Monday, September 26, 2022

Report: Pender has “inadequate capacity to convey water” to coastal area, over $122 million needed

One of two water tanks supplying the Hampstead area that ran dry over Memorial Day Weekend, when the county's water capacity reached 97 percent. (Port City Daily photo/Mark Darrough)
One of two water tanks supplying the Hampstead area that ran dry over Memorial Day Weekend, when the county’s water capacity reached 97 percent. (Port City Daily photo/Mark Darrough)

PENDER COUNTY — A study commissioned by county commissioners found the county’s water system has “inadequate capacity to convey water” to the densely populated coastal corridor surrounding Highway 17, where a vast majority of new development is taking place.

Calling for critical upgrades “to provide uninterrupted drinking water to customers,” the study proposed alternative improvements ranging from $122.6 million to $198.9 million in capital costs, and annual operating expenses ranging from $1.5 to $4.4 million. One option is to build a new pipeline to supply two tanks in the Hampstead area, while the recommended option is to build a new groundwater treatment plant in Hampstead.

RELATED: Pender could double water capacity, ease regional water issues with two additional plant operators

The water transmission system between the water treatment plant near the county’s southwestern border and the coast “has become limited in capacity to support future growth,” according to the report. Significant growth is projected for areas served by Pender County Utilities (PCU).

“By the near-term (2025), the water demand within PCU’s water and sewer districts is anticipated to double,” according to the report. “By the long-term (2040), the water demand … is projected to be approximately 4 times the existing demand, with an additional 1.0 mgd projected as bulk water sales to the Town of Topsail Beach. To support this growth, particularly in the eastern portions of the system, additional transmission mains, pumping, storage facilities, and water supply are needed.”

The system’s maximum daily demands (MDDs) was measured at 2.16 million gallons per day (mgd) — well over the water treatment plant’s capacity of 2 mgd and consistent with the “operational difficulties experienced during recent maximum day demand conditions,” according to the report.

Drought conditions over the summer caused a water shortage affecting residents of the Hampstead area for more than 50 days, a period in which mandatory water restrictions were placed on one-fifth of the county’s residents who use county water. Both tanks supplying the area ran dry over Memorial Day weekend.

County commissioners earmarked $169,000 in July for Raleigh-based engineering firm CDM Smith to conduct the study, which finalized its findings in mid-December.

A CDM Smith report shows existing and future water demands in four Pender County water and sewer districts, comparing average day demands (ADD) to maximum day demands (MDD). The company projects a doubling of water demands by 2025. (Port City Daily/Courtesy Pender County)

Recommendation: New water tank

Out of five alternative scenarios, CDM Smith recommended the construction of a new reverse osmosis groundwater treatment plant in the Hampstead area to be fully owned and operated by PCU.

The plant would be built near Topsail High School and would have a 3-mgd capacity, expandable to 5 mgd by 2040. The $122.6-million option also includes an expansion of the current water treatment plant from 2 mgd to 6 mgd, new pipes built parallel to existing pipes from the west to Rocky Point, and new elevated tanks in both Rocky Point and Scotts Hill.

All scenarios include a fee to Brunswick County for planned raw water pipeline upgrades that would double capacity of regional supplier Lower Cape Fear Water & Sewer Authority. PCU’s portion of the $40-million project was agreed at 12 percent, or $5 million.

"Alternative 2" calls for a new groundwater treatment plant in Hampstead, new tanks in Rocky Point and Scotts Hill, new parallel pipes coming from western portions of the county, and upgrading capacity at the current water treatment plant (WTP) from 2 mgd to 6 mgd. (Port City Daily/Courtesy CDM Smith)
“Alternative 2” calls for a new groundwater treatment plant in Hampstead, new tanks in Rocky Point and Scotts Hill, new parallel pipes coming from western portions of the county, and upgrading capacity at the current water treatment plant (WTP) from 2 mgd to 6 mgd. (Port City Daily/Courtesy CDM Smith)

The additional water source would improve the reliability of PCU’s water system while giving the county the ability to recover costs in roughly 16 to 20 years after the new plant is put into operation, according to the report.

“Although upfront costs are substantial, this alternative provides PCU full control of water quality, production and distribution and eliminates additional stakeholder coordination when making decisions,” the report states. “This option also allows better rate structure control.”

“Critical upgrades are required”

CDM Smith also recommends interconnections with the town of Topsail Beach, located on the southern end of Topsail Island, and New Hanover supplier Cape Fear Public Utility Authority (CFPUA).

A pipeline would be built beneath the Intracoastal Waterway to Topsail Beach, allowing PCU to provide up to 1 mgd of water for purchase by 2030. The firm also recommended the construction of a new pump station to receive water from CFPUA during high-usage demand periods, although the report states that the new plant, tanks, and pipelines make such an interconnection less urgent.

The study was conducted using hydraulic modeling based on flow tests at strategic locations in the system, where tank levels, pump flow, and pump discharge pressure data was recorded during each flow.

The model found that the system meets minimum pressure and velocity requirements during average conditions, but during peak summer demand, a significant amount of pressure loss exists between the Malpass tank in the west and the Rocky Point tank in central Pender County. This essentially creates a bottleneck as the water flows eastward.

“Under existing maximum day demands (MDD), the system has inadequate capacity to convey water to the eastern portions of the service area,” the report concluded. “Storage tanks empty and minimum pressures cannot be maintained in the distribution system … Due to these limitations, critical upgrades are required to provide uninterrupted drinking water to customers.”

The report will be discussed at Monday night’s monthly commissioner meeting and examined in more detail during an early March retreat of county leaders.

Five competing alternatives

All five scenarios outlined by CDM Smith are found below. Each calls for various pipeline improvements, the expansion of the existing water treatment plant (WTP) to at least 6 mgd, and a new 700,000-gallon tank in Rocky Point and a new 300,000-gallon tank in Scotts Hill.

ALTERNATIVE 1: Surface water supply from Pender County Water Treatment Plant (WTP) only; transmission along Hwy. 210 routing.

  • New parallel pipeline routes from the WTP to Highway 17 follow existing alignments
  • New Highway 210 booster pump station
  • Expand the existing WTP capacity from 2 mgd to 10 mgd 
  • Install a new 700,000-gallon elevated storage tank (EST) in Rocky Point
  • Install a new 300,000-gallon EST in Scotts Hill 

ALTERNATIVE 1A: Surface water supply from Pender County WTP only; alternative transmission routing through New Hanover County. 

  • New pipeline alignment running south from existing WTP along Highway 17, following I-140 corridor to Scotts Hill
  • Other parallel pipeline improvements following existing alignments
  • Expand the existing WTP capacity from 2 mgd to 10 mgd
  • Install a new 700,000-gallon EST in Rocky Point
  • Install a new 300,000-gallon EST in Scotts Hill

ALTERNATIVE 1B: Surface water supply from Pender County WTP only; alternative transmission routing from Hwy. 421 to Hwy. 210.

  • New pipeline alignment between Hwy. 421 to Hwy. 210; additional pipeline improvements along Hwy. 210 to Hwy. 17 following existing alignments
  • New Highway 210 booster pump station
  • Expand the existing WTP capacity from 2 mgd to 10 mgd
  • Install a new 700,000-gallon EST in Rocky Point
  • Install a new 300,000-gallon EST in Scotts Hill

ALTERNATIVE 2: New PCU-owned reverse osmosis (RO) groundwater WTP  (recommended option)

  • New reverse osmosis WTP in the Hampstead area (PCU-owned and operated; 3 mgd initial capacity expandable to 5 mgd by 2040)
  • Miscellaneous pipeline improvements 
  • Expand the existing WTP capacity from 2 mgd to 6 mgd
  • Install a new 700,000-gallon EST in Rocky Point
  • Install a new 300,000-gallon EST in Scotts Hill 
A conceptual map of a new groundwater treatment plant in Hampstead adjacent to Topsail High School and the future Hampstead Bypass northern bypass. (Port City Daily/Courtesy Pender County)

ALTERNATIVE 2A: New privately-owned RO groundwater WTP 

  • New reverse osmosis WTP in the Hampstead area designed, built and operated by a private water company (PCU would purchase water from the private water company; 3 mgd initial capacity with 5 mgd provided by 2040)
  • Miscellaneous pipeline improvements 
  • Expand the existing WTP capacity from 2 mgd to 6 mgd 
  • Install a new 700,000-gallon EST in Rocky Point
  • Install a new 300,000-gallon EST in Scotts Hill

Read the full report below:

CDM Smith Study – Eastern Pender Water System Improvements

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