Osborn, Bridget, Osborn

Bridget works as a Water Resource Engineer at HR Green offering experience in hydrologic and hydraulic modeling, storm sewer system analysis and best...

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About Osborn, Bridget

Bridget works as a Water Resource Engineer at HR Green offering experience in hydrologic and hydraulic modeling, storm sewer system analysis and best management practice (BMP) design, as well as flooding mitigation. Using her communication and coordination skills, she has managed and completed projects and permits with multiple clients and agencies. Throughout the years, she has earned numerous awards for her project leadership and technical expertise such as the 2016 ACEC Young Professional of the Year Award.

Osborn, Bridget

Titles from this speaker

Improving Wilmes Lake, One Dose at a Time

Abstract

Wilmes Lake is a 30-acre shallow lake within the South Washington Watershed District (SWWD), located on the east side of the Minneapolis/St. Paul metro area in Minnesota. With a rapidly developing suburban watershed of over 3,200 acres, Wilmes Lake suffers from excessive nutrient loading and routinely exhibits annual total phosphorus concentrations of 0.06 to 0.09 mg/L, Wilmes Lake has been listed on the Minnesota Section 303(d) impaired waters list since 2006. SWWD has established an annual total phosphorus reduction goal of 153 pounds for Wilmes Lake as it attempts to make substantive water quality and clarity improvements. Several small stormwater management projects have been constructed in partnership with the City of Woodbury (MN) and modest in-lake phosphorus reductions have been observed in recent years. SWWD completed a regional Best Management Practice (BMP) feasibility study in 2019 (Hinds, 2019) which identified a stormwater treatment facility with in-line chemical dosing as the most cost-effective and impactful option to reduce phosphorus loads to Wilmes Lake. HR Green joined SWWD's team in 2020 to complete an alternatives assessment (HR Green, 2020) to determine the preferred chemical dosing and concept design for the stormwater treatment facility within an adjacent city park. This presentation will focus on the processes behind the alternatives assessment, key features of the design, a unique SWWD/City partnership, expected outcomes, cost effectiveness, as well as construction and permitting hurdles. Using SWWD's water quality and flow data for Wilmes Lake, information from a similar local treatment facility (Pilgrim, 2005), a survey of park features and input from SWWD and City staff, HR Green developed a facility concept that pumps water from the primary influent channel of Wilmes Lake to the chemical dosing station. The team reviewed the use of both aluminum sulfate (alum) and ferric chloride for phosphorus reduction treatment. Alum was chosen based on reduced corrosion potential and operation and maintenance needs. The potential introduction of additional chloride residue was another unique concern in our northern climate where road salt use in the winter already threatens lakes, streams and groundwater supplies. The proposed facility consists of a lift station, force main, chemical treatment building and settling basin. Once alum is mixed into the stormwater, the resulting flocculent settles out in a constructed basin before treated (clean) stormwater drains to the lake. With treatment flows of one to three cubic feet per second (cfs) during open water seasons, the facility is expected to remove between 95 and 283 pounds of phosphorus per year in addition to other associated pollutants, achieving SWWD's overall phosphorus reduction goal for Wilmes Lake. Construction of this project required approximately $4.5 million in capital funding, which was solely provided by SWWD. This is reflective of both the project's importance to the watershed district and its expected impact. SWWD has entered into an agreement with the City of Woodbury whereby the City's experienced public works staff will operate and maintain the facility. SWWD has budgeted approximately $180,000 per year to fund facility operation (staff, chemical, electricity, maintenance, etc.). Over an initial 25-year expected life span, the project is conservatively expected to achieve a cost/benefit ratio of $1,900/lb P/year, which is favorable compared to other types of stormwater BMPs in Minnesota's northern environment. For a system like this, expected operation and maintenance activities include refilling alum storage tanks, removing flocculent solids from the settling basin, removing accumulated sediment at the lift station sumps, maintaining chemical feed hoses, pumps, and electronics, and conducting routine sampling activities. HR Green reviewed the operations and maintenance plan with SWWD and the City during design to manage expectations and costs associated with the facility. Collaborative conversations empowered the project team to design and specify system components that improved the accessibility, feasibility and ease of operation and maintenance protocols for City staff. This also results in reduced O&M cost to SWWD over time. Construction began in the summer of 2023 and is expected to be complete in the summer of 2024. While many conversations and considerations were addressed during preliminary design, there are always lessons learned on every project. The presenters will share what worked well and what might be done differently next time. Some examples include the coordination on funding, operations and maintenance, and data security as well as considering costs for aesthetics and other site features.

SWWD set out to implement a regional project to improve water quality in Wilmes Lake beginning with an alternatives analysis that focused on alum treatment. Final design resulted in a facility that will treat both base flow conditions and moderate stormwater runoff volumes removing 95 to 283 pounds of phosphorus annually. With a lifetime cost/benefit ratio of approximately $1,900 per pound of phosphorus removed, this project represents a good value compared to other BMPs employed in Minnesota.

SpeakerAxtell, Kyle

Presentation time

16:30:00

17:00:00

Session time

15:30:00

17:00:00

SessionAdvancements in Nutrient Removal: Insights from Urban Watersheds

Session number428

Session locationRoom 344

TopicAdvanced Level, Stormwater and Green Infrastructure, Watershed Management, Water Quality, and Groundwater

Author(s)

Axtell, Kyle, Osborn, Bridget

Author(s)K. Axtell1, B. Osborn2

Author affiliation(s)1South Washington Watershed District, MN, 2HR Green, Inc., MN

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date Oct 2024

DOI10.2175/193864718825159574

Volume / Issue

Content sourceWEFTEC

Word count9

Working Toward A Common Goal To Help The Mighty Mississippi

Abstract

Background:
In May 2003, South Washington Watershed District (SWWD) consolidated with the East Mississippi Watershed Management Organization and assumed taxing authority for stormwater management for the communities of Newport, St. Paul Park, and Grey Cloud Island, Minnesota. The three communities are located in shallow bedrock along the Mississippi River with bluff and floodplain topography that contributes approximately 10 square miles of runoff to the river. In this area, the Mississippi is impaired for total suspended solids (TSS) and has an approved Total Maximum Daily Load (TMDL) by the Minnesota Pollution Control Agency (MPCA). Taking a programmatic approach, SWWD began planning for the area by first assessing existing conditions. They completed WINSLAMM models to assess water quality and completed a Subwatershed Retrofit Analysis for Newport and are in the process of completing a Subwatershed Assessment in St. Paul Park to identify locations and types of best management practices (BMPs) to primarily reduce the amount of TSS entering the river. They also worked with engineering consultant HR Green to obtain data for the existing storm sewer systems and create 2D XPSWMM models for each city. During this process, SWWD and HR Green met with City staff members to explain the planning and implementation strategy to spend collected tax dollars for each community. This not only helped with stakeholder buy-in early on, but it also helped identify any drainage problem areas and potential retrofit locations. Newport and St. Paul Park are MS4 cities, so these retrofits also supplement their stormwater management efforts.
Methodology: SWWD completed subwatershed assessments for each catchment area within the East Mississippi Watershed to determine potential stormwater treatment locations to reduce TSS loading. They ranked priority projects based on the cost benefit analysis of each retrofit based on pollutant removals and practice type. As they go down the priority list, SWWD and HR Green meet on site with the communities to review feasibility of these projects and cost share responsibilities. SWWD covers the design and installation costs, and the city provides the available property and helps with regular maintenance. SWWD and HR Green use the retrofit analysis as a guide to complete an alternatives assessment for each location. They look at the location of the nearby storm sewer trunklines and amount of flow expected for the treatment source, as well as nearby utilities. With bedrock anywhere from zero to five feet below the surface, infiltration practices aren't feasible; therefore, they typically look at a compact proprietary device that meets the treatment goals for the contributing area. Cost of bedrock excavation, effectiveness of nutrient removal and maintenance feasibility using city resources typically drive the decision on which device is installed. Once a device is agreed upon, it is designed and constructed. The goal with these devices is to establish a regular maintenance schedule to ensure the consistent sediment capture prior to discharging to the river. To do that, SWWD and the communities need to understand what activities are needed and how often they are needed. In the beginning, this requires more frequent monitoring and has a steeper learning curve. These discussions are a top priority for these projects. While planning for the continuous installation of these projects, SWWD uses this opportunity to provide treatment for nearby projects that could not meet permitting requirements due to site limitations. For example, a Spanish immersion school in St. Paul Park was renovating an existing building and could not meet the total phosphorus (TP) treatment requirements of the stormwater construction permit. SWWD worked with the school to instead restore a portion of the unused greenspace onsite to a native prairie. With the already established relationships, they were then able to coordinate with the City to install storm sewer stub outs along the trunkline of the nearby street that was being reconstructed to allow for a water quality device to make up for the lost treatment. Without the relationships and planning efforts of SWWD, water quality treatment in that area would have been much more costly.
Status: To date, SWWD has installed one treatment device in Newport and one in St. Paul Park. The device in Newport was constructed in spring of 2020 and has already gone through one maintenance cycle. It is proving to be very effective at TSS removal, and has many lessons learned for the next maintenance period. The device in St. Paul Park was installed in fall of 2021 and will require a bit more maintenance. The internal filters to remove TP will require more effort than what the City can provide, but the City will vacuum out the pretreatment device on a regular basis. Another alternatives assessment is in the works for two more locations in Newport, and design on one of them will start in early 2022.
Significance: Like any common goal, all stakeholders involved need to be onboard, and a plan needs to be formulated in order to see actions with measurable outcomes. SWWD, Newport and St. Paul Park have been working together to help lessen the load on the Mississippi, and their collaboration will help ensure it continues. Teamwork makes the dream work.

South Washington Watershed District (SWWD) completed subwatershed assessments to determine potential stormwater treatment locations to reduce nutrient loading on the Mississippi River. A cost benefit analysis ranked priority projects based on pollutant removals, practice type and projected 20-year costs. Once the retrofits were prioritized, SWWD met with the cities within the watershed to discuss preferred types and locations based on physical and financial constraints.

SpeakerOsborn, Bridget

Presentation time

11:25:00

11:40:00

Session time

10:30:00

12:00:00

TopicIntermediate Level, Nutrients, Watershed Management, Water Quality, and Groundwater

Author(s)

Osborn, Bridget

Author(s)Bridget Osborn1; Tony Randazzo2

Author affiliation(s)HR Green, Inc., St. Paul, MN1; South Washington Watershed District, Woodbury, MN2