Field Based Hydraulic Conductivity Testing and its relationship to Stormwater LID features

Here at Watearth, we take pride in performing several field-based Hydraulic Conductivity Tests to determine design infiltration rates of various soil types for the construction of Low Impact Development (LID) design, including Green Infrastructure (GI).

Field testing is crucial for baseline field parameters, including soil parameters, and establishes a framework for the development of LID. In addition to soil group type, texture, and depth, field testing can be used to ground truth desktop research and confirm actual field conditions, such as conductivity rate and design infiltration rate. The design infiltration rate is ultimately used for portions of geotechnical engineering design.

Watearth’s Adam Susskind – DRI Test in Los Angeles

What is Hydraulic Conductivity and Design Infiltration Rate?

Hydraulic conductivity is defined as the ability of soil to transmit water over a given period. Sometimes the hydraulic conductivity is referred to as the “water infiltration rate” when tested over extended periods of time. The hydraulic conductivity of soil is defined by the ability of the soil to infiltrate water under saturated or nearly saturated conditions over time. The infiltration rate can be provided in various units but is typically provided in inches/hour (in/hr).

Hydraulic conductivity can be affected by a multitude of factors. In soils, texture, particle size, distribution, roughness, shape, and structure each affect the overall hydraulic conductivity, or infiltration rate, of a soil. Soil classifications are often helpful descriptors when discussing hydraulic conductivity and include Hydrologic Soil Groups (A, B, C, and D) and the 12 soil textures (sand, loamy sand, sandy loam, loam, silt loam, silt, sandy clay loam, clay loam, silty clay loam, sandy clay, silty clay, and clay).

The Design Infiltration Rate is ultimately the rate that is used for engineering design and the development of LID. The design infiltration rate is a combination of the equalized infiltrations rates determined by testing, and an incorporated Reduction Factor (RF). RF is determined by weighted criteria and is calculated to afford the design an appropriate margin for error and margin for change of conditions over time; this combination provides a value that represents the long-term performance of the proposed design and construction.

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Examples of Field Tests

At Watearth, after years of experience performing field tests for hydraulic conductivity, there are two tests in particular that we have found to be not only efficient but extremely accurate.  

The first test is the Double-Ring Infiltrometer (DRI). Following ASTM D3385 – 18, the tests require driving two rings into the ground where they are filled with water. The outer ring is driven into the ground further than the inner ring, so the inner ring represents only the downward movement of water.

Two Mariotte Tubes, one with 10,000 milliliters (mL) of capacity to fill the outer ring and one with 3,000 mL volumetric capacity to fill the inner ring, are used to fill the rings and maintain a constant head pressure throughout the testing period. The volume of water infiltrated into the rings is then converted to an infiltration rate, using the ASTM calculation methods.

Constant head pressure is a constant reading created by the pressure of water in the graduated column. It can be further described by the Mariotte Tube Principal: “a Mariotte siphon is based on the principle of a Mariotte bottle, which discharges liquid at constant pressure. Moreover, the difference in height between the bottom of the air tube and exit hole of the siphon maintains a constant head in the inner infiltrometer ring” (Bouwer et al.).

Second, Constant Head Permeameter (CHP) testing utilizes a Guelph Permeameter (GP) to obtain infiltration rates for soils. The GP uses the Mariotte tube principle maintaining a constant head within a borehole, as opposed to the falling head test, which is similar in that soils are tested once saturated, but differs in that the head pressure (the volume of water present at the top) is not required to be maintained . This device consists of a tripod assembly; a support tube and lower air tube fittings; a water reservoir and fittings; and well hydraulic head scale and upper air tube fittings. The GP maintains a constant head as water infiltrates into the soil within the borehole. This rate of infiltration is documented and calculated by the water reservoir volume (Δh) against time (Δt).

Both testing options can be used separately or in combination based upon field scenarios, accessibility, or accuracy techniques.

Watearth’s Jeremy Liby – CHP Testing in Texas

What is LID?

Low Impact Development (LID) refers to systems and practices that use or mimic natural processes that result in the infiltration, evapotranspiration, or use of stormwater to protect water quality and associated aquatic habitat (EPA, 2021).

At Watearth, we utilize field-based hydraulic conductivity testing to determine the design infiltration rate to design and construct different types of LID to promote preferred hydrologic, water quality, and habitat conditions locally and regionally. Watearth deals in many of the popular LID alternatives: rain gardens, bioretention, biofiltration, permeable pavement, vegetated swales, bioswales, green roofs, trees, vegetation, infiltration basins, green streets, blue roofs, subsurface detention, rain barrels, and cisterns.

Watearth’s work

Watearth takes on numerous jobs that involve DRI and CHP testing for LID design.

We worked with Los Angeles County Public Works (LACPW) on their Adventure Park Regional Stormwater Capture and Integrated Water Resources project. Along with work involving civil design, site assessments, and groundwater monitoring on this project, we created an Operations & Maintenance Plan for Low Impact Development and completed a bioretention LID design featuring native and low water use plans. These designs incorporated DRI.

We have additional work incorporating DRI and CHP testing for LID design for private oil and gas clients and work in a public park.  

Contact Watearth today with your project needs.  

Stream restoration: Improving environmental health

What is stream restoration?

The United States Department of Agriculture National Resources Conservation and Service defines stream restoration as, “the reestablishment of the structure and function of ecosystems. Ecological restoration is the process of returning an ecosystem as closely as possible to predisturbance conditions and functions.” The restoration process “reestablishes the general structure; function; and dynamic, but self-sustaining, behavior of the ecosystem.”

Stream restoration improves the biodiversity, flood management, and landscape of the local and downstream ecosystems.

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Why is it important to restore streams?

The United States Environmental Protection Agency lists numerous benefits to restoring streams.

One important aspect of stream restoration is its ability to preserve and protect aquatic resources. The EPA writes, “existing, relatively intact ecosystems are the keystone for conserving biodiversity, and provide the biota and other natural materials needed for the recovery of impaired systems.”

This is not to say that stream restoration gets rid of the need to protect water resources, rather, it is an additional step that environmental scientists and engineers factor in with other acts of protection and preservation.

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As humans build, construct, and shift ecosystems, the Earth suffers the consequences. Animal and aquatic species are affected; in this instance, streams, rivers, and wetlands lose a lot of their function. When governments recognize this and take on projects to restore these areas, we can help reconstruct the function of these important aquatic resources.

Regarding restoring natural structure, the EPA writes, “Many aquatic resources in need of restoration have problems that originated with alteration of channel form or other physical characteristics, which in turn may have led to habitat degradation, changes in flow regimes and siltation. Stream channelization, ditching in wetlands, disconnection from adjacent ecosystems and shoreline modifications are examples of structural alterations that may need to be addressed in a restoration project.”

While we cannot restore most streams to their precise original form, we can approximate the sites original physical attributes, resulting in improved water quality and habitat conditions.

Natural stream ecosystems are one tool (like green infrastructure) – that provide tremendous water quality and ecological benefits without the need for other forms of mechanized or chemical treatment that have their own set of auxiliary negative environmental impacts, like consuming energy and material resources.

Stream restoration techniques

Stream restoration is not a one-size-fits-all approach to ecological redevelopment. The Montgomery County, Maryland Department of Environmental Protection highlights some of these techniques:

  1. Brush layering: Placing layers of branches along the stream encourages new plants to grow from the branches and prevents erosion.
  2. Grading/Planting: If a bank of a stream is steep, it can be graded into sloping steps, facilitating stream flow during heavy rainfall. Planting creates roots which hold banks in place.
  3. Log vane: Logs are placed in the stream as a means of diversion away from eroding banks. Additionally, this creates small pools below the vane where various aquatic creatures can live.

Watearth’s work

Watearth has worked on several projects for the City of Austin restoring streams. For the City of Austin Thompkins Tributary Stormwater Control Measures Stream Restoration project, we performed a desktop evaluation of flood plains, soils, range of infiltration rates, topography, land use, aerial photographs, critical environmental features, utilities, and impervious cover within the watershed. Additionally, we performed site reconnaissance to evaluate hydrologic and hydraulic features of sites and vicinities at four locations. We developed six sustainable stormwater control measures at four locations determined by City staff, including an elementary school, vacant lot, an existing flood control wet pond, and a tributary (in conjunction with proposed stream restoration measures).

Watearth additionally worked on the City of Austin Walnut Creek Wells Branch Willow Bend Stream Restoration project. We developed three sustainable stormwater control measures at 10% design. Watearth developed 10% planning-level design alternatives in GIS and evaluated alternatives for water quality performance, multi-use features, flood control benefit, construction cost, O&M cost, life-cycle cost, available right-of-way, utility conflicts, and other criteria used by the City for project development.

Contact Watearth today for all your stream restoration project needs.

Watearth: Everything flows in the right direction

Watearth is happy to share our debut animated explainer video with you. This video highlights our capabilities and our mission to deliver practical and grounded solutions for green infrastructure, water, and environmental projects in service of the triple bottom line. Contact us today with your project needs.

Video transcript:

At Watearth, we understand grey and green infrastructure, water, and the environment. From field work and data collection to planning, modeling, design, and construction. Watearth is a specialized firm and will ensure your project is streamlined from start to on-time finish. Watearth will bring technical expertise to policy development and regulatory understanding to design. We turn your project challenges into opportunities for multi-functional, resilient, and sustainable solutions. Watearth is mindful of client and stakeholder needs; and considers communities down stream of both project sites and planning documents. And we package solutions for practical use, financial, social, and ecological. At Watearth, everything flows in the right direction. Connect with us today to discuss your project needs.

California: A history of drought and fire

What conditions determine a drought?

A drought is defined as “a period of time when an area or region experiences below-normal precipitation.” A lack of rain and snowfall can have a great impact on agriculture, business, and ecosystems. This leads to water shortages, loss of crops, and reduces volumes in water bodies. Droughts are very expensive; the second most costly natural disaster behind hurricanes.

It is often difficult for weather and climate scientists to pinpoint an exact beginning and end to a drought, as meteorological conditions can change suddenly. Droughts can last anywhere from weeks to months to years.

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California’s history with droughts

The state of California has experienced many droughts in recorded history. There was a five-year event between 2012-2016, with other large-scale droughts during the 2007-2009, 1987-1992, and 1976-1977 periods. In a technical paper published to ASCE Library, California’s drought from 2012-2016 was “one of its deepest, longest, and warmest historical droughts.”

The 1976-1977 drought affected the agricultural industry the most, with an estimated $500 million in losses to the farm industry – particularly related to livestock – in 1976 alone. Adjusted for inflation, that would be over $2 billion in 2021.

The drought in California between 2007 and 2009 also hit agriculture particularly hard – almond, tomato, and lettuce crops were affected the most – resulting in reduced production. California’s hydroelectricity production usually accounts for 15% of all the state’s electricity. In these years it fell to as low as 8% due to lack of water to produce the electricity.

From 2012 through 2016, California’s drought led to water shortages at hydroelectric power plants, reservoirs, aquatic ecosystems, and in the agriculture industry. This drought killed 102 million forest trees and pushed aquatic species such as Chinook salmon close to extinction, in addition to costing billions of dollars in lost income.

How droughts and wildfires intersect

Wildfires are a direct result of droughts. Droughts are a result of dry climates – leading to a lack of moisture in soil. Wildfires can be ignited when lightning strikes dry ground or as a result of damaged utility lines, industrial accidents, and human error (or intent).

Where is California today?

California is amid another drastic drought. The state’s 1,500 reservoirs are presently 50% lower than they should be this time of the year. For example, California’s largest reservoir located in Shasta is only a quarter full.

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As of right now, all of California is in a drought – no area is untouched. Northern California’s Lake Oroville is a reservoir that serves as a hydroelectric power plant and will likely shut down for the first time since it originally opened in the 1960s.

While this is all happening, California is battling numerous forest fires across the state. In El Dorado County, the Caldor Fire looms close to the resort city of Lake Tahoe, scorching 217,946 acres, destroying 778 houses, and is 53% contained.

Further north, the Dixie fire reached 900,000 acres and is soon to become the largest fire in state history. The largest fire by acreage is the August Complex which burned over 1 million acres last year.

Massive fires are becoming more common at an alarming rate. According to the Mercury News, “Of the top 20 largest wildfires since 1932, 17 have occurred since 2000; 11 since 2016; five in 2020 — and three from this year.”

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Long range weather forecasts are difficult to produce accurately, though many are hopeful and predict that the fall and winter months – particularly October and November – will bring rain to Northern California. The Peninsula, East Bay, and North Bay have above-normal significant fire potential, and are in need of some rainfall.

Watearth’s Work

Watearth takes pride in our work in water supply and water conservation. On the California central coast, we worked with Cal Poly San Luis Obispo on their Water Resources Master Plan: Technical Studies for EIR, Water Supply Assessment, Wastewater Feasibility, and Reclaimed Water Facility Impacts Evaluation project. For this project Watearth prepared an SB 610 Water Supply Assessment (WSA) for a multi-use development as part of preparation for the EIR. We also performed water supply analysis, demand analysis with water use, and water supply mitigation and performed water distribution system modeling, validating with metered data and incorporating conservation BMPs, including irrigation, fixtures, low water use vegetation, and alternative supply sources, including recycled water, groundwater, and purchased sources.

In Texas, Watearth worked with the Texas Water Development Board on their Statewide Water Conservation BMPs Modeling Tool. This Texas Water Development Board project utilized water demands, user classes and projected demands to create a water conservation BMP model for indoor and outdoor use. BMPs included utilizing recycled water for indoor and outdoor water use. Life-cycles, annual participation rates, incentive program costs and potential cost-benefit to public agencies were analyzed. Climate adaption and resiliency strategies were incorporated into the model.

Additionally, throughout the state of California, Watearth has worked on several solar projects, moving sustainable energy forward.

More broadly, our green infrastructure projects nationwide look at water supply and water quality, with the ultimate aim of infiltrating available stormwater runoff back into local soils.

Ida: The Cost of Hurricanes

Hurricane Ida made landfall on the 16-year anniversary of Hurricane Katrina, both storms similar in their seasonal timing and in the threat they posed.

Katrina’s impact spawned discussions ranging from federal government response to development of additional flood prevention infrastructure such as levees.

Part of Katrina’s massive devastation was due to the failure of the levees. In New Orleans particularly, the extreme amount of water overwhelmed drainage canals and the existing levees, resulting in 80% of the city experiencing flooding.

With the news that Hurricane Ida would hit Louisiana, many worried we would again witness great ravages.  However, NPR has reported that, “the levees, floodwalls and floodgates that protect New Orleans held up against Hurricane Ida’s fury, passing their toughest test since the federal government spent billions of dollars to upgrade a system that catastrophically failed when Hurricane Katrina struck 16 years ago.”

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Specifically, the federal government spent $14.5 billion on flooding and storm surge protection in the wake of Katrina. In an interview with Municipal Water Leader, Colonel Michael Clancy (who served as District Commander for the New Orleans District from June 2016 to June 2019) discussed the renovations and new protections that were made post-Katrina. One of their greatest construction efforts was a 130-mile wall of levees and concrete flood walls that surrounded the five parishes of New Orleans.

While the urban areas of New Orleans are presently in better shape than they were after Katrina, the suburbs are more effected. In Jefferson Parish, LA, there was unprecedented flooding as a levee failed leaving “more than 200 people in imminent danger.”

In the Town of Alliance, a floodgate failed and all residents were urged to evacuate immediately.

As of today, over 1 million Louisiana residents and businesses are still without power, nine people have been declared dead as a result of Hurricane Ida in the state of Louisiana and many houses are underwater. Some estimate the total damage cost of Ida in Louisiana will reach $80 billion.

This is a marked improvement over Katrina’s 1,800 fatalities and $164 billion in economic loses, and demonstrates the value of investment in flood control infrastructure.

Ida’s devastation progressed into the week, storming through the Northeastern United States with heavy rainfall and flooding. The death toll on the East Coast currently lies at 46.

As climate change becomes a growing issue, it is important that the federal government consider investing more in flood prevention infrastructure.

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Natural disasters like Katrina and Ida cost billions. Hurricane Sandy, which hit New Jersey, Connecticut and New York in 2012, left behind $63 billion in damages.

One study, published in Nature vol. 12, attributed $8 billion of damage from Hurricane Sandy to rising sea levels caused by climate change. The study postulates that an additional 70,000 people were affected by Hurricane Sandy due to climate change than would have been otherwise.

As hurricane-related flooding becomes more frequent, flood prevention infrastructure becomes a more important investment. While levees are the primary form of flood prevention infrastructure in New Orleans, other cities call for other measures.

Green infrastructure (i.e. rain gardens) is demonstrably effective at managing flood risk. It reduces runoff volumes considerably and approaches the problem from the perspective of infiltration rather than routing.

Watearth’s work on managing flood risk dates back to 2008 and has recently included work for the City of Austin on their drainage criteria manual. This manual plays a crucial role in protecting and restoring the health of the city’s watersheds. It also evaluated stormwater runoff and rainfall events – all key to helping to mitigate flooding. Watearth has written and updated more than a dozen such criteria manuals and master plans and considers it the foundation for informed design in complex urban environments.

FEMA and Flood Plain Mapping: What you need to know

What is FEMA?

FEMA stands for the Federal Emergency Management Agency and was established via Executive Orders 12127 and 12148 signed by then-President Jimmy Carter. Carter gave FEMA the “dual mission of emergency management and civil defense.”

Today, FEMA’s mission is defined as, “helping people before, during and after disasters, and our guiding principles help us achieve it.” FEMA supplies numerous services from disaster unemployment assistance to risk management information and grants.

Flood Maps

One key service FEMA provides is flood maps. Floods are meteorologically unpredictable and are increasingly a result of climate change. Most recently, areas of western Europe have been hit with massive flooding, completely washing away roads and homes. Germany and parts of Belgium were hit the hardest, with a confirmed death toll above 160 people. In the United States, Tennessee suffered a flash flood as a result of 17 inches of rain falling in a 24 hour period. At this point in time, the death toll lies at 20. 270 homes were destroyed and another 160 experienced significant damage.

These heavy and sudden rainfalls are attributed to climate change and are likely to become more common as average global temperatures rise annually. As the atmosphere warms, it holds and precipitates more water. Additionally, in areas that experience regular snowfall, the snow melts faster and earlier, leading to spring flooding. There has also been an increasing frequency of hurricanes and sea levels are rising, all factors contributing to an increase in flooding.

FEMA provides flood maps online via their FEMA Flood Map Service Center (MSC). These maps aim to help communities understand the flood risk in their areas, and can help guide decisions regarding reducing or managing flood risk.

Flood maps work by indicating the flood risk within a zip code area in the United States. These maps are very localized, and can even indicate where the level of an individual stream is likely to rise. FEMA designates any area that has a 1% chance or higher of experience a flood each year as a high-risk location. The 1% annual exceedance probability (AEP) is the basis of the National Flood Insurance Program. A 1% AEP flood has a 1 in 100 chance of being equaled or exceeded within a year, it has a recurrence interval of approximately 100 years – meaning it is a “100-year flood.”

FEMA also allows revisions to the flood maps. These include Conditional Letter of Map Revision (CLOMR), Letter of Map Revision (LOMR), and Letter of Map Amendment (LOMA). A CLOMR does not revise a National Flood Insurance Program (NFIP) map, it indicates whether a proposed project (i.e. modifying a floodway) would be recognized by FEMA. A LOMR is FEMA’s modification to an effective map. These are based on physical measures implemented in an area that would affect the hydrologic/hydraulic characteristics of a flood source. A LOMA is an official amendment to a NFIP map.

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Watearth’s Work With Floods

Here at Watearth, we understand the importance of floodplain mapping and other preventative measures. We take on numerous projects to help with drainage master plans and flood plain management.

Our CEO, Jennifer J. Walker, P.E., D.WRE, CFM, ENV SP, QSD, worked with the City of Houston Regional Detention Stormwater Master Plan (Including Water Quality Analysis). This high-profile project, initiated by the Mayor, identified, analyzed, and selected regional detention sites to mitigate City Capital Improvements Plan (CIP) projects and reduce flooding. During the project, Watearth also performed watershed and impacts analysis in HEC-HMS, performed a cost-benefit analysis, and targeted TSS and bacteria for impaired watersheds. Additional project components included evaluating, analyzing, and recommending stormwater quality Best Management Practices (BMPs) for CIP roadway, LID, and drainage projects. Watearth also included recommendations for stormwater quality BMPs associated with regional detention facilities and drainage features within park land for educational purposes.

Additionally, Watearth collaborated with the City of Austin on their Stormwater Drainage Criteria Manual (DCM). Watearth worked on the forward-thinking drainage criteria manual that played a crucial role in protecting and restoring the health of the City’s watersheds and also protects the City’s investment in stream restoration and natural channel design projects. Updates to the DCM were incorporated into City code following City protocols and code update processes. Watearth performed a literature review and data evaluation related to methods used nationwide to address excess urban runoff volume and provided recommendations for stormwater control/management strategies to achieve volumetric detention goals for the City of Austin. The project recommendations complied with federal, state, and local regulations for stormwater quality. We developed Volumetric Design Procedure criteria and recommended incorporation of Green Infrastructure and Hydromodification Management techniques. Additionally, Watearth developed guidance and criteria for developing stage hydrographs and tailwater criteria for detention routing and performed peer review of natural channel design criteria revisions. Other project elements included performing HEC-HMS modeling (hydrology) and evaluating the effect of rainfall distribution on peak flows and estimated detention volumes for the 25-year and 100-year rainfall events using updated NOAA Atlas 14 rainfall depths.

Watearth also worked on three watershed studies and a prepared Letter of Map Revisions (LOMR) submittals to the Federal Emergency Management Agency (FEMA) to remove filled areas within the regulatory flood plain for three project sites; Cedar Brook Ridge, Creekside Hills, and Heartwood Park (TX). Also in Texas, Watearth has updated FEMA’s floodplain maps and these were integrated into FEMA’s digital geospatial flood inundation mapping tool, which aims to accurately reflect observed and modeled hydrodynamic conditions to improve communication, understanding, and public safety before flood events occur.

If you’d like to learn more about Watearth’s work with hydrology and hydraulics and the services we offer, please visit our website.

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Rain Gardens: Beautiful & Functional

Rain gardens are an excellent combination of beauty and function. They brighten up a space and provide a habitat for local wildlife and insects, while they also filter pollutants out of stormwater, help prevent flooding, and keep our waterways clean.

What Rain Gardens Do

Rain gardens are recessed areas in landscape planted native flowers and shrubs that collect water runoff, known as stormwater, and allow it to soak into the ground. Water ponds within the rain garden temporarily before it is filtered into the ground either into the underlying soils or an underdrain. While the water filters through the soil it is also absorbed by the vegetation planted in the garden. Pollutants in the water are removed as they filter through the soil and are absorbed by plants. More complex rain gardens with underdrains and amended soils are called bioretention.

A wide range of vegetation can be used in rain gardens, including grasses, trees, flowering perennials, and shrubs. Depending on the location within the rain garden, plants can have a variety of water needs from water-loving plants in the ponding area of the garden to drought-tolerant plants along the outside edge of the garden.  

Sewage Overflow Warning

The Importance of Managing Stormwater

Stormwater is any precipitation that does not get directly absorbed into the soil and instead flows over the ground. When stormwater is absorbed into the ground, soil and plants can filter out pollutants. However, when stormwater flows over hard or paved surfaces there is nothing to filter out the pollutants in the water. Stormwater can include many pollutants such as fertilizers, pet waste, litter, oil and grease from vehicles, soaps, and other chemicals that have leaked or been spilled on the ground.

Stormwater runoff typically occurred during large storms when the rate of rainfall exceeded the rate at which the ground could absorb the water. However, today with increased development and more paved and impervious surfaces, stormwater runoff has increased. In cases where stormwater is flowing directly into rivers, streams, or other bodies of water, stormwater pollutants also flow into those bodies of water. In many cities stormwater flows into sewer systems where the water then goes to a treatment facility. However, when these sewer systems overflow, the excess untreated water is often discharged directly into local bodies of water, increasing the level of pollutants and sewage in the water. With the increase in impervious surfaces in cities, stormwater can frequently overload the sewer system causing an overflow. By incorporating rain gardens into landscapes, stormwater is better managed and runoff can be avoided. Learn more about stormwater sources and solutions.

Watearth Rain Gardens & Bioretention Projects

Watearth believes bioretention is best when it comes to stormwater and water quality.

Shortly after the Louisville, KY Metropolitan Sewage District rain garden was completed there was a 100-year event that tested its capabilities. Water poured out of the downspout from the roof of the building filling the rain garden. The rain pooled in the garden and was ultimately absorbed and drained out of the rain garden avoiding flooding and an overflow of stormwater. Erosion control measures were put into place to form the downspout into the rain garden and proved very functional during the rain event allowing water to flow directly into the rain garden.

If you would like to learn more about Watearth and our services, please visit our website. We are happy to discuss your stormwater and bioretention project needs.

For more information about Watearth’s work with Rain Gardens and Bioretention, please see the Watearth webinar on Engineering Rain Gardens and Bioretention presented by Watearth President Jennifer J. Walker, P.E., D.WRE, CFM, ENV SP, QSD.

Green infrastructure’s impact on regional water quality

Gray from the beginning

Urbanization in America grew exponentially in the first part of the 20th Century, primarily due to the increase in industrialism (steel mills, factories), as well as increased immigration from Europe. Over the last century, fantastic feats in architecture and engineering have included sprawling highways built to connect the coasts, buildings that touch the sky, and concrete channels ensuring our massive cityscapes have access to water.

While these inventions are impressive, we are learning more about the impacts of gray infrastructure and urban areas on our environment. Approximately 70% of greenhouse gas emissions worldwide come from gray infrastructure. These dense, urban areas also cause the urban heat island effect, which directly affects our energy intake, increasing temperatures and health issues. 

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One of the predominant issues caused by gray infrastructure is poor water quality. During heavy rains or snowstorms, stormwater falls to the surface. In urban areas, this water falls into gray infrastructures such as pipes, channels, and sewers which can result in sewage getting into our water.

Gray infrastructure often plays a role in directing stormwater into our water sources, so stormwater does not return to the earth where pollutants are eliminated. This is where green infrastructure (GI) comes into play.

What is green infrastructure?

The Water Infrastructure Improvement Act defines green infrastructure as “the range of measures that use plant or soil systems, permeable pavement or other permeable surfaces or substrates, stormwater harvest and reuse, or landscaping to store, infiltrate, or evapotranspirate stormwater and reduce flows to sewer systems or to surface waters.”

In essence, green infrastructure can store and infiltrate stormwater and prevent or lessen its impact on water systems used in urban areas. One example of green infrastructure is green roofs. These roofs are covered with plants and vegetation that allow rainfall infiltration and evapotranspiration of the stored water. These are extremely beneficial in urban areas and cost-effective. It does not involve much construction; it simply allows these gardens to bloom on top of the already constructed gray infrastructure.

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Another popular form of green infrastructure is bioswales. Bioswales serve as an alternative to traditional concrete gutters and storm sewers. They also serve as a form of beautification, as they are much more aesthetically appealing than standard drainage systems; they create a more natural appearance in an otherwise extremely urban landscape. Bioswales use vegetation and plants at ground level, allowing the soil to absorb stormwater. They can assimilate local and native plants specific to an area, leading to a potential home for wildlife.

Smaller green infrastructure helps with water quality as they are cost-effective and clean soil and water of potentially dangerous contaminants. This process is called phytoremediation, and it involves filtration, extraction, stabilization, and stimulation, with plants serving as a filter for contaminants such as lead, aluminum, and arsenic. With the right soil and plants, these seemingly “small” projects can have a large cumulative impact.

These are just a few examples of the many possibilities green infrastructure presents. Each of these brings different benefits and aesthetics, helping to improve water quality. These limit stormwater runoff that could potentially affect drinking water or water that is a habitat to wildlife. While gray infrastructure allows runoff to flow freely, green infrastructure prevents runoff and thereby improves our water quality.

Working with water quality and green infrastructure

Here at Watearth, water resources are our bread and butter. We are extremely passionate about improving water quality through the use of green infrastructure. Watearth takes on numerous projects every year that focus on stormwater management and control.

In the Houston, Texas area Watearth worked with the Harris County Flood Control District (HCFCD) on their Green Infrastructure Stormwater Control Measure Backslope Swale Stream Stability Retrofit of Flood Control Channel project. This project included retrofitting and restoring native vegetation in the riparian portion of urban flood control channels. Watearth evaluated hydrology and water quality improvements using GI retrofits. EPA Storm Water Management Model (SWMM) Low Impact Development (LID) models were developed to evaluate the effectiveness of modifying a backslope drainage system to be considered an Integrated Management Practice (IMP) that meets green infrastructure criteria and enhances surface water runoff.

Watearth also worked with the Los Angeles County Public Works (LACPW) on the Adventure Park Regional Stormwater Capture and Integrated Water Resources project. Watearth took on numerous roles for this project, including designing a rain garden. Also known as a Biofiltration area, the rain garden features plants that thrive in dry and wet climate conditions, and it serves as a filtration system for Adventure Park’s surface runoff. The rain garden collects and filters park pollutants such as chemicals, oils, and debris. This was intentionally designed and constructed in an area of the park to capture as much runoff as possible.

If you would like to learn more about Watearth and our services, please visit our website. We are happy to discuss your stormwater and green infrastructure project needs.

CEQA Initial Study Outcomes: What you need to know

CEQA – or the California Environmental Quality Act – was passed in the State Congress and signed into law by then-Governor Ronald Regan in 1970. CEQA was a direct response to the federal government passing the National Environmental Policy Act (NEPA) some months prior. These policies both exist to ensure environmental protection.

CEQA requires state and local governments to inform the public about environmental impacts of proposed projects, and to try and reduce these impacts when possible. It’s important to understand how CEQA works, as well as the benefits of this act.

What is a negative declaration?

If a project is believed to not cause any detrimental impacts to the environment, a negative declaration (ND) can be declared. It can only be stated after filling out the CEQA checklist (which includes topics such as aesthetics, agricultural research, and air quality) and acknowledging there will not be significant environmental harm. An ND is issued after the initial study (IS) has been prepared and is a “positive” project outcome.

The opposite of a “positive” project outcome is a “significant adverse impact” outcome, meaning considerable environmental damage is possible if the project is approved. Land, water, air, wildlife, mineral resources, and cultural resources could be at great risk, and should be avoided if possible.

Once a project is approved with a ND, a Notice of Determination (NOD) is filed at the county clerk’s office saying the project does not have a significant impact on the environment in which the project is taking place.

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What is a mitigated negative declaration?

A mitigation measure is required to reduce or eliminate environmental damage caused from building by a project. An example is if a development caused tree removal, then a requirement could be to redesign the project to save more trees and strategize how to replace any trees that could not be saved. A mitigated monitoring and reporting program (MMRP) is required by California law and ensures mitigation measures are properly carried out and environmental damage will be prevented or lessened.

If a significant impact is identified that cannot be mitigated, an Environmental Impact Report (EIR) is required. Significant impact is defined as a substantial adverse change in the location’s physical conditions. If you must prepare an EIR, it goes to the lead agency and then to public review (generally within a month). Next, the lead agency will prepare a final EIR including a response to comments provided during the public review. Finally, the lead agency responds to public agencies within a minimum of 10 days before the EIR is certified.

CEQA is important—it helps prevent potentially significant damage to the environment, while also allowing communities affected by projects to have a voice in decisions. It also enables stakeholders to take a big-picture view of the project.

Watearth and CEQA

Here at Watearth, we frequently work with CEQA, have staff that specialize in CEQA, and have successfully completed numerous projects involving CEQA.

Our work with the City of Oakland for their Mosswood Community Center CEQA project involved creating the Initial Study (IS) gathered topographic data, and developing a preliminary design recommendation along with other project documents. Additionally, Watearth conducted CEQA analysis and drafted technical memorandums.

We also have significant experience in creating EIRs. In southern California, we worked with the City of Los Angeles Zoo assisting with their Master Plan and Zoo Vision Plan EIR Hydrology and Water Quality Technical Studies. We prepared water resources and sustainability sections of the Master Plan and the EIR. This included NEPA/CEQA and water quality impacts to the Los Angeles River.

Deck overlook surround by vegetation and shallow pool of water
Image from Watearth’s LA Zoo project.

We also worked with the Los Angeles Bureau of Engineering (LABOE) on their Venice Auxiliary Pumping Plant (VAPP) EIR Hydrology and Water Quality Technical Studies project. On this assignment we prepared the water resources sections of EIR for NEPA/CEQA for a 0.5 acre auxiliary pumping plant. This included a detailed HEC-RAS hydraulic analysis from scratch, Hydrology, and water quality.

If you would like to learn more about Watearth and our services, please visit our website. We are happy to discuss your CEQA/NEPA project needs.

The Urban Heat Island Effect

Well over 140 million acres of America’s forests are located in urban areas. While many of us encounter trees within our cities and towns daily without a second thought, perhaps we should consider the implications of a sidewalk or other public space without trees.

As we see significant changes in climate and temperatures rapidly increasing over time – the 10 warmest years on record have all occurred over the last 16 years – planting trees is an effective way to combat these issues and provide a valuable resource: shade. It’s time to start treating trees like infrastructure by providing adequate space for roots and selecting appropriate trees for water use, climate resiliency, shade. Trees should be considered as elements in road right-of-ways, parking lots, and as resources within urban areas.

Shade canopies are particularly necessary in highly developed areas, which are more likely to experience the urban heat island effect. Urban heat islands occur when cities replace natural shade covers with areas that absorb heat, such as pavement, buildings, and asphalt.

Urban heat islands have numerous concerning outcomes, including health issues for those living in the impacted areas, as well as increasing greenhouse gas emissions and energy usage. From heat stroke to increased use of air conditioning and electricity, not prioritizing green solutions will be detrimental to humankind. Looking ahead, we can see the benefits of prioritizing green solutions such as clean air and renewable energy.

example of heat island landscape with sidewalk and wall without shade

Stock image via Pexels.

In recent years, however, cities and constituents have taken a growing interest in climate change solutions, including investments in urban forestry. However, not all forests are created equal, and in many areas lower income persons of color are on their own island.

In Los Angeles, former redlined areas are 7.6% warmer than their wealthier neighbors, who take up the majority of the shade. However, in 2021, LA is looking for a more equitable approach to make improvements in impacted areas. The City of Los Angeles is seeking to plant 90,000 more trees in 2021, with a special emphasis in previously neglected areas; they are hoping to increase their canopy by over 50% in the next seven years.

view of the city of Los Angeles

Stock image of Los Angeles via Pexels.

If Los Angeles and other American cities can remain consistently dedicated to improvements in urban forestry and continue to grow these forests, the results will be immense in the era of global warming. Shaded areas can often be between 20-45F cooler than unshaded areas, leading to less energy consumption. Additionally, health will improve as several environmental factors do. With more trees planted, we will see a massive decrease in greenhouse gas emissions and reduced air pollution. Water quality will also improve as trees infiltrate more groundwater and reduce surface runoff.

Here at Watearth, we are proud to work on projects that make our cities sustainable for the future. We are working with the City of Houston within the communities of Gulfton and Kashmere Gardens to provide planning services on their sidewalks to limit flooding and surface run off. Additionally, in Los Angeles, Watearth has worked with the city in creating an Environmental Impact Report (EIR) for the city sidewalks, specifically addressing tree canopy cover, examining the water quality impacts, and developing mitigation plans. Furthermore, Watearth has worked with the Orange County Transportation Authority (OCTA) looking at ways shade-providing plants can create safer railway stops for people waiting for their ride.

OCTA urban heat island index - October 2020
OCTA urban heat island index – October 2020

If you would like to learn more about Watearth and our services, please visit our website. We are happy to discuss your sustainability or resiliency green infrastructure projects.

If you’d like to learn more about how you can help low canopy areas in Los Angeles, visit the City Plants website.