Drainage Improvement System a Hole in One

Joe Mastronardo, PE
Pennoni Associates Inc.
The erratic weather of the past year has caused many to reevaluate their current stormwater management designs. Rain and precipitation have put a lot of strain and tested the limits of residential, commercial, and municipal drainage systems. Concerned about a drainage channel between a golf course and residential properties, Springfield Township in Delaware County asked its township engineer, Pennoni Associates, to examine the system and give recommendations on improvements if necessary.
EXISTING SYSTEM

The existing stormwater runoff flowed from a portion of the Springfield Country Club golf course in a southeasterly direction into a drainage channel within the woods. The channel discharged into a constructed swale along the rear yards of the Golf View Estates properties. The swale drained into two sumped inlets, which conveyed runoff to the storm sewer system tributary to a stormwater detention basin that was owned and maintained by the Golf View Estates Homeowners Association (HOA).
Based on Pennoni’s field view, the drainage channel on the golf course had eroded and did not appear to contain adequate stabilization and capacity for the amount of runoff from the tributary drainage area. Additionally, sediment from the channel had deposited and deteriorated the capacity of the constructed swale on the residential properties. Runoff depths in the rear yards had approached the first floor levels of the adjacent condominium units as a result of the channel erosion and sedimentation in the swale.
PROPOSED DESIGN

The objective for improvement to the Springfield Country Club/Golf View Estates drainage system was to re-establish the design for existing controls and minimize erosion and sedimentation that compromises designed capacities. The proposed design consisted of the following components:
Springfield Country Club: The existing drainage channel on the golf course fairway and through the woods adjacent to the fairway needed to be re-graded and stabilized to prevent further erosion of the channel bed and side slopes. In accordance with the township and the Pennsylvania Department of Environmental Protection standards, the channel needed to be re-graded establishing a uniform trapezoidal cross section and lined with permanent rock protection.

Golf View Estates HOA: In order to improve the ability for the storm sewer collection system to capture runoff discharge from the rock-lined channel, the storm sewer system needed to be extended and the rear yards re-graded to prevent bypass flows from surcharging towards the condominiums. Extending the storm sewer to the end of the rock lined channel allowed for the installation of a headwall so that the normal flows from the channel could directly enter the storm sewer pipe. While flow will continue to enter the storm sewer through the headwall, grading the swale and re-establishing a berm in the rear yards will provide a secondary overflow allowing runoff to enter the storm sewer system through the existing sumped inlets.
 
IMPACT
Springfield Township followed through on Pennoni’s design, and Pennoni coordinated with the Golf View Estates HOA to make the improvements required on the section of the system that extended on to the privately owned property. Construction of the proposed improvements was completed and tested within the first six months when rainfall amounts of close to 6 inches were contained in the rock lined drainage channel, filled the restored swale, and crested the overflow system. The homeowners and the municipality are pleased that they were able to collaborate on drainage improvements that provided a mutually beneficial, low-maintenance solution to protect their properties from damaging storm events.
Joe Mastronardo, PE, is a senior engineer with Pennoni Associates. He serves as township engineer in Springfield Township, PA. Corey Fenwick from Pennoni Associates also contributed to this article.