6789 Quail Hill P arkway, # 421 • Irvine, California 92603
DRAFT TECHNICAL MEMORANDUM
TO: TOM CROWLEY, PE
FROM: JON WELLS, PE
REVIEW: STEPHEN DOPUDJA, PE
CC:
SUBJECT: IMPACT OF SIXTH CYCLE HOUSING ELEMENT ON WATER/WASTEWATER UTILITIES WITHIN THE CITY OF RIALTO
DATE: OCTOBER 27, 2022
This Technical Memorandum (TM) is comprised of the following sections:
• Background
• Identification of Rezoned and Upzoned Parcels Within City • Impacts of Rezoned and Upzoned Parcels to Water Utility Capacity Requirements • Impacts of Rezoned and Upzoned Parcels to Wastewater Utility Capacity Requirements
BACKGROUND
As described in Plan to House Our Rialto, 6 th Cycle Housing Element 2021-2029, Adopted March 8, 2022 (Housing Element), the Housing Element is a state-mandated chapter of the City of Rialto General Plan that identifies and analyzes the City’s housing needs and includes a detailed outline and work program of the City’s goals, policies, and quantified objectives related to housing. The Housing Element also addresses the maintenance and expansion of the housing supply to accommodate households currently living and expected to live in the City during the specified housing cycle. The Housing Element identifies available candidate housing sites and establishes the City’s official housing policies and programs to accommodate the Regional Housing Needs Assessment (RHNA) goals as determined by the Southern California Association of Governments (SCAG). The programs and policies established within the Housing Element guide future decision- making to achieve the City’s housing goals for the 2021-2029 planning period.
Most importantly from a water and wastewater utility perspective, the Housing Element identifies parcels through the City that would require “Rezoning” or “Upzoning” to meeting housing unit goals within the City. These Rezoned and Upzoned parcels are projected to contain a housing
Rialto Housing Element Utility Impact TM 002_22_02
density higher than that allowed by the adopted General Plan; the potentially greater number of housing units on these parcels would require more water and wastewater utility capacity than that required by the adopted General Plan. Because the City’s Water Master Plan and Wastewater Master Plan have been developed based upon ad opted General Plan housing densities, as is typical, implementation of the Housing Element potentially would require water and/or wastewater capacity beyond that projected in the two master plans. The following sections of this TM provide an evaluation of the impacts to water and wastewater capacity requirements within the City if the Rezoning and Upzoning opportunities identified in the Housing Element were to be implemented.
IDENTIFICATION OF REZONED AND UPZONED PARCELS WITHIN THE CITY Appendix B of the Housing Element contains the “Inventory of Adequate Sites” for housing within the City. This inventory contains both parcels that are currently underutilized for housing under existing densities, and parcels whose housing density could be increased to allow more housing units. The latter group of parcels were identified for Rezoning and Upzoning.
The parcels identified for Rezoning and Upzoning are presented in several tables and figures in Appendix B of the Housing Element. For this evaluation, the Upzoned and Rezoned parcels were consolidated into a single Geographical Information System (GIS) database to allow for mapping and for location-based evaluation of water and wastewater utility system impacts. The Rezoned and Upzoned parcels fro m the Housing Element are presented on Figure 1. The parcels are grouped by general development area. The net increase of housing units in the City beyond those projected by the adopted General Plan are summarized in Table 1. To arrive at these values, the housing units allowed on a specific parcel under the adopted General Plan density were subtracted from those allowed by the Rezoned or Upzoned density for each individual parcel. In most cases, the Rezoned or Upzoned density was projected to be 35 housing units per acre. As can be seen in Table 1, the net increase in housing units resulting from the Rezoned or Upzoned parcels is approximately 5,600 units.
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Figure 1. Rezoned and Upzoned Parcels Identified in Appendix B of Housing Element %
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Table 1. Housing Units Above Adopted General Plan Totals From Rezoned or Upzoned Parcels General Development Area Net Increase in Housing Units
Foothill Boulevard Specific Plan 2,963
North Riverside Avenue 397
Gateway Specific Plan 697
Central Area Specific Plan 442
Baseline Parcels 146
Baseline Shopping Center 836
Randall Avenue Sites 111
Project Pipeline 14
Total 5,606
IMPACTS OF REZONED AND UPZONED PARCELS TO WATER UTILITY CAPACITY REQUIREMENTS The City of Rialto is served by three separate water utilities: City of Rialto Water Serv ices, West Valley Water District, and Fontana Water Company. Therefore, the impact of Rezoned and Upzoned parcels depends on the location of the parcel, and the resulting water utility service area into which it falls.
Figure 2 overlays the Rialto Water Service Area, including pressure zone delineation, with the Rezoned and Upzoned parcels shown previously on Figure 1. As can be seen on Figure 2 , the majority of the Rezoned and Upzoned parcels are found within the Rialto Water Service a rea. A small number of these parcels in the north of the City are found within the W est Valley Water District; a still smaller number are found at the western edge of the City along Foothill Boulevard in the Fontana Water Company service area. The net increase in housing units is broken down by water utility in Table 2. As can be seen in the table, 89% of the net housing unit increase is found in the Rialto Water Service Area. The majority of the housing unit increase is found within Pressure Zone 2 of the Rialto Water Service distribution system.
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Figure 2. Rezoned and Upzoned Parcels Overlaid with Water Utility Service in the City of Rialto %
West Valley
Water District
Fontana Water
Company
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Table 2. Housing Units Above Adopted General Plan Totals by Water Service Utility General Development Area
Rialto Water
Service
West Valley
Water District
Fontana Water
Company Total
Foothill Boulevard Specific
Plan 2,803 - 160 2,963 North Riverside Avenue - 397 - 397 Gateway Specific Plan 697 - - 697 Central Area Specific Plan 442 - - 442 Baseline Parcels 105 41 - 146 Baseline Shopping Center 836 - - 836 Randall Avenue Sites 111 - - 111 Project Pipeline - 14 - 14 Total 4,994 452 160 5,606
Demand factors from the City of Rialto Water Master Plan were used to estimate the increased water demand for each water utility in the City. Values of 95 gallons per day per capita (gpdc) and
3.85 people per housing unit were used in these estimates; both values are appropriate for high density residential development.
The resulting water demand increases can be seen in Table 3. As shown in the table, the total required supply increase is 2,200 acre feet per year (AFY). 2,000 AFY of this value is required in the Rialto Water Service Area.
Table 3. Housing Units Above Adopted General Plan Totals by Water Service Utility with Required Water Supply
General Development Area
Rialto Water
Service
West Valley
Water District
Fontana Water
Company Total
Foothill Boulevard Specific
Plan 2,803 - 160 2,963 North Riverside Avenue - 397 - 397 Gateway Specific Plan 697 - - 697 Central Area Specific Plan 442 - - 442 Baseline Parcels 105 41 - 146 Baseline Shopping Center 836 - - 836 Randall Avenue Sites 111 - - 111 Project Pipeline - 14 - 14 Total 4,994 452 160 5,606 Required Supply
Increase (AFY) 2,000 180 60 2,280
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The required water supply increase for the Rezoned or Upzoned parcels is compared to the available water supply for each utility in the City in Table 4. The available water supply for each utility was taken from the utility’s 2020 Urban Water Management Plan . As shown in the table, small increases in available water supply would be required for Rialto Water Service and Fontana Water Company. Hydraulic improvements are not required in the Rialto Water Service distribution system to serve the increased water supply.
Table 4. Water Supply Requirements Compared to Available Supply Desciption
Rialto Water
Service
West Valley
Water District
Fontana Water
Company Total
Water Supply Available
Above Demand in 2045
Per UWMP (AFY) 1,742 4,464 0 6,206
Required Supply Increase
for Rezoned and Upzoned
Parcels (AFY) 2,000 180 60 2,280
Potential Supply Surplus
(Shortage) in 2045 with
Rezoned and Upzoned
Parcels (258) 4,284 (60) 3,926
IMPACTS OF REZONED AND UPZONED PARCELS TO WASTEWATER UTILITY CAPACITY
REQUIREMENTS
The City of Rialto provides wastewater utility service to the entire City, and therefore there is only one wastewater utility impacted by the Rezoned and Upzoned parcels. The Rezoned and Upzoned parcels are presented in overlay of the wastewater collection system on Figure 3.
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Figure 3. Rezoned and Upzoned Parcels Overlaid with City of Rialto Wastewater Collection System
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Table 5 provides the wastewater flow projections for the collection system as developed for the Wastewater Master Plan. As shown in the table, the maximum flow projection for the collection system from the Wastewater Master Plan is 10.03 million gallons per day (mgd). This value is increased to 10.83 mgd with the addition of the Rezoned and Upzoned parcels . The increased projection remains less than the average permitted capacity of the City’s Wastewater Treatment Plant, which is 11.7 mgd. Treatment capacity increases will not be required for the Rezoned and Upzoned parcels of the Housing Element.
Table 5. Future Flow Projections for City of Rialto Wastewater Service Area (Source: Wastewater Master Plan)
Timeframe
Average Flow,
mgd
Peak Flow,
mgd
Existing 7.01 11.07
Near-Term Development 7.66 12.18
Build-Out Future 9.57 15.22
Future with Potential Septic Conversion 10.03 15.75
Future with Potential Septic Conversion Plus Rezoned and Upzoned Parcels 10.83 16.44
In terms of the wastewater collection system impact, the Rezoned and Upzoned parcels fall into two main geographic categories . There are a significant number of such parcels at and north of Baseline Avenue in the eastern half of the City. This portion of the City was identified in the Wastewater Master Plan as being deficient in trunk gravity main capacity, and the increased housing units in the Rezoned and Upzon ed parcels will exacerbate this lack of capacity. T he Sycamore Avenue Trunk Capacity Project identified in the Wastewater Master Plan must be implemented to provide sufficient capacity for these parcels.
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The second main geographic category contains the parcels along Foothill Boulevard. In general, there is sufficient trunk capacity along and running south from Foothill Boulevard to c onvey the increased flow away from the impacted parcels. However, between Larch Avenue and Cactus Avenue along Foothill Boulevard, there is a reach of 10-inch diameter pipeline which is insufficient to convey the increased flows. 2,600 feet of 10 -inch gravity main should be upsized to 12 -inch gravity main if th e Rezoned and Upzoned parcels are implemented. This reach can be seen on Figure 4.
Figure 4. Gravity Main Capacity Increase Required Along Foothill Boulevard. 2,600 Feet of 10-inch
gravity main to be upsized
to 12-inch gravity main.