Overview

We were retained by the Hemlock Farms Community Association, a 4,500 acre planned, residential community located in Lords Valley, Pennsylvania, to develop a stormwater master plan.

When the residential development was originally planned, the stormwater management facilities were inadequate. Based upon site observations, the development had an improperly sized drainage conveyance system (swales and culverts), flooding conditions in low areas that have no method of freely draining, direct discharges to the lakes without means of filtering the water before it enters the lakes and no methods of removing sediment and debris before stormwater discharges to the lakes. Severe erosion problems were also observed

Solution Details

Before a stormwater plan could be developed, a site survey of the Community had to be developed. We contracted Aerocon to complete the necessary aerial mapping and to develop the topographic site drawings prepared for this project. A further manual site survey was performed to locate and size culverts and determine invert elevations. With the total Community mapped, we were able to evaluate stormwater drainage issues and document findings and recommendations.

Based upon a series of site inspections, drainage area evaluations and eyewitness accounts as reported to us, a conceptual design was performed utilizing the following design concepts:

• Provide stabilized conveyance devices along roads and to lakes and ponds via sufficiently sized swales and culverts. The existing lakes create natural detention facilities.
• Provide water quality controls to remove sediments and pollutants from the stormwater run-off prior to discharging into the lakes.
• Minimize point source discharges into lakes and off-site properties by use of level spreaders.
• Provide localized detention where current conditions create an immediate downstream impact onto current properties located within the Community and where the re-configuration of the downstream conveyance alone would not alleviate localized run-off problems.
• Provide infiltration where possible for water quality controls and utilize infiltration beds as a primary run-off to other facilities.
• Minimize impacts on existing trees, and replace trees and vegetation when disturbed.
• Protect the potable water well head protection zones.

As a result of the master plan, over $36 million of potential projects were outlined to control the Communities stormwater.