CASE STUDY

Howard County, MD

Flood Mitigation in Historic Ellicott City, MD and Water Quality Improvements along the Anacostia River

The Challenge

Located in the Chesapeake Bay Watershed, Howard County’s MS4permit places stringent requirements on municipalities to reducestormwater pollution into local waterways and the Bay. In addition towater quality concerns, the historic community of Ellicott City hasexperienced intense flooding in recent years, prompting urgent actionfrom the County to mitigate flood risk. The County was tasked withtreating stormwater runoff from approximately 2,000 acres ofimpervious surfaces by the end of 2019, and complying with futurestormwater targets in the next cycle of their MS4 permit.

The Solution

As part of the Clean Water Howard initiative, the County implementedOpti technology at two existing stormwater ponds located on bothcommercial and public property. Opti predicts and responds to theweather forecast, enabling the system to maximize storage capacityand retention time in each pond. Opti adaptively controls the outletstructures of the ponds, enabling it to draw down volume ahead of wetweather, mitigate peak flows during storms, and retain water for up totwo days after the storm.

At a Glance

• $14,000 a year in costsavings to landowners
• 4X retention time and waterquality improvement

“We are harnessingtechnology to meetwater quality andquantity goals.”

Lindsay DeMarzo
Stormwater Programs
Manager, Howard County
Government

ECONOMICAL
70% Savings
$15k vs. $50k per acre

RESILIENT
90% Peak Flow Reduction
Average annual performance
‍
PEACE OF MIND
Safety and Compliance
Achieve MS4 and flood
mitigation goals

Results

Opti technology increased wet weathercapture and retention time, mitigating theimpacts of downstream flooding.

In addition to flood mitigation, Opti provided$14,000/yr in cost savings to landownerspaying Watershed Protection Fees, anddelivered an additional 19.4 acres of waterquality credits towards Howard County’s MS4permit.

Based on one year of data, Opti’ adaptivecontrol system outperformed traditionalpassive management by 2.3−3.9X.

Opti delivered 2.3X more stormwater runoff capture and 3.9X moreaverage retention time

Watershed Flood Assessment

After a year of adaptive management at thetwo Ellicott City ponds, Opti performed anassessment for Howard County. MarylandDepartment of Natural Resources (DNR)providing support for the project through theChesapeake Bay Implementation Grant (CBIG),which are EPA funds the DNR administers onbehalf of the State of Maryland. Over 1,400sites were evaluated and ranked based on theirdownstream flood mitigation potential,providing a critical knowledge base forexpanding adaptive stormwater managementon the watershed scale. The top sixhighest-ranked ponds were chosen for furtheranalysis.

Assessment results: Opti adaptive controls reduced flows by asmuch as 76% during modeled 24−hour storm events
Geospatial analysis: GIS was used to integrate floodplain andsite data during the assessment

About OptiRTC

Opti ,an Aliaxis company, is the leading provider of digital adaptive stormwater control solutions.With over 300 deployments to date, Opti empowers customers and partners to address theimpacts of climate change, aging infrastructure, urbanization, and water pollution, enabling themto secure the sustainability of our communities and natural resources Opti’s cloud-basedplatform optimizes stormwater asset performance through instant actionable insights to provideeconomic savings, resilient solutions, and peace of mind. With our commitment to innovation, weare driving a resilient and brighter future for all.