Downstream Defender® helped to protect Portsmouth, New Hampshire from sediment, trash and other stormwater pollution.

Situation

Pease International Maritime Terminal, located directly on the coast of historic Portsmouth, New Hampshire operated for years as a scrap metal depot that would ship materials overseas for recycling. During routine effluent stormwater sample testing, which is required of any company operating under a US Industrial General Stormwater Permit (IGSP),

Pease discovered they were exceeding their benchmarks for Total Suspended Solids (TSS). Under penalty of fines and legal action from the New Hampshire Department of Environmental Services, they had to find a solution to their sediment problem.

Problem

Despite implementing a daily sweeping of the site and use of catch basin inserts called “silt socks” designed to catch sediment, Pease Terminal continued to be over their benchmarks. 

Sediment pollution from the terminal’s stormwater had the potential to wreak havoc on the aquatic life in one of America’s oldest Northeast Port Cities.

Solution 

Three 6-ft Downstream Defender® stormwater separators were chosen for the site because of their ability capture large amounts of sediment and trash without risk of washout. Additionally, the Downstream Defender can treat high peak flows in a small footprint and it works well on sites with tail water or tidal conditions which was applicable for Pease Terminal given their coastal location. 

The systems were installed on site in September of 2012, primarily to address sediment but are also proven to remove:

• •TSS
• •Trash
• •Hydrocarbons
• Sediment-bound metals

The Downstream Defender® was proven to remove over 90% of sediment particles larger than 500 micron, and third party testing has proven that the Downstream Defender® has a TSS removal percentage of over 80% when flow rates are 113 L/s or less.