Remembering Local Landscapes: North Park Lake
The Problem with Sediment

North Park Lake, the largest manmade body of water in Allegheny County, lost nearly half of its capacity after uncontrolled runoff deposited sediment into the lake. ACCD staff remembers this local landmark and the county’s changing landscape on the District’s 75th Anniversary.

Created after the completion of Pine Creek Dam in 1936, North Park Lake was initially 75 acres in size. For decades, uncontrolled runoff deposited an estimated 5,200 tons of sediment into the lake every year. By 2001, the lake lost 12 acres of open water and nearly half its capacity.

Sediment harms aquatic habitat and takes away a waterbody’s capacity to hold water after rain events. The lake’s loss of depth caused problems for boating, fishing and other recreation.

Fixing North Park Lake

In order to remove sediment, the lake had to be drained first. After it was drained in 2009, contractors built bypass channels to carry stream flow around the work area.

The contractors excavated sediment, loaded it into dump trucks and transported it to a waste area elsewhere in North Park. In total, crews removed at least 315,000 cubic yards of sediment. Before the lake was allowed to refill, fish habitat structures were installed on the lake bed.

What's the Problem With Sediment?

Sediment is the most common pollutant in waterbodies and while erosion is a natural process, man-made erosion causing excessive amounts of sediment pollution can harm ecosystems and degrade water quality.

This type of pollution most frequently comes in concentrated levels from active construction sites, including housing plans, commercial buildings and single-family homes.

Sediment pollution causes flooding due to blocked storm drains and catch basins, increases the cost of drinking water treatment, creates a hospitable environment for toxic algae to grow and harms wildlife.

What We’re Doing to Prevent Pollution

The regulatory team at ACCD combats sediment pollution both in the office and out in the field. Resource Conservationists review construction plans to ensure that construction sequences and proper Best Management Practices (BMPs) are in place to reduce the amount of sediment leaving the site.

In the field, staff inspects these BMPs to verify they are installed per plan and properly maintained. ACCD may also request that BMPs are added or modified to better protect the surrounding waterbodies. By reducing the amount of sediment in streams, rivers and lakes, ACCD protects the health of Allegheny County's ecosystem.