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North
Park Lake
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Construction Update |
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In late April the PA Fish & Boat Commission (PAFBC) stocked some seedlings and some fish salvaged from Hereford Manor (lake being breeched in Beaver County). The lake drainage valve will be completely closed once Allegheny County completes the work on Irwin Run (2 - 3 weeks). Installation of the fish habitat structures is nearing completion. Artificial fish habitat structures comprised of rock and logs were designed and laid out by the PAFBC. These fish habitats provide protection from predators as well as providing an ideal spawning habitat for many species of fish. The PAFBC partnered with the Corps in this effort, including coming out during installation to provide any final details in the layout of the structures. Coir logs are now being installed on the shoreline at North Park Lake. The coir logs will be installed in various places to stabilize the lake banks and will allow for the establishment of planted and naturally colonizing vegetation. Plantings which are also commencing include emergent wetland plantings and shoreline scrub-shrub plantings, which will help to protect the banks as well as reestablishing the native vegetation. Some of the plantings include fox sedge, cardinal flowers, and silky dogwood. Overall there will be more than 30 different varieties of plantings used. |
Construction Photos |
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| A system of fish habitats has been installed throughout the lake. (March 2011) | Coir logs will help stabilize the banks. (April 2011) |
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| The installation of coir logs along the banks will allow for the establishment of planted and naturally colonizing vegetation. (April 2011) | Fish habitats made of wood and rock provide protection from predators and ideal spawning grounds. |
MORE PHOTOS...
Location & Description
North Park– located in Hampton, McCandless and Pine Townships, Allegheny County, Pennsylvania – was created by Allegheny County in the 1920’s. The signature piece of this 3,010 acre county park is its lake. North Park Lake is a man-made lake at the confluence of Pine Creek and the North Fork of Pine Creek. When first constructed in 1935, the surface area of North Park Lake was approximately 75 acres and its depth was approximately 24 feet near the dam face. At that time, the watershed surrounding North Park Lake generally consisted of rural agricultural fields, pastures and isolated woodlots.
As the process of uninhibited urbanization progressed outward from the City of Pittsburgh, the landscape began to change. As development around the park continues to progress, forest cover and vegetated riparian buffers along streams are being removed and soils are being disturbed and covered instead by residential and commercial buildings, roads and parking lots.
Uncontrolled surface runoff carrying sediment to the lake from residential and commercial development in the Pine Creek basin in the mid to late 20th Century has resulted in a loss of 12 acres of open water and a loss of about half of the lake’s original depth. Due to enrichment from the excessive runoff, the lake has become eutrophic (low oxygen levels) and has seen an undesired increase in aquatic macrophyte (algae) growth. These factors have not only reduced the size of the original lake but also severely degraded the remaining aquatic habitat. For example, a shallower lake results in warmer water with less oxygen which in turn results in less variety of fish and other aquatic species. If nothing is done to improve the degradation caused by excessive sedimentation, the lake will eventually fill-in completely and become wetlands, and then a meadow. This will result in a loss of open water habitat and the ability to fish in the lake.
History & Status
At the request of the project’s local sponsor, the County of Allegheny, the Corps of Engineers initiated this project in 1999 and the Preliminary Restoration Plan was completed and approved in August 2001. Extensive testing and measurement of the amount of sediment in the lake was conducted and documented in the Sediment Characterization Report, published in January 2003 as part of the feasibility process.
A number of alternatives were considered during the course of the feasibility investigation. Initial alternatives considered ways to reduce the sediment load to maintain what aquatic habitat remained. Studies performed on these alternatives revealed that this approach was not feasible largely because of lack of sufficient area upstream of the lake to construct properly sized sediment basins. After these alternatives were eliminated, the Corps explored ways to removed accumulated sediment to restore open water habitat. It was determined that removing the accumulated sediment to original contours would give a useful project life of approximately 100 years with regular maintenance before sediment would again have to be removed. Various levels of dredging were investigated to determine cost effectiveness.
In August 2006, the Corps’ Pittsburgh District completed the Draft Detailed Project Report that considers alternatives to restore the degraded aquatic ecosystem of North Park Lake. The Detailed Project Report contains an integrated Environmental Assessment that evaluates the potential impacts of alternative solutions.
In January 2008 the Final Detailed Project Report was approved. The following will be completed under sec 206 authority:
- dredge 104,000 cubic yards of sediments from 33 acres of the North Fork Arm of the lake
- enhance existing emergent wetlands and create new wetlands<
- create aquatic habitat structure within the lake to increase cover for benthic organisms and fish
- construction of two osprey nesting platforms
The benefits of the recommended actions include:
- helping to maintain open water aquatic habitat in North Park Lake;
- providing an engineering solution to minimize aquatic ecosystem degradation within the lake; and
- enhancing existing emergent wetlands and creating new wetlands.
Authority
The North Park Lake project is being conducted under Section 206 of the Water Resources Development Act of 1996, Public Law 104-303. Known as the Aquatic Ecosystem Restoration Program, Section 206 provides authority for the U. S. Army Corps of Engineers to undertake restoration projects in aquatic ecosystems such as rivers, lakes and wetlands. The Corps evaluates projects that benefit the environment through restoring, improving or protecting aquatic habitat for plants, fish and wildlife. A project is accepted for construction after a detailed investigation shows it is technically feasible, environmentally acceptable and provides cost effective environmental benefits. Costs for Section 206 projects are shared between the federal government and a non-federal sponsor with the non-federal sponsor assuming responsibility for operation and maintenance of the project upon completion. The maximum Federal expenditure per project is $5 million, which includes both planning and construction costs.
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Updated: 05-Dec-2011