Designing on-site wastewater treatment systems in the Hamptons and across the East End of Long Island comes with its own unique set of challenges—poor-draining soils, fluctuating high groundwater levels, restrictive lot sizes, and increasingly stringent environmental regulations. For civil and septic engineers working on high-end residential projects, the demand for systems that are both compact and environmentally sound has never been greater.

One advanced leaching system increasingly specified for these types of sites is the Pressurized Shallow Drainfield (PSD). As part of the broader family of Innovative/Alternative Onsite Wastewater Treatment Systems (I/A OWTS), PSDs are engineered to deliver treated effluent uniformly into the most biologically active soil layers—optimizing performance while minimizing site disruption. This makes them a compelling option for engineers and developers seeking smart, sustainable infrastructure solutions that meet the technical and aesthetic demands of high-end construction.

In this article, we examine how PSDs work, when they make sense, and what civil engineering factors—like site constraints, soil conditions, and regulatory requirements—drive their specification, particularly on high-end residential projects in sensitive or space-limited areas like the Hamptons.

What is a Pressurized Shallow Drainfield?

A Pressurized Shallow Drainfield (PSD) is a type of onsite wastewater dispersal system designed to deliver pretreated effluent into the uppermost layers of soil—typically between 6 and 24 inches below grade. Unlike traditional gravity-fed leach fields, PSD systems use low-pressure pumps to distribute wastewater evenly across narrow trenches through perforated pipes. These trenches are shallow, level, and often filled with gravel or specialized chambers to promote even infiltration.

This shallow placement takes advantage of the soil’s most biologically active zone, where naturally occurring microbes help break down contaminants before they reach groundwater. For Hamptons civil engineers and septic system designers, the PSD approach is particularly valuable on properties with restrictive site conditions—such as high water tables, poor-draining soils, or limited space.

PSDs are typically part of a broader Innovative/Alternative Onsite Wastewater Treatment System (I/A OWTS), which means they’re engineered to meet stricter environmental standards and can be customized for luxury homes, coastal parcels, and other sensitive development areas. In regions like the East End, where traditional systems may not be permitted or practical, the PSD offers a code-compliant, high-performing alternative that fits seamlessly into high-end residential design.

How PSD Systems Work

At the core of a Pressurized Shallow Drainfield system is a controlled dosing process that delivers pretreated wastewater evenly across the soil surface using small-diameter distribution pipes. The system typically includes the following components:

• Septic tank or advanced treatment unit: Effluent, which is the liquid portion of wastewater after solids have been removed, first passes through a conventional septic tank or a more sophisticated treatment unit, such as an I/A OWTS, which utilizes a combination of aerobic and anaerobic treatment to reduce solids and organic load.
• Pump chamber: From the treatment tank, effluent enters a pump chamber equipped with floats or a timer control panel. When the volume reaches a preset level, the pump doses a measured amount of effluent through the system.
• Pressure manifold and laterals: The effluent is pushed through a pressure-rated main line into a network of perforated lateral pipes. These pipes, usually ¾” to 2” in diameter, have precision-drilled orifices spaced at regular intervals.
• Shallow trenches with media: The laterals are placed in level, shallow trenches filled with gravel or lined with distribution chambers or half-pipe systems. The half-pipe/chamber configuration distributes the effluent evenly over the trench bottom, promoting biological activity and effective dispersion. Effluent exits the orifices and disperses uniformly into the surrounding soil, where it enters the soil for further treatment.

The key to PSD performance is uniform dosing—each application of effluent is small, consistent, and evenly distributed. This prevents oversaturation, reduces the risk of biomat buildup, and allows the effluent to receive maximum treatment in the biologically active soil layer near the surface.

This controlled distribution is especially important when working on sites with variable slopes, irregular lot lines, or zoning restrictions. PSD systems allow for fine-tuned layouts that work around trees, retaining walls, or landscape features—ideal for high-end residential projects where design flexibility is essential.

When to Use PSD Systems

Pressurized Shallow Drainfields are often the go-to solution when standard septic system leaching structures—like leaching pools or galleys—aren’t viable due to site constraints. On Long Island and across the Hamptons, these constraints are common and often unavoidable:

• Limited vertical separation to groundwater or restrictive layers: Many properties have only a narrow band of permeable soil between the surface and either a restrictive soil horizon or the water table. PSDs take advantage of this upper soil layer, dispersing effluent within the biologically active zone where treatment is most effective. 
• High groundwater table: Especially in coastal areas, high groundwater levels can make traditional deep systems unsafe or noncompliant. PSDs operate at shallower depths, offering a code-compliant solution that protects water quality.
• Tight soils or extreme percolation rates: Sites with clay-heavy soils that percolate too slowly pose treatment challenges. The controlled dosing of PSDs helps regulate infiltration rates, ensuring that effluent remains in contact with soil long enough for proper filtration and microbial breakdown.
• Irregular lot shapes and limited buildable area: High-end residential sites often include pools, retaining walls, or architectural footprints that reduce available space for a conventional drainfield. PSDs offer layout flexibility and shallower installation depths than other leaching systems, making them easier to integrate into constrained or irregular sites—even if their total footprint isn’t always smaller than leaching pools or galleys. 
• Regulatory compliance: In many parts of Suffolk County, particularly under the Suffolk County Health Department (SCHD) standards for I/A OWTS, PSDs are often the only practical way to meet separation, dosing, and dispersal requirements—especially on constrained or environmentally sensitive parcels.

Site and Soil Testing Requirements

Specifying a Pressurized Shallow Drainfield is a data-driven decision rooted in site-specific conditions, confirmed through soil testing and observation during the early phases of project planning. Two key tests determine whether a PSD is the appropriate system for a given site:

• Percolation or permeability testing: This test measures how quickly water moves through the soil, which helps engineers evaluate whether the native soil can absorb and treat wastewater effectively. Soils that drain too slowly (like dense clays) may not be suitable for conventional leach fields, making pressure distribution necessary to control flow rates and ensure treatment.
• Deep hole observation: Also known as a test boring, this assessment helps identify the seasonal high groundwater table and any restrictive soil layers—such as hardpan or bedrock. Health departments typically require a minimum vertical separation between the bottom of a drainfield and these features. If there’s not enough room for a conventional system, a PSD may be the only code-compliant option.

These findings are central to system design. When site conditions limit depth, loading rate, or available area, PSDs allow engineers to design within those constraints without compromising performance or regulatory compliance.

Benefits of PSD Systems

Pressurized Shallow Drainfields are more than just a workaround for difficult sites—they offer clear engineering advantages that make them a smart choice for modern wastewater design, especially in high-end residential contexts.

• Effective treatment on challenging sites: PSDs make it possible to safely and sustainably manage wastewater on properties where traditional systems can’t be permitted. Whether the issue is shallow soil, poor percolation, or a high water table, PSDs are engineered to adapt.

• Enhanced biological treatment in upper soil layers: Because the effluent is dispersed within 6–24 inches of grade, it interacts with the most oxygen-rich, biologically active zone of soil. This improves nitrogen and organic material breakdown, resulting in cleaner effluent before it reaches the water table.
• Minimized site disturbance: The shallow installation depth reduces excavation and trenching requirements. For properties with extensive landscaping, tree cover, or grade-sensitive design features, PSDs help preserve the natural terrain.
• Fits tight or irregular footprints: With narrow trench widths and flexible lateral configurations, PSDs can be tailored to fit around architectural elements, utilities, or existing structures. When properly designed, they offer an efficient solution for lots with limited open space—a common scenario in Long Island’s denser or topographically constrained neighborhoods.
• Uniform dosing for long-term performance: Pressure distribution prevents overloading individual areas of the drainfield, which minimizes biomat formation and extends system life. This uniformity is key to reliability, especially in engineered systems where consistent performance is expected.
• Compliance with modern codes: In jurisdictions like Suffolk County, PSDs can often be the most practical method for meeting I/A OWTS standards. For project teams navigating complex permitting pathways, PSDs provide a code-compliant path forward.

By combining smart design with shallow, biologically active dispersal, PSDs deliver long-term reliability and regulatory peace of mind—making them a strong fit for projects in the East End and other high-performance residential applications.

Choosing the Right Septic System: PSD vs. Alternatives

When designing onsite wastewater systems, engineers must weigh multiple variables—site conditions, regulatory requirements, client preferences, and long-term performance. Pressurized Shallow Drainfields are one of several options, but they serve a specific niche that distinguishes them from more conventional approaches.

System Type	Best For	Limitations
Pressurized Shallow Drainfield (PSD)	Sites with shallow soil, high water tables, or limited open space; properties requiring I/A OWTS compliance	Requires pump and electricity; ongoing maintenance; not traffic-bearing
Gravity-fed Leach Field	Sites with deep, well-draining soils and sufficient separation to groundwater	Inconsistent effluent distribution; prone to localized overloading and biomat formation
Leaching Pools or Galleys	Historically common on Long Island; suitable for sandy soils with ample depth	While compliant with modern SCHD/I/A OWTS requirements, offer lower treatment performance than PSDs
Mound System	Sites with extremely shallow or impermeable soils; need for full above-grade treatment	Large footprint; visually intrusive; more complex to build and landscape

For many projects in the Hamptons, PSDs strike the right balance between regulatory compliance, site adaptability, and long-term reliability. While gravity systems may be preferred where conditions allow, or mounds may be necessary in extreme cases, PSDs offer a flexible middle ground—particularly for high-end residential projects where minimizing visual and physical disruption is a priority.

Choosing the right system ultimately depends on a combination of soil testing, percolation rates, hydraulic loading needs, and municipal or county health department guidelines. PSDs provide engineers with a high-performance option that’s code-compliant, adaptable, and well-suited to the complex constraints often found on East End properties.

What Homeowners Should Do Next

If your design team has proposed a Pressurized Shallow Drainfield, don’t be alarmed—it doesn’t mean your site is “problematic,” and it doesn’t mean your system will be more complicated to live with. PSDs are commonly used on high-end residential projects across the East End, and they’re fully approved under Suffolk County’s I/A OWTS program.

Here’s what to keep in mind as you move forward:

• Ask questions early: Understand what the system entails, where it will be located, and how it may affect your landscaping or yard use. For example, the drainfield area won’t be traffic-bearing, and some planting restrictions may apply.
• Plan for maintenance: Like other advanced treatment systems, PSDs require periodic upkeep—such as pump inspections, flushing lines, and filter cleaning. Your installer or maintenance provider will outline a schedule that keeps your system running efficiently.
• Trust the process: Your engineer has recommended this system for a reason—it’s the most effective, code-compliant way to manage wastewater on your site. With proper installation and maintenance, a PSD offers long-term reliability and environmental protection.

If you have concerns, speak with your engineer or system designer. Their job is to translate site conditions into a system that not only works—but works well for the long term.

Why Site-Specific Septic Engineering Matters

Designing reliable septic systems in the Hamptons requires more than just technical know-how—it demands a deep understanding of local soil conditions, groundwater behavior, and evolving health department regulations. On tight sites with limited separation, high water tables, or sandy soils, standard systems like leaching pools often fall short. That’s where Pressurized Shallow Drainfields come in—not as a workaround, but as a precise, code-compliant solution tailored to the realities of East End building.

At DiLandro Andrews Engineering, we approach each residential project with a holistic view—integrating civil, structural, and mechanical considerations from the start. Whether we’re coordinating with the architect on grading strategies or resolving setbacks through innovative wastewater design, our goal is always the same: to deliver durable, high-performing systems that support the home’s function without compromising its form.
To see how these solutions come to life in the field, explore our portfolio of residential engineering projects across the East End.