An oceanfront resort complex consisting of hotels, condominiums, a restaurant and pool house had a 50-year-old septic system that was showing signs it had run its course.

David Christiansen of DPM Partners, who manages the property, brought in Gary MacConnell, owner of MacConnell & Associates to engineer a new system for the Sea Ranch Resort. Located on the Outer Banks of North Carolina, in Kill Devil Hills, the tight quarters and proximity to the ocean required a design with low-pressure pipe distribution and TS-II pretreatment, which would allow for a 50% reduction in the drainfield size compared to the existing field. Due to the seasonal nature of the resort, the project team had only six months to design, permit, construct and place into operation the onsite system.

Reducing the footprint while improving the effectiveness was challenging enough. Pair that with installing the new system while keeping the resort up and running and you have exactly what installer Jon Harris, owner of HHLD (dba H&H Land Development) and his crew did.

“It was important with this project to keep as much of the hotel, restaurant, pool house and everything else going, so the whole business wasn’t shut down all at once,” Harris says. “We had to tackle this one in stages.” To make it happen, Harris used pieces of the existing system combined with newly installed tanks and temporary plumbing.

Once all phases of the job were complete, a web of wastewater flow from numerous buildings met in a system that achieved the objective treatment.

Effluent flow

The resort consists of multiple buildings — an oceanfront, two-story hotel with 24 rooms, an oceanfront, five-story structure with 28, two-bedroom condominiums, a non-oceanfront hotel with 26 hotel rooms, a restaurant and a pool house.

Wastewater exiting the five-story, oceanfront condominium first enters a series of four 2,500-gallon precast concrete septic tanks plumbed in a series connected by 6-inch PVC pipe. The tanks are traffic rated with 8-inch walls due to their placement under the resort’s parking lot. At the discharge end of each tank are Polylok PL-525 effluent filters.

Effluent leaving these septic tanks gravity flows to another series of traffic-rated septic tanks also positioned under the parking lot — two 10,000-gallon tanks plumbed in-line, each containing three Polylok PL-525 filters at the exit.

It’s in these tanks that effluent exiting the oceanfront, two-story hotel enters the system and starts treatment. Wastewater leaving the non-oceanfront hotel also enters the system here after passing through an existing 3,000-gallon precast concrete septic tank.

The now-combined wastewater from the hotels and condominiums travels through the 10,000-gallon septic tanks before entering a 10,000-gallon traffic-rated flow equalization tank where it is discharged using a pair of Pentair Myers ME45 effluent pumps. Effluent is pumped through 2-inch PVC into a series of two 10,000-gallon, traffic-rated recirculation tanks.

“The recirculation chambers serve as holding tanks for both the septic tank effluent and E-Z Treat treatment unit effluent,” MacConnell explains.

Inside each recirculation tank are eight Pentair STEP50 effluent pumps that move water from the recirculation tanks to eight E-Z Treat Model 4-L treatment units, where the wastewater undergoes treatment to further remove BOD and suspended solids and before returning to the recirculation tanks.

“An E-Z Treat effluent bypass valve located in the recirculation chambers will separate the flow once the unit is dosed,” MacConnell says. “Effluent will be recirculated through the E-Z Treat treatment units until additional septic tank effluent enters the recirculation tank, causing the bypass valve to close. Then excess effluent flows through the bypass valve to the second recirculation tank or field dosing chamber.”

The field dosing tank is also a 10,000-gallon traffic rated tank. “Effluent from the second recirculation tank is disinfected by ultraviolet light prior to entering the field dosing tank to be irrigated,” MacConnell says. Four E-Z Treat Model UV 404 units are being used. 

Within the dosing tank, two Myers ME3 pumps push water through 1 1/4-inch PVC back in the system flow to the second 10,000-gallon septic tank for further denitrification, while two Pentair STEP30 pumps route water to an EZ-Treat Model 600 calcite treatment unit. This filter provides alkalinity to assist with nitrogen removal. Water that enters the treatment tank gravity drains through 4-inch PVC and reenters the system in the recirculation tanks.

High quality effluent exiting the field dosing tank is moved by means of two Barnes Model 3SE-DS, 3 hp pumps (Crane Pumps & Systems) through a 2-inch force main en route to the drainfield located across the street.

The drainfield is an LPP bed measuring 100 feet by 100 feet. To plumb the 2-inch force main PVC that supplies the drainfield, horizontal directional drilling was needed to bore 5 feet under the existing street. The bed is made up of 2,000 feet of LLP plumbing broken down into 20 100-foot lines dispersed every 5 feet on center. Piping used is 1-1/2-inch PVC plumbed inside 4-inch HDPE perforated pipe installed in a 12-inch-deep bed of washed No. 67 stone.

The entire system, rated for 18,000 gpd, is controlled by a Duplex Demand Dose Control Panel Model 122 by SJE Rhombus.

Separate flows

The resort’s restaurant required its own septic system. Wastewater exiting the kitchen enters an existing 2,000-gallon grease trap before making its way to a newly installed TOPP Industries FB60X120 fiberglass duplex pump station measuring 10 feet deep by 6 feet in diameter.

From the pump station, effluent is transferred using a pair of Myers ME45 effluent pumps into a 3,160-gallon precast concrete, traffic-rated septic tank containing a Model 300 VBT aeration unit from Advanced Aeration to reduce BOD, TSS and FOG. It then flows into a 3,600-gallon traffic-rated pump tank installed directly next to the septic tank.

Effluent is dosed from the pump tank into a separate, LPP gravel bed drainfield approximately 69 feet long by 25 feet wide, located on the property next to the hotel and restaurant.

Equipment

A lot of machinery was brought in for this project, and all but the rented cranes are owned by HHLD. The majority of work was done using the following equipment:

• 2016 LC350 Hitachi excavator
• 2014 Hitachi ZX 135 excavator
• 2005 Takeuchi TB 135 mini-excavator
• 2014 John Deere 650J bulldozer
• 262B CAT skid-steer
• Kubota 6800 tractor

Installation challenges

A lot had to fall into place for the installations to go smoothly, and it did, a credit to the design and project coordination from Christiansen, MacConnell, Harris and E-Z Treat’s Mike Stidham.

“The 10,000-gallon tanks were delivered here from Wieser Concrete in Wisconsin, with one half of each tank per trailer,” Harris says. “In total, 25 trailers came to the site making deliveries from Wisconsin.”

Harris’s crew cut asphalt out of the parking lot before the tanks arrived and organized the rental of a 300- and 120-ton crane for setting the tanks. “Each half of the 10,000-gallon tanks weighed 45,000 pounds,” Harris says. “So we brought in cranes and operators from Rose Crane Service out of Columbia, North Carolina, to move and set them.”

Weight wasn’t the only complication Harris and his crew had to deal with when setting the massive tanks. “We also had to dewater this project,” he says. “Being right here on the ocean, we hit the water table around four feet down and we had to set these tanks 18 feet deep.”

The solution was dewatering, and to do so they used roughly 50 

wellpoints, two 6-inch water pumps and several hundred feet of header pipe. “There was nowhere to discharge water on site at the time either,” Harris says. “We had to bore under the highway with a temporary 6-inch pipe and run the discharge around houses to get to a storm box to dewater this thing.”

The pumps ran for seven days to get the water table to a level where Harris and his crew could install the tanks. They were filled with water immediately as another precaution after installation to avoid flotation.

Utilizing old tanks and plumbing for temporary reroutes to keep the resort running, demolishing old tanks to make room for new ones, heavy tanks, coordination of deliveries, a high water table and a compact site sum up the many challenges the installers and engineer had to work with for this project.

Despite the long list of obstacles, the Sea Ranch Resort’s effluent treatment has a major facelift and is equipped to handle its regular high-volume of guests.