Hydrodynamic Separator Systems

A hydrodynamic separator is a below-grade vault, manhole, or precast concrete structure that uses vortex flow or deflective flow to separate sediment, floatables, hydrocarbons, and trash from stormwater runoff. The treated water exits to the downstream system; the pollutants settle into a sump where they stay until a maintenance truck removes them. The EPA recognizes hydrodynamic separation as an approved stormwater treatment BMP. Most municipalities count these units as compliance credit in drainage reports.

What You Should Know

Hydrodynamic separators are usually installed during construction and then forgotten until a city inspector opens a manhole lid and finds a sump full of sediment. By that point the unit has stopped treating runoff, water is short-circuiting through the structure, and the site is out of compliance.

If you bought a commercial property, took over an HOA, or assumed property management on a site built after about 2005, there is a good chance at least one hydrodynamic separator lives somewhere under your parking lot or in a drainage easement. The first step is finding it. The second step is inspecting it. The third step is cleaning it on a maintenance cycle the manufacturer and your municipality agree on.

Stormceptor

Stormceptor is a Contech product line, manufactured under license by precast concrete suppliers regionally. The Stormceptor EF and EFO models are two of the most common variants in installations. The unit is a two-chamber precast concrete structure. Runoff enters the upper chamber, drops into the treatment chamber, and exits after sediment and hydrocarbons separate from the water.

Stormceptor maintenance requires manhole access, a vactor truck capable of reaching the sump, and disposal of the captured material. Units typically need cleaning when the sump reaches 50 percent capacity, which ranges from annually on heavy-sediment sites to every three to five years on stable, low-traffic sites.

Vortechs

Vortechs is a Contech hydrodynamic separator that uses a swirl chamber and baffles to separate solids, floatables, and hydrocarbons. The shallow profile makes Vortechs a common pick on constrained sites where a deeper Stormceptor will not fit under existing utilities.

Maintenance access is from the top of the unit through manhole covers. A vactor truck removes accumulated sediment, oil, and floatables from the separation chamber and the floatables baffle. Red River’s inspection staff pull sediment depth readings and produce a written report documenting sump level, structural condition, and recommended clean-out timing.

Contech Jellyfish Filter

The Contech Jellyfish Filter is a membrane filtration system that uses suspended filter cartridges to treat stormwater for smaller particle sizes and dissolved pollutants that pure hydrodynamic separation does not capture. Jellyfish units are often specified where a site needs a higher level of water quality treatment than a standard Stormceptor or Vortechs can provide.

Maintenance on a Jellyfish unit involves sediment removal from the pre-treatment chamber, inspection of the filter cartridges, and cartridge replacement when the differential pressure or the inspection log triggers it. Our team handles both the routine vactoring and the cartridge replacement on service contracts.

Other Brands

Other sites also have CDS units (Continuous Deflective Separation, another Contech product line), StormTrap systems, Imbrium Stormceptor legacy models, and ADS Barracuda separators. The maintenance principle is the same across brands: inspect the sump or the separation chamber on a schedule, clean when accumulation hits the trigger, document the work, and keep the maintenance log where the city inspector can find it.

If you are not sure what brand or model you have, pull the as-built drawings for your site and look for the stormwater management section. If the drawings are missing, our inspectors can identify the unit on site and pull the correct operation and maintenance manual from the manufacturer.

Inspection Services

Red River inspects hydrodynamic separators as stand-alone work or as part of a post-construction BMP inspection contract covering all the stormwater structures on your site. A separator inspection covers:

• Access confirmation and manhole condition
• Sump or separation chamber sediment depth
• Floatables and hydrocarbon accumulation
• Structural condition of baffles, weirs, and internal components
• Inlet and outlet condition
• Filter cartridge status on Jellyfish and similar media units
• Clean-out trigger evaluation against the manufacturer’s operation and maintenance manual

The deliverable is a written inspection report with photographs, measured values, and a recommended maintenance schedule. Our inspection staff hold the CESSWI credential. A licensed Professional Engineer certifies any reports for any municipalities that may require.

Maintenance and Vactoring

Maintenance on a hydrodynamic separator means removing the captured material before the sump fills and the unit bypasses. Red River handles the full maintenance cycle:

• Traffic control and safe access to the structure
• Confined space entry per OSHA when internal work is required
• Vactoring of sediment, floatables, and free oil from the sump
• Disposal of captured material per state and local regulations
• Manifests and documentation sufficient for city MS4 records
• Post-maintenance inspection and report

For sites on recurring service, we track cleaning cycles per unit and schedule the next visit against the measured sediment accumulation rate rather than a fixed calendar.

Compliance Context

Hydrodynamic separators installed as compliance BMPs are almost always named in the site’s original drainage report or stormwater management plan. The report assigns maintenance responsibility, typically to the property owner or the HOA, and in many jurisdictions the owner is required to submit annual inspection documentation to the city.

If a city notice references a structural control, a water quality control, or a permanent BMP on your site, and there is a manhole cover in the parking lot you have never looked under, that manhole is usually where the conversation starts.

Service Area

Red River Stormwater services hydrodynamic separators across Texas, including Austin, San Antonio, DFW and Houston.

Build compliant. Build with confidence. Contact Red River Storm Water for hydrodynamic separator inspection, maintenance, and vactoring.

Frequently Asked Questions