Standard STS Configuration
The following four images are examples of standard configurations or typical site plans for the StormTreat System. These drawings are not to be used for construction, but to provide some common options for configuring the system. Please take a few minutes to study and read through the descriptions. For a larger view, click this link to open all four pages as a pdf: Standard Configuration PDF.
First off, it's important to note that the majority of projects dealing with stormwater require treatment of a minimum quantity of the total runoff, known as the water quality volume (WQV). Therefore, the following four "Cases" include detention systems (proprietary and conventional), external from the STS units, that are sized to detain a specific WQV (3630cf in this case). This configuration is often referred to as an "end of treatment train" approach, where catchment, pretreatment and detention are all upstream of the STS. System sizing is volume based.
Case # 1: Closed Pipe Storage
This first option presented utilizes 36-inch diameter, corrugated, polyethylene pipe, prefabricated to function as a watertight detention system. Influent stormwater enters on the far left via the flow splitting manhole and proceeds through the detention system and STS units, exiting via the outlet structure on the far right. We are happy to recommend shops where these systems can be custom fabricated for your project.
1. Capable of capturing and treating any volume necessary without losing any untreated stormwater to infiltration.
2. Preferable in sensitive areas, and/or areas with high pollutant loads where immediate health concerns for humans, wildlife and the environment exist (ie. coastal areas, near water supplies, transfer stations, industrial areas, etc.)
3. Outlet valve can be shut to contain spills consisting of hazardous materials and can be pumped from detention and STS units.
4. Assures STS wetland plants get watered with every storm event (no infiltration loss).
5. Prefabricated nature allows for less involved installation than other proprietary systems that generally require a concrete base, layers of stone, geotextile fabrics, liners, etc.
6. Offers pretreatment settling zone inside of detention chambers.
1. May be slightly more costly than other options due to custom fabrication of detention system.
Case # 2A: Dry Detention Basin with Combined Outfall
This configuration shows a conventional detention basin and combined outfall. Influent stormwater is detained and pretreated in the open basin, then directed to the StormTreat units in the outlet structure. Volumes exceeding the design WQV bypass the StormTreat via the weir wall in the outlet structure and are directed to the same discharge location as the StormTreat outlet.
1. Open basin provides sedimentation pretreatment.
2. Use of a non-proprietary detention system results in lower materials cost.
3. Combined outfall option also reduces cost (Note: this feature can be utilized with any detention system).
1. Open pond limits location of detention system and is likely to consume more space than a subsurface system.
2. Detention basin may allow significant loss of influent due to infiltration, resulting in lower treatment performance of total WQV.
Case # 2B: Dry Detention Basin with Separated Outfall
This configuration varies from # 2A above in two main areas:
1.The StormTreat outlet structure (far right) handles only the outflow from the StormTreat tanks.
2. Bypass of higher flow volumes takes place via the high flow bypass pipe in the detention basin.
Also make note of the optional outlet structure (far right) which utilizes a sized orifice to set the design outflow rate. A shut-off valve should still be installed in addition to the orifice control for the purpose of containment in the case of a hazardous waste spill.
1. Allows for high flow bypass in different location from StormTreat outflow.
2. Orifice flow control option reduces need for flow rate setting and monitoring (flow should still be checked and monitored during inspection and maintenance).
1. May require an additional structure at the high flow bypass discharge.
Case # 3: Arch-Shaped Detention / Infiltration Chambers
This option offers the potential for detention and / or infiltration via the proprietary arch-shaped chambers. The area surrounding the arch chambers may be lined or not, depending on native soil type, to allow infiltration or not. Other than that, the system is very similar to Case # 1 above.
1. Arch chambers are open to a crushed stone base, which offers additional detention volume.
2. Sedimentation and filtration in arch chamber system offers significant pretreatment.
3. If configured for infiltration, recharge standards can be met.
1. Arch chambers require layered stone base and on-site assembly, adding to project cost.
2. If design calls for liner to avoid infiltration, additional cost and installation efforts are required.
Backfill Detention / Infiltration / Recharge
The excavated area surrounding the footprint of the STS units can be utilized as a detention or infiltration area. This can allow the system to meet recharge requirements and offers inexpensive detention.
Additionally, there are certainly instances where STS units can be installed without an external detention system. For example, when the WQV is small, the processing rate combined with detention volume available within the STS units and contributing pipe is adequate to meet quantity requirements. Or, when an LID approach is desired, the STS units can be placed sparsely throughout the site with little or no detention. Advantages of this approach are a smaller excavated footprint (LID), less expensive due to omission of detention system and more flexibility on placement of units throughout the site.