Town Highway Yard Drainage Design and Oversight, Nassau, NY

A local Town has operated a satellite highway yard for many years on Town owned property.  The yard was an asphalt paved lot that stored various trucks, equipment, debris and salt, while having no drywells or other storage/infiltration structures to provide on-site drainage storage capacity. In recent years, in an effort to decrease annual truck miles, the Town has increased the use of the yard and required more permanent facilities including: a salt storage dome; diesel fueling dispenser; office building; and storm water collection, treatment and recharge system.

After the New York State Department of Conservation (NYSDEC) issued a violation due to the yard discharging stormwater directly into a nearby stream, Walden was directed to design site improvements to meet the expanded role for this Highway Yard while complying with all applicable State and Local requirements.  Walden completed a storm water evaluation and drainage system design for the yard. The storm water drainage design consisted of property shaping/grading to channel water to a collection system including: four (4) catch basins with sediment traps that will collect gross pollutants, litter and debris; and a recharge system consisting of perforated piping channeling water to seventeen (17) precast drywells. The system is designed to manage storm events up to 5 inches in intensity and should a large storm occur, the drywells overflow to two (2) hydrodynamic separators where oil and grease will be removed and additional sedimentation will prevent the re-suspension of captured pollutants and reduce turbidity. The drainage system overflow is discharged into nearby surface waters through flared end piping. The outfall is protected from erosion by a series of stone-filled gabion baskets for stream bank protection. The storm water is controlled by a combination of re-grading and installation of a curb and gutter system installed around the perimeter of the Site to keep the storm water on the property and direct it to the catch basins.

Walden presented the design and all required documentation to the Nassau County Department of Public Works (NCDPW) for a permit to construct and to NYSDEC for a general industry MS4 storm water permit.  Once permits were obtained, Walden prepared technical specifications and bid documents and helped the Town through the complete bidding process. Walden then assisted the Town throughout the complete construction phase performing contractor oversight, contractor invoice review, and preparation of as-built drawings. The completed project allows the Town to increase usage of the yard and begin to store more equipment and materials while still complying with all applicable regulations.


Posted on

July 17, 2020