Managing stormwater on your property? Here’s a quick breakdown of dry wells and infiltration trenches, two effective solutions:

• Dry Wells: Compact, underground structures ideal for small areas (up to 1 acre), like rooftops or driveways. They store water vertically and work best in sandy, well-draining soils.
• Infiltration Trenches: Long, shallow systems designed for larger areas (up to 5 acres), like roads or parking lots. They disperse water horizontally and require well-draining soils with low clay content.

Quick Comparison:

Both systems help reduce flooding, improve water quality, and recharge groundwater. Choose based on your property size, soil type, and runoff source.

Stormwater Management: Infiltration Trenches

Design Features

When it comes to managing stormwater, understanding the structural differences between dry wells and infiltration trenches can help you choose the right solution for your needs.

Dry Well Structure

Dry wells are compact, underground structures designed to manage stormwater effectively. They are typically cylindrical or square-shaped and range in size from 3–12 feet deep and 3–6 feet wide at the surface ^[1]. Each dry well includes several key components that work together to control water flow.

Here’s what a standard dry well setup usually consists of:

• Perforated concrete or plastic storage unit to hold water temporarily.
• Clean-outs for easy maintenance access.
• Pipes that connect the dry well to drainage sources.
• Protective landscape fabric to prevent clogging.
• Stone foundation to provide stability.

For smaller applications, mini-drywells (about 2 feet in diameter) can handle runoff from areas as large as 500 square feet ^[4]. To handle heavy rainfall, overflow pipes are often included, allowing excess water to flow downstream ^[3].

Infiltration Trench Structure

Infiltration trenches are quite different in design. These systems are long, rectangular, or trapezoidal excavations that typically range from 3 to 6 feet in depth. They are capable of managing runoff from areas as large as 5 acres ^[1].

Key components of infiltration trenches include:

• Clean, crushed angular stone (1.5–3 inches in diameter) to store water.
• High-quality geotextile filter fabric lining to prevent sediment clogging.
• Perforated HDPE or PVC drainage pipes with at least a 200 mm interior diameter.
• Optional void-forming structures to increase water storage capacity.

Some designs also include a 6–12 inch sand filter layer at the bottom for added filtration ^[1].

Design Differences

The table below highlights the main structural differences between dry wells and infiltration trenches:

Both systems share some common requirements. The soil must have a minimum permeability rate of 0.3 inches per hour, and there should be at least 2 feet of separation from the groundwater table ^[1]. Additionally, neither system is suitable for runoff from contaminated areas, such as gas stations, unless the water is pre-treated ^[1]. These design differences directly influence how each system performs in managing stormwater.

How Each System Works

Dry Well Operation

The operation of dry wells revolves around three key steps: collecting water through surface drains or pipes, temporarily storing it in the well chamber, and gradually allowing it to infiltrate into the surrounding soil. Research conducted in Portland, Oregon, revealed that about 75% of precipitation hitting impervious surfaces is directed into dry wells, accounting for 38% of the total groundwater recharge in urban areas ^[2].

Each dry well is capable of transmitting up to 5 acre-feet of water annually into the underlying aquifers. To put that into perspective, this is enough water to meet the annual needs of around 10 households ^[5]. This impressive capacity is due to the well’s ability to bypass the less permeable surface layers and reach deeper, more permeable soil zones.

Infiltration Trench Operation

Infiltration trenches, on the other hand, manage stormwater through a horizontal system that gradually releases water along its length. These systems are particularly effective when designed with the right balance between impervious and pervious areas. They are best suited for managing runoff from small drainage areas (under 5 acres) and typically drain within 72 hours after a rainfall event ^[1].

The trenches use crushed stone to disperse water evenly, allowing it to absorb into the surrounding soil. Design guidelines suggest the following impervious-to-pervious area ratios for optimal performance:

These ratios are widely accepted as standard for infiltration trench design ^[6]. These distinct methods of operation highlight the differences in how each system manages water.

Water Management Comparison

When applied to Maryland’s diverse soil conditions, the operational differences between dry wells and infiltration trenches become even more evident. Studies show that 77% of dry wells operate as intended, with 91% contributing to water quality improvements ^[2].

Here’s a side-by-side comparison to help illustrate their performance:

Interestingly, research has found that five dry wells can infiltrate more water than a 70-meter diameter infiltration basin ^[8]. These findings underscore the efficiency of dry wells in certain contexts, while infiltration trenches excel in others depending on soil type and drainage needs.

sbb-itb-843f8be

Best Uses for Each System

Small Property Applications

Dry wells are a practical solution for managing runoff from roofs and paved surfaces, especially in tight urban spaces. Their vertical design takes up minimal room, making them perfect for properties with limited drainage areas. These systems work best in areas with well-draining soils, ensuring efficient water absorption.

Large Property Solutions

For properties with large impervious surfaces, multiple infiltration trenches can effectively handle runoff. The design of these trenches requires careful consideration of the site’s slope and soil conditions, particularly in regions like Maryland, where environmental factors play a significant role.

Here’s what proper installation of infiltration trenches involves:

Maryland-Specific Factors

Maryland’s diverse soils and climate demand extra attention when choosing and designing stormwater systems. Research indicates that less than half of infiltration trenches maintained long-term functionality, with only about one-third remaining effective after five years ^[9].

"Infiltration structures are ideal for infiltrating runoff from small drainage areas (<5 acres), but they need to be applied very carefully." – MAPC Fact Sheet ^[1]

For Maryland properties, these factors are especially important:

• Soil Composition: High-clay soils are unsuitable for infiltration trenches ^[9].
• Groundwater Protection: Both dry wells and trenches require a 2–5 foot separation from the seasonally high groundwater table ^[9].
• Karst Topography: Avoid using infiltration trenches in areas with limestone or karst formations to prevent sinkhole risks ^[9].

Additionally, any system should be designed to infiltrate stored water within 72 hours of rainfall ^[1]. If you’re in Maryland and need expert guidance on stormwater management, reaching out to a professional service like Pro Landscapes MD can provide tailored solutions for your property.

Setup and Upkeep

Installation Steps

Dry wells and infiltration trenches serve different purposes in managing runoff. Dry wells are compact systems designed for specific points, while infiltration trenches are linear setups better suited for managing larger areas.

Here’s how a typical dry well is installed:

• Site Preparation
  Start by digging a 4-foot wide by 4-foot deep hole, along with a sloping trench leading toward it. Make sure the excavation is far enough from nearby structures to avoid any issues.
• Assembly Process
  Line the hole with landscape fabric, install PVC piping from the downspout with the correct slope, and place a perforated plastic barrel on a bed of stones. Surround the barrel with clean stones and finish by adding an overflow emitter ^[10].

For an infiltration trench, the process is slightly different:

• Trench Excavation
  Dig a trench sized according to the drainage area and ensure it meets frost depth requirements.
• System Construction
  Line the trench walls and top with geotextile filter fabric, backfill it with clean, crushed angular stone, and add perforated distribution pipes ^[6].

Both systems require careful installation to work effectively, and regular maintenance is key to their long-term success.

Regular Upkeep

Keeping these systems in good shape involves a straightforward maintenance routine. Here’s a quick overview:

Sticking to this schedule helps ensure the systems function as intended and reduces the risk of costly repairs.

Price Breakdown

Understanding the costs involved can help you plan better for installation and upkeep.

Infiltration Trench Costs:

• Installation: Around $5 per cubic foot of stormwater treated ^[9].
• Maintenance: Typically between 5% and 20% of the construction cost annually ^[9].

These costs can vary based on factors like the type of runoff being managed and local soil conditions. For example, in Maryland, property owners may face unique challenges due to regional soil and climate. Hiring experienced contractors, such as Pro Landscapes MD, can ensure the system is installed correctly, which might save on maintenance costs in the long run by preventing issues from the start.

Conclusion

Dry wells and infiltration trenches serve as practical solutions for managing stormwater, each suited to different property sizes and needs. Dry wells work best for smaller areas, like residential rooftops, managing runoff effectively for properties under one acre. However, they do require regular maintenance to avoid clogging ^{[11] [5]}. On the other hand, infiltration trenches are designed for larger properties, handling runoff from areas up to five acres. Their linear design makes them particularly effective for roads and recreational spaces ^{[1] [7]}.

The success of either system depends heavily on proper soil conditions. A professional evaluation is key to ensuring the right system is chosen and implemented correctly. Pro Landscapes MD’s team of drainage experts can assess your property and recommend solutions tailored to Maryland’s unique soil and climate conditions.

Routine maintenance is essential for keeping these systems functional over time. While dry wells generally require less upkeep than infiltration trenches, both systems can provide reliable stormwater management when matched appropriately to the property.

For expert advice and tailored stormwater solutions in Maryland, reach out to Pro Landscapes MD. They’re ready to help you protect your property effectively.

FAQs

How can I tell if my soil is suitable for a dry well or an infiltration trench?

If you’re wondering whether your soil is suitable for a dry well or an infiltration trench, a percolation test can give you the answer. Here’s how to do it: dig a hole about 12 inches wide and 12 inches deep, then fill it with water. Check back after 24 hours – if the water has completely drained, your soil is likely a good candidate for these systems.

For optimal performance, the soil should allow water to infiltrate at a rate of at least 0.5 inches per hour. Additionally, it should contain less than 20% clay and no more than 40% combined silt and clay. If the water doesn’t drain as expected, your property might not be suitable for these stormwater management methods. In that case, reaching out to a professional for a detailed assessment could be a wise next step.

What maintenance is needed to keep dry wells and infiltration trenches working efficiently?

To keep dry wells working efficiently, regular maintenance is a must. Start by inspecting gutters, downspouts, and the area surrounding the dry well to spot any debris or pooling water – these can indicate blockages. Clean your gutters seasonally, clear debris from water flow paths, and think about adding gutter guards to minimize buildup. It’s also a good idea to check the dry well annually, and if needed, hire a professional to clean it and maintain its performance.

For infiltration trenches, make it a habit to clear debris from inlets and outlets every month and check for sediment buildup twice a year. If the top layers of pea gravel or filter fabric become clogged, replace them as needed. Aerate the trench once a year to keep it functioning well. Every five years, remove sediment from the bottom to restore its ability to absorb water. Keeping an eye on water levels after heavy rainfall can also help you catch clogs early and ensure proper drainage.

By staying on top of maintenance, you can keep both systems running smoothly and effective for managing stormwater over the long haul.

What are the key differences between dry wells and infiltration trenches in groundwater recharge and water quality improvement?

Dry wells and infiltration trenches are both effective tools for managing stormwater, though they function a bit differently.

Dry wells are designed to direct stormwater straight into the ground, helping to recharge underground aquifers. As the water seeps through the soil, some pollutants can be filtered out, which can enhance water quality. However, there’s a potential risk of groundwater contamination if the stormwater isn’t treated beforehand.

Infiltration trenches, by contrast, are shallow systems filled with gravel that allow stormwater to gradually soak into the soil. This method not only helps replenish groundwater but also does a better job of filtering out sediments and pollutants during the process.

Both options contribute to effective stormwater management, but their use depends on factors like the type of soil, specific site conditions, and how much water treatment is needed.

Related posts

• Retention vs. Detention Ponds: Key Differences
• Top Drainage Solutions for Patios
• Underground Detention Systems: Long-Term Environmental Impact
• Stormwater Infiltration Systems for Maryland Homes