with your concerns – the lake should not be this low. The lake valve was open over the weekend to lower the levels, as they were still higher than the required level on Thursday afternoon (7/1/2021). Triangle Contracting is required to monitor the levels when they are being lowered, and they did not perform the required monitoring over the weekend. The valve should have been shut over the weekend. The valve was shut as of this morning (7/6/2021). There is water coming into the Lake now so it should rise a little today. The levels are currently about 2 feet lower than they should be (6 feet lower than normal).”

The DEP staff, along with MVF staff and residents completed a review of conditions of the lake caused by the over-draining on Wednesday, July 7. During that tour there were thankfully no deceased wildlife seen; however, it was identified that signage should go up around the lake, and that trash should be cleared from the lake shoreline. MVF staff had been requesting access to the fenced off lake shoreline to clear the trash and had been waiting for DEP approval.   MVF staff got the approval to enter the fenced off lake area on Wednesday, July 7 to begin trash removal as soon as permitted. Trash removal has taken a team of 10 staff, 3 days to clear. During the trash removal process staff have thankfully not seen any deceased wildlife. Signage also went up once signs were received from DEP on Friday, July 9.

Since the initial incident, the water level has continued to rise, and on July 12, DEP staff confirmed that the lake was back to its 4’ level. On July 14, a DEP staff representative attended the meeting of the MVF Committee on the Environment (COE). At the meeting the DEP representative completed a presentation on the scope of work for the project and covered the mechanisms that Montgomery County has put in place to ensure that the over-drainage of Lake Whetstone does not happen again, which includes: daily logs of valve status, county notification requirement when opening or closing the valve, county monitoring on-site including weekends when valve is open, and written updated policy. Staff hope that there are no further issues on this project, which is anticipated to last until December 2021, and cost the county in the region of $800,000.

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