Creative Approach Solves Sewer Extension Problem

Queen Anne’s County is using a different approach to wastewater collections to better serve rural residents and protect the Chesapeake Bay.
Creative Approach Solves Sewer Extension Problem
A crew from Schummer Inc. digs a trench to grade for a new wastewater line on Kent Island. Residential STEP systems will feed into the line.

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Sometimes collections systems are simple: Bury some pipe and let gravity do the work. Sometimes, it takes a more creative approach.

The Department of Public Works of Queen Anne’s County, Maryland, is committed to providing safe and efficient wastewater services to residents in unincorporated areas. Bringing sewer service to just 1,500 isolated homes experiencing septic system failure on South Kent Island has been a longtime goal. By combining an efficient septic tank effluent pumping system with a new county ordinance for property owners, the DPW expects to have the problem licked as early as 2025.

The DPW’s service area is on the Delmarva Peninsula and straddles Kent Island, the largest island in the Chesapeake Bay. Untreated wastewater can quickly enter the ecologically sensitive waters of Chesapeake and Eastern bays, so it’s a major focus of the department’s energy.

“The South Kent Island (SKI) sewer extension project has been on the books since the mid-1970s,” says Todd Mohn, P.E., director of the county’s DPW. “But now it’s full speed ahead.”

A newer system

The county’s 128-mile sewer system was built in 1981, one of many of the federal government’s Clean Water Act initiatives. Wastewater is primarily transported by vacuum sewer to overcome flat topography and high water tables, and the sewer network was once the largest vacuum system in the country.  

Pipes are made of PVC with a little ductile iron and HDPE. They range in diameter from 3 inches on the vacuum side to 24 inches on transmission force mains.

“It’s a relatively young system and its condition is very good,” says Mohn. “The area soil is quite corrosive, so when we do have leaks it’s in the ductile iron pipe, which we replace with HDPE or PVC. Our biggest challenge is I&I drawn into the vacuum system through damaged gravity-fed service laterals and broken clean-outs. That can make the system sluggish.”

In-house crews perform most repairs and small construction projects. A high groundwater table means trenching is difficult, so pipes are located close to the surface. Full replacement is often cheaper than trenchless rehabilitation, but horizontal directional drilling is used to cross roads and streams.

The vacuum system is self-scouring, so cleaning and maintenance is primarily relegated to valve pits and other accessible infrastructure. The department owns two vacuum trucks (International chassis with Transway Systems vacuum equipment) and a Vivax-Metrotech vCam-5 camera system.

Across the bridge

The SKI project has its roots in the construction of the Chesapeake Bay Bridge in 1952, which connected rural eastern and urban western shores. “We saw new subdivisions with houses on small lots and a lot of land speculation on the island. The county didn’t even have a zoning ordinance during this time, all you had to do is record a plat in the land records and start selling lots,” Mohn says. “New residents relied on septic tanks.”

Failing septic systems were recognized as a problem by the mid-1970s. The county’s original Kent Narrows/Stevensville/Grasonville (KNSG) wastewater treatment plant was completed in 1981, utilizing rotating biological contactor technology to serve the affected communities along Route 50. The plant was replaced and expanded with an enhanced nutrient removal technology in 2007 as part of the Chesapeake Bay cleanup initiative.

Failing septic systems in the communities of Cloverfields and Bay City, also on Kent Island, were eliminated when vacuum sewer service was extended in the mid-1990s.

A County Health Department sanitary survey conducted in 1995 confirmed that 80 percent of remaining septic systems on the island discharged directly into groundwater — a condition meeting the regulatory definition of a failure. However, officials faced three major challenges in fixing the problem — a lack of treatment capacity, finding the appropriate technology to convey wastewater, and a host of vacant lots, potentially doubling the island’s population.

The treatment capacity problem was addressed in 2004, when the county commissioners reserved 500,000 gallons of sewer treatment capacity from the pending expansion at the KNSG treatment plant. Selecting the right collection technology was the next hill to climb.

Choosing a system

The DPW considered a vacuum system, but concerns over cost and I&I on private property ruled out that approach.

“We also looked at a pressurized system with grinder pumps,” Mohn says. “But that would have required the extra cost of intermediate pumping stations.”

Working with consultant H50 Solutions, of Roseberg, Oregon, the county developed a proof-of-concept design using a septic tank effluent pumping (STEP) system as manufactured by Orenco Inc.

“We traveled to Oregon and Washington where these systems have been used successfully for 20 years,” Mohn says. “Operators said the system was easy to operate and maintain. It’s simple technology, essentially a waterline in reverse.”

The Queen Anne’s County system includes a 1,500-gallon seamless two-compartment concrete tank located in the yard of each homeowner. Wastewater drains into the tank by gravity. A baffle allows solids to settle in the larger compartment of the tank, and liquid to spill into a pump chamber. Individual filtered electric pumps switch on when necessary to transport liquid effluent to the collection lines and main trunk, then on to the treatment plant.

“The STEP high-head well pumps drive enough pressure to convey the liquid portion of the wastewater all the way to the treatment plant without the use of intermediate pump stations,” Mohn says. “If a pump goes out, only that one homeowner is inconvenienced. The pumps last a minimum of 20 years and cost about $500 apiece, so they’re relatively cheap to switch out.”

Audible alarms will sound if the system fails or if a float reaches a high-level mark. At that point, DPW crews are dispatched to repair the system and pump out the tank. Mohn says a typical tank would need to be pumped out an average of every five to seven years using a standard vacuum truck.

Expensive lots

Limiting the number of installations was essential to getting the project built.

“Infill was the gorilla in the room,” Mohn says. “Our objective was to provide a permanent solution and correct the environmental problems created by the existing homes affordably. We had 1,500 houses in the proposed service area, but 1,600 additional infill vacant lots could build with a sewer extension. We were constrained by a state law that required a new sewer system to connect to all properties, even vacant lots, if the collections system passed in front of the vacant lot. We weren’t ready to extend sewer lines down streets that existed only on paper, so these larger blocks of vacant lots were strategically excluded from the defined service area.”

Many infill lots were as small as 5,000 square feet. In 2013, the county drafted an ordinance that required adjacent lots under common ownership to be merged. This provided a means to achieve current land use and zoning regulations and limit new infill development. The county assumed the costs of lot mergers under a streamlined legal process.

“The limited service area boundaries and merger ordinance eliminated 1,000 lots,” Mohn says. “That number allowed us to move forward on the project.”

The project didn’t initially qualify for Maryland’s State Bay Restoration Fund, which pro-hibited funding for projects outside of identified priority zones. County representatives went straight to the General Assembly of Maryland to convince representatives to change the law and succeeded in obtaining a $15 million grant.

“We became the poster child for the new law,” Mohn says. “With state funding, we were able to offer the system to existing resident homeowners at less than $100 per month over a 20-year term.”    

Another funding provision the county used was the Economic Benefit Premium. This policy applied to vacant lots that became buildable with the extension of a public sewer collections system. The county completed an appraisal study that concluded a vacant unbuildable lot became significantly more valuable than a developed lot with a septic system when public sewer was provided. This provided the option of assessing an additional EBP fee to vacant lots in the service area, which also helped keep the cost lower for current homeowners.

Construction begins

Construction is proceeding in four overlapping phases on a geographic basis, grouping small population centers:

  • Phase 1: Kent Island Estates 1 Romancoke on the Bay, from 2016 to 2021
  • Phase 2: Tower Gardens, from 2019 to 2023
  • Phase 3: Queen Anne’s Colony & Kentmorr, from 2020 to 2024
  • Phase 4: Chesapeake Estates, Sunny Isle of Kent, Normans & Matapeake Estates, from 2021 to 2025

“Construction contracts for Phase I were awarded in August 2016, and the first homes should be going live by the summer of next year,” Mohn says. “Once complete in 2025, the project will meet 33 percent of our goal under the Chesapeake Bay Watershed Implementation Plan, reducing our yearly nitrogen discharge by 17,300 pounds. That may allow our wastewater treatment plant to be rerated for additional flow. The entire project is a great achievement for us and for the Chesapeake Bay ecosystem.”

Drone rangers

Todd Mohn recently sought the shade of a tree and heard a buzzing above his head.
“I thought it might be bees,” he says.

“But 10 feet above my head, I saw our drone.”

Mohn is director of the Department of Public Works in Queen Anne’s County, Maryland. The department likes to stay on top of current technology, but this latest purchase — a pair of camera-equipped drones — has put the technology on top of the county.

The drones were purchased from Aerial Media Pros for joint use by the county’s IT department and QACTV, the county’s public video network. Aviation Company ASEC Inc. provided operator training and helped to establish the county’s drone program.

The Federal Aviation Administration once required organizations operating a drone to keep a licensed pilot on staff, but regulations passed in summer 2016 relaxed those requirements and allowed staff to operate a drone after obtaining a Remote Pilot Certificate with a Small Unmanned Aircraft Systems (sUAS) endorsement.

Two GIS staff members have completed drone certification and typically fly the units 30 to 40 feet above the ground while collecting information that’s incorporated into the county’s digital asset maps using ArcGIS by Esri. Cloud-based software, Drone Deploy, is used for flight control and imagery processing.  

“We’ve had drones for about a half-year, but they’ve already proved very useful, particularly on our South Kent Island sewer expansion project,” Mohn says. “We’ve used them for surveying and mapping and to get photographic records of as-builts and open trenches. We’ve also used them to locate and map division valves, collection points, valve pits and fire hydrants. We’re incorporating all of this into our GIS system.”

Aerial photography is not only valuable to the DPW — photos are also used to keep residents informed of key construction milestones. For example, recent photos
of directional drilling on the SKI project were uploaded to Facebook.

“Everyone’s eager to think of new uses for the technology,” Mohn says.


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