Filtration Your Way

Site-specific options for filtering runoff and removing pollutants

Sw1906 24

Requirements limiting the amount of pollutants in stormwater runoff that can be released into rivers, lakes, and other water bodies are more stringent than just a few years ago. To meet this challenge, new filtration products are being designed, installed, and tested in many areas of the country. The products range from huge underground vaults to catch basin inserts to planted wetlands. The choice depends on the site, the pollutants to be removed, and the space available. With the number of products available, you can find a workable solution for your project.

Kearny Point Industrial Park
Kearny Point Industrial Park in South Kearny, NJ, is being redeveloped into a creative employment hub. In the past, the 130-acre site was zoned for industrial use and the Kearny Point Shipyard. The location is at the confluence of the Hackensack and Passaic rivers, next to Newark Liberty International Airport and the Port of Newark. The planned development will completely change the environment and usage of the area.

This large project will proceed in four phases. The site design calls for some very large buildings to be gutted and repurposed for creative office spaces, artisanal manufacturing, and other businesses. Restaurants and indoor food markets are included, as well as natural areas and trails. A waterfront development will add a marina and boat storage.

The plans of site owner, Hugo Neu Corp., incorporate best practices green infrastructure, including:

  • demolition of 28 acres of impervious surfaces;
  • installation of bioswales and green/blue roofs;
  • inclusion of rain harvesting; and
  • end-of-pipe (EOP) applications to capture pollutants.

The inclusion of these BMPs will reduce stormwater runoff to the Hackensack River by as much as 6 million gallons per year.

Before release into the river, however, the remaining runoff needs filtration. The products chosen for the task are from AbTech Industries, based in Scottsdale, AZ. Bruce Gan, site project manager for AbTech on the Kearny Point project, says, “The primary goals were to capture and reduce the amount of hydrocarbons, heavy metals, and TSS [total suspended solids] that flow through the storm drains back into the Hackensack River.” The target was collection of 80% hydrocarbons, heavy metals, and TSS larger than 300 microns.

Three different types of absorption media were installed in catch basins—Smart Sponge for hydrocarbon removal; Smart Sponge HM, which primarily removes heavy metals; and Smart Sponge BC (BioChar/EcoChar), which removes both heavy metals and hydrocarbons.

Smart Sponge technology is hydrophobic and oleophilic to ensure capture of hydrocarbons. The Smart Sponge stays buoyant in water so that the entire product is available for hydrocarbon capture. Once the hydrocarbons are captured, they are stabilized so that there is no leaching. Smart Sponge HM is designed to collect and entrap heavy metals and it also inhibits growth of mildew and mold.

AbTech Ultra Urban Filters (UUF) drain inserts loaded with Smart Sponge products were placed on the inlet side of the drains. These inserts can handle large flows of water while removing up to 80% of the pollutants. They are also fully recyclable and are easy to replace when needed. The usual lifespan is about two years if they are properly maintained.

Stainless steel custom collars were installed with the inlet catch basins. The collars help divert flow into the UUFs and also allow for bypass if the catch basin filters get plugged for some reason. This prevents flooding in the case of filters being impassable.

End-of-pipe applications by AbTech were also installed in three outfall pipes at Kearny Point. Concrete vaults were constructed and media cages were installed in two compartments. The first compartment where the runoff enters contains Smart Paks of the Smart Sponge media to remove hydrocarbons. The second, slightly smaller compartment holds Smart Paks with Smart Sponge HM and BC media. The media cages are made of high-grade stainless steel to withstand the salt environment close to the ocean.

Shawn Lolling, project manager with AbTech, says that the EOPs were specially designed for Kearny Point. The existing pipe and outlets are 48 inches in diameter, so the AbTech equipment was custom-engineered to fit that pipe rather than downsized.

Gan notes a few challenges with the installation. Heavy rains had fallen just before the installation started, leading to an excess of groundwater and less-than-ideal conditions for construction. High-tide conditions occasionally sent water backing up into the vaults.

The vaults at the EOP installation will need to be serviced regularly, especially as construction continues at the site. AbTech is conducting training for this work, and a comprehensive schedule will be put in place.

When asked what advice he would give someone starting a similar project, Gan says, “Try to plan as far in advance as possible and coordinate activities between different suppliers to eliminate any last-minute issues. It’s always best to remedy any problems in the shop rather than on the job site.”

Stopping Trash in California
Trash floating along in stormwater runoff is a major problem for filtration systems. In California, a new requirement to capture trash and prevent it from entering streams and the ocean has been implemented. The trash amendments apply to all Phase I and II permittees. Each municipality must show progress towards 100% compliance with the trash amendments from 2015 to final compliance in 2030. Regional water-quality boards act as the permitting authorities.

The city of Mountain View, CA, sits on the San Francisco Bay. Stormwater runoff flows from the mountains to the south and moves toward the bay on the north. Much of the city discharges into Stevens and Permanente creeks and then into the bay.

Schaaf & Wheeler, a civil engineering company based in Santa Clara, CA, prepared a feasibility plan for Mountain View. The city was facing a requirement from the Regional Municipal Permit (MRP) Provision C.10 for a 70% reduction in trash found in runoff. Schaaf & Wheeler analyzed the existing storm drainage system and trash capture systems to find the best alternatives to meet the stringent goal.

Caitlin Gilmore of Schaaf & Wheeler was senior project manager for the recent installation of a stormwater trash capture system. The system needed to handle stormwater draining from about 960 acres of the city. “The intent of the project was to divert low flows to a trash collection unit, which removes debris down to five millimeters, per the NPDES MRP,” she explains. The project had to remove the trash and still allow for a 10-year bypass capacity with minimal upstream head loss and flooding.

There were some challenges with the project. The system was installed on a public easement on private property, requiring coordination with the property owner. This process extended the start of construction by a few months. It is on a drainage culvert between two streets. The runoff drains into the Casey Forebay, which discharges by pump to the bay.

In addition, the location has high groundwater, making major dewatering and stormwater management necessary during construction. High tailwater and a shallow depth to system invert (only 2 feet of cover on the system) were also concerns, limiting the type of trash removal devices that would work.

The product chosen for trash capture was the Nutrient Separating Baffle Box (NSBB) from Suntree Technologies Inc., headquartered in Cocoa, FL. In 2018, Oldcastle Infrastructure began distributing Suntree Technologies’ products in California. This was the first trash capture project with  Oldcastle Infrastructure as the distributor. The Suntree NSBB is approved as a trash capture device by the California State Water Resources Control Board.

Gilmore says the NSBB was chosen because it could treat the large flow rate under low head requirements and the product is listed on the California State Water Board’s approved list.

The construction took place in the winter. The contractor was JMB Construction Inc. The company had 6 to 12 people at a time working onsite. The project started in October 2018, and the NSBB was installed in December.

The diversion structure and the device storage structure were cast in place. The NSBB comes in a variety of sizes. For this project, the NSBB 11-34 was used, measuring 11 feet by 34 feet. The NSBB has a triple-chamber design, allowing high TSS removal even with extra-fine particulates. The patented screen system collects and stores foliage and trash and keeps it in a dry chamber above the water level, minimizing odor, nutrient leaching, and bacterial growth. The screening baskets have a capacity of several cubic yards, depending on the size of the unit. Sediment chambers can also hold several cubic yards.

The NSBB has demonstrated removal efficiencies up to 19% phosphorus, 20% nitrogen, and 90% TSS. The addition of the SkimBoss floating skimmer provides hydrocarbon removal. The skimmer moves with the water level, allowing maximum sediment settling. The SkimBoss is part of Suntree’s Hydro-Variant Technology (HVT). Capturing leaves, trash, and sediments can create head loss, impeding water flow and increasing the chance of flooding upstream. The HVT system adjusts to the water level and balances flow rate with maximum pollutant capture.

Maintenance on the NSBB should be performed at least twice a year. Trash and sediment can be easily removed by a Vactor truck.

Taking Care of Chesapeake Bay
In April 2017,  Oldcastle Infrastructure was one of the sponsors for an Earth Day educational fair at the US Coast Guard’s shipyard in Baltimore, MD. To celebrate the day, the Coast Guard had three stormwater filtration planters installed on the campus. The Coast Guard had approached Oldcastle Infrastructure for ideas on how to treat runoff effectively on a high-density site with acres of impervious surfaces. A larger volume of runoff needed treatment in a smaller footprint than in the usual rain gardens.

Oldcastle Infrastructure manufactured three BioMod precast concrete retention and filtration units. The units were made at the company’s plants in Edgewood, MD, and Fredericksburg, VA. Two of the bioretention planters were installed at grade and one above grade.

The BioMod uses filtration, sorption, and biological uptake to remove TSS, metals, nutrients, trash and debris, and hydrocarbons from stormwater runoff. The system consists of concrete sections filled with layers of aggregate, bioretention media, plantings, and mulch. The bottoms can be open to enhance infiltration of water onsite. Plants as large as trees can be accommodated. The modules are available in a variety of sizes.

A 4-foot by 24-foot by 6-foot planter was installed near a parking lot. Runoff from nearby streets and parking lots will run into this planter. Diversion into the planter was accomplished by a culvert designed by the site contractor. Another planter, 4 feet by 25 feet by 6 feet, was situated next to a building for retaining and filtering stormwater from the roof. This technique of rooftop disconnection intercepts the stormwater before it runs off, so the amount of pollutants is reduced before the water even enters the planter. The third planter is 4 feet by 10 feet by 6 feet and was installed above grade next to another building; runoff is piped directly into this planter.

Harvest RGI planned the filtration media and layers for the Coast Guard project, following the State of Maryland’s specifications. David Lundberg, director of business development at the company, says, “Harvest RGI is the largest supplier of bioretention soils in Maryland and is very excited to be involved in this dynamic BioMod system developed by Oldcastle Infrastructure.”

Sw1906 28

California Community
The Porter Ranch community of Los Angeles, CA, is a master-planned development. It has already received the Builder of the Year award from the Building Industry Association of Los Angeles and Ventura. Besides housing subdivisions, the development plan calls for a 50-acre park, a community school and town center, hiking trails, and a high-end retail center.

The site is spread out but has steep hillsides. The neighborhoods have a network of drainage flumes and catch basins, producing a large amount of runoff that requires treatment before release into the City of Los Angeles storm drain system. Space is at a minimum, so a small-footprint solution was needed to meet stormwater requirements.

The Modular Wetlands stormwater BMP is approved by the Los Angeles Water Quality Control Board as an “alternative compliance solution” for onsite biofiltration. The product is from Bio Clean Environmental, based in Oceanside, CA. A combination of high-performance media and the patented horizontal flow provides pollutant removal in a smaller space. It is also a flexible system with the ability to accept a variety of inlet configurations.

For the Porter Ranch installation, several catch basins were routed to a single Modular Wetlands unit, eliminating the need for media filtration at each point. This leads to a significant cost savings. Modular Wetlands units are customizable, with varying heights and sizes. At Porter Ranch, the units are all shallow so that utilities could be placed under the system to reach building pads and streetlights. The first installation used a Modular Wetlands 8-16 model at a depth of 4 to 5 feet. Some can be as shallow as 3 feet.

The Modular Wetlands System Linear is the only system with horizontal flow, which enhances removal of pollutants, reduces the footprint, and minimizes maintenance requirements. The horizontal flow also decreases the amount of clogging. All water flow is subsurface.

The first section separates out trash, sediment, and debris. Then the flow enters pre-filter cartridges that contain BioMediaGREEN filter media. This step removes over 80% of TSS and 90% of hydrocarbons.

Then comes the biofiltration section of the system. The stormwater enters a chamber packed with BioMediaGREEN filter media, which removes additional pollutants, including phosphorus. The media has 48% void space, giving more surface area for pollutant capture. The patented perimeter void area also maximizes the surface area of the media.

Plants can be added to the system, adding more pollutant removal and a pleasing aesthetic quality. Most people pass by thinking it’s a planter, not realizing all the work that is going on to clean the stormwater runoff.

Maintenance is needed for the pretreatment chamber that captures trash, sediment, and hydrocarbons. The chamber can be cleaned out with a Vactor truck. Occasionally the pre-filter cartridges need to be replaced.

As construction of the Porter Ranch community continues, more Modular Wetlands units will be installed to handle stormwater runoff.

Growing in Florida
Another type of wetlands system is growing plants in Florida. The plants clean up stormwater, create estuarine habitat, and stabilize shorelines. After accomplishing these jobs, the mature plants can be harvested and used in other natural shoreline stabilization projects. The plants can also be composted and used as fertilizer. Removing the plants prevents the ­accumulated nutrients from reentering the ecosystem.

The product is Beemats Floating Wetlands, made by Beemats, headquartered in New Smyrna Beach, FL.

Mats measuring 48 by 96 inches are joined with nylon clips and washers. Connection points are reinforced with plastic tabs and stainless steel grommets. Plant containers are set inside the mat. They can be either single-use biodegradable pots or polypropylene plastic reusable aerator pots. The plants are a mixture of native aquatic plants and flowering or vegetable plants that will grow hydroponically.

A park pond in Titusville, FL, experiences heavy nutrient loads in stormwater runoff from a large drainage basin. In 2015, Beemats installed 8,756 square feet of floating wetlands in the 4-acre pond. The wetlands is handling the nutrient load, removing 401 grams of nitrogen per square meter per year and 49 grams of phosphorus. The heavy nutrient load means that plants are harvested and replanted twice a year.

A new project for the Beemats Floating Wetlands started in June 2018 at Jackson Lake in Escambia County. The installation involved 36 floating wetlands covering 20,800 square feet. The plantings included 52,000 native grasses and rushes. The mats will be replanted each year, not only benefitting the lake with nutrient removal and shoreline stabilization, but adding a beautiful stand of plants to please the eye.

Amtrak Installation
Amtrak commissioned a study to evaluate stormwater treatment BMPs for the removal of total petroleum hydrocarbons (TPH) and TSS at its facilities. Published data for stormwater treatment BMP performance and regulatory approval of BMP technologies can vary widely or be difficult to compare, which complicates the selection of a particular technology or manufactured device. The desired outcome of the study was to identify a product that removes these pollutants and is cost-effective, easy to construct, reliable, and low maintenance. The study was conducted by Wood’s environment and infrastructure business and the University of New Hampshire (UNH) Stormwater Research Center.

The evaluation identified the following factors that have the greatest influence on pollutant removal efficiency:

  • Adequate sizing of the BMP structure
  • Ability to bypass high flows by either an offline configuration or an engineered flow bypass
  • Storage capacity for sediment and floatable components, including floating hydrocarbons
  • Ease of maintenance

One of the main conclusions was that an offline, deep-sump catch basin with a hooded outlet performed as well as other devices to remove TSS and TPH. Data developed by UNH showed removal of 73% of TSS and 62% of TPH. In general, the study showed that the incremental cost incurred by installing a proprietary BMP does not necessarily result in an increase in pollutant removal efficiency.

Amtrak’s aim was to find a “standard practice” for a stormwater BMP that could be used at any facility across the country. This would significantly reduce the costs involved with site-by-site design and construction.

Sw1906 30

After the study, Amtrak decided to install deep sump catch basins with the SNOUT stormwater quality improvement system, manufactured by Best Management Products of Lyme, CT. The SNOUT is a vented catch basin hood that can be installed where a deep sump is available or can be constructed. Best Management Products recommends that the minimum sump depth be two and a half or three times the outlet pipe size. The SNOUT device comes in a variety of sizes and configurations, such as flat and rounded. An additional BioSkirt can be added to enhance hydrocarbon removal.

So far, Amtrak has installed six structures at facilities in Boston, MA, and Groton, CT, and has plans to install more at the Amtrak facility in Oakland, CA.

The variety of sizes and configurations of the device allows some flexibility to match up with site constraints and various standard manhole sizes, as needed. The main challenge with the Amtrak installations has been nearby utilities and space constraints for excavation next to an existing drainage structure.

The installation at Groton included five offline deep-sump catch basins with SNOUTs that tied back into the existing adjacent catch basins fitted with solid manhole covers. The total construction cost was $70,000.

Installation of the manholes and SNOUTs was straightforward and required a crew of five: one foreman, two laborers, and two operators. The process consisted of installing the manhole, SNOUT, frame, and grate, and site restoration including backfill or paving. Installation of each structure took about three days.

The catch basins are inspected quarterly as part of the facility’s stormwater permit requirements. The manhole and SNOUT configuration has a solids storage capacity of approximately 1.45 cubic yards (50% sump to outlet) and static petroleum storage of about 115 gallons. Maintenance includes removal of floatables and sediment using a Vactor truck. One advantage of this manhole configuration with a SNOUT is that it allows for easy access for inspection and maintenance.

Rich Niles, project ­manager with Wood, says, “The product was easy to install and allows for flexibility with multiple options [models] for different size manhole structures and pipe configurations.”

His advice for a similar project is to develop a good site-wide stormwater management plan so there is flexibility in selecting BMP retrofits that meet treatment objectives for the lowest cost.

Rob Graham, senior project manager for environmental compliance with Amtrak, says, “The approach of using a standard manhole in an offline configuration with the SNOUT is a simple solution that Amtrak can easily install and maintain during the course of construction projects at our facilities. This project allowed us to take out the guesswork of selecting a product for future use.”

More in BMPs