Twentynine Palms City Council
February 22, 2022

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3.3.1 Current Population
The 2010 UWMP estimates the City of Twentynine Palms to have a population of 18,975 as of the close of 2010. Estimates and analysis of current conditions were performed using this projection. This projection estimates the number of dwellings per major Land Use category using the number of connections, as shown in Table 3-2, and estimates population by factoring the number of connections against average residential dwelling densities.

3.3.2 2035 Population
Similar to the current population estimate, future projections in the UWMP were made by estimating the number of dwellings and adding up the population within those dwellings.

Projections of growth calculated in the 2010 UWMP were estimated at 30,931 in 2035. Tables 3-5 and 3-6 present the historic population from 2006 to 2010 and the 2035 projected population, respectively.

TABLE 3-5

HISTORIC POPULATION ESTIMATES
2006 2007 2008 2009 2010
18,462 18,716 18,736 18,737 18,795
TABLE 3-6

POPULATION PROJECTIONS
2015 2020 2025 2030 2035 Build-Out
22,135 25,476 27,339 29,202 30,931 102,963

3.3.3 Build-Out Population
In determining the build-out population for the area within the District, several sources were referenced to create a viable projection. Current population data available through the 2010 Census showed that the average household in Twentynine Palms contained 2.63 persons. The Twentynine Palms General Plan (General Plan) was referenced in order to determine the number of dwellings zoned to be built on an acre (DU/acre) of each specific land use. Land Use data supplied by the City of Twentynine Palms and the County of San Bernardino was used to determine the number of parcels and the area of land by land use.

The largest component of land use was RL 1ac, which is rural living, zoned for 1 dwelling per acre. Following that, higher density rural single family land use was the second largest proportion, which allows for up to 2.5 dwelling units per acre, or a minimum of 0.4 acres per dwelling unit. The third largest land use category belonged to higher density single family residential, allowing 3 to 4 dwelling units per acre. Lastly, High density single family and multifamily make up a large percentage of the remaining residential land.

Dwelling unit per acre factors were applied to each of the parcels to generate a maximum allowable population for the District service area. Per procedures laid out in the General Plan, this figure was reduced by 20 percent to reflect inefficiencies in development, rights of way, public spaces like parks and other spaces that will go undeveloped and thus not be available.

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A large portion of the District service area was, until recently, not incorporated within the City of Twentynine Palms, and thus, much data was not readily available. These areas consist of the area East and North of the City of Twentynine Palms, and the City’s Sphere of Influence (SOI) which extends to several small areas directly outside of City boundaries that are expected to experience growth due to City activity. The populations for these areas were calculated in a similar manner as the incorporated region, assuming that the average dwelling unit would house

2.63 persons. There are currently only three land uses in these areas, which are RL 1, RL 5 and RC. RL 1 allows for 1 dwelling per acre, and accounts for approximately 26 percent of the District’s unincorporated service area. RL 5 allows 1 dwelling unit per five acres and accounts for approximately 61 percent of the District’s unincorporated area. RC is resource conservation land and does not allow any building and accounts for approximately 13 percent of the unincorporated area.

As part of this Plan, the build-out population was estimated which included the unincorporated area and the City’s SOI population, based on the formula below and population data shown in Table 2-4:

Build-out population = Total City build-out population - Marine Base population + Unincorporated population (adjusted) + SOI population outside of City boundary As mentioned above, based on the new land use/zoning of the City boundary, the City boundary has recently been extended and the City boundary extends beyond the City limits and more closely matches that of the District and includes the unincorporated areas. The build-out population projection accounts for this change. Based on the discussions with City’s Staff (refer to Appendix A - email attachment by Matt McCleary 2014) and General Plan, the City build-out population is 103,275 and the Marine Base population is 22,500. Since the Marine Base is served by sewer systems, based on the discussion with the City Staff the Marine Base population was excluded from the City build-out population calculations. The City’s SOI population is 7,586, based on population estimates from the City General Plan. The total unincorporated population is estimated to be 17,253, but a small southern portion of the unincorporated area falls within the City SOI; thus it is adjusted to account for the population of 14,602 that corresponds to the area but outside of the City’s SOI. The unincorporated area covers a large area with a very low population density.

TABLE 3-7

PROJECTED BUILD-OUT POPULATION ESTIMATE
City’s Build-out population* 103,275
Marine Base population** 22,500
Total City Population** 80,775
Unincorporated population (adjusted)*** 14,602
City Sphere Of Influence population** 7,586
Total build-out population 102,963
*Per City Staff Matt McCleary
** Per City of Twentynine Palms General Plan
*** Area included in Twentynine Palms Water District service area. Land use and housing estimates derived from County of San Bernardino planning data. Effective population estimated in accordance with the City of Twentynine Palms Land Use Plan.

Figure 3-5 shows graphically the areas used for the calculation of the ultimate Build-out population.

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Section 4: Wastewater Flows
Evaluation of the wastewater flows is a fundamental element in evaluating the infrastructure requirements for the project area. Based on the historic water usage data, UWMP population and land use projections, General Plan preferred expansion and GIS areal coverage’s, wastewater loadings were calculated for the three planning scenarios discussed in Section 3.

This Section describes the evaluation of the wastewater flows for the area and describes the data sources used for the development of these wastewater loading factors.

4.1 Wastewater Flow Projections Approach
As discussed in Section 3, the general approach used in the WWMP for the evaluation of the wastewater loading rates was primarily based on two scenarios i.e. Current and Build-out (worst case scenario).

For the calculation of the wastewater loadings, there are two major categories of onsite system wastewater – residential and non-residential in the Twentynine Palms area. Single family and multifamily households all fall under the residential dwellings. A variety of commercial (e.g., restaurants and hotels) and institutional (e.g., school) establishments and facilities fall into the non-residential wastewater category. Residential wastewater flow projections are based on population and per-capita unit flow factors. Non-residential wastewater flows have been calculated on a per acre basis, with differentiations for high density non-residential, such as hotels and restaurants, and low density non-residential, such as warehouses and storefronts.

4.1.1 Key Assumptions for Flow Calculations
The following main assumptions were made for the calculations of the wastewater flows for the current and the build-out conditions:

4.1.1.1 Water to Sewer Return Ratios
Generally, the development of land-use based wastewater generation factors can be estimated from field generated flow measurement and mass loading calculations. However, since the study area is not currently sewered, actual per capita wastewater flows are not available. In the absence of this data, the District’s actual potable water billing consumption data for each land use category was used to predict wastewater flow rates based on water to sewer return ratios for the system. The amount of water estimated to return to the sewer was assumed to be the amount which would be collected through the wastewater system. Hence the wastewater system infrastructure was based on the flows from the septic systems as if they were to be collected by a wastewater sewer system.

Since all the water that is used is not converted to sewer flow, water to sewer return ratios were applied to calculate the loading for the area. For the Twentynine Palms area an assumption of 80% water to sewer return ration was applied. Experience in the region suggested that an average water to sewer conversion of 80 percent of water use is discharged to local septic systems is a reasonable assumption.

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To estimate the wastewater values, potable water usage billing information was evaluated to segregate between interior and exterior water usage. This water to sewer ratio represents indoor water use, which will have an almost complete transfer to sewer loading. In most communities, summer irrigation is the main use of potable water that does not return to the sewer and water usage in the winter months is generally in excess of 80% used for interior usage. Water use during summer and winter months was analyzed using current billing data and used to verify that the 80 percent water to sewer conversion is a good indicator for the average indoor water usage as an average sewer loading rate. This is a reasonable and commonly used approach to estimate recharge from septic tanks from other areas in the vicinity, such as the Yucca Valley and High Desert areas.

4.1.1.2 Per Capita Water Demand for Current Scenario
Current scenario residential loadings were based on the current population and per capita water demand. Current per capita unit flows for residential areas were based on historical calculations of per capita water consumption. In 2010, Twentynine Palms experienced an approximate average residential consumption of 1,900,000 gallons per day. That average usage and the existing population estimate was used to calculate the average water use of 101 gallons per day per capita (gpcd). A 80 gpcd sewer loading rate was calculated for the Twentynine Palms area using the 80% water to sewer return ration described in the section above.

The 80 gpcd sewer loading rate used for the Twentynine Palms area for the Current Scenario is comparable with sewer loading rate from the communities in the vicinity. For comparison, a percapita waste water flow rate of 83 gpcd was considered for the Yucca Valley (MWH, 2009) and 80 gpcd for the High-Desert Water District. The 80 gpcd is considered relatively conservative compared to findings of several other studies that evaluated the residential indoor water use in detail. A study funded by AWWARF that involved the largest number of residential water users ever characterized (1,188 homes in 12 metropolitan areas in North America) wastewater discharges and included a detailed indoor water use characterization of approximately 100 homes in each of the 12 study area using continuous data loggers and computer software that quantified the end uses of water. These data were derived from some 1 million measured indoor water use events in 1,188 homes in 12 suburban areas.

The study found that the average gpcd wastewater discharges ranged from 57 to 83.5 with the average of about 69 gpcd in all 12 study sites (Mayer et al., 1999). The previous studies estimated average daily wastewater flows are approximately 50 to 70 gpcd, typical for residential dwellings built before 1994, with homes built after 1994 retrofitted with energy and water–efficient appliances would have typical average daily wastewater flows in the 40 to 60 gpcd. As such, the 80 gpcd used herein is above the average estimates and is therefore considered a conservative estimate for sewer loading at this time.

4.1.1.3 Per Capita Water Demand for Build-out Scenario
The approach used for calculating the loadings for build-out conditions was based on the UWMP base daily per capita water use, maximum allowable daily water use target for SBX 7-7 compliance and current gpcd water. Per capita sewer loading rate was calculated to be

73.5 gpcd for 2035 and build-out scenarios compared to 80 gpcd for the current condition. This accounts for a reduction in sewer loading rate proportional to the reduction in the per capita water use. As reported in the 2010 UWMP and discussed above, per capita water use is estimated to be 147 gpcd and is projected to reduce to 135 gpcd to meet the water reduction

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compliance by 2020 by water conservation. This is equivalent to 8 percent reduction in the gpcd. As described above, the sewer loading rate for the Current Scenario is 80 gpcd. With the 8 percent reduction, sewer loading rate with water conservation is projected to be 73.5 gpcd.

It was assumed that once the water use target by 2020 is achieved, the intent is to keep it at that level. Therefore, the 73.5 gpcd is considered applicable for projecting sewer loading beyond 2020 and used as a reasonable approximation for the build-out scenario.

The 73.5 gpcd is considered reasonable for future projections. Beginning in recent years, greater attention is being given to water conservation and the installation of water-conserving devices and appliances, including in the District service area. With the energy use standards that went into effect since 1994, indoor retrofits are expected to reduce water use in indoor appliances. Homes built after 1994 or retrofitted with energy and water–efficient appliances would have typical average daily wastewater flows in the 40 to 60 gpcd (Mayer et al., 2000).

The reduced 73.5 gpcd results in reduced wastewater flows, thus decreasing the quantity of CECs discharged to the waste stream.

Indoor residential water use and resulting wastewater flows are attributed mainly to toilet flushing, bathing, and clothes washing. Toilets, showers, and faucets in combination can represent more than 70 percent of all indoor use. Residential wastewater flow reduction can therefore be achieved most dramatically by addressing these primary indoor uses. Installing indoor plumbing fixtures that reduce water use and replacing existing plumbing fixtures or appliances with units that use less water are successful practices that reduce wastewater flows.

4.1.2 Residential Loadings
The approach used to estimate residential sewer loading for the scenarios rely on the estimated population and projected per capita sewer loading rate. Total residential sewer loading for the current and build-out scenarios was calculated using the population numbers presented in Section 3. The water to sewer conversion is assumed to remain at 80 percent for both the current and build-out scenarios. Future land development associated with the Build-out Scenario is anticipated to occur to accommodate the increased population projection. While the population projection was previously estimated within the District service area and readily available to use in this study, the exact locations of future land development and land use density are uncertain at this time. For the purpose of this assessment, the spatial distribution of sewer loading by each subbasin is needed to assess the potential impact of future septic loading. Therefore, for the wastewater flow analysis, a reasonable assumption was made to distribute the total future projected septic loading among the subbasins proportional to the Current Scenario septic loading in each subbasin.

4.1.3 Non Residential Loadings
For non-residential land use such as commercials and institutions, flow rates are generally expressed in terms of quantity of flow per unit area. The results of previous studies have demonstrated that in many cases nonresidential wastewater is considerably different from residential wastewater.

Total non-residential sewer loading was calculated based on the non-residential water use of based on area and 80 percent water to sewer conversion factor. Similar to the residential, the 80 percent conversion factor was used to represent indoor water use and the portion of water

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use returning to sewer tanks. Average winter water usage was compared with 80 percent of annual water usage to verify that the 80 percent water to sewer conversion factor is reasonable for the non-residential sector.

Based on the GIS aerial image, the acreages of the non-residential land use were identified and high and low density areas were estimated. Using the GIS based acreages and the assumed sewer rates (gal/day/acre); total sewer rate for high density commercial was calculated. The remaining sewer loading was distributed between the low density commercial and institutions based on the acreages estimated from land use data. It is anticipated that non-residential sewer loading varies depending on the land use density and types of activities. Site specific data from different water use sectors are unavailable to differentia sewer loading for high and low density non-residential sectors. Sewer loading rates for the high density commercial, low density commercial, and institutions were assumed to be 900, 320, and 320 gal/day/acre, respectively, based on data available from nearby communities and simplifying assumptions. A sewer loading rate used for the communities in the vicinity ranged from 800 gal/day/acre for the HighDesert Water District to 1,000 gal/day/acre for the Yucca Valley (USGS, 2003). For the Twentynine Palms area, high density commercial sewer loading rate was assumed to be 900 gal/day/acre as an average of the ranges used for the nearby communities.

4.2 Wastewater Flows
Using the approach described above, wastewater flows were calculated for current and buildout conditions. These values were then used for the allocation of demands for various sub catchments in the hydraulic model to analyze the system. Table 4-1 below shows the summary of the population projections, per capita water and wastewater use, wastewater flow etc. for the current, 2035 and build-out conditions.

TABLE 4-1

SUMMARY OF WASTEWATER FLOW ESTIMATES
Current - 2010 2035 Projections Build-out
Population 18,795 30,931 102,963
Residential - Includes single family and multi-family (Within and Outside District) Water usage (gal/day) 1,898,295 2,845,652 9,472,596
Water Usage (gal/day/person) 101 92 92
Water to sewer factor 0.8 0.8 0.8
Indoor water use (gal/day/person)
(sewer loading) 80 73.5 73.5
Sewer loading (gal/day) (total) 1,518,636 2,276,522 7,578,077 Non-Residential - Includes commercial, institutions, and industrial.

Water usage (gal/day) 251,137 507,579 2,328,613
Water to sewer factor 0.8 0.8 0.8
Acreage (total) 385 778 4,312
Sewer loading (gal/day/acre)
Non-residential (high density) 900 900 900
Non-residential (low density) 320 320 320
Institutional/Industrial 320 320 320
Total Wastewater Flows (MDG) 1.71 2.67 9.3

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4.3 Data Sources for Wastewater Flow Estimation
The main sources of land use and flow data available for use in estimating wastewater flows are listed in Table 4-2. The table provides a brief description of each data source, its description, format, and use. Details on how each of these data sources was used are covered in subsequent sections of this chapter.

TABLE 4-2

DATA SOURCES FOR WASTEWATER FLOW ESTIMATION
Data Description
Data
Format Used for Calculating
Land Use and
Parcel Data Land Use element by Parcel GIS Shapefile
Expected water use on
a per parcel basis
Unincorporated
Area and Sphere of
Influence (SOI)
Land Use and
Parcel Data
Land Use element by Parcel
for the Unincorporated region
GIS
Shapefile
Water use on a per
parcel basis in the
Unincorporated area
Street Grid Southern California Streets GIS
Shapefile Pipeline alignments
Water District
Potable Distribution
System
Twentynine Palms Water
District potable water
distribution grid
GIS
Shapefile Pipeline alignments
Digital Elevation
Model (DEM)
Elevation data for the City
and surrounding areas
GIS
Shapefile
Model required pipeline
elevations
City and Water
District Boundaries
City of Twentynine Palms and
Twentynine Palms Water
District Boundaries
GIS
Shapefile
Extents of parcels that
influence expected
sewer loading in City
and Unincorporated
areas
Sewer Loading
Sub-catchment
Boundaries
Boundaries of sewer subcatchment loading GIS
Shapefile
Loading at Sewer subcatchment boundaries
Sewer Loading
Factors
Calculations of per dwelling
unit water use (residential)
and per acre water use (nonresidential)
Excel Loading at sewer subcatchments
Historical Water
Data
Several years of data for total
water use Excel
Development of
expected wastewater
flows
Population Data
Estimations of past and
current population and
projections of future
population
Excel
Develop an accurate
estimation of
wastewater flow based
on per capita water use
Housing/Land Use
Inventory/Parcel
Data pertaining to zoned land
uses and parcel shapes,
sizes and locations.

SHP Categorize production
of wastewater flow.

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Data Description
Data
Format Used for Calculating
General Plan Data
29 Palms General Plan,
containing info relating to
development of the City
PDF Accurate assumptions
relating to the City
Aerial GIS
Coverage
Recent detailed aerial
photography of the region SHP
Current extents of
development for current
flow projections

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Section 5: Wastewater Hydraulic Model
Hydraulic distribution models are frequently used for the planning, design and operational management of wastewater collection systems. In order to evaluate wastewater system hydraulics, computerized modeling software using complex mathematical equations are used.

These models serve as tools to identify potential deficiencies in the system, size future facilities and develop long range planning studies. This section describes development of the hydraulic model of the proposed wastewater system. As described above, the hydraulic model is the primary analytical tool used to determine pipe sizing, and flow distribution.

To assess the appropriate sizing of the wastewater collection and treatment systems, the buildout conditions were used and integrated in a newly developed wastewater model. A main-trunk skeleton hydraulic model of the District was created using Digital Elevation Models (DEM) and the GIS based sewer modeling software H2OMap Sewer. The model was used as an analytical tool to determine the infrastructure system requirements that would be needed for the potential collection and treatment systems to meet the District’s/City’s near and long term needs. From these findings, a Capital Improvement Program (CIP) and Implementation Plan were developed.

A cornerstone element of the CIP and Implementation Plan was derived based on the findings from the Salt and Nutrient Management Plan, prepared by Kennedy/Jenks Consultants and submitted under a separate cover.

The study has outlined the extent of the proposed sewer area, the location of the trunk lines along with identified major collector pipelines, the WWTP and the catchment areas. Sewer loadings were calculated based on the historic water consumption data, in conjunction with the growth projections defined in the UWMP 2010 and the duty factors developed in the GWMP.

5.1 Modeling Software
K/J’s modeling team selected Innovyze’s H2OMap Sewer (version 10.5) software to use for this project. H2OMap Sewer uses Innovyze’s proprietary hydraulic engine, which provides a fully dynamic solution for modeling stormwater and sanitary sewer systems. The program has a GIS-based model interface and features many useful tools for model development, calibration, and simulation results analysis.

5.2 Data Sources
H2OMap Sewer uses a GIS based interface. In order to accurately construct the model, the District and the City provided several pieces of vital GIS information that were used as the basis of the model. Additionally, PDFs of Land Use maps were provided by San Bernardino County and were used to help determine properties of the Unincorporated Area and SOI. As previously discussed, the following data sources were used in the development of the hydraulic model:
 Land use data
 Parcel level data
 Street Grid

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 Water District Potable Distribution System
 Digital Elevation Model (DEM)
 City and Water District Boundaries
 Sewer Loading Sub-catchment Boundaries
 Sewer Loading Factors
 Current and Historic Water Usage Data
 Population Data
 Aerial GIS Coverage

5.3 Model Construction
The following sections describe the model building process and software terminology. The analysis was conducted using a computerized static model. As discussed in the earlier sections, the information required for the model (pipe diameters and lengths, invert and ground elevations, etc.) was obtained from the City’s GIS database and validated to ensure the information was comprehensive enough to support this planning effort.

5.3.1 Basic Terminology of Model Data
The model data consist of these basic components:

5.3.1.1 Nodes
This component includes manholes and pump station wet wells. The primary data for nodes is ground elevation. Pump station wet wells also have other attribute data like chamber roof elevations, chamber floor elevations, and cross sectional areas.

5.3.1.2 Links
The model represents physical connections between two nodes as links. Links are mostly pipes but also include flow control structures such as pumps, weirs, sluice gates, and orifices. A model link requires an upstream and a downstream node. Attribute data for pipes also include pipe type (gravity or force main), length, diameter, upstream and downstream invert elevations, Manning’s roughness coefficient, and headloss coefficient. Modeling pump operation requires discharge flow rate data (or pump curves for actual pumps) and pump on and off levels. For other flow control structures, the model also requires dimensional inputs.

5.3.1.3 Sub-catchments
Multiple sub-catchments combine to form watershed area tributary to a node. Attribute data for sub-catchments include loading node identification (ID), contributing acreage, and land use ID.

Land use ID information are specific wastewater diurnal flow pattern, flow factor, RDI/I

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parameters assigned to a particular shed. Wastewater flows are generated from the subcatchments and routed through the piping network.

5.3.1.4 Model loads
Model loads are residential and non-residential dry weather flows and I/I (which is neglected for this study). As a sum, they represent the total wastewater flow applied to modeled pipes.

5.3.1.5 Models
Models are the combination of a modeled network, its associated sub-catchments and loads, and other data files (e.g., diurnal profiles) that comprise a specific model scenario.

5.3.2 Model Building
This section describes how the network for the model sewers and service areas was defined and built. The extension of the model to cover currently undeveloped areas is described later in this chapter. Selection of the area to be sewered is based on key parameters including SNMP findings, topography, General Plan build-out population projections, water usage etc. The planning approach for identifying the extents of the sewered area includes the ultimate buildout conditions based on the City’s General plan and phasing/implementation plan based on high density commercial, industrial, residential etc. parcels that can primarily drain by gravity in a single direction. The need for lift stations was evaluated based on topography and pumping to a higher elevation point, if needed. Gravity sewer flows from the parcels was collected using a Trunk Sewer model and a wastewater treatment centralized plant was cited using GIS spatial DEM analysis to evaluate the most feasible lowest point in the basin. These discussions follow in the later sub-sections.

5.3.2.1 Network Trunks
Determination of the modeled location of the sewer trunks was based on several factors. The first factor was the location of current water distribution mains. These were chosen as appropriate sewer trunk locations for ease of internal facility tracking and maintenance access.

Topography was also a large consideration in the placement of trunk lines. In such cases where a sewer pipeline could not appear to parallel an existing water main, alternate alignments were selected. Land use data was also used to align the trunk with the major population centers. These factors helped create the modeled alignment which includes over 25 miles of sewer trunk, over 18 miles of which is gravity sewer, and over 7 miles of which is force main.

The conceptual alignment of local trunk locations is shown in Figure 5-1.

5.3.2.2 Delineation of Trunk Sheds
The project area was divided into individual trunk sheds by sewer tracing. Each trunk shed was characterized by its downstream interceptor connection to the main line. Starting from its discharge point into a main trunk interceptor, a sewer shed was selected by performing upstream traces. The trunk sheds were identified based on: (1) Its corresponding existing main street and (2) The shed location.

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5.3.2.3 Sub catchment and Watershed Definitions
The sewer area was divided into a number of geographic units called sub-catchments. Each subcatchment is a tributary area for which wastewater flows are computed and then loaded to a manhole on a modeled sewer pipeline. Tributary flow from each subcatchment was geoprocessed using watershed delineation and depends upon topography, direction of drainage, area of the sub-catchment. Since this study involves a Trunk-Sewer model and is not a detailed collection system model with collectors and laterals, subcatchments were combined to form a representative watershed area and the total load of each watershed area allocated to a pour point in the model. Note that these pour points were strategically selected based on the watershed delineation to optimize gravity flow for each watershed. Wastewater loadings were calculated for the Build-out scenario using these watershed loadings and the City’s General Plan preferred land use and acreages. The Build-out scenario was used to size infrastructure for the project area. The various sewer trunk watershed areas are shown in Figure 5-2.

5.3.2.4 Manholes
Manholes shown in the model serve several purposes. Their first purpose is to serve as load manholes and apply a load to the sewer trunk which serves a region of the modeled area. To that end, each manhole represents the pour point of a tributary area within the District. At a minimum each trunk shed has one pour point representative of the loading for that watershed.

Additionally, several trunk sheds have sewer lift stations which require a wet well to pump from.

In the model these wet wells require a manhole prior to the pump and force main. These manholes are referred to in the model as chamber manholes. Such manholes do not receive any load. The final variety of manhole seen in the model generated for this project is also a load manhole. These manholes do not delineate any boundary of a trunk shed, but rather were chosen because the stretch of pipe required to traverse a trunk shed was too large for a single manhole. These manholes served the purpose of allowing for additional elevation information and more accurate modeling of the associated pipe, and additional locations to spread the load of a trunk shed. Not all of these manholes received a load in the model.

5.4 Hydraulic Design Criteria and Boundary Conditions
Evaluation of the wastewater hydraulic system requires the system meet key industry design criteria. Design criteria include the pipeline peak-flows, minimum/maximum velocities, d/D, crown depth requirements, minimum allowable pipeline slopes, etc. Based on industry standards, comprehensive experience in wastewater modeling and discussions with staff, these criteria are documented below and incorporated in the development of the hydraulic model and hydraulic system analysis.

5.4.1 Dry Weather Peak Design Flows
The District’s sewer system was sized to accommodate the peak dry weather flow (PDWF) observed within the District’s service area. This assumption takes into account the limited precipitation and the high temperatures within the area.  For collector sewers less than 18-inches in diameter, the design peak flow was assumed to be equal to 3 times the average day flow.

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 For trunk sewers greater than or equal to 18-inches in diameter, the design peak flow was assumed be equal to 2.5 times the average day flow.

The District pipelines have been sized to accommodate additional wet weather flows when the design peak flows are greater than 3.0 times the average day flow. Additional pipeline capacity is accounted for in the pipeline design criteria, d/D (flow depth/sewer diameter) ratio, listed in the sub-sections that follow.

5.4.2 Wet Weather Flows - Infiltration/Inflow (I&I)
I/I is infiltration and inflow that is directly related to rainfall events. I/I may also enter the sewer system through joints in pipes and manholes, as well as through direct surface drainage connections such as illegally connected roof and yard drains or storm drain cross connections.

The magnitude of I/I flows are related to the following:
 Intensity and duration of the rainfall
 Relative soil moisture at the time of the rainfall event  Condition of the sewers
In order to evaluate the effect of wet whether precipitation data were obtained from the Western Regional Climate Center (WRCC) for the Twentynine Palms Station (049099). Annual precipitation data are available for the period of record of 1935 through 2012. Annual total rainfall during this period of record averaged 4.24 inches per year. Average monthly rainfall data are provided in Table 5-1 below.

TABLE 5-1

AVERAGE MONTHLY PRECIPITATION DATA FOR
TWENTYNINE PALMS STATION (1935-2012)
Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual Rainfall 0.5 0.41 0.36 0.12 0.07 0.01 0.54 0.74 0.42 0.29 0.28 0.51 4.24 Note: Rainfall is in inches per month; Source: http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?ca9099 The record maximum for daily rainfall total is 2.49 inches, occurring on 22 August 1968. The record annual maximum rainfall was 21.14 inches, recorded in 1983. The 24-hour duration, 1,000-year storm event would produce an estimated 3.14 inches of rain, according to the WRCC. Figure 5-3 shows the daily precipitation average based on historical data collected for the Twentynine Palms Precipitation station. As shown, the average daily rainfall is minimal and has never exceeded 0.09 inch for the past 78 years showing the area to be predominantly dry.

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Figure 5-4 shows the probability of a 0.01 inch quantity of precipitation over varying time periods. Similarly, the figure shows that the probability does not exceed 30% for a combined 5 day period, again confirming the arid nature of the area and its general lack of significant precipitation.

Studies have shown that for newly-constructed sewers, the infiltration component is insignificant. Since the system being evaluated will be new, it is expected that the infiltration will be negligible. Additionally, taking into account the dry climate for the District’s service area, soil types present in the region and WRCC precipitation data, it is unlikely that soil and precipitation conditions would be such that infiltration would occur in a sewer of almost any age or condition.

As such, neither infiltration nor inflow is expected to occur and thus have been formally omitted in the construction of the model. Sewer flows were therefore calculated based on peak dry weather flows, with infrastructure sizing based on peak flow conditions. Of note, while I&I has essentially be omitted from the future sewer system demands, it is believed that sewer system sizing has accounted for various planning contingencies by using conservative per capita flow values.

5.4.3 Diurnal Peaking Factors
Figure 5-5 below shows the typical daily diurnal curves for daily wastewater flow generation by primary customer type. These curves were developed for nearby agencies (Hi-Desert/Yucca Valley) and used to represent the variation in sewer flows for each land use type during a typical 24-hour period.

5.4.4 d/D Ratios
Typically, sewer systems are designed to account for extraneous flows by designing pipes to have a d/D ratio of 0.5 for peak dry weather flows (PDWF). For example, when PDWF conditions are exceeded, pipelines designed at a maximum d/D ratio of 0.5 will have 50 percent of the pipeline remaining to accommodate additional flows. For the District’s proposed sewer system the maximum d/D ratio for all sewers that are less than 18-inches in diameter shall be

0.50 and the maximum d/D ratio for all sewers that are greater than or equal to 18-inches in diameter shall be 0.66.

5.4.5 Pipeline Slopes
All trunk and collector sewers have been designed to meet minimum slope criteria of

0.4 percent in order to allow for sufficient velocities at the peak day flow rate. As a secondary criteria, trunk sewers should have a velocity of 3 feet per second (fps) or greater at peak day flow to have adequate cleansing velocity to avoid sedimentation in the pipes.

5.4.6 Maximum Allowable Velocity
In addition to the pump station capacity and wet well cycling considerations, the potential construction of new force mains in the system also requires the need for a force main maximum velocity design criteria. The suggested criterion to be used for the evaluation or design of a new sewer force main is for the velocity to not exceed six (6) feet per second.

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5.4.7 Facilities
It is assumed that manholes shall be installed on sewers at all changes in slope, size of pipe, or alignment and at all intersections of main line sewers. The maximum spacing allowable between manholes should be 500 feet unless otherwise approved. However, for the purpose of modeling the system manholes have been installed only at areas of significant change in slope, change in size of pipe, changes in pipe alignment and at pipe intersection.

5.4.8 Crown Depth
When designing sewer trunks it is important to keep in mind the depth of the pipe, as the sewer trunk should be located at a greater depth than the adjacent water main lines, to avoid any infiltration of sewage into water lines in the case of a sewer break. For this concept planning model, such detailed criteria were not considered, and all pipelines were modeled with a minimum crown depth, also known as cover, of three (3) feet and a maximum cover of fifteen (15) feet.

5.5 Demand Loading
Flows are loaded into the model at “load manholes,” each of which represents the point where flows from un-modeled sewers discharge into the modeled network. Parcels connected to unmodeled sewers were grouped into sewer sub-catchments, each with a unique load manhole in the modeled network. Sub-catchments were given identifiers consistent with the identifiers of their load manholes. In the outlying sub-catchments, 1, 9 and 10, loads were applied at multiple points. Due to the fact that these areas do not have upstream flows, but will still require a trunk running through their region it was appropriate to split up the load within that sub-catchment to more accurately model those areas and determine necessary pipe sizes. A total of 11 representative sewer watersheds were defined to represent the build-out model loads and sewer alignment.

Table 5-2 below shows the above, their respective load manholes, the loads applied at each manhole, as well as the flow received from upstream. The loads shown below are derived from an average per capita loading of 73.5 gpcd.

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TABLE 5-2

MANHOLE LOADING
Watershed
Load
Manhole(s)
Manhole Load
(Max.)
(cfs)*
1 1100
1130
1180

0.67 0.67

0.67 2 1200 1.68
3 1305 2.24
4 1400 0.49
5 1500 1.59
6 1600 0.96
7 1700 0.41
8 1800 9.06
9 1900
1930
1940

3.22 3.22

3.22 10 2000
2020

2.27 2.27
11 2100 3.93
*Flow values are not cumulative
Following the initial setup of the model and calculation of watershed loads, the load manholes at the outlet of each sub-catchment were applied the appropriate load(s) and the model simulation performed. The model was updated iteratively in order to meet the design criteria and boundary conditions described in Section 4.1.5. System updates included:
 Updating pipe sizes to meet maximum and minimum d/D, velocity and slope criteria,  Updating of pipe upstream and downstream inverts as pipe sizes changed, and  Evaluation of multiple scenarios to determine proper load application at load manholes.

The hydraulic model is used in subsequent sections to evaluate the infrastructure needs of the community’s build-out scenario, and prepare concept level alignments and cost considerations for future wastewater collection and treatment systems.

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Section 6: Wastewater System Evaluation
The main objective of this Plan is to prepare a concept plan for the potential the need for sewers based on the findings of the Salt and Nutrient Management Plan study for the Twentynine Palms area. The findings of the SNMP determination the WWMP infrastructure needs and are described in the sections that follow. This section describes the hydraulic analysis used for infrastructure sizing for the City. The evaluation was based on the build-out population conditions discussed in Section 3. The build-out scenario was chosen because it would provide an estimation of the cost of the infrastructure needed if the service area were to develop in accordance with adopted land use plans and ultimately convert to a regional sewer system.

The Section also discusses various treatment technologies and options for disposal of the wastewater generated. Finally a staging plan for the treatment plant is also discussed in this section.

6.1 Evaluation Approach
The hydraulic capacity analysis of the system incorporated approximately 25 miles of pipeline for the areas which included all large trunk sewers in the study area. The analysis was conducted using a computerized dynamic model (H2OMap Sewer, a GIS based-hydraulic modeling software). The information required for the model (pipe diameters and lengths, invert and ground elevations, etc.) was populated, and the hydraulic capacity evaluated by checking its conformance with the planning criteria described in Section 5.

The future flows in the modeled sewers were estimated by dividing the study area into a number of sub-catchments/watersheds based on delineation. Various sub-catchments were then combined into approximately 11 watersheds areas and flow loadings for the build out period were computed for each of those areas. The primary sources of information used included the District’s population and water use projections, and land use performed as part of the City’s General Plan Update. Other data sources used in estimating flows included census data, general and specific plans, parcel-level land use and other water consumption records.

The population within the District’s Sphere of Influence is projected to increase to an estimated 102,963 at build-out. The unit flow factors (e.g., flow per capita and per acre) and 24-hour flow profiles used to convert the population and acreage estimates to wastewater flows. Sewer loadings were thus developed using historical water use data and population projections primarily as defined in the UWMP 2010 and discussed in Section 4.

The capacity of the modeled sewers was assessed under peak dry weather flow conditions as defined in Section 5. Peak wet weather flow conditions were omitted due to the fact that wet weather conditions are sparse and when they do occur there is rarely the potential that it will influence sewer flow due to the arid climate and extremely dry soils. See Section 5.4.2 for additional discussion based on precipitation evaluation using the Twentynine Palms rain gage station.

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6.2 System Capacity Analysis
Section 6.2 discusses system alignment, trunk-sewers, pipe sizes and types of pipes in the system model.

6.2.1 System Alignment
The system alignment was chosen primarily based on the location of existing Twentynine Palms Water District distribution mains. The District’s largest mains run along its major roads: Two Mile Road and Twentynine Palms Highway running East-West, and Lear, Adobe and Utah Trail running North-South. Similarly the sewer trunks were modeled to be placed along the City’s main roads for ease of construction and to serve as main lines to collect wastewater flows from the highly populated areas. Sewer trunks run south on Lear and Adobe down to Two Mile Road.

Trunks run east on Two Mile Road and Twentynine Palms Highway and Amboy, where they are presumed to be treated at a future WWTP. Trunk lines also run north on Utah trail as they collect from the south eastern portion of the District. Note that though the majority of laterals and collector lines were not modeled as it was beyond the scope of work for this study, it is assumed that the customer will be responsible for getting these flows to the main trunk-lines.

Infrastructure requirements for getting flows to the trunk sewers have not been accounted for in this study.

Twentynine Palms resides in a relatively flat, desert region which provides additional challenges for sewer system planning. In order to avoid extremely deep sewer lines and ease excavation costs during construction and maintenance in the future, pipes have been modeled in compliance with the maximum crown depth criteria of fifteen (15) feet. Extremely flat regions connecting to higher elevation areas are assumed to require sewer lift stations in order to meet the specified modeling criteria. Additionally, extremely flat areas within each of these subcatchments also included the placement of lift stations to stay within maximum depth criteria. In reality a more focused study of ground contours in the planning of the sewer system may eliminate the need for some, require additional, or change the location of these concept level, sewer lift stations. The collection system for the Twentynine Palms area has been conceptually designed to service all properties within the service area. The majority of flow was modeled to operate under gravity flow conditions for disposal at a future WWTP facility.

6.2.2 Trunk-Sewer Pipelines
After the model construction and hydraulic simulations have been performed, the model outputs were closely analyzed to determine where the system needed to be adjusted in order to meet the established planning criteria. Multiple iterations of the model adjustment and simulation analysis process were performed to achieve overall system conformance with the design criteria. In designing a trunk sewer layout that efficiently and cost effectively collects (maximize gravity sewers) and send all sewer flows to a potential treatment plant, it is necessary to have a mix of gravity and force mains. Though majority of the pipelines were gravity, a few force mains were also included due to the system’s need for area specific lift stations.

Recommended pipe sizes for the modeled system for gravity lines ranged from 10 inches in the sparsely populated un-incorporated area to 42 inches at the head of the system heading to the wastewater treatment plant where the entire flow for the system gets accumulated. Force mains ranged from 6 inches to 30 inches for the system. The majority of the gravity trunk pipelines

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were 18 or 24 inches in size. Table 6-1 below summarizes the recommended pipe sizes and modeled lengths for all trunk lines in the system.

TABLE 6-1

SEWER SYSTEM PIPE TYPES, SIZES AND LENGTHS
Pipe Size (inches)
Gravity Total Length (ft)
10 9,100
12 4,700
15 19,000
18 28,500
24 31,900
36 4,200
42 4,900
Force Mains
6 1,200
8 1,600
10 3,400
12 3,900
18 21,400
30 1,300

6.2.3 Wastewater Treatment Plan
Selection criteria used to evaluate the siting of the WWTP included a number of criteria. These included available area, land use, non-proximity to residential areas, maximizing use of gravity flow, drainage patterns etc.

6.2.3.1 Mainside Facility
The Mainside WWTP treats all of the wastewater generated from the Mainside area including the Marine Palms, Adobe Flats, camp Wilson area and Ocotillo Heights base housing area.

Because of several concerns sited in previous studies regarding the implementation of a joint facility for both MCGACC and the City, it was assumed that the mainside treatment facility will be used in the future to treat flows for the population residing in the Base area. The concerns for building a joint use facility include ownership and operation of the facility, large pipeline costs to transfer the City flows to the mainside facility, control over regulating treatment policies and water reclamation issues. The continued use of the Mainside WWTP is assumed to treat wastewater collected from that area. The existing infrastructure and operating processes are already in place and is assumed to continue to serve the Base population. Due to the increase in population, upgrades will be needed to the current facilities to accommodate the increase in population and flow rates in the future.

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6.2.3.2 New WWTP for Area Flows
A number of sites locations were considered and evaluated for a potential future WWTP. Based on the selection criteria, need for overarching cost control measures, and discussions with the City and District staff, a generalized location for the wastewater plant is suggested in the vicinity of Amboy Road and Bagdad Road. Based on our siting discussions, no particular area was selected at this time. The topography of the project area tends to generate a drainage pattern which slopes towards the South West therefore it was taken into consideration that having a treatment facility in that area would maximize the use of gravity sewers. As per earlier studies, it shows that approximately 70 acres of land may be available for the WWTP in this area. This allows for the treatment plants layout and siting, and future facility expansion if desired. The area is mainly undeveloped and may be a suitable location for a centralized treatment facility.

Note that for future refinement, the project would need to go through the environmental review process. California Environmental Quality Act (CEQA) and National Environmental Policy Act (NEPA) studies will be required for further refinement of the plan siting. After the environmental process, the best location for siting this facility should be determined. The location of the treatment facility determines the direction of flow, lift stations needed, and sizes of the pipelines.

Figure 5-1 reflects the generally alignment and location of a potential trunk sewer system and the accompanying lift stations associated with conveying wastewater to a wastewater plant in this general location.

6.3 Treatment Disposal Technologies and Options
Various treatment disposal technologies and options were evaluated for the disposal of the wastewater generated. The objectives for the proposed wastewater treatment plant are to:
● Provide a long term build-out capacity of approximately 9.3 MGD ● Process domestic strength (commercial and residential) wastewater ● Produce a reliable Title 22 (2.2 tertiary) effluent for disposal to surface spreading grounds
● Process the sludge to a Class B standard for disposal ● Have the ability to gradually accept flows from less than 1.0 MGD to the ultimate plant capacity level

6.3.1 Cost Effectiveness of Staging
There are two overriding challenges that are critical and could affect the process. The first is the large capital cost of the total plant capacity being allocated to a small customer base that would initially be available to fund both capital and operating costs. A basic cost could exceed $40,000 per single family household unit, solely for the treatment plant, excluding the cost of the collection system improvements. The second, is challenge associated with facility staging, an issue that is inherent with building small treatment process units for 1 MGD with the need to either demolish or attempt to integrate unequally sized process units as the facility expands to its ultimate 9.3 MGD capacity. Operating a plant with a multitude of process unit sizes, all trying

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to perform identical tasks is an un-desirable outcome. However, there is a solution that overcomes these two challenges.

In developing communities, the dilemma of how to cost effectively “grow” a wastewater treatment plant efficiently is a common one, and is generally resolved by building system flexibility and cost effectiveness into the long-term facility needs. The staging technique focuses on building process units that become conversions for expanded plant capacity. As such, as expansion is needed, a “re-labeling” process is derived so that existing tanks originally designed to perform a specific function is “re-labeling” in the expansion to do a different function. The potential plant development scenario derived herein is explained below.

6.3.2 Plant Development Scenario
The following scenario describes how the above might work for Twentynine Palms:
 Initially a sequencing batch reactor (SBR) plant, fabricated from three circular tanks, would be installed for a Stage 1, capacity of 1.0 MGD. Install the basic process units for producing tertiary effluent. Include a site footprint for the final treatment plant, allowing the SBR units to be located in the area where solids treatment will occur. Include a single building that serves as combination housing for electrical MCC, operations center, and shop. This building would eventually become the shop facility for the final 2.0 MGD layout.
 Create a different process plant for 2.0 MGD. Incorporate the SBR process units and convert them into two aerobic digesters and a holding tank. Add a portion of the nonprocess buildings that are planned for the Stage 2, 2.0 MGD plant layout  Expand the 2.0 MGD Stage 2 plant by duplicating parallel process units for a combined capacity of 4.0 MGD of the Stage 3 plant. Complete the addition of the non-process buildings by adding the administration building.
 Expand the Stage 3, 4.0 MGD plant to the final Stage 4 plant with the projected ultimate capacity of 9.3 MGD. This final expansion, as in Stage 3, would be completed by building parallel units.
 There are two options for this particular plant: either make the 2 MGD the common unit size or make 4 MGD the common unit size. If 2 MGD becomes the common unit size, then Stage 2 is the starting point for a change from the SBR process to the selected final process. If, however, 4 MGD becomes the common unit size, then Stage 2 continues with the SBR process (by duplicating Stage 1) and Stage 3 becomes the starting point for the selected final process.
 The advantage of making Stage 2 the starting point is that the necessary “standby” process unit required for Title 22 compliance is smaller and less expensive.  The advantage of making Stage 3 the starting point is that more capital costs become deferred later.

By following the above pattern, the below mentioned important benefits would occur. No capital would be invested prematurely in fixed assets before they are capable of being used and useful.

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Also, the plant capacity would always be used at or above the minimum operating capacity. An important factor in operations is that a wastewater treatment plant cannot be successfully operated below a threshold minimum capacity (20 to 25 percent of the rated capacity).

Additionally, very nominal asset value would be lost in transition from one capacity to another and finally at no time, would the plant configuration result in an inefficient operation.

By following this plant development scenario of plant construction and operation, the results would be:
 Cost-effective implementation
 Completion of the “plan” for the final stage of plant layout  Operational performance that is efficient as the flow vs. capacity follows a parallel growth  Treatment objectives remain at a constant standard
 The groundwater resources are protected equally well at each stage of plant capacity

6.3.3 Treatment Process Selection
An important decision is the process selection at each of the stages of the plant expansion.

Initially, an SBR plant provides the flexibility to operate within a wide flow and loading range and also allows the process units to be integrated into a larger capacity plant in a different role and sludge processing units. After stage 1, a process selection should be made that can be replicated with parallel units for the ultimate plant capacity of 9.3 MGD.

6.3.3.1 Sequencing Batch Reactor
Construct three above ground circular tanks. Two will be batch reactors and the third a sludge aeration vessel. These will provide a nitrified and de-nitrified secondary effluent followed by a cloth disk filtration unit (Title 22 certified). Include one more disk inside the tank as a standby tertiary unit. Follow the tertiary treatment with a sodium hypochlorite disinfection system.

Provide adequate contact time to include a 90 minute modal contact time at peak dry weather flow.

Once the SBR system is converted, the larger two tanks will serve as sludge aeration basins for meeting Class B sludge and the smaller tank will serve as a holding tank for recirculating streams (tertiary backwash, rejected effluent, drainage). If dual SBR systems (1 MGD each), are constructed, all four of the larger tanks will serve as sludge aeration basins and the two smaller tanks can be dedicated for separate purposes; one for recirculating streams and one as an effluent equalization basin.

6.3.3.2 Extended Aeration Membrane Bioreactor
The advantages and dis-advantages of this process have been considered in other reports 1, 2 the process depends largely on the technological advances that have been made in the fine pore membrane manufacture. It does produce an exceptionally high quality effluent, even to a quality that exceeds the Title 22 requirements for the effluent that will be disposed by surface

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spreading on the ground for percolation. In addition to the stringent turbidity and coliform standards, it will also meet very low nitrogen limits as well.

However, in the past decade, the operating aspect of membrane bioreactors has raised the issue of maintenance. The membranes are submerged in the mixed liquor. Periodically, cleaning requires the membranes to be removed from the mixed liquor in the reactor basins, raised to a level where maintenance workers can physically hand clean the cassettes of membrane fibers. This procedure has been considered a negative aspect of the membrane technology. Several wastewater agencies have refused to use MBR due to this particular aspect of their use.

6.3.3.3 Modified Ludzack Ettinger
The mLE process consists of two stages of reactor basin; an anoxic zone and an oxic zone. The anoxic zone precedes the oxics zone and receives the influent wastewater together with recycled mixed liquor rich in nitrate, and return activated sludge. The nitrate is reduced to elemental nitrogen gas. The oxic zone oxidizes organic matter and the ammonia and organic nitrogen. The section below illustrates the process in a schematic format.

This technology is currently in place in many wastewater plants in southern California and provides wastewater treatment that also meets the requirements for a Title 22 effluent and will meet a nitrogen limit of between 5 mg/l and 8 mg/l. This range is typically what is permitted for inland discharges in southern California. The mLE process is a subset of the “extended aeration” process. It provides the long detention time for solids and it also provides nitrification and de-nitrification. It can be tailored to reduce total nitrogen to a concentration as low as 5 mg/l. Lower than that number, a five-stage process called the Five-Stage Bardenpho (often simply referred to as “Bardenpho”) that can reduce total nitrogen to 1 mg/l and total phosphorus as low as 0.2 mg/l.

6.3.3.4 Five Stage Bardenpho
The Bardenpho process is simply an mLE process with three added stages. It includes in sequence Anaerobic-anoxic-oxic-anoxic-oxic. The purpose of this extended version of the mLE process is to create more recirculation and further reduce not only total nitrogen but also phosphorus. It can produce nitrogen and phosphorus concentrations not feasible from the mLE process. It is only necessary to use where an mLE process is not adequate for phosphorus removal.

6.3.4 Recommended Process for Twentynine Palms
Studies conducted for wastewater treatment for other regions like the High Desert favors an extended aeration MBR. For various reasons, this process was estimated to be the most attractive. However, the MLE process can provide the necessary water quality and perform at a lower capital cost and lower maintenance cost. The total process train would consist of:
● Influent screen and flow meter
● Grit tank and grit separation equipment
● Anoxic basin(s)

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● Oxic basin(s)
● Secondary clarifier(s)
● Recycle pumping (RAS and MLR)
● Tertiary filtration
● Disinfection
● Sludge aeration
● Sludge drying beds
● Effluent spreading ground

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Section 7: Capital Improvement Program (CIP)
This section includes a summary of the potential capital costs for the infrastructure of the trunksewer wastewater system derived to meet a build-out scenario for Twentynine Palms. The system includes the modeled system backbone, wastewater treatment facility, major laterals and lift stations as discussed in Section 5 and Section 6.

7.1 Cost Estimating Criteria
Capital costs were developed for the potential build-out sewer trunk system, trunk system facilities, wastewater treatment facility based on Class 5 conceptual stage design concepts and with the guidance of recent regional project experience, vendor quotes and cost estimating reference standards. Costs presented herein are considered to be conceptual level planning costs and should not be used for design purposes. This following section summarizes the methodology used to develop the base cost criteria for developing preliminary opinions of probable capital costs for the capital improvement projects. All costs presented in this section have been adjusted to an Engineering News Record (ENR) construction cost index, which represents the average 2012 ENR cost index for the Los Angeles Area.

Total project costs include a summation of all construction materials costs, engineering, management costs, taxes and standard overhead and profit margins. Soft costs (engineer, project administration and construction management) were estimated to be 25% of the construction cost for system facilities. Taxes on materials were estimated to be 7.75% and Contractor overhead and profit were estimated to be 15%.

7.1.1 Trunk Sewer Costs
Unit costs per linear footage for the various sizes for both gravity sewer and force main are presented below in Table 7-1. The pipe material for the gravity sewers was assumed to be high density polyethylene (HDPE) for small and medium diameter pipes and concrete for large diameter pipes. The material for the force mains was assumed to be polyvinyl chloride (PVC).

TABLE 7-1

SEWER TRUNK SYSTEM UNIT COSTS
Sewer Type Pipe Size (in) Unit Project Cost ($/LF)
Gravity Sewer 10 218
15 262
18 281
24 349
36 696
42 859
Force Main 6 203
8 218
10 247
12 286
18 392
30 619

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Table 7-3, in the following sections, shows the summary of the total cost for both the gravity sewers and the force mains for the trunk sewer and the major laterals evaluated for the system.

Detailed cost estimates are included in Appendix B.

7.1.2 Manholes Costs
For the purpose of estimating on a per linear foot basis, manholes were added to the cost of the pipes. Manholes were assumed to be placed every 500 feet, as per the planning criteria, on the pipelines and for the purpose of estimating were assumed to be between 6 and 10 feet deep based on the size of the pipe. Manholes ranged in cost from $3,700/each to $10,925/each, installed, depending on the size and depth of the manhole, which is a function of the size of the pipe. Table 7-3, in the following sections, shows the summary of the trunk sewer pipeline costs which includes the total cost for the manholes evaluated.

7.1.3 Collector and Laterals Costs
Generating a complete CIP also required that there be costs associated with a collector system for local areas within the city that drain to the trunk system. Due to the level of complexity and the intricacy of planning and design that go into this system it was unrealistic to estimate the quantity of collectors required. The cost for the collector and lateral pipelines was calculated on a standard 8 inch pipeline unit cost. This is shown to be a realistic estimate based on previous experience and studies in other parts of the region. Table 7-3, in the following sections, shows the summary of the total cost for the collector pipelines.

7.1.4 Trunk System Lift Stations
Conceptual estimates of trunk system lift station costs were also developed based on anticipated lift station sizes and flows. Lift stations were sized to handle peak flows modeled through the section of trunk being served. Flows ranged from 300 gpm in the outlying and unincorporated areas to over 10,000 gpm at the lift stations near the head of the system leading up to the treatment plant. Lift stations were estimated based off of total estimated completion cost with phasing not taken into account.

Note that as the system was modeled for ultimate build-out flows, many of these facilities may not be needed for years because the area would not reach its build-out population. For example lift stations in earlier phases may not require that they be completed because the full flows to be served by those lift stations will not be expected for several years. Costs associated with intermediate time frame have not been evaluated as scope of this project and should be evaluated as part of a feasibility study in future. The basic purpose for the CIP cost estimation for this study is to get an idea of how much the City/District will need to spend if it looks at the option of building a wastewater collection system in accordance with its General Plan growth and land use trends and if it would be realistic to spend a huge amount of capital to construct a collection system to treat the areas wastewater.

List station costs for the area lift station facilities are provided in Table 7-2 below. Smaller lift stations (near and below 1,000 gpm) were generally assumed to be package facilities using submersible pumps (see Section 6 for more details). For the purpose of cost estimating, larger facilities were generally assumed to be vertical turbine pump (VTP) facilities including a wet

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well-dry well. These larger facilities were also assumed to require backup power generation.

Detailed cost estimates are included in Appendix B.

TABLE 7-2

LIFT STATION CIP COSTS
Facility Total Cost
Submersible Pump Stations $4.0 M
Sub-catchments: 1, 2, 6, 10
Vertical Turbine Pump Stations $17.2 M
Sub-catchments: 3, 9, 10

7.1.5 Wastewater Treatment Facility
As discussed in Section 6, the wastewater treatment facility for Twentynine Palms is projected to initially be designed with an SBR process and then modified to a mLE process in subsequent phases to more efficiently treat additional flows. The estimated cost of this facility is approximately $150 million dollars. This cost includes the cost for earthwork, concrete, equipment for a 9.3 MGD facility.

7.2 Total CIP for Entire Area
A summary of the total estimated cost for each CIP component is presented in Table 7-3, with the majority of these facilities shown graphically on Figure 7-1. The estimated capital cost for the combined CIP is approximately $290 million. The single largest cost component is for the wastewater treatment facility. The configuration of the trunk facility system was based primarily on the topography and overall drainage patterns of the Twentynine Palms service area.

TABLE 7-3

ESTIMATED CIP COSTS FOR BUILD-OUT AREA
Note: Total build-out CIP to support Twentynine Palms service area.

It should be noted that a large portion of the area modeled and planned for in this study is located outside of the City of Twentynine Palms and is known as the Unincorporated Area north of the City. A screening assessment was performed to identify the influence of this area on the total CIP cost. For this assessment, the facility sizes and flow volumes downstream of the Unincorporated Area were retained, suggesting a narrow focus on the facilities located outside of the City. In that way, a separate cost comparison could be derived. The results of this assessment are shown in Table 7-4 below. As shown, there would be a reduction of approximately $25 million by excluding the unincorporated area piping from the long-term Facility Total Cost Million $
Trunk Sewers System $46 M
Lift Station Facilities $21 M
Collectors and Laterals $72 M
Wastewater Treatment Facility $150 M
Total Approximate Capital Cost $290 M

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system build out cost considerations. The build-out system plan, adjusted to extract the unincorporated area, is graphically depicted in Figure 7-2.

TABLE 7-4

ESTIMATED CIP COSTS EXCLUDING NORTHERN UNINCORPORATED AREA It is important to note that there are multiple alternative configurations and alignments that could be developed to support the potential phasing of a wastewater collection and treatment system for the Twentynine Palms area. For example, in addition to the exclusion of the large northern Unincorporated area, additional scrutiny could be provided to extract large rural areas with a prevalence of large parcels (refer to Appendix C) as sewering these areas likely provides minimal benefit to reducing septic loadings on the groundwater basin and may not be economically feasible to construct additional sewer infrastructure.

At the City’s request, one such scenario was developed to consider excluding low density residential land use parcels throughout the City. For this scenario, low density residential parcels (GP land use-RL 1-ac, RL 2.5-ac, RL 5-ac, SRF E, Tribal Land, OSR, OSR-40) with a density less than or equal to 1 DU/ac were excluded from future sewer system considerations.

Excluding the 26,000 acres and approximately 8,700 potential dwelling units from future sewage system requirements, would further decrease future flows by approximately 1.7 MGD for the above areas and further reduce the capital improvement program by approximately $100 million. The results of excluding the Unincorporated area and these low density areas would suggest the need for a 6 to 6.35 MGD sewer collection and treatment system at a planning level cost of approximately $170 - $190 Million.

As exemplified from this section of the Master Plan, should sewers be needed in the Twentynine Palms area, there are a number of alternative configurations and sewering strategies that may meet that need. Therefore, as future groundwater, septic and wastewater evaluations are conducted and the need for sewers is appropriate, additional implementation programs and costs should be developed to derive a suitable sewer system phasing plan for the Twentynine Palms community.

7.3 Overview of the SNMP Findings and Influence on the CIP The following Section discusses the findings and recommendations of the SNMP and discusses how these influence the WWMP process.

7.3.1 Existing and Future Wastewater Systems
As discussed earlier, the area of Twentynine Palms is currently served by septic systems. When properly designed, sited, installed, and maintained, conventional septic tanks are capable of Facility Total Cost Million $ Difference in Cost
Trunk Sewers System $39 M $7M
Lift Station Facilities $18 M $3M
Collectors and Laterals $57 M $15M
Wastewater Treatment Facility $150M -
Total Capital Cost $265 M $25M

FINAL Twentynine Palms Wastewater Master Plan Page 7-5
approximately 65 percent removal of suspended solids, and biodegradable organic compounds.

Most traditional systems rely primarily on physical, biological, and chemical processes in the septic tank and in the unsaturated soil zone below the septic tanks (commonly referred to as a leach field or drain field) to sequester, or attenuate pollutants of concern. In areas with appropriate soils and hydraulic capacities, they are designed to treat the incoming waste load to meet public health, groundwater, and surface water performance standards.

Nitrogen, phosphorus, pathogens, and other contaminants are present in significant concentrations in most wastewaters treated by onsite systems. Although most can be removed to acceptable levels some may remain in the effluent exiting the system. More recently, however, certain pollutants present in wastewater from septic systems are raising concerns in the regulatory compliance, including nutrients (e.g., nitrogen and phosphorus), pathogenic organisms, toxic organic compounds, and metals. In response to this recent increased concern for threats to groundwater quality from septic tanks, the City and the District retained Kennedy/Jenks Consultants to prepare a Salt and Nutrient Management Plan (SNMP) to assess the long-term potential impacts to groundwater quality from the use of current septic tanks in the Twentynine Palms area. This plan, being prepared under a separate cover, proposes a longterm groundwater quality monitoring plan and other appropriate wastewater management practices.

As population growth continues in the area and more lands are urbanized, groundwater pumping within the District service area is anticipated to increase. Potential effects of these changes on the water use and on the sewer loading to groundwater are important elements of a sustainable water supply for Twentynine Palms. It is for these reasons that the Ground Water Protection Plan suggests the need for additional groundwater management programs.

7.3.2 Salt and Nutrient Management Plan Overview
The guidelines prepared for salt/nutrient management plans to was used to develop a comprehensive strategy to monitor and protect the groundwater resources in the area, analyzes nutrient loadings for the various groundwater basins in the area and evaluates loading reductions to balance these basins to avoid potential water quality impacts because of septic systems in the Twentynine Palms area. In addition to the objectives of the SNMP, the premise of developing the Wastewater Master Plan (WWMP) was that if the continued discharges from septic systems would unreasonably degrade the groundwater quality and result in widespread groundwater pollution and compliance issues, the need for a community wastewater collection, treatment, and disposal system would be promoted through the WWMP. This will help the District and the City make informed decisions on wastewater management while protecting groundwater resources. Collectively, the SNMP and WWMP serve as two major elements of the overall management plan developed by the City and District for assessing the potential impact on groundwater quality from the existing septic systems and anticipated future development.

Current, future (year 2035) and build out salt and nutrient loading conditions were evaluated in the SNMP using an Excel ™-based groundwater models (see SNMP for details). The analysis was based on measured historical groundwater quality data collected by the District to show the historical conditions of groundwater quality in each basin and to look for evidence of increasing trends in salt and nutrient concentrations and related effects on groundwater. Data related to septage, primarily for salt (total dissolved solids) and nutrients (nitrate) was evaluated to see if concentrations exceed or threaten to exceed water quality objectives based on the primary and

FINAL Twentynine Palms Wastewater Master Plan Page 7-6
secondary maximum contaminant levels (MCLs) for chemical constituents in drinking water. The models were developed to identify major inflows into and out of the groundwater basins underlying the Twentynine Palms area and evaluate concentrations of the salt/nutrients. The results of the models were used as the basis to quantify the volume of water contributing to each basin, including recharge from septic tanks, with the corresponding water quality of water entering the aquifer system.

Groundwater outflows were identified to evaluate the resulting mass and concentration of salt and nitrate in groundwater exiting the aquifer system. The WWMP utilizes the results of the analyses above. The need for sewer infrastructure was based on the underlying principal that if projected salt/nutrient loadings, calculated using the GW models, exceeded the assimilative capacity of the groundwater basins, then a wastewater system will be needed to manage the salt/nutrient excess loadings for a given basin. Based on the mass balances of contaminants within each groundwater basin, the areas that could be considered for sewers were identified.

The above approach took into account that acceptable salt and nutrient regulatory requirements were met and did not violate the water quality requirements as specified by the Regional Water Quality Board.

7.3.3 Salt and Nutrient Management Plan Findings
Because the infrastructure requirements of the WWMP are driven by the results evaluated in the SNMP, the general approach for a phasing program is based on a time-based quantitative assessment of salt and nutrient loading to the groundwater system. The Current and 2035 conditions were evaluated by analyzing both spatial distribution and temporal trends for each groundwater basin. The assessment at the basin scale accounts for spatial variations in land use, water demand, and basin hydrogeological conditions.

To demonstrate temporal trends and the potential effects of changes in land and water use, results of the Current and 2035 Scenarios were compared based on the assumption of the continued discharges from septic systems from future anticipated land use development and the increase in water demand. The primary objective of the salt and nitrate balance models is to estimate the mass loading into groundwater basins underlying the septic tanks and resulting concentration in groundwater with the mixing of septic recharge with the existing groundwater.

An analysis and documentation of the regional water balance, nutrient loadings, and groundwater impact analysis was performed in the SNMP. As noted therein, these key criteria were derived based on available data.

Based on the calculated loadings, critical basins were identified and a prioritized phasing program based on specific area-wide impacts of nitrogen was established. The phasing approach looked at prioritizing and converting the septic areas to a sewer system where the groundwater quality regulations were being violated under given conditions. Areas where these requirements were not being met under current conditions were of primary concern and considered for inclusion in a Phase 1 sewering plan.

Among the four basins underlying the project area, the Mesquite Lake South basin showed the highest septic nitrogen loading (45 ton/yr), consistent with the highest population and density in this area. Under current conditions, the results of the mixed cell models showed that the northern portion of the Mesquite Lake basin is about 15 ton/yr, representing one third of the loading estimated for the southern portion. The areas overlying the Indian Cove, Fortynine

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Palms and Eastern basins are less populated; thus, nitrogen loading from septic tanks in these basins is estimated to be relatively small, ranging from 7 ton/yr to 9 ton/yr. Nitrogen contribution through exchange flows is the highest for the northern Mesquite Lake basin, as a result of groundwater flowing toward the northern Mesquite Lake basin from the southern Mesquite Lake basin as well as the three smaller basins (Indian Cove, Fortynine Palms, and the Eastern). In summary, the Mesquite basin South and the Eastern basin appear have the highest potential need for mitigation and therefore should be considered for inclusion in Phase 1 of the potential mitigation plan.

The amount of wastewater flow that should be removed from the basin (through a sewer system) is calculated to balance these basins in accordance with appropriate regulatory requirements. As such, the reduction in N loading was calculated to achieve the MCL by removing septic loading for the Current scenario under Phase 1. The Mesquite Lake and Eastern basins are both above MCL in the mixing cell model.

To reach the MCL in Eastern, septic flow needs to be reduced from 200 AFY to 83 AFY. This is a reduction of 117 AFY or 0.104 MGD. Similarly, to reach the MCL in Mesquite Lake South, the septic flow should be reduced from 1038 to 460 AFY. This is a reduction of 578 AFY or

0.516 MGD. The resulting total septic flow reduction is approximately 0.72 MGD. A Phase 1 wastewater system alignment was selected to match the reduction in flow needed and spatially cover the high density areas in the Eastern and Mesquite Lake South, where these flows get generated.

Note that, this alignment was a sub-set of the baseline alignment developed for the build out conditions. Based on topographical and watershed analysis the location of the treatment plant was selected to be in the eastern part of the projects area (near North Amboy Road and Bagdad Road). All phased alignments assumed that if critical areas were converted from septic to sewer infrastructure the flows will be treated at the selected treatment plant site. Hence, during the phasing approach the baseline alignment formed the backbone system and was divided into time-phased infrastructure required to satisfy the given reduction in the loading for each subbasin.

7.3.4 Groundwater Protection Sensitivity Analysis and
Implementation Plan for Phasing of Improvements
It is important to note that that SNMP clearly indicates the need for additional data, because loading estimates were based on various assumptions i.e. percentage septic loading removal, septic effluent concentration, etc. These assumptions were based on typical industry standards and accepted values in the vicinity areas of Twentynine Palms. As such, a sensitivity analysis was performed to evaluate the impact of increasing or decreasing these assumptions on the Phase 1 base case. A summary of the assumption adjustments and findings is show in Table 7-5 and discussed below.

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TABLE 7-5

SEPTIC LOADING RATE

SENSITIVITY ANALYSIS (CURRENT CONDITIONS)
Parameter/Findings Base Case Low Loading High Loading
Septic Effluent Concentrations 40 mg/L 30 mg/L 50 mg/L
Percent Loss in Nitrogen 20% 10% 30%
Summary of Findings
Nitrogen Findings
MCL 10 mg/L 10 mg/L 10 mg/L
Eastern Sub basin 7-9 ton/yr Update Values Update Values Mesquite Sub basin 45 ton/Year Update Values Update Values Volume of Flow Required for N Removal (MGD)
Eastern Sub basin 0.104 0.040 0.130
Mesquite Sub basin 0.516 0.043 0.750

7.3.4.1 Revised Lower Loading Conditions
As expected, with reduced loading conditions, no additional basin was affected. Moreover, it is important to note that both the Mesquite Lake South and Eastern basins are very near the MCL in this analysis.

For the low loading case, the septic effluent concentration was decreased from 40 to 30 mg/l Nitrate as N, and the percent septic loading removal in leach field was increased from 20% to 30%. To reach MCL in Eastern, septic flow needs to be reduced from 200 to 155 AFY. This is a reduction of 45 AFY or 0.040 MGD. To reach MCL in Mesquite Lake South, reduce septic flow from 1038 to 990 AFY. This is a reduction of 48 AFY or 0.043 MGD. Total septic flow reduction is 0.083 MGD.

As shown in Table 1, under the revised lower loading conditions, only the Mesquite Lake South basin has a material variation from the adopted MCL, suggesting that Phase 1 of a potential sewering plan could be limited to remediating the potential degradation of this basin. Phase 2 or a Phase 1a of a sewering plan could also consider the inclusion of the minimal additional flows from the Eastern basin.

7.3.4.2 Revised Higher Loading Conditions
Under the higher loading conditions analysis, the Mesquite Lake South and Eastern basins remain as the only basins above MCL, albeit at higher levels of potential degradation. Phase 3 of the WWMP was developed to remediate these two basins under current conditions and the revised higher loading rates.

Under Phase 3, the septic effluent concentration was increased from 40 to 50 mg/l Nitrate as N, and the percent septic loading removal in leach field was decreased from 20% to 10%. To reach MCL in Eastern under this case the septic flow needs to be reduced from 200 to 55 AFY.

This is a reduction of 145 AFY or 0.130 MGD. Similarly, to reach MCL in Mesquite Lake South, reduce septic flow from 1038 to 200 AFY. This is a reduction of 838 AFY or 0.750 MGD. Total

FINAL Twentynine Palms Wastewater Master Plan Page 7-9
septic flow reduction is 0.88 MGD. This flow was assumed to be removed using sewers in order to balance the groundwater basins. Phase 3 infrastructure requirements were calculated based on the above flow reductions.

The next phase, Phase 4, of the WWMP was based on the 2035 model results at the baseline loading rates. Under 2035 condition, the Mesquite Lake and Eastern basins are also above MCL in mixing cell model. To reach MCL in Eastern, reduce septic flow from 309 to 100 AFY.

This is a reduction of 209 AFY or .187 MGD. To reach MCL in Mesquite Lake South, reduce septic flow from 1633 to 890 AFY. This is a reduction of 743 AFY or .663 MGD. Total septic flow reduction is .85 MGD. The wastewater system alignment will be very similar to previous phases with extensions to the south west and west part of the Twentynine Palms area.

The SNMP recommends a series of strategic tools such as the monitoring plan and BMPs to help with the management of the basin. Due to the availability of limited data during the preparation of these plans one of the critical recommendations is to consider comprehensive monitoring programs to gather useful data over the next several years. This data collection will help in the refinement of the underlying assumptions made as part of this plan and develop updates based on concrete field data. Currently, except for industry standards and values used for developing similar plans by nearby agencies, there is little data underlying these assumptions. Additional monitoring data collected, specific to the Twentynine Palms area, would be valuable in improving the accuracy of water usage, salt and nutrient loading and load reduction estimations, and would result in more reliable and efficient groundwater management plans and programs. It would also facilitate additional refinements to the groundwater basin remediation needs and the potential need for localized sewers as part of this project.

Due to the above data limitations, it is assumed that no facilities would be constructed until the SNMP recommendations have produced additional data and further analysis performed. At that time, the assumption in this master plan can be updated and, if appropriate, a sub-basin specific phasing plan derived for the remediation of potentially impacted groundwater basins.

7.3.5 Ultimate Build-Out of Wastewater Improvements
While the City’s General Plan shows land use designations for the build-out, it is currently unknown how the ultimate land use development would occur in the future. In general, uncertainties associated with potential system demands and impacts increase as projections move further into the future. Based on the relatively slow historical growth rate and economic down turn conditions in recent years, the build-out of the City based on the General Plan is anticipated to take place over several decades, perhaps even a century. Given the high uncertainty and remote possibility of the ultimate build-out land development in the long-term planning horizon, qualitative discussion for the build-out scenario is included in the SNMP to highlight the uncertainties and water supply and water quality issues anticipated with the buildout. While a quantitative analysis was for these ultimate build-out conditions was not performed in the SNMP, a potential ultimate sewer infrastructure program was derived in this WWMP to provide an important perspective on the magnitude and financial consequences of such a system. It should be noted that this ultimate system was developed herein to provide a framework for long-range planning purposes and presumably would never be implemented.

FINAL Twentynine Palms Wastewater Master Plan Page 7-10

7.4 Conclusion and Recommendations
As shown, the infrastructure costs associated with a sewer system for the entire area to serve its build-out population are extremely high. Moreover, it is reasonably certain that many, many years will pass before this area would reach it’s built-out population. Since the WWMP is driven by the SNMP, implementation should be based on the finding and analyses derived from future monitoring activities as an element of the SNMP. The critical features of the SNMP monitoring and protection plan include increased sampling frequency of existing district production wells, long-term monitoring well network from existing well, detailed monitoring at key locations as identified in the SNMP and conducting sampling event. Additional Sewer System Management Elements are provided in the SNMP with the goal of proactively managing the quality of local groundwater.

The focused recommendations of the SNMP are to implement measures to improve the overall groundwater monitoring and to implement a Septic System Management Program to limit further impacts to the groundwater. Since the current nitrate concentrations in the District's production wells show relatively stable concentrations, it is considered appropriate to gather more data to support the preparation of a more detailed assessment.

The SNMP also recommended that the District and City adopt a Septic System Management Program to properly manage septic tanks by limiting loading rates as part of an integrated effort to protect groundwater quality. The elements of this Program are designed to provide mechanisms to reduce loading at the source before entering the groundwater system. A Septic System Management Program is presented to outline the approach for such a program, and are contained in the accompanying SNMP.

It is anticipated that after three to five years of monitoring and implementation of the SNMP and Septic System Management Program, a comprehensive assessment will be conducted to evaluate the impacts of septic systems on the groundwater. The outcome of this evaluation can then be used to support the development of local septic system policies and update the WWMP to reconsider the need for sewer system infrastructure at that time. Proceeding in this methodical manner would provide a cost effective strategy for short-and long-term groundwater management and protection.

FINAL Twentynine Palms Wastewater Master Plan Page R-1
References
California Department of Water Resources (DWR), 1984. Twentynine Palms Ground Water Study, California Department of Water Resources, Southern District, Los Angeles, CA, 109pp.

California Department of Water Resources (DWR), 2003. California’s Groundwater, Bulletin 118, Update 2003, California Department of Water Resources, Sacramento, CA, 265pp.

California Regional Water Quality Control Board (RWQCB), 2007. Water Quality Control Plan, Colorado River Basin Region 7, June 2006.

California Regional Water Quality Control Board (RWQCB), 2011. Water Quality Control Plan Resolution/Amendment, Colorado River Basin Region 7, May 2011.

California Regional Water Quality Control Board, Colorado River Basin Region 7 (RWQCB), 2006. Order No. R7-2002-2006. Waste Discharge Requirements for United States Marine Corps Base, Owner/Operator Mainside Wastewater Treatment Plant and Wastewater Collection and Disposal Systems, Twentynine Palms – San Bernardino County.

California Regional Water Quality Control Board Colorado River Basin Region 7 (RWQCB), 2011. Staff Report in Support of a Basin Plan Amendment to Prohibit the Discharge of Wastewater into the Ground from Septic Systems in the Town of Yucca Valley. May 2011.

California Regional Water Quality Control Board Colorado River Basin Region 7 (RWQCB), 2011. Guidelines for Sewage Disposal from Land Developments, Resolution No. 79-42, March 14, 1979.

City of Twentynine Palms, 2012. Twentynine Palms Water District Water Pipelines Map, 2012.

City of Twentynine Palms, Twentynine Palms, CA.

Dibblee, T.W. Jr., 1968. Geologic map of the Twentynine Palms quadrangle, San Bernardino and Riverside Counties, California, U.S. Geological Survey Miscellaneous Geologic Investigations Map I-561, U.S. Geological Survey, 1pl.

Dudek & Associates, Inc., 2006. Wastewater Feasibility Study, dated May 31, 2006, report prepared for Joshua Basin Water District.

Environmental Systems Research Institute. ArcGIS. Version 10.1. Redlands, CA: Environmental Systems Research Institute, Inc., 2010.

Environmental Systems Research Institute. World Topographical Map, 2010. Redlands, CA:

Environmental Systems Research Institute, Inc., 2010.

Freckleton, J.R., 1982. Ground water in the Twenty-Nine Palms Indian Reservation and vicinity, San Bernardino, County, California, U.S. Geological Survey Water-Resources Investigations Report 82-4060, U.S. Geological Survey, Sacramento, CA, 50pp.

Freeze, R.A. and J.A. Cherry, 1979. Groundwater, Prentice Hall, Upper Saddle River, NJ, 604pp.

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Haley and Aldrich, Baseline Report, 2000, Compilation of Groundwater and Wells Information within the Twentynine Palms Water District Service Area, December 2000.

Jenssen, P.D. and R.L. Siegrist (1990). Technology assessment of wastewater treatment by soil infiltration systems. Water Science & Technology, Vol. 22, No. 3-4, pp. 83-92.

Kennedy/Jenks Consultants, 2001. Final Groundwater Management Plan, report prepared for Twentynine Palms Water District, Kennedy/Jenks, Ventura, CA, 50 pp.

Kennedy/Jenks Consultants, 2005. 2005 Urban Water Management Plan Update, report prepared for Twentynine Palms Water District, Kennedy/Jenks, Ventura, CA, 131pp.

Kennedy/Jenks Consultants, 2008. Groundwater Management Plan Update, report prepared for Twentynine Palms Water District, Kennedy/Jenks, Los Angeles, CA, 126pp.

Kennedy/Jenks Consultants, 2009. Shallow Groundwater Investigation- Twentynine Palms Water Treatment Plant Revised Report of Waste Discharge, letter report prepared for Twentynine Palms Water District, dated 22 October 2009, Kennedy/Jenks, Irvine, CA, 10pp.

Kennedy/Jenks Consultants, 2010. Groundwater Study for the Mesquite Lake Subbasin, report prepared for Twentynine Palms Water District, dated March 2010, Kennedy/Jenks, San Francisco, CA, 328 pp.

Kennedy/Jenks Consultants, 2011. 2010 Urban Water Management Plan Update, report prepared for Twentynine Palms Water District, Kennedy/Jenks, Ventura, CA.

Li and Martin, 2011, Geohydrology, simulation of regional groundwater flow, and assessment of water management strategies, Twentynine Palms area, California, USGS Scientific Investigations Report: 2010-5249
Mancl, K., and B. Slater, 2001, Septic System Maintenance, the Ohio State University Extension Fact Sheet AEX-740-01, Columbus, OH. http://ohioline.osu.edu Mayer, P.W. and W.B. DeOrea. 1999. Residential End Uses of Water. Published by the American Water Works Association Research Foundation.

Deoreo, W.B., A. Dietemann, T. Skeel, P.W. Mayer, D.M. Lewis, and J. Smith. 2001. Retrofit Realities. American Water Works Association Research Foundation.

Metcalf and Eddy, 1991, Wastewater Engineering Treatment Disposal and Reuse, 3rd Edition 1991.Metcalf and Eddy 2004. Wastewater Engineering Treatment & Reuse. 4th Edition. 2003 TDS in septigae
Miller, T.H., 2007, Septic Systems and Their Maintenance, University of Maryland Extension, http://extension.umd.edu/environment/water/files/septic.html Mojave Water Agency (MWA), 2004. 2004 Regional Water Management Plan, Mojave Water Agency, Apple Valley, CA, 252pp.

Moyle, W.R., Jr., 1984. Bouguer anomaly map of Twentynine Palms Marine Corps Base and vicinity, California, U.S. Geological Survey Water-Resources Investigations Report 84-4005, U.S. Geological Survey, Reston, VA, 1 map.

MWH, 2009a. High-Desert Water District Sewer Master Plan Final Report. January 2009.

MWH, 2009b. High-Desert Water District Water Reclamation Facility Preliminary Design Report. Volume 1, January 2009.

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NBS/Lowry Engineers & Planners, 1997. Master Plan of Drainage, report prepared for San Bernardino County Flood Control District, dated April, 1997. NBS/Lowry Engineers, San Bernardino, CA.

Riley, F.S. and J.S. Bader, 1961. Data on water wells on Marine Corps Base, Twentynine Palms, California, U.S. Geological Survey Open-File Report 61-128, U.S. Geological Survey, Long Beach, CA, 18pp.

Hogle-Ireland, Land Use Designations Map, 2012. Hogle-Ireland, Inc., Fullerton, CA 2012.

State Water Resources Control Board (SWRCB), 2012. Proposed Policy Water Quality Control Policy for Siting, Design, Operation, and Maintenance of Onsite Wastewater treatment Systems. June 5, 2012.

State Water Resources Control Board (SWRCB), 2012. Statement of Policy with Respect to Maintaining High Quality of Waters in California. October 28, 1968.

Taylor, 2003, Evaluating Groundwater Nitrates from On-Lot Septic Systems, A Guidance Model for Land Planning in Pennsylvania. Penn State Great Valley School of Graduate Professional Studies.

Thompson, D.G., 1921. Routes to desert watering places in the Mohave Desert region, California, U.S. Geological Survey Water-Supply Paper 490-B, U.S. Government Printing Office, Washington, D.C., 206pp.

Tom Dodson & Associates, 2009. Initial Study/Environmental Assessment: Hi-Desert Water District Water Reclamation Facility, Wastewater Treatment Plant and Sewer Collection System Project, report prepared for Twentynine Palms Water District, dated June 2009, Tom Dodson & Associates, San Bernardino, CA.

Twentynine Palms Water District, 2012. Twentynine Palms Water District Pipeline Map, 2012.

Twentynine Palms, CA.

U.S. Census Bureau, 2009. TIGER/Line County Subdivision Map, 2009. Washington, D.C., Bureau of the Census, 2009.

U.S. Department of the Interior, 2012. National Environmental Policy Act Finding of No Significant Impact. Report No. 12-SCAO-002-FONSI, Bureau of the Interior, Temecula, CA.

Winzler & Kelly Consulting Engineers, 2008. Wastewater Treatment Plant Joint-Use Study, report prepared for NAVFAC Southwest, dated April 2008, Winzler & Kelly Consulting Engineers, San Diego, CA.

Woodward-Clyde Consultants, 1985, Twentynine Palms Groundwater Study Final Report, report prepared for Twentynine Palms Water District, dated 6 May 1985, Woodward-Clyde Consultants, Santa Ana, CA.

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DATURA
AVE

LEAR AVE

MOJAVE RD

BULLION
AVE

RAYMOND DR

ADOBE RD

CANYON RD
SUNNY

SANDS DR
COUNTY
RD
COVE

VIEW RD

T MI OTHY AVE
UTAH
TRL
UTAH
TRL

TWENTYNINE
PALMS

TWENTYNINE PALMS HWY HWY
CHIA
AVE

TWENTYNINE
PALMS
HWY

SIESTA DR

JOSHUA DR

MOUNTAIN
RD

MORONGO
RD

SAMARKAND
DR
TWO

MILE RD
INDIAN

COVE RD
LOS
OLIVOS
AVE

FOOTHILL
AVE

LOS OLIVOS
AVE

EL PORTAL
AVE
SUNNY

SLOPE DR

MORONGO
RD
FLYING
H RD

TEPEE RD
F.C.

CH

BULL OI N

MOUNTA NI RD

AMBOY RD
ADOBE
RD
AMBOY
RD

VALLE VISTA RD

AMBOY RD AMBOY RD
UTAH
TRL
GODWIN

RD AMBOY RD
COPPER

MOUNTAIN RD

ADOBE RD
UTAH
TRL

MORONGO RD MORONGO RD

AMBOY RD
PEARL

SPRING AVE

ALFALFA
AVE
CANYON
RD

AMBOY RD

TACO DR

MESQUITE SPRINGS RD
Sources: Esri, DeLorme, NAVTEQ, TomTom, Intermap, increment P Corp., GEBCO, USGS, FAO, NPS, NRCAN, GeoBase, IGN, Kadaster NL, Ordnance Survey, Esri Japan, METI, Esri China (Hong Kong), swisstopo, and the GIS User Community Twentynine Palms
San Bernardino County, California
Area Populations
K/J 1283001*00
September 2013
Figure 3-5
Kennedy/Jenks Consultants
³
0 3,500 7,000
Scale: Feet
Path: I:\Projects\TwentyninePalms\Events\20121120_Figures\MXD\Fig_3_5_v2.mxd Legend
SOI Boundary
Twentynine Palms City Boundary
Roads
General Plan Land Use
Commercial
Downtown Economic Revitalization SP
Floodways
IC Non Overlay
Military
Open Space Reserve
Rural
Residential
Tribal Land

Appendix A
Wastewater Flow Calculations

8/24/2012 version
Twentynine Palms - Population, Water Usage, and Sewer Loading Assumptions Ref. No. Current - 2010 2035 Projections Build-out Comments and Data Sources 1 Population 18,795 30,931 102,963
2010 Population: UWMP 2010 (within the District service area) 2035 Population: UWMP 2010 (within the District service area). Population outside of the District service area (approx. 1,385 acres) is unknown, but sewer loading (approx 19 AFY) was estimated for this area and accounted for in the total sewer loading.

Build-out population = Total City build-out population - Marine Base population + Unincorporated population (adjusted) + SOI population outside of City boundary
City's build-out = 103,275 (Source: City Staff- Matt McCleary email to K/J ); Marine Base population = 22,500 (Source: City of 29 Palms General Plan 2010); Total unincorporated area population = 1,7,253 (Source: Population calcs using the San Bernardino County land use map); Adjusted unincorporated area population = 14,602.

SOI population (total) = 7,586 (City of 29 Palms General Plan 2010, Table LU-18). The total SOI population was distributed 1) within the unincorporated area within District boundary (1,887) and 2) the remaining SOI outside of City's boundary (5,699). 2 Residential - Includes single family and multi-family residential 3 Total residential acreage - within and outside District 29,862 35,010 66,756 Total residential acreage within and outside of the District service area, including the City's SOI. 4 Residential acreage within District 28,477 33,624 51,471 2010: Based on GIS analysis of current land use using aerial mapping and digitizing. 2035: Residential acreages were projected proportional to the increase in sewer loading from 2010 to 2035 relative to the total build-out sewer loading. Assumed population growth and residential land use expansion to occur within the District service area only and the residential land use outside of District to remain the same as in 2010.

Build-out: Based on the City of 29 Palms General Plan land use dated Dec 22 2011. 5 Residential acreage outside of District 1,385 1,385 15,286 Sewer loading estimates below are for the areas within the District boundary but accounts for a small area of 1,385 outside of the District for 2010 and 2035 but includes the City's SOI residential land use for the build-out. 2010: Based on the current conditions, a small area of residential falls outside of the District service area (1,385 acres), but within the groundwater subbasins.
2035: Assumed the areas outside of the District service boundary (i.e., 1,385 acres) remains the same as in 2010.

Build-out: Approx. 15,286 acres is outside of District, but within the City and City's SOI, based on the GIS map of the General Plan land use map (dated Dec 22, 2011).
6 Water usage (ccf) 926,307 1,388,587 4,622,323
2010: Based on current water usage records consistent with UWMP. 2035: Based on the 2035 population projection, reported in the UWMP and the estimated 73.5 gpcd of sewer loading (or 92 gpcd of water usage).

Build-out: Estimated based on the population and 92 gpcd. Assumed the water usage and indoor water usage to remain the same as in 2035 conditions at 73.5 gpcd. Since the build-out population includes the City's SOI population, residential water usage and sewer loading accounts for areas within the City's SOI.
7 Water usage (gal/day) 1,898,295 2,845,652 9,472,596 Calculated total residential water usage in units of gallons per day. 8 Water Usage (AFY) 2,126 3,188 10,611 Calculated total residential water usage in units of acre-feet per year. 9 Water Usage (gal/day/person) 101 92 92
2010: Calculated based on the population and water usage within District service area. 2035: Calculated based on the population projection and water usage within District service area.

Build-out: Assumed the same water usage per capita as in 2035 conditions.

Note: High-Desert WD has 102 gpcd based on 2007 water use data, based on an average of 2.5 persons per household. 10 Water to sewer factor 0.8 0.8 0.8
2010: Based on historical water usage data (both annual and winter), UWMP, W&K, and Hi-Desert MP. 2035: Assumed water to sewer rate to remain the same as historical data.

Build-out: Assumed water to sewer rate to remain the same as historical data.

Note: Yucca Valley septic nitrogen loading calculations assumed 83% water to sewer factor.

High-Desert WD used 80% in its sewer master plan (MWH, 2009). 11 Indoor water use (gal/day/person)
(sewer loading) 80.00 73.50 73.5
2010: Estimated based on the UWMP water usage data, 2010 population, and 80% water to sewer conversion. 2035: Estimated based on the 73.5 gpcd sewer loading rate, the 2035 population projection, and 80% water to sewer conversion. the

73.5 gpcd sewer loading corresponds to 92 gpcd water usage, based on the 80% water to sewer conversion.

Build-out: Assumed the same sewer loading rate as in 2035.

Note: High-Desert WD has 82 gpcd of sewer flow (MWH, 2009). 12 Sewer loading (gal/day) (total) 1,518,636 2,276,522 7,578,077 14 Within District 1,501,645 2,259,530
15 Outside District 16,991 16,991
16 Sewer loading (AFY) (total) 1,720 2,569 8,488
18 Within District 1,701 2,550
19 Outside District 19 19
20 Sewer loading (gal/day/acre) 51 65 114 Calculated as total sewer loading in units of gallons per day divided by total acreages of the build-out. 21 Sewer loading (AFY/acre) 0.06 0.07 0.13 Calculated as total sewer loading in acre-feet per year divided by total acreages of the build-out.

Assumed sewer loading to be 80% of water usage, in units of gallons per day. 7,578,077
2010: Includes sewer loading within and outside of the District. 2035: includes sewer loading within and outside of the District Build-out: Includes sewer loading within the District, the City and City's SOI.

Assumed sewer loading to be 80% of water usage, in units of acre-feet per year. 8,488
2010: Includes sewer loading within and outside of the District. 2035: Includes sewer loading within and outside of the District Build-out: Includes sewer loading within the District, the City and City's SOI.

8/24/2012 version
Twentynine Palms - Population, Water Usage, and Sewer Loading Assumptions Ref. No. Current - 2010 2035 Projections Build-out Comments and Data Sources 22 23 Water usage (ccf) 122,547 247,682 1,136,288
24 Water usage (gal/day) 251,137 507,579 2,328,613
25 Water usage (AFY) 278 561 2,608
26 Water to sewer factor 0.8 0.8 0.8
2010: Based on historical water usage data (both annual and winter). 2035: Assumed water to sewer rate to remain the same as historical data.

Build-out: Assumed water to sewer rate to remain the same as historical data.

Note: High-Desert WD estimated wastewater flow at commercial land use as 80 % of water use (MWH, 2009). 27 Sewer loading (AFY) (total) 222 449 2,087 Total non-residential sewer loading within the District and outside of the District, but within the City's SOI. 28 Non-residential (high density) 131 264 840
29 Non-residential (low density) 44 89 858
30 Within District 44 89 753
31 Outside District 0 0 104
32 Institutional/Industrial 48 96 389
33 Within District 48 96 266
34 Outside District 0 0 123
35 Acreage (total) 385 778 4,312
36 Non-residential (high density) (within District) 130 262 833 37 Non-residential (low density) 123 248 2,393
38 Within District 123 248 2,102
39 Outside District 0 0 291
40 Institutional/Industrial 133 268 1,086
41 Within District 133 268 742
42 Outside District 0 0 344
43 Sewer loading (gal/day/acre)
44 Non-residential (high density) 900 900 900
45 Non-residential (low density) 320 320 320
46 Institutional/Industrial 320 320 320
47 Sewer loading (AFY/acre)
48 Non-residential (high density) 1.0 1.0 1.0
49 Non-residential (low density) 0.4 0.4 0.4
50 Institutional/Industrial 0.4 0.4 0.4
51 Sewer loading residential and non-residential (AFY) 1,942 3,018 10,575 Calculated as total sewer loading from residential and non-residential. 52 Within District 1,923 2,999
53 Outside District 19 19
54 Loading from the Mainside WWTP evaporation ponds 0.0 0.0 0.0 Assumed zero loading, based on the review of previous studies and reports (RWQCB Region 7, WDR Order # R7-2002-0006) 10,575
2010: Includes sewer loading within and outside of the District. 2035: Includes sewer loading within and outside of the District Build-out: Includes sewer loading within the District, the City and City's SOI.

Non-Residential - Includes commercial, institutions, and industrial. No industrial water usage reported in the UWMP for the 2010 and 2035 conditions, but the General Plan build-out land use includes industrial land use. 2010: Based on current water usage data, consistent with UWMP. 2035: Based on the 2010 UWMP (Table 2-4).

Build-out: Calculated based on acreages with the same sewer loading rate as in 2010 and 2035. 2010: Assumed higher water usage and sewer loading for high density commercial and lower water usage and sewer loading for low density, institutional, and industrial. To account for the total loading of 222 AFY from the entire comm acres of 385, the lower loading rate of 320 gal/day/acre was used for the lower density comm/inst. 2035: Acres of non-residential estimated for 2035 multiplied by the same sewer rate (gal/day/acre).

Build-out loading: Acres from the build-out land use multiplied by the same sewer rate (gal/day/acre). Build-out includes areas of nonresidential outside of the District to account for the City's SOI.

Non-residential broken down to higher and lower density and other institutional and industrial. 2010: Based on GIS analysis of current land use using aerial mapping and digitizing. 2035: Acreages were projected to increase proportional to the increase in water usage and resulting sewer loading.

Build-out: Based on the City of 29 Palms General Plan.

General Plan shows 1,472 acres of community industrial within District and 280 acres of community industrial outside of the District compared to no industrial water usage in 2010 and 2035 based on the UWMP. In the absence of historical water use data for industrial, assumed sewer loading of 320 gal/day/acre for community industrial, similar to the rate used for the lower density commercial.

For the build-out, industrial and institutional acreages (and also sewer loading) are shown together. 2010: Sewer loading was calculated based on the sewer loading for each sub-non-residential areas divided by the corresponding acreages. Assumed the same loading rate (gal/day/acre) for 2035 and build-out.

Note reference commercial loading rates from other studies:

Assumed the high density comm. (non-residential) loading is set to 900 gal/day/acre as the average of the High-Desert (800 gal/day/acre) and USGS (1000 gal/day/acre) value (current and Build-out) used for the Yucca Valley. High-Desert : 800 gal/day/acre. For Yucca Valley, USGS assumed 1,000 gal/day/acre for the septic N loading calculations based on a previous study (Linsley and Franzini, 1979).

Calculated as total sewer loading in acre-feet per year divided by total acreages.

Appendix B
CIP Cost Estimates

OPINION OF PROBABLE CONSTRUCTION COST KENNEDY/JENKS CONSULTANTS Project: City of Twenty Nine Palms Wastewater Master Plan Prepared By: JLH Date Prepared: Sep-12
Building, Area: Sewer Gravity and Force Mains K/J Proj. No. 1283001*00 Current at ENR
Estimate Type: Conce
ptual Construction Escalated to ENR
Preliminary (w/o
plans) Chan
ge Order Months to Mid
point of Construct
Design Development @ __________ % Complete
Spec. Item Materials Sub-contractor $/LF Incl
$ Total Incl Comments
Section No. Description Qty Units
$/Unit Total
$/Unit Total
$/Unit Total Sub-Total Markups Markups
FORCEMAIN SEWER Pi
pes in Streets
Remove Pavin
g 2,067 S
Y 7 14,467 14,467 6' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 3,100 LF 6.19 19,189 19,189 2' wide, 6' deep 0:1
Beddin
g 3,100 LF 1.60 4,960 0.81 2,511 7,471 2' wide 0:1
Trench Boxes (2) 16 D
Y 330.00 5,115 5,115 200 LF/DA
Y
6" HDPE Pipe 3,100 LF 9.15 28,365 5.91 18,321 46,686 Means 6" Plu
g Valve 2E
A 3,600.00 7,200 300.00 600 7,800 1 at each end of the line Pavin
g 2,067 S
Y 75 155,000 155,000 6' wide, 6" thick
1" Combination Ari/Vac Valve 2E
A 1,250.00 2,500 300.00 600 3,100 Ever
y 1500'
Traffic Control 16 D
Y 240.00 3,720 1,450.00 22,475 26,195
SUBTOTAL 46,745 68,811 169,467 285,023 203 $ 628,410 $
Remove Pavin
g 3,200 S
Y 7 22,400 22,400 6' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 4,800 LF 6.19 29,712 29,712 2' wide, 6' deep 0:1
Beddin
g 4,800 LF 3.46 16,608 1.76 8,448 25,056 2' wide 0:1
Trench Boxes (2) 24 D
Y 330.00 7,920 7,920 200 LF/DA
Y
8" HDPE Pipe 4,800 LF 12.50 60,000 7.00 33,600 93,600 Means 8" Plu
g Valve 2E
A 4,200.00 8,400 350.00 700 9,100 1 at each end of the line Pavin
g 3,200 S
Y 75 240,000 240,000 6' wide, 6" thick
1" Combination Ari/Vac Valve 3E
A 1,250.00 3,750 350.00 1,050 4,800 Ever
y 1500'
Traffic Control 24 D
Y 240.00 5,760 1,450.00 34,800 40,560
SUBTOTAL 94,518 116,230 262,400 473,148 218 $ 1,045,633 $ Remove Pavin
g 2,267 S
Y 7 15,867 15,867 6' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 3,400 LF 6.19 21,046 21,046 2' wide, 6' deep 0:1
Beddin
g 3,400 LF 3.53 12,002 1.80 6,120 18,122 2' wide 0:1
Trench Boxes (2) 23 D
Y 330.00 7,480 7,480 150 LF/DA
Y
10" HDPE Pipe 3,400 LF 19.75 67,150 7.49 25,466 92,616 Means 10" Plu
g Valve 2E
A 5,500.00 11,000 400.00 800 11,800 1 at each end of the line Pavin
g 2,267 S
Y 75 170,000 170,000 6' wide, 6" thick
1" Combination Ari/Vac Valve 2E
A 1,250.00 2,500 400.00 800 3,300 Ever
y 1500'
Traffic Control 23 D
Y 240.00 5,440 1,450.00 32,867 38,307
SUBTOTAL 98,092 94,579 185,867 378,537 247 $ 839,803 $
Remove Pavin
g 2,600 S
Y 7 18,200 18,200 6' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 3,900 LF 6.19 24,141 24,141 2' wide, 6' deep 0:1
Beddin
g 3,900 LF 3.61 14,079 1.83 7,137 21,216 2' wide 0:1
Trench Boxes (2) 26 D
Y 330.00 8,580 8,580 150 LF/DA
Y
Installation
X
Sewer and PSta Estimates_Final.xlsPipe Estimate Page 1 of 4 Date Printed: 4/2/2013

Spec. Item Materials Sub-contractor $/LF Incl
$ Total Incl Comments
Section No. Description Qty Units
$/Unit Total
$/Unit Total
$/Unit Total Sub-Total Markups Markups
Installation
12" HDPE Pipe 3,900 LF 31.00 120,900 8.62 33,618 154,518 Means 12" Plu
g Valve 4E
A 7,200.00 28,080 450.00 1,755 29,835 1 at each end of the line Pavin
g 2,600 S
Y 75 195,000 195,000 6' wide, 6" thick
1" Combination Ari/Vac Valve 3E
A 1,250.00 3,750 450.00 1,350 5,100 Ever
y 1500'
Traffic Control 26 D
Y 240.00 6,240 1,450.00 37,700 43,940
SUBTOTAL 173,049 114,281 213,200 500,530 286 $ 1,116,727 $ Remove Pavin
g 14,267 S
Y 7 99,867 99,867 6' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 21,400 LF 13.37 286,118 286,118 4' wide, 6' deep 0:1
Beddin
g 21,400 LF 6.10 130,540 3.09 66,126 196,666 2' wide 0:1 Trench Boxes (2) 178 D
Y 330.00 58,850 58,850 120 LF/DA
Y
18" HDPE Pipe 21,400 LF 46.50 995,100 19.10 408,740 1,403,840 Means 18" Valve 21 E
A 12,600.00 269,640 800.00 17,120 286,760 1 at each end of the line Pavin
g 14,267 S
Y 75 1,070,000 1,070,000 6' wide, 6" thick
2" Combination Ari/Vac Valve 14 E
A 2,500.00 35,000 600.00 8,400 43,400 Ever
y 1500'
Traffic Control 178 D
Y 240.00 42,800 1,450.00 258,583 301,383
SUBTOTAL 1,473,080 1,103,937 1,169,867 3,746,884 392 $ 8,385,365 $ Remove Pavin
g 1,156 S
Y 7 8,089 8,089 8' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 1,300 LF 18.70 24,310 24,310 4' wide, 8' deep 0:1
Beddin
g 1,300 LF 9.05 11,765 4.60 5,980 17,745 2' wide 0:1
Trench Boxes (2) 13 D
Y 330.00 4,290 4,290 100 LF/DA
Y
30" HDPE Pipe 1,300 LF 90.00 117,000 38.75 50,375 167,375 Means 30" Valve 1E
A 18,000.00 23,400 1,000.00 1,300 24,700 1 at each end of the line Pavin
g 1,156 S
Y 75 86,667 86,667 8' wide, 6" thick
2" Combination Ari/Vac Valve 1E
A 2,500.00 2,500 750.00 750 3,250 Ever
y 1500'
Traffic Control 13 D
Y 240.00 3,120 1,450.00 18,850 21,970
SUBTOTAL 157,785 105,855 94,756 358,396 619 $ 804,519 $ GRAVITY SEWER PIPES in Streets
Remove Pavin
g 4,800 S
Y 7 33,600 33,600 6' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 7,200 LF 6.19 44,568 44,568 2' wide, 6' deep 0:1
Beddin
g 7,200 LF 3.53 25,416 1.80 12,960 38,376 2' wide 0:1
Trench Boxes (2) 36 D
Y 330.00 11,880 11,880 200 LF/DA
Y
10" PVC Sewer Pipe 7,200 LF 12.70 91,440 3.83 27,576 119,016 Means Manholes 4' ID/ 6' deep 14 E
A 2,025.00 29,160 1,675.00 24,120 53,280 ever
y 500'
Pavin
g 4,800 S
Y 75 360,000 360,000 6' wide, 6" thick
Traffic Control 36 D
Y 200.00 7,200 1,200.00 43,200 50,400
SUBTOTAL 153,216 164,304 393,600 711,120 218 $ 1,573,156 $ Remove Pavin
g 13,667 S
Y 7 95,667 95,667 6' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 20,500 LF 13.37 274,085 274,085 4' wide, 6' deep 0:1
Beddin
g 20,500 LF 5.90 120,950 3.00 61,500 182,450 3' wide 0:1 Trench Boxes (2) 137 D
Y 330.00 45,100 45,100 150 LF/DA
Y
15" PVC Sewer Pipe 20,500 LF 15.15 310,575 5.27 108,035 418,610 Means Manholes 4' ID/ 6' deep 51 E
A 2,025.00 103,781 1,675.00 85,844 189,625 ever
y 500'
Pavin
g 13,667 S
Y 75 1,025,000 1,025,000 6' wide, 6" thick
Traffic Control 137 D
Y 200.00 27,333 1,200.00 164,000 191,333
SUBTOTAL 562,640 738,564 1,120,667 2,421,870 262 $ 5,363,628 $ Sewer and PSta Estimates_Final.xlsPipe Estimate Page 2 of 4 Date Printed: 4/2/2013

Spec. Item Materials Sub-contractor $/LF Incl
$ Total Incl Comments
Section No. Description Qty Units
$/Unit Total
$/Unit Total
$/Unit Total Sub-Total Markups Markups
Installation
Remove Pavin
g 19,000 S
Y 7 133,000 133,000 6' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 28,500 LF 18.70 532,950 532,950 4' wide, 8' deep 0:1
Beddin
g 28,500 LF 6.10 173,850 3.09 88,065 261,915 3' wide 0:1 Trench Boxes (2) 190 D
Y 330.00 62,700 62,700 150 LF/DA
Y
18" PVC Sewer Pipe 28,500 LF 17.35 494,475 6.31 179,835 674,310 Means Manholes 4' ID/ 6' deep 71 E
A 2,025.00 144,281 1,675.00 119,344 263,625 ever
y 500'
Pavin
g 19,000 S
Y 75 1,425,000 1,425,000 6' wide, 6" thick
Traffic Control 190 D
Y 200.00 38,000 1,200.00 228,000 266,000
SUBTOTAL 850,606 1,210,894 1,558,000 3,619,500 281 $ 8,017,387 $ Remove Pavin
g 21,267 S
Y 7 148,867 148,867 6' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 31,900 LF 18.70 596,530 596,530 4' wide, 8' deep 0:1
Beddin
g 31,900 LF 8.90 283,910 4.52 144,188 428,098 4' wide 0:1 Trench Boxes (2) 266 D
Y 330.00 87,725 87,725 120 LF/DA
Y
24" PVC Sewer Pipe 31,900 LF 31.00 988,900 7.04 224,576 1,213,476 Means Manholes 5' ID/ 8' deep 80 E
A 4,250.00 338,938 2,600.00 207,350 546,288 ever
y 500'
Pavin
g 21,267 S
Y 75 1,595,000 1,595,000 6' wide, 6" thick
Traffic Control 266 D
Y 200.00 53,167 1,200.00 319,000 372,167
SUBTOTAL 1,664,914 1,579,369 1,743,867 4,988,150 349 $ 11,120,372 $ Remove Pavin
g 3,733 S
Y 7 26,133 26,133 8' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 4,200 LF 29.80 125,160 125,160 6' wide, 8' deep 0:1
Beddin
g 4,200 LF 15.90 66,780 8.05 33,810 100,590 6' wide 0:1 Trench Boxes (2) 58 D
Y 330.00 19,250 19,250 72 LF/DA
Y
36" RCP w/ PVC linin
g 4,200 LF 99.00 415,800 39.20 164,640 580,440 Means
Manholes 6' ID/ 8' deep 11 E
A 5,225.00 54,863 3,400.00 35,700 90,563 ever
y 500'
Pavin
g 3,733 S
Y 75 280,000 280,000 8' wide, 6" thick
Traffic Control 58 D
Y 200.00 11,667 1,200.00 70,000 81,667
SUBTOTAL 549,109 448,560 306,133 1,303,803 696 $ 2,923,143 $ Remove Pavin
g 4,356 S
Y 7 30,489 30,489 8' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 4,900 LF 30.25 148,225 148,225 6' wide, 10' deep 0:1
Beddin
g 4,900 LF 20.00 98,000 14.50 71,050 169,050 6' wide 0:1 Trench Boxes (2) 82 D
Y 330.00 26,950 26,950 60 LF/DA
Y
42" RCP w/ PVC linin
g 4,900 LF 140.00 686,000 48.20 236,180 922,180 Means
Manholes 6' ID/ 10' deep 12 E
A 6,600.00 80,850 4,325.00 52,981 133,831 ever
y 500'
Pavin
g 4,356 S
Y 75 326,667 326,667 8' wide, 6" thick
Traffic Control 82 D
Y 200.00 16,333 1,200.00 98,000 114,333
SUBTOTAL 881,183 633,386 357,156 1,871,725 859 $ 4,209,887 $ Subtotals 13,414,643 12,762,215 15,160,962 17,525,820 46,050,675 Markups Applied:Location Factor 6.1%Div 1, Mob,Demob, B&I 10%Sales Tax on Materials 7.75%OH&P 15% Sewer and PSta Estimates_Final.xlsPipe Estimate Page 3 of 4 Date Printed: 4/2/2013

OPINION OF PROBABLE CONSTRUCTION COST KENNEDY/JENKS CONSULTANTS Project: City of Twenty Nine Palms Wastewater Master Plan Prepared By: JAJ Date Prepared: Oct-12
Building, Area: Pump Stations K/J Proj. No. 1283001*00
Current at ENR
Estimate Type: Conce
ptual Construction Escalated to EN
R
Preliminary (w/o
plans) Chan
ge Order Months to Mid
point of Construct
Design Development @ _________ % Complete
Spec. Item Materials Sub-contractor
No. No. Description Qty Units
$/Unit Total
$/Unit Total
$/Unit Total Total
Submersible Pum
p Stations 1 1,173,874 782,582.54 782,583 1,956,456
Wet Well-Dr
y Well Pum
p Stations 1 5,120,282 3,413,521.49 3,413,521 8,533,804 Subtotals 6294156.04 4196104.03 10,490,260Division 1 Costs @ 10% 629415.60 419610.40 1,049,026
Subtotals 6923571.64 4615714.43 11,539,286Taxes - Materials Costs @ 7.75% 536576.80 536,577
Subtotals 7460148.44 4615714.43 12,075,863Taxes - Labor Costs @ 5.00% 230785.72 230,786
Subtotals 7460148.44 4846500.15 12,306,649Contractor Marku p for Sub
@ 12% -
Subtotals 7460148.44 4846500.15 12,306,649Contractor OH&P @ 15% 1119022.27 726975.02 1,845,997
Subtotals 8579170.71 5573475.17 14,152,646Estimate Contin genc
y
@ 50% 7,076,323
Subtotals 21,228,969
Escalate to Mid
point of Construct
@ 2% -
Estimated Bid Cost 21,228,969
Total Estimate 21,228,970
* See Pump Station Estimation sheet for more detailed calculations* Assumed 60% of construction costs allocated to materials* Contingency raised from 30% to 50% due to lack of detailed design criteria and to account for land acquisition costs +50% -30% +50% Total Est. -30%
$31,843,455
$21,228,970
$14,860,279
Installation
Estimate Accuracy
Estimated Range of Probable Cost
X
Sewer and PSta Estimates_Final.xlsPump Estimate 2 Page 1 of 1 Date Printed 4/2/2013

OPINION OF PROBABLE CONSTRUCTION COST KENNEDY/JENKS CONSULTANTS Project: City of Twenty Nine Palms Sewer Master Plan Prepared By: JLH Date Prepared: 5-Sep-12
Building, Area: Sewer Collectors, Gravit
y K/J Proj. No. 1283001*00
Current at ENR
Estimate Type: Conce
ptual Construction Escalated to ENR
Preliminary (w/o
plans) Chan
ge Order Months to Mid
point of Construct
Design Development @ % Complete
Spec. Item Materials Sub-contractor $/LF Incl $ Total Incl Source Section No. Description Qty Units
$/Unit Total
$/Unit Total
$/Unit Total Total Markups Markups
GRAVITY SEWER PIPES in Streets
Remove Pavin
g 177,760 S
Y 7 1,244,320 1,244,320 6' wide, 6" thick
Trenching: Excav., backfill & load spoil, compaction, remove excess spoil 533,280 LF 6.19 3,301,003 3,301,003 2' wide, 6' deep 0:1 Beddin
g 533,280 LF 3.53 1,882,478 1.80 959,904 2,842,382 2' wide 0:1 8" PVC Sewer Pipe 533,280 LF 7.85 4,186,248 2.81 1,498,517 5,684,765 Means Manholes 4' ID/ 6' deep 1,067 E
A 2,025.00 2,159,784 1,675.00 1,786,488 3,946,272 ever
y 500'
Pavin
g 177,760 S
Y 75 13,332,000 13,332,000 3' wide, 6" thick
Traffic Control 1,778 D
Y 200.00 355,520 1,200.00 2,133,120 2,488,640 300' per da y
SUBTOTAL 8,584,030 9,679,032 14,576,320 32,839,382Subtotals 17,168,061 19,358,064 29,152,640 $ 72,866,497 137 $ Markups Applied:Location Factor 6.1%Div 1, Mob,Demob, B&I 10%Sales Tax on Materials 7.75%O&HP 15%Engineering /Construction Management 25%Contingenc y 30%
Assumes no dewatering, utility
interferences, native backfill. Escalation not included.

Installation
Assumed 80 miles of PL inside the city and 21 miles of PL outside (101 total miles) X
Sewer and PSta Estimates_Final.xlsBy Area_Collectors Page 1 of 1 Date Printed: 4/2/2013

Appendix C
Twentynine Palms Parcel Size Map

Budget Act of 2021 – Wastewater Infrastructure Appropriation Revised January 6, 2022
Overview
The Budget Act of 2021 (Senate Bill 129 and Senate Bill 170) appropriated $1.55 billion to the State Water Resources Control Board (SWRCB) in item 3940-106-0001 (the Infrastructure Appropriation). The budget bill specifies that $650 million (M) is for wastewater projects, with priority given to septic-to-sewer conversions.

Key Provisions:
· Up to 5% for SWRCB administrative costs (leaves $617.5 M for wastewater grants). · Up to 10% may be utilized for technical assistance (TA) and capacity building in DACs. · Must be encumbered by June 30, 2024.
· Must be liquidated by June 30, 2026.

Wastewater Grant Eligibility
SWRCB Resolution No. 2021-0030, dated August 18, 2021
· Authorized the Division of Financial Assistance (DFA) to encumber up to $100 M of the wastewater allocation from the Infrastructure Appropriation. · This grant funding is awarded consistent with the eligibilities, conditions, and processes set forth in the - State Fiscal Year (SFY) 2021-22 Clean Water State Revolving Fund (CWSRF) Intended Use Plan (IUP).
· Any programmatic or project-specific funding cap set forth in the CWSRF IUP can be waived for the purposes of awarding the Infrastructure Appropriation Funds, as are several CWSRF cross-cutting compliance obligations.

Implementation Plan for remaining $517.5 M available:
· DFA intends to rely on existing funding processes outlined in the CWSRF IUP as the basis for administering the wastewater infrastructure funds. Targeted amendments to the SFY 2021-22 CWSRF IUP are proposed, to streamline funding processes and maximize opportunities for eligible projects. Key next steps in the process include:
o NEW Draft Implementation Plan posted for public comment – January 6, 2022 § Public Notice
§ Draft 2021-22 CWSRF IUP Amendments (Track Changes)
§ Draft 2021-22 CWSRF IUP Amendments (Clean Version)
o Board Workshop on Draft Implementation Plan – January 20, 2022 o SWRCB consideration of Implementation Plan – March 15, 2022 Summary of Past Stakeholder Meetings
o Wastewater Stakeholder Meeting - October 20, 2021
§ Presentation
§ Recorded Meeting

Budget Act of 2021 – Wastewater Infrastructure Appropriation Revised January 6, 2022
Stay Informed:

Subscribe for email updates at:
www.waterboards.ca.gov/resources/email_subscriptions/swrcb_subscribe.html · Click on “Financial Assistance”
· Check box titled “Clean Water State Revolving Fund”