Underground Detention System Installation
Underground detention systems capture and store stormwater runoff below grade, releasing it at a controlled rate to reduce peak flows, prevent downstream flooding, and protect adjacent properties. In Northern Virginia's dense and rapidly developing landscape, these systems play a critical role in meeting Virginia DEQ standards, local MS4 permit requirements, and Chesapeake Bay watershed goals.
Getting the installation right is essential. Systems built outside of engineered plans and specifications underperform, create compliance exposure and are costly to remediate. Ongoing maintenance is equally important. Sediment accumulation, blocked inlets, and deteriorating components reduce storage capacity and can put a project out of compliance without warning.
From permitting support through installation and into long-term maintenance, Capital Stormwater Services delivers underground detention systems that perform as designed protecting downstream properties, satisfying regulatory requirements and keeping your project in compliance.
Stormwater Infrastructure You Can Count On. Installed with Precision. Built to Last.
Capital Stormwater Services manages underground detention system installation from initial plan review through final closeout documentation. We install large-diameter HDPE pipe systems, chamber systems, inlet and outlet structures and associated components for commercial, residential and public projects across Northern Virginia bringing the specialized knowledge, trained crew, and in-house equipment needed to keep installations on schedule.
Our process begins with a thorough review of PE-stamped civil plans, coordination with the site general contractor and verification of subgrade, aggregate and geotextile requirements. Our crews self-perform all critical work - excavation, bedding, structure installation, pipe connections, aggregate placement, backfill, and compaction - in strict accordance with project specifications. No critical work is subcontracted, which means fewer handoffs, fewer delays, and greater accountability at every phase.
From proper bedding and geotextile placement to compaction sequencing and final backfill, our installation practices are designed to protect system integrity and ensure long-term performance under load. At project completion, we provide as-built measurements and photo documentation for owner, engineer, and county records supporting permit closeout, regulatory compliance and long-term maintenance planning.
Underground Stormwater Detention has become a core requirement of modern development in Northern Virginia.
As communities grow and impervious surfaces expand, managing stormwater on-site becomes both a regulatory obligation and an engineering challenge. Underground detention systems provide the below-grade storage capacity needed to control peak flow rates, reduce downstream flooding and support water quality goals without sacrificing valuable surface space for parking, green space or future development.
In Northern Virginia's dense and fast-growing corridor, these systems are a cornerstone of compliant site design. Virginia DEQ standards, local stormwater ordinances and Chesapeake Bay watershed requirements all demand that new and redeveloped sites manage runoff effectively. Where surface area is limited and land values are high, underground detention is often the most practical and efficient solution available.
WHY UNDERGROUND DETENTION
Captures and stores stormwater runoff below grade, out of sight and off the surface
Releases stored runoff at a controlled, pre-approved rate to reduce peak flows
Reduces flooding, erosion, and downstream impacts on adjacent properties and infrastructure
Supports compliance with local stormwater ordinances and Virginia DEQ regulations
Preserves valuable surface area for parking, green space, and development
Requires scheduled inspection, maintenance, and reporting to sustain long-term performance
UNDERGROUND DETENTION SYSTEMS WE INSTALL
We install underground detention systems to project specifications and local stormwater requirements. Done Right and On Schedule
HDPE Pipe Detention Systems
High-density polyethylene pipe systems deliver reliable underground stormwater storage with excellent structural integrity, chemical resistance, and long-term durability. Lightweight and adaptable relative to concrete alternatives, HDPE systems are well-suited for linear installations, sites with limited excavation depth and projects requiring efficient mobilization and installation.
Each system is assembled using corrugated or smooth-wall pipe, headers, laterals, fittings, access structures, and engineered stone bedding creating subsurface storage capacity beneath parking lots, access roads, green space and developed sites across Northern Virginia.
Available in a wide range of diameters and configurations to meet varying storage volume and site geometry requirements
Designed and manufactured for gravity-flow storm sewer and subsurface drainage applications
Suitable for both conveyance and detention applications, including controlled-release and retention systems
Performs reliably beneath parking lots, access roads and developed surfaces subject to vehicle and traffic loading
StormTech SC & DC Chamber Systems
StormTech modular chamber systems provide high-capacity underground stormwater storage through an arch-shaped, interlocking design that maximizes subsurface void space while minimizing excavation volume. Lightweight and efficiently staged, chambers are well-suited for sites where storage demand is high, installation windows are tight or surface constraints limit conventional pipe-based approaches.
StormTech systems are engineered for structural performance across a wide range of soil conditions and loading scenarios and are adaptable to both detention and retention applications depending on site and regulatory requirements.
High void ratio delivers maximum storage capacity per cubic yard of excavation
Engineered to accept traffic and vehicle loads with proper cover depth and design
Fully compatible with filter fabric, stone bedding, and aggregate surround for structural support and water quality integration
Modular, interlocking design allows flexible layout configuration to fit irregular sites and varying storage volume requirements
Widely specified and accepted by Virginia DEQ and local stormwater review agencies across Northern Virginia
Inlet & Outlet Control Structures
Inlet and outlet structures manage how stormwater enters, moves through, and discharges from a detention or conveyance system. Custom precast and cast-in-place structures control system hydraulics, provide maintenance access, and ensure the system performs to design intent and regulatory requirements.
Capital Stormwater Services installs precast concrete manholes, junction boxes, outlet control structures and energy dissipators for stormwater detention, conveyance, and discharge systems. Riser assemblies, orifice plates, trash racks, and related outlet control components are installed, inspected and documented at completion supporting proper system performance and satisfying closeout requirements for engineers, owners and local review agencies.
Precast concrete and cast-in-place structure options to meet site-specific design requirements
Weir walls, orifice plates, and flow control devices for regulated stormwater release
Manholes, access points, and safety grates for long-term inspection and maintenance access
OUR INSTALLATION PROCESS
Plan Review
We review approved civil plans, hyrology calculations and manufacturer’s specifications to confirm requirements.
Site Preparation & Excavation
Excavation is completed to the required grades with attention to safety and access.
Subbase Preparation
Stone bedding and geotextile are placed to create a stable foundation
System Placement
Chambers or pipes are installed to plan with proper alignment and spacing.
Structures & Connections
Inlets, outlets. and flow control structures are connected and sealed per design.
Backfill & Compaction
Backfill is placed in lifts and compacted to meet structural and traffic load requirements.
Closeout & Documentation
As-built documentation, photos and inspection reports are provided for compliance.
Recent Projects
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