Estrella Village Issues

Below is a listing of existing issues regarding development the Estrella Village Area

REVISED PROCEDURE FOR ALLOCATING LIFT STATION CAPACITY TO NEW DEVELOPMENT IN ESTRELLA

Introduction:

This document provides new information on monitored and projected wastewater flows in Estrella and a revised procedure for the allocation of additional remaining capacity in interim wastewater lift stations 61 and 62.

Background:

Southwestern Estrella , an area that can be roughly defined as south of Buckeye Rd., west of 43 rd Avenue, north of the Salt River , and east of 107th Avenue , is currently experiencing temporary restrictions on development associated with wastewater capacity limitations of interim lift stations. This area, which will be largely developed using a wastewater collection network that is distinct from systems in other parts of southwest Phoenix , relies on lift stations that transport flows to the 91st Avenue Wastewater Treatment Plant. Although some existing residential and commercial development has been permitted to flow into the large SRO and SAI interceptor lines, capacity in these facilities is now very limited, and grades are such that a separate wastewater network is required in southwest Estrella. Currently this separate network is serviced by two interim lift stations – Station 61, which is located at 4325 South
107th Avenue , and currently has a capacity of 5.5 million gallons per day (mgd), and Station 62, which is located at 9059 West Broadway Road , and is being upgraded from 2.5 mgd to 5 mgd.

The area’s ultimate lift station solution is master planned to be a 40 MGD capacity facility which will be located at 107th Avenue and Roeser. This facility is currently in the Wastewater CIP to be designed in FY 2008/09 and constructed the next fiscal year. Because the two existing interim lift stations cannot provide adequate service for all residential development in the entire south Estrella area, the Water Services Department (WSD) has only permitted a certain number of units to be built in Estrella pending the construction of the permanent 107th Avenue lift station. Projections were made by the Department of the maximum capacity that could be accommodated using the two interim lift stations, and master plans and site plans in the drainage areas of the lift stations were only approved up to the maximum capacity for those areas. Once the capacities were allocated, developers were told that they could either wait for the design and construction of the 40 mgd lift station (and associated gravity sewers and force mains) by the City through its regular CIP process in 2008/09, or initiate the design and construction of the project themselves. Because the project is projected to cost approximately $57 million to design and construct, and because the City has already accelerated the project initiation to FY 2008/09, developers in these areas have not yet elected to fund a further acceleration of the station’s design/construction.

Recent monitoring of actual wastewater flows in the interim lift stations indicates that additional capacity may be available in these facilities. Although it is difficult to estimate current wastewater flows on a per unit basis because the area is seeing rapid development and because many constructed units appear to be unoccupied, WSD is confident that per unit flows are lower than those previously anticipated. As a result, WSD will be allowing additional developments to utilize the capacity available at Lift Station 61 and 62.

Information Provided by Recent Monitoring and Analysis:

• Lift Stations 61 and 62 are currently operating at far below maximum capacities. Lift station 61 is experiencing peak day flows of approximately 900,000 gallons per day and lift station 62 is experiencing peak day flows of about 710,000 gallons a day, significantly less than the 5.5 mgd and 5 mgd capacities associated with those facilities.
  
• At approximately 257 gallons a day, the average single family wastewater generation estimated draining into Lift Stations 61 and 62 is less than the 320 gallons assumed in the City’s design guidelines, which were used to estimate lift station capacities for purposes of allocating space in the interim stations. The average measured dry peak factor of approximately 1.6 is less than the WSD standard of 2.5. This indicates that some level of capacity should be available in the interim stations for additional residential development.
  
• Although the current wastewater flows recorded at Lift Stations 61 and 62 and average and peak flows estimated for single family units in Estrella provides evidence that additional capacity exists (once all units in approved master plan and site plans have been constructed), the high number of apparently unoccupied units and the existence of a significant inventory of approved but not yet built units indicates that caution is warranted. With about 9,500 units either constructed and not occupied, or approved but not yet constructed, versus only about 3,400 units constructed and occupied, WSD has to be conservative in projected additional available capacity at the existing interim stations. In addition ADEQ rules require wastewater facilities to be designed to provide enough capacity for wet weather infiltration and inflow based on a 10-year, 24-hour storm event. No such event occurred during the flow data collection period so no peak wet weather flows were measured. The actual peak flows measured only represent a dry weather peak flow. A safety factor, therefore, had to be added to the projected peak flow per unit to account for potential infiltration and inflow.

New WSD Procedure Regarding Lift Stations 61 and 62 (01/16/07):

• In 2007 WSD will approve 1,500 more single or multifamily units in area served by Lift Station 61 and 1,750 more single or multifamily units in area served by Lift Station 62. In accordance with the process described in WSD Engineering Policy P-103, approvals will be issued on a first come first serve basis and will be granted in the order of submittal, based on log-in date and time, of PCD master plans or preliminary site plans.
  
• In January 2008, WSD will reassess the growth rate in Estrella and determine if additional units can be approved in 2008.