Northwest Regional Wastewater System

History

The Northwest (NW) wastewater collection system serves the communities of N Lakeport, Upper Lake, Nice, Lucerne, Kono Tayee, and Paradise Valley. Many portions of the collection system were constructed 25 to 30 years ago when construction standards and materials were not as comprehensive as they are today. Due to the age of the collection system, the close proximity to the lake, and seasonal high lake levels, Inflow and Infiltration (I/I) are common and contribute to a large percentage of winter flows.

The high seasonal flows force lift stations to operate for extended periods of time and almost continuously during multi-day storm events. During these same periods, the District frequently hires emergency pumper trucks and crews to avoid or minimize reportable spills in compliance with regulatory requirements. Treated wastewater is recycled at the Geysers steam field for electricity production.

Customer Statistics & Infrastructure

The Northwest Regional Wastewater Collection and Treatment System currently include:

• 4,088 Connections (5,602 Single Family Dwelling (SFD) equivalents).
• In 2001, the NW started accepting flows from the City of Lakeport. The City of Lakeport can send up to 800 Residential Unit Equivalents (RUEs) to the NW System.
• Over fifteen hundred manholes and 90 miles of pipe within the gravity collection system.
• 23 lift stations and over 15 miles of force main piping conveying wastewater to the NW Treatment Plant.
• 20 miles of 16-inch force main and two pump stations for the geysers recycled Water Pipeline

Status

Many areas within the collection system were originally constructed 30 years ago for much smaller communities and typically before substantial development occurred. Several sections of the collection system within several Nice/Lucerne hillside neighborhoods have been cut off from access for routine collection system maintenance and cleaning by development. Expansion and growth have also resulted in capacity challenges (both collection and pumping) in several key locations within the NW system. We've focused on source control. I/I reduction, and line cleaning. Comprehensive smoke testing and point repairs in the Upper Lake area have been completed recently.

Outlook

The District continues to implement aggressive I/I mitigation and Hydraulic Modeling for evaluating structure and capacity within the NW collection system. The model evaluates storage capacity and flows within the main sections of the trunk line serving the collection system. The model can be expanded into additional locations within the service area for evaluating impacts associated with new development. According to the Master Plan (December 2005), the service area has a potential capacity for 7379 connections. All projects greater in size than 19 Single Family Dwelling Equivalents (SFDs) are required to utilize the NW model. The model identifies the areas within the collection system where infrastructure improvements are necessary to accommodate the development, capacity mitigation and costs, and shared costs for infrastructure replacement based on a percentage of use.

Treatment Plant: Northwest

Type: Aerated lagoons
Connections: 4088
Dry/wet flow: 1.6-4.1 million gallons per day (MGD)

• Collection area: N Lakeport (AD 7-1)
  Connections: 922
  Population: 2,228
• Collection area: Upper Lake (AD 3-4)
  Connections: 365
  Population: 820
• Collection area: Nice (AD 3-1)
  Connections: 1,195
  Population: 2,561
• Collection area: Lucerne (AD 3-2)
  Connections: 1,333
  Population: 2,871
• Collection area: Kono Tayee (AD 3-3)
  Connections: 131
  Population: 286
• Collection area: Paradise Valley (AD 3-5)
  Connections: 72
  Population: 140

With the recent success of the Blue Frog biosolid removal system being employed at the Southeast Regional Treatment Plant, this technology was installed during the fall of 2015 at the Northwest Regional Treatment Plant.

Sanitary Sewer Maintenance Plan (PDF)