Stormwater Facility Major Projects

Lake Hallowell Sediment Removal Project

Lake Hallowell (the Lake) is a regional stormwater management pond designed to capture, and treat stormwater runoff. The Lake was built in 1989 by constructing a dam across a tributary to Hawlings River in the Patuxent River watershed. The dam is designated as a low-hazard dam by the Maryland Department of the Environment (MDE) Dam Safety office and is owned and operated by Lake Hallowell Homeowner Association. Maintenance of the pond is shared between Montgomery County Department of Environmental Protection (MCDEP) and the Lake Hallowell HOA. To date, the Lake has never been dredged, resulting in nearly 30 years of sediment accumulating at the bottom of the lake and a reduction in water capacity.

Project Scope:

Based on the study, it was determined that approximately 10,000 cubic yards (approximately 1,000 truckloads) of sediment will need to be removed from the southern portion of the Lake to improve its water quality and capacity. The Contractor will be using general construction equipment (e.g., excavator) to perform the dredging. The Lake will be partially drawn down using pumps and pipes, siphoning, or a similar application to divert the water around the proposed dredge area (Figure 2, shown in red) so that work can be performed in drier conditions. To prevent erosion and sediment migration, control measures will be installed during excavation. The excavated sediment will be loaded directly into lined trucks for transport to an onsite staging area (see map above, shown in yellow), where the material will be processed and conditioned, as required, to meet the transport and disposal requirements to an off-site commercial disposal facility. The construction activities will take place in the Lake and along the north half of the western shoreline. During this project, portions of the walking path will be closed to ensure public safety. The trucks transporting the sediment to the approved disposal facility will likely be utilizing one of the two proposed access roads (Figure 2, shown in green) along Old Baltimore Road. Once the dredging is complete, the staging area and access roads will be returned to pre-existing conditions.

Map Location:

Click the image above for a larger view

• View the Lake Hallowell project fact sheet (PDF, 419 KB)
• View the Lake Hallowell community presentation (PDF, 5.3 MB)

Lake Whetstone Riser Repair

Lake Whetstone is in the heart of Montgomery Village. The Lake was created in the late 1960s by building a dam across Whetstone Run in Great Seneca subwatershed. It was originally designed to be a recreational lake and provide stormwater management benefits. The Department of Environmental Protection (DEP) is responsible for structural maintenance of the Lake.

Stormwater management ponds require control structures to regulate pond drainage. Lake Whetstone’s flow control structure is a concrete riser. An inspection in 2011 found that several components were in need of an engineer’s evaluation and possible repair. An engineering consultant was hired by DEP to perform an evaluation, and subsequently recommended repair work.

Repair Details:

Lake Whetstone’s concrete riser contains a sluice gate (this controls water levels and flow rates) and has a metal grate on top of it (to stop large debris from entering the structure).

The repair project will include removing the metal grate and sending it to a shop for cleaning and re-coating. Additionally, deteriorated concrete inside the structure will be repaired and the sluice gate will be replaced. This will require lowering the lake’s water level by approximately 4 feet.

Repair work will begin in mid-November. As part of this repair work, platforms and a crane will be located on the lake. Orange safety fencing will surround the lake, and the lake's water level will be reduced by approximately 4 feet for the duration of the project which is slated to be completed by March.

Map Location:

 

This map shows the location of Lake Whetstone in shaded yellow dots.

• Download a PDF of the map (1.9MB)

Pueblo Road Pond Retrofit

The Pueblo Road Pond is located in a stream valley in the Seneca Creek Watershed approximately 600 feet downstream from Pueblo Road in Gaithersburg.  The pond is the last and most downstream in a sequence of several stormwater management ponds.  The pond is located adjacent to Quince Orchard Manor neighborhood.

Stormwater management ponds in the County are routinely inspected for function and safety. An inspection found that several components of the Pueblo Road Pond were in need of repair. An engineering consultant was hired by DEP to perform an evaluation, and subsequently recommended repair work.  The consultant report indicated that the pond is not in conformance with current standards for larger storms. Additionally, the consultant indicated that the dam is in need of repair.

The consultant determined that the pond should be retrofitted to provide the stormwater control for the contributing drainage area.  The new dam embankment will be constructed to meet the current safety standards.

A new concrete weir wall (this regulates water release) structure will be employed. Because of space constraints and the existence of an 8" sewer line through the dam, the weir is designed as a labyrinth weir wall structure in order to maximize the weir wall length while minimizing the footprint of the structure.

In addition, the existing sewer line in the affected area will be replaced with a new 8" ductile iron pipe.  The pipe will be encased in a 21" reinforced concrete pipe sleeve under the dam to protect the pipe and for easy access for maintenance purposes.

Public Meeting:

Past:

• Sept 28,2016

• ​June 21, 2007 Quince Orchard Library

Map Location:

Site Design Plan:

DEP hires project engineers to prepare Site Design Plans which outline the construction and design or redevelopment of stormwater facilities that have either failed to operate or no longer meet current Stormwater Management standards. The Site Design Plan is done in three stages: 30% Design Stage, 60% Design Stage and 100% or Final Design Stage. Once the Final design is complete, construction will begin.

90% Design Plan (PDF, 14.9MB)

Persimmon Tree Pond Retrofit

The Persimmon Tree Ponds are located in a stream valley in Bethesda that drains to Great Falls Tributary, which flows into the Potomac Direct, and eventually into the Potomac River.

The two facilities are located within a triangular area enclosed by I-495, Persimmon Tree Road, and MacArthur Boulevard.



The facilities were built in the late 1970’s. Each stormwater management facility has a corrugated metal riser with a corrugated metal principal spillway pipe.  The developer transferred the facilities to the Persimmon Tree Community Association (HOA) in November 1981.Over the years, the facilities were not maintained.

The Department of Environmental Protection (DEP) inspection reports between 1999 and 2002 indicate that each facility was in need of dredging and major repairs.  In September 2004, DEP prepared a report for the HOA detailing the possible repair, replacement, or abandonment of each facility.  However, the costs of all options were estimated to be too high for the HOA to handle.  In the years since, further deterioration resulted in a total riser collapse at Facility #11030. The CMP riser in Facility #11074 is still intact, but the barrel has significant corrosion.  After the HOA petitioned the County, DEP accepted the facilities into its stormwater facility maintenance program in as-is condition. The transfer of structural maintenance responsibility was finalized in 2013.

Since 2013, both facilities were put on the Capital Improvement Project (CIP) List. Task order was issued in 2016, repair/retrofit design work started in September 2016. First public meeting was held in April 2017, concept design options were presented at the meeting.

Link to 2017 public meeting PowerPoint presentation.

Currently the project is at final stage of design, permitting is underway, and the proposed design will achieve maximum possible stormwater treatment control.  Pond 11074 will remain a dry extended detention pond with a new riser structure and slip-lined principal spillway pipe.  Pond 11030 will be converted to a riprap stormwater outfall channel to dissipate flow velocities and provide safe conveyance of water.  The existing embankment is proposed to be removed. 

Proposed Design for Pond 11030



Proposed Design for Pond 11074

Current Public Meeting Information:

January 24, 2019 Meeting Notice
1/24/19 Presentation

For questions, contact:

DEP Engineer: Julia Liu
Julia.Liu@montgomerycountymd.gov
240-777-7762

DEP Planner: Doug Marshall
douglas.marshall@montgomerycountymd.gov
240-777-7767

Wheaton Branch Flood Mitigation Project

Background

The Wheaton Branch Regional Stormwater Management Pond, designed and constructed in 1975, drains a 770-acre watershed that is over 50% impervious landcover and provides many benefits downstream in lower Wheaton Branch and Sligo Creek.  These benefits include; 1) reduced stream channel erosion as stormwater captured in the pond is slowly released after storms, 2) water quality treatment as sediment and pollutants settle out in the pond, and 3) provides flood control for the downstream area. The pond was retrofitted to its current configuration as a three celled wet pond in 1988 to add water quality treatment. It controls stormwater runoff from a large shopping mall and commercial complex around the Wheaton Metro Station, and other commercial and residential developments between Wheaton and Dennis Avenue along the intensively developed Georgia Avenue corridor.

Issues with flooding were noted in 2006 and 2010 by residents living upstream of Dennis Avenue. A floodplain study commissioned by the Montgomery County Department of Environmental Protection (DEP) revealed that the previously approved Federal Emergency Management Administration (FEMA) map did not reflect the actual floodplain conditions. As a result, FEMA issued a Letter of Map Revision (LOMR) in 2018 that now includes five (5) adjacent residences near the intersection of Glenhaven Road and Dennis Avenue, and several roadways, in the 100-year floodplain. There are an additional eight (8) residential properties impacted by the 100-year floodplain. It was determined that the extensive flooding was caused by water backing up from undersized Dennis Avenue bridge and Wheaton Branch Stormwater Management Pond.  To mitigate the flooding the bridge must be replaced in conjunction with floodplain and pond modifications. Montgomery County’s Department of Transportation (DOT) is responsible for the bridge replacement project.

DEP’s flood mitigation project will entail three primary improvements:

1. Lower the flood plain on the west side of Wheaton Branch upstream of Dennis Avenue Bridge to provide additional water storage and flood relief. 
2. Modify the existing Pond riser structure. 
3. Dredging to remove accumulated sediments from Cell 1 in Wheaton Branch Stormwater Management pond.

Montgomery County’s Department of Transportation and the Department of Environmental Protection are collaborating on these two projects to address the flooding of Dennis Avenue and nearby private properties.


Wheaton Branch Flood Mitigation Map (JPG, 451KB)
Wheaton Branch Flood Mitigation Map (PDF, 3MB)

Project Design Plan

DEP’s engineering contractor has prepared site design plans which detail the design and construction of the Wheaton Branch Stream channel upstream of the Dennis Avenue bridge.  The site design plan, currently in the final design stage will reduce flooding by providing more water storage capacity.  Additional water storage capacity will be accomplished by; 1) widening both the stream channel and the adjacent flood plain and 2) dredging accumulated sediment from the first cell of the Wheaton Branch stormwater management pond. Once the Final design is complete, construction will begin.

Wheaton Branch - Existing 100 Year Flood Plain (JPG, 414KB)

Wheaton Branch - Proposed 100 Year Flood Plain  (JPG, 405KB)

Completed Project (Rendering)  (JPG, 398KB)

Completed Projects:

Chadswood Dry Pond Emergency Repairs

An emergency situation developed at the Chadswood Regional Stormwater Management Pond Dam located on Cross Laurel Drive between Valley Bend Drive and Blunt Road in Germantown, Maryland. During an inspection of the pond, Montgomery County Department of Environmental Protection (MCDEP) discovered three sink holes in the dam and damage to the pipe going through the dam.

DEP designed a repair to the dam and is replacing the damaged pipe.

Project Facts:

Past Public Meetings:

Monday, October 27, 2014

• Presentation  (PDF, 5.28MB)
• Fact Sheet  (PDF, 354KB)

Thursday, October 3, 2013

Map Location:

Site Design Plan:

DEP hires project engineers to prepare Site Design Plans which outline the construction and design or redevelopment of stormwater facilities that have either failed to operate or no longer meet current Stormwater Management standards. The Site Design Plan is done in three stages: 30% Design Stage, 60% Design Stage and 100% or Final Design Stage. Once the Final design is complete, construction will begin.

Final Design Plan (PDF, 17.3MB)

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Montgomery Auto Park Regional Pond

Montgomery Auto Park Pond, owned by Montgomery County, is formed by a 28-ft high earth embankment dam located off Briggs Chaney Road in Silver Spring, MD and adjacent to Inter-County Connector (ICC) (MD-200). The dam is currently designated as a high hazard dam by the Maryland Department of the Environment (MDE). The dam was originally designed to provide stormwater management control for a 238-acre watershed.

In 2006, a routine inspection revealed a seepage problem near the toe of the dam. The MDE Dam Safety Division declared the dam unsafe and ordered the repairs. The ICC recent construction diverted a large portion of the flow away from the pond. DEP's repair and retrofit work included:

• Lowering of the dam height;

• Widening of the emergency spillway;

• Modifications to the concrete control structure;

• Repairing the seepage in the dam; and

• Removing sediment from the pond bottom.

The repairs are completed.

The retrofitted pond will provide stormwater control for the residential and commercial areas draining to the pond. The Montgomery Auto Park Pond also helps to protect the Anacostia River, which drains to the Potomac River and the Chesapeake Bay.

Map Location:

This map shows Montgomery Autopark Regional Dam. The location of the pond is shaded in yellow along MD-200.

Download a PDF of the map  (298KB)

Site Design Plan:

Site Design Plans are printed drawings and details that the project engineers prepare to outline the construction plan for design or redevelopment of a stormwater facility that has either failed to operate or no longer meets Stormwater Management standards. The Site Design Plan is done in three stages; 30% Design Stage, 60% Design Stage and 100% or Final Design Stage. Once the Final design is completed, construction begins.

• Final Design Plan (PDF, 33MB)

The 100% or Final Design Plan was approved on March 03, 2013.  Construction is complete.

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Brookville Bus Depot

This project evaluated existing onsite stormwater management facilities and their effectiveness at controlling runoff from the Brookville Bus Depot.

DEP's improvements included:

• Installation of new underground stormwater management facilities;

• Modification of existing stormwater facilities and drainage structures;

• Removal of sediment and retrofit of existing stormwater pond

The new stormwater improvements will help to protect Rock Creek, which drains to Potomac River and the Chesapeake Bay.

Project Schedule:

Construction is complete.

Map Location:

This map shows the Brookville Bus Depot. The location of the pond is indicated by the circle on the left hand side of the image.

Download a PDF of the map  (PDF, 182KB)

Site Design Plan:

Site Design Plans are printed drawings and details that the project engineers prepare to outline the construction plan for design or redevelopment of a stormwater facility that has either failed to operate or no longer meets Stormwater Management standards. The Site Design Plan is done in three stages; 30% Design Stage, 60% Design Stage and 100% or Final Design Stage. Once the Final design is completed, construction begins.

• Final Design Plan (PDF, 32MB)

The 100% or Final Design Plan was approved on March 03, 2013. Construction is complete.

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