When 10 deer recently got stuck in steep wastewater storage ponds at the Napa Resort Improvement District Wastewater Treatment Facility near Lake Berryessa in Napa County, Calif., engineers and contractors had to act quickly and adjust current upgrade plans to construct a wildlife safety barrier. 

“The deer were most likely seeking shelter from the cooler temperatures during the evening,” says Kevin Berryhill, Water Resources engineering manager for the Napa Berryessa Resort Improvement District, which operates the facility. “They were stranded at the bottom of the ponds because of the steepness of the slopes coupled with the slickness of the liner.” 

Animal control officers were brought in to free the deer. The district has since put deer fences around the four wastewater ponds to prevent future incidents. 

The wastewater treatment plant is a ready-to-operate microBLOX membrane bioreactor system from OVIVO that processes 30,000 mgd. The district provides water and wastewater services to about 1,100 people in a small residential community and resort located on land owned by the U.S. Bureau of Reclamation. 

Proper fencing was not in place around the ponds because the ponds were under construction as part of a facility upgrade mandated by a cease and desist order by the California Central Valley Regional Water Quality Control Board as a result of treated wastewater discharges during storm events. 

“The watershed is a no discharge basin and the waste discharge requirements prohibit the district from discharging treated wastewater to the disposal sprayfields when it is raining or when the sprayfield is saturated,” Berryhill explains. “The violations are primarily due to insufficient storage capacity of the wastewater facilities. Before we started construction, the district had 1.2 million gallons of wastewater storage capacity. Once the ponds are completed, we will have 20.4 million gallons of storage capacity. 

“When the district was originally formed in the 1960s, it was intended to be a seasonal resort with limited winter residents, but today the subdivision consists of year-around residents. The new wastewater storage ponds are sized for the ultimate build-out of the subdivision as well as the connection to the resort. ” 

The district was under a strict schedule to complete the ponds in compliance with the CDO, and failure to meet the deadline could have resulted in fines totaling $10,000 per day. 

Berryhill says the construction of such large wastewater storage facilities in a remote area with steep slopes make the situation unique. Immediately after the deer were discovered and rescued, the district used deer repellent around the ponds to deter any more deer until the fencing was completed. 

“Had we anticipated the unintended hazard to wildlife and weren’t under a strict deadline for completion, we may have been able to schedule the phasing of the construction to install the deer fencing as each pond was completed, but we did not have that option due to the mandated deadlines,” Berryhill says. 

The 7.5-foot fencing has been successfully installed around all four ponds to prevent future dangers to wildlife. 

“Total cost for fence construction was around $65,000, which includes all the swing gates necessary for access and operation of the ponds and surrounding areas,” Berryhill says. “That was not part of the original budget and scope of work, but we have been able to reduce costs in other areas of the project to be able to install the deer fence to address the unintended hazard to wildlife safety.”