Sallie Mae Stormwater Pond Retrofit

This award winning project for a pond retrofit features a 950-foot long walking path around the 300-foot wide, landscaped stormwater pond. A walkway crosses over the pond on a dramatic 6-foot high stone weir that creates an 8,000-gallon upper pond that feeds water to the 96-foot wide waterfall to the lower pond retaining over 1 million gallons of water. A boardwalk at the waters’ edge for nature viewing, exercise stations, and picnic areas offer enjoyment on site for the company’s employees.

Landmark was retained by the corporate owner to work with their project team to prepare design and construction plans to improve the capacity and function of the existing stormwater pond at their Delaware HQ during a facility expansion. The landscape architectural concept plan addressed the owner’s desire for pond beautification and the addition of recreational amenities on the constrained site along the westerly side of I-95, but did not focus on the state’s stormwater management or water quality requirements.

Landmark provided the necessary design, analysis and construction plan preparation to facilitate the approval and construction of the pond, while meeting or exceeding all regulatory requirements for stormwater and water quality. Design innovation succeeded in meeting aesthetic and recreational criteria while removing the pond from service to expedite construction.

Environmental Services:

A slow draw-down of the existing pond allowed Landmark’s trained ecologists to gather and humanely relocate turtles, fish, eels and geese from the pond prior to construction. Environmental staff selected the most appropriate plant species and a custom seed mix for two different “planting zones” pertaining to the new pond’s benches based on predicted hydrology and the client’s needs. A Planting Plan was produced including a list of species per planting zone, their densities and spacing, planting methods, and post-planting instructions for the new retrofitted retention pond. New Castle County approved the Retention Pond Planting Plan in 2013 and it was executed in Spring 2014.

Award-Winning Project

This innovative, visually appealing and recreational project won two engineering excellence awards in 2015 – the Conceptor Award from ACEC Delaware and the National Recognition Award from ACEC in Washington, D.C.