preliminaryhydrogeological study city san buenaventura ... · groundwater consultants, inc....

PRELIMINARY HYDROGEOLOGICAL STUDY

CITY OF SAN BUENAVENTURA

WELL SITE FEASABILITY STUDY

(Excerpt from the Full Report dated March 2015)

City of San Buenaventura

1B

XXX

C:\HGC\JOB FILES 2015\01-009-04B\WELL SITING STUDY\REPORT_TEXT 3-30-15.DOCX - 1 -

INTRODUCTION

Presented in this report is a summary of the findings, conclusions, and recommendations developed from the Mound Well No. 2 well site feasibility study conducted by Hopkins Groundwater Consultants, Inc. (Hopkins) for the City of San Buenaventura, Ventura Water (City). The study was performed to evaluate potential sites that may be suitable for constructing municipal water supply wells in the Mound Groundwater Basin (Mound Basin). The central portion of the City’s service area within the Mound Basin, which was the focus of this study, is indicated on Plate 1 – Study Area Location Map.

GENERAL STATEMENT

The proposed Mound Well No. 2 is intended to replace the failed Victoria Well No. 1 in order to restore system reliability. The new well is intended to have an operational capacity of up to 3,000 gallons per minute (gpm) of potable quality water and if practicable, and to be located near an existing raw water conveyance line as a cost savings measure. Because well operation will be simultaneous, where other proximate City wells operate at the same time, a sufficient distance separating the wells must be provided to prevent inordinate interference drawdown, which could affect well production rates and operational costs.

In 2009 the City conducted a study at the Ventura Community Park, located at the corner of Kimball Road and Telephone Road. This study supplements the previous study and expands the study area. The Ventura Community Park proposed well site is included in this study to allow a comparison with the new sites identified.

PURPOSE AND SCOPE

The purpose of the project was to identify and compare the merit of additional well sites within the Mound Basin to facilitate planning for site acquisition and future maintenance of the City’s Mound Basin Wellfield.

The scope of work for this study was developed through conversations with Mr. Omar Castro, Water Utility Manager, and Mr. Joe McDermott, Principal Civil Engineer. As developed, the work tasks for this study include:

Reviewing past data and reports relating to hydrogeology, water quality, wellproduction,

Meeting with City staff to discuss study criteria and obtain water systeminformation,

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Performing a field survey of potential sites within the study area to determine sitesuitability,

Developing a rating system of the candidate sites with regard to hydrogeologicsuitability (water quality and well yield), environmental considerations (noise andpublic safety), permitting issues, proximity to water system infrastructure, wellsite construction, and operation and maintenance constraints,

Preparing this final report summarizing the findings of the evaluation and aranking of the identified sites.

Sources of information used for this study include available geologic mapping and hydrogeological studies, City files, groundwater data from United Water Conservation District (UWCD) and Ventura County Watershed Protection District (VCWPD), and well logs from California Department of Conservation, Division of Oil, Gas, & Geothermal Resources (DOGGR) and Hopkins’ in-house library.

FINDINGS

WELL SITE IDENTIFICATION AND FIELD SURVEY

Well construction in developed areas that contain residential and other commercial and industrial land uses is complicated by the inherent difficulty of conducting well drilling operations that are typically noisy and require 24-hour-operation during critical portions of construction. Conducting this type of construction around established domestic land uses often requires implementation of measures to mitigate large vehicle access, construction site safety, and noise mitigation to comply with local ordinances. Well sites that can accommodate these measures must accordingly be of suitable size, which was the initial criteria used in identifying potential sites. Well site identification for this study was initiated through discussions with City staff and by conducting reconnaissance level well site surveys to review site conditions and surrounding land uses. The locations of the potential well sites specifically identified within the study area are shown on Plate 2 – Well Site Location Map. Plates 3 through 10 – Potential Well Site Nos. 1 through 8, respectively, show an expanded view of each potential well location.

A field survey of each potential well site was conducted to identify general logistical constraints that could affect well construction and permanent facility operations and observe geologic outcrops of formation materials. Aerial photographs of well site conditions are included in Appendix A – Well Site Logistics. The map view of each potential well site shows the potential well location, approximate work area, site access, and if possible, the water supply and well discharge locations. During the field survey, well site photographs were taken to document conditions at the time of the study. These photographs are included in Appendix B –


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Well Site Photographs. Upon completion of the field surveys, the potential well sites were correlated with local hydrogeological conditions. Table 1 – Well Site Identification provides a site name, the present land use, and the owner status of each parcel considered as a potential well site by this study.

Table 1 – Well Site Identification

SITE NUMBER

SITE NAME PRESENT LAND USE OWNER

1 ARROYO VERDE PARK CITY PARK CITY

2 BIRD OF PARADISE FARM AGRICULTURAL PRIVATE

3 CAMPBELL PROPERTY AGRICULTURAL PRIVATE

4 DAY ROAD PROPERTY UNDEVELOPED PRIVATE

5 VENTURA COMMUNITY PARK CITY PARK CITY

6 VENTURA COUNTY GOVERNMENT CENTER LANDSCAPE AREA VENTURA COUNTY

7 MONTALVO PROPERTY UNDEVELOPED CITY

8 COPLAND DRIVE PROPERTY UNDEVELOPED PRIVATE

EVALUATION METHOD

Conditions that could affect the suitability of each site for a potential well facility were identified and used by the study as criterion for the purpose of rating the sites and subsequently establishing a final ranking system. Site rating criteria that are often significant to well construction projects include potential environmental considerations, hydrogeologic suitability, permit requirements, accommodations for the well construction activities, future well maintenance operations, and future well replacement potential. As part of our evaluation, we have determined that some of these criteria are virtually the same for all the City well sites identified and are not appropriate for use in rating and ranking well locations for this project. These factors include project permitting and environmental considerations. Since these factors were found to be virtually the same for all sites, the primary effort of the study was focused on the remaining constraints that will affect the cost and perhaps the success of the well project. A discussion of each project consideration is provided in the following sections.


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ENVIRONMENTAL CONSIDERATIONS

Noise

During the drilling and construction phase of the proposed project, noise is considered one of the greatest impacts to nearby housing developments. All of the proposed well sites will require measures to mitigate excessive noise generated during the drilling and construction phases of the project. The erection of temporary sound barriers to attenuate the noise of construction is the most common form of noise control and is anticipated to be required at all sites because of the proximity to residential structures. Likewise, noise resulting from routine operation and maintenance of the facility after construction is virtually the same for all locations and will include daily pump motor noise (which can be mitigated by constructing appropriate enclosures) and small vehicle traffic, this issue was considered to be substantially similar or the same for all sites and not considered in the rating criteria.

Public Safety

Public health and safety risks for the installation, operation, and maintenance of the proposed well facility are minimal and determined to be virtually the same for all locations. Because there is no potential bias, this factor was not utilized in the rating of the well sites.

PERMIT CONSIDERATIONS

All sites will require a well construction permit from the County of Ventura and acceptance by the California Department of Public Health (Drinking Water Source Assessment Program) as a community supply. A National Pollution Discharge Elimination System (NPDES) permit will also be required to allow discharge to the local storm drain system. Because permitting constraints are found to be virtually the same for all well sites, this criterion was also not used for well site rating.

WELL SITE RATING

The three most significant factors that will influence the success of the project include hydrogeological suitability, site accommodations for construction and future operation, and the difficulty of connecting the well to the existing system. While the hydrogeological considerations will ultimately govern the well’s ability to produce reliably under all basin conditions, the construction and connection considerations will directly affect the project capital costs. To emphasize the significance of these factors, we have allocated the scoring criteria indicated in Table 2 – Evaluation Criteria and Weighting Factors. Hydrogeological suitability was provided the highest weighting because the reliability of a well to produce a sufficient quantity of water is of paramount importance.


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Table 2 – Evaluation Criteria and Weighting Factors

CRITERIA MAXIMUM POSSIBLE POINTS

HYDROGEOLOGICAL SUITABILITY CONSTRUCTABILITY AND OPERATIONS CONSTRAINTS EASE OF SITE ACQUISITION

50 30 20

TOTAL POINTS 100

A discussion of these evaluation criteria is presented in the following sections of this report along with an explanation of the method used for scoring the separate categories. The final section in the findings of this report compiles the rating of individual criterion into a comprehensive score sheet that is sorted to rank the sites in accordance with their overall score.

HYDROGEOLOGICAL SUITABILITY

Target Aquifer Zones

The study area lies within the Mound Basin, which for the purpose of this study includes the bedrock outcrop area within the Ventura Foothills. As part of this study, Hopkins reviewed available data to determine if well locations could provide a better quality supply, greater well production/well performance, result in lower well construction costs, and better distribute pumping stresses within the basin. Available data indicate that the well construction depths and well production characteristics will likely vary between well sites in the study area.

The geology beneath the City service area consists of (formations from youngest to oldest):

Surficial Sediments (Qa)

Older Dissected Surficial Sediments (Qoa)

Saugus Formation (QTs)

Las Posas Sand Formation (QTlp)

Older undifferentiated Tertiary age bedrock (Tu)

Plate 11 – Hydrogeological Cross-Section and Well Location Map shows the location of hydrogeological cross-sections constructed to provide an interpretation of the subsurface geology within the study area. The approximate location of wells historically drilled in the study and which provided useful hydrogeological information are also shown on Plate 11. For this


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study, the geology that was mapped by Thomas Dibblee (Dibblee, 1990) was used along with information compiled by the California Division of Mines and Geology (CDMG, 1973). Utilizing available geophysical electric logs and the mapped geological structure in the bedrock outcrop areas, an interpretation of the subsurface geology beneath the study area was constructed. The resulting geological profiles are provided on Plates 12, 13, and 14 – Hydrogeological Cross-Section A-A’, B-B’, and C-C’ and Geologic Legend, respectively. Plate 14 also contains a geologic legend that provides a description of the geologic formations along with other pertinent geologic information. The geologic complexity of the area is significant. This is a result of tectonic activity that was occurring during deposition of the formation sediments, as well as subsequent faulting and folding that further shaped the groundwater basin and aquifer zones that control the occurrence and movement of groundwater.

Tectonic activity that occurs during deposition of formation sediments that subsequently form aquifer units, can affect the energy of water flow (onshore and offshore),

which will deposit materials of differing grain-sizes. Ground movement which results in uplifting, down dropping, or tilting of an area can also affect the formation thickness during original deposition and subsequent erosion, along with the present burial depth. The geologic structures in the area (faulting and folding) predominantly have an east-west orientation with the deepest portion of the Mound Basin lying centrally along the axis of the Ventura Syncline. Appendix C – Geologic Interpretations contains surficial and structural mapping (Dibblee, 1990 and CDMG, 1973), along with interpretations from a compilation of sources (UWCD, 2012).

As shown by Cross-Section A-A’ (see Plate 12), the Mound Basin is effectively subdivided by major faulting into 3 subbasins which are defined by this study as the North, Central, and South Mound Subbasins. Plate 15 – Mound Subbasin Boundary Map shows the areas included in each basin subdivision. The subbasins are each delineated to the east by their boundary with the Santa Paula Groundwater Basin, and to the west by the Pacific Ocean. The North Mound Subbasin extends south from the base of the Las Posas Sand Formation outcrop boundary on its northern side down to the Ventura Fault Zone on its southern side (see Plate 15). The Central Mound Subbasin extends from the Ventura Fault Zone that forms its northern boundary to the Oakridge Fault Zone which forms its southern boundary. The South Mound Subbasin lies between the Oakridge Fault to the north and the Mound Basin boundary to the south, which is delineated by the Montalvo Anticline (see Plate 15).

Available data indicate previous wells constructed for groundwater production in the Mound Basin mostly targeted aquifer zones in the Saugus and Las Posas Sand Formations (cumulatively equivalent to the San Pedro Formation). Based on available lithological descriptions and geophysical surveys, we anticipate that the new wells will also utilize these same aquifer materials. Appendix D – Inferred Well Site Hydrogeological Information contains a table that lists the relationship between the approximate well site elevation, the estimated depth


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of a well at each site, the depth to water under low basin conditions, and the pumping water level anticipated from historical well performance in the area.

Well Depth

Faulting and folding of the formation materials in the Mound Basin during and after deposition results in a highly variable depth to the target aquifer zones beneath each proposed well site. The depth required for wells to penetrate productive aquifer materials ranges from 1,000 to 2,500 feet below ground surface (bgs). The required depth will not only influence the cost of construction, it will determine the difficulty and cost of maintenance throughout the life of the well. For this reason the well depth was used to rate each well site in accordance with the scoring criteria listed in Table 3 – Well Depth Rating Criteria. Appendix E – Preliminary Well Designs shows the preliminary design for each site based on the available data. These preliminary well designs were used for scoring the sites with this criterion.

Table 3 – Well Depth Rating Criteria

WELL DEPTH (FEET BGS)

POINTS

2,000 (+) 1

1,600 TO 1,999 3

1,400 TO 1,599 5

1,001 TO 1,400 8

500 TO 1,000 10

Well Performance

At the time of construction, the historical specific capacity values for the City’s deeper Mound Basin wells Victoria Well Nos. 1 and 2 were 101 and 63 gallons per minute per foot of drawdown (gpm/ft). We anticipate a similar well performance for wells at the proposed locations given prudent well designs, well drilling, and construction practices. Well performance data in close proximity to most of the well sites are not available; however, historical data obtained from Water Well Drillers Reports for wells in the Mound Basin are summarized in Table 4 – Historical Well Production Data. Based on these available data, it is reasonable to infer that the productivity of the target aquifer zones at the identified well locations will vary across the study area, but will be sufficient for a municipal supply. The data in Table 4 were utilized along with a correlation of specific aquifer zones inferred to be produced by these


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historical wells in order to develop a preliminary well design and estimate well performance from similar aquifer zones at each well site. This effort was facilitated by the hydrogeological cross-section interpretations (see Plates 12, 13, and 14).

Table 4 – Historical Well Production Data

STATE WELL NO. MOUND

SUBBASIN

TEST PRODUCTION

RATE (GPM)

SPECIFIC CAPACITY (GPM/FT)

2N/22W-08F01 CENTRAL 3,000 63

2N/22W-08L01 CENTRAL 5,800 101

2N/22W-09K05 CENTRAL 2,500 34

2N/22W-09K07 CENTRAL 1,600 28

2N/23W-13E01 CENTRAL 2,500 100

2N/23W-13G01 CENTRAL 2,000 125

2N/23W-13K01 CENTRAL 2,900 41

2N/23W-13K03 CENTRAL 2,800 70

2N/23W-13K04 CENTRAL 2,000 90

2N/22W-17M02 SOUTH 800 25

2N/22W-17Q04 SOUTH 3,000 78

The well depths proposed at each well site include a well screen section that incorporates multiple aquifer zones and provides a production zone that is 200 to 500 feet in cumulative thickness. The preliminary well designs are intended to result in wells that can produce up to 3,000 gpm. Because there are no wells to provide data in the vicinity of Well Site Nos. 1A, 1B, and 2, these well locations were assigned a reduced production rate of 2,500 gpm. Table 5 – Well Production Rating Criteria provides the scoring criteria developed for well depth evaluation.


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Table 5 – Well Production Rating Criteria

WELL PRODUCTION RATE (GPM)

POINTS

1,000 TO 1,499 1

1,500 TO 1,999 3

2,000 TO 2,499 5

2,500 TO 2,999 8

3,000 AND OVER 10

The operational production of a well is supported by the well’s performance. Wells with high specific capacity values will support higher production rates under a reasonable aquifer stress. While it is anticipated most of the wells at the sites selected can support up to 3,000 gpm, the amount of drawdown in the well (the level of stress on the well) required to produce that operational capacity will vary. For this reason, the inferred specific capacity value was selected as a scoring criteria to identify potentially better sites for the higher well production rates desired. Table 6 – Well Performance Rating Criteria shows the scoring system that was assigned based on anticipated well specific capacity values. Because there are no wells to provide data in the vicinity of Well Site Nos. 1A, 1B, and 2, these locations were assigned a reduced 35 gallons per minute per foot of drawdown (gpm/ft) (see Table D1).

Table 6 – Well Performance Rating Criteria


POINTS

LESS THAN 30 1

30 TO 40 3

41 TO 60 5

61 TO 74 8

75 OR GREATER 10


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Well Interference

All the proposed well sites are located within the City boundaries a significant distance away from other existing groundwater users. For this reason, well interference is not considered to be a concern at any of the potential well sites and is therefore, not believed a significant factor in the suitability of the identified well sites.

Pumping Lift and Available Drawdown

Available drawdown in a well can be an important constraint for reliable well production. The difference between the historical low groundwater levels and the top of the aquifer zone (well screen) is the approximate drawdown available during groundwater production. Figure 1 – Mound Basin Groundwater Elevation Hydrograph shows the range of groundwater fluctuations from 1930 to the present. Water levels generally ranged between highs approximately 60 feet above mean sea level and lows approximately 20 feet below mean sea level.

Figure 1 – Mound Basin Groundwater Elevation Hydrograph

Because the preliminary well designs include well screen intervals that are located at depths at least 200 feet below the historical low water levels, the use of available drawdown was not included as a scoring criteria. However, the pumping lift will dictate the required energy


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cost over the lifetime of the well facility. The pumping water level contributes to the total dynamic head, which dictates the horse power size of the motor, thicker line shaft materials, and more expensive pump bowl designs. These requirements all contribute to greater energy consumption.

Utilizing the design production rate and the specific capacity values designated in Appendix D (see Table D1), the anticipated drawdown in each well was calculated. The drawdown was combined with the historical low groundwater level inferred at each site, based on available data, to establish the pumping water levels used for well site comparison. The resulting pumping water level was scored based on the point system provided in Table 7 – Depth to Pumping Water Level Rating Criteria.

Table 7 – Depth to Pumping Water Level Rating Criteria

DEPTH (FEET)

POINTS

GREATER THAN 300 2

250 TO 299 4

200 TO 249 6

150 TO 199 8

LESS THAN 150 10

Water Quality

The groundwater in the Mound Basin has historically been of poor quality and fails to meet the State Water Resources Control Board Division of Drinking Water standards for total dissolved solids (TDS) concentrations (1,000 milligrams per liter [mg/l]). The groundwater quality is typically degraded by elevated concentrations of sulfate, iron, manganese, and total hardness. The TDS concentrations in groundwater samples have historically ranged between 1,000 and 6,000 mg/l and the groundwater generally has a calcium sulfate chemical character. Because the water quality variation is significant, the target production zones of the proposed new well sites are in formation materials that have historically provided a better quality along with higher production.

Available water quality test results of Victoria Well Nos. 1 and 2, and Mound Well No. 1 samples indicate the groundwater varies between discrete aquifer zones and is of fair to brackish


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quality. It is anticipated that new wells constructed in the Saugus and Las Posas Formation (Fox Canyon Aquifer equivalent) will have a similar water quality and chemical character to the existing wells in the Mound Basin that are completed in comparable aquifer zones. Because water quality is transient and a result of many factors that can vary significantly over time, and because available data are insufficient to effectively prioritize well locations based solely on water quality criteria, water quality was used only as one of the five factors included in the hydrological suitability rating. The anticipated water quality was scored based on the point system provided in Table 8 – Water Quality Rating Criteria.

Table 8 – Water Quality Rating Criteria

TOTAL DISSOLVED SOLIDS CONCENTRATION

(MG/L) POINTS

1,201 TO 1,500 2

1,001 TO 1,200 4

801 TO 1,000 6

500 TO 800 8

LESS THAN 500 10

The hydrogeological rating criteria provided from the previous sections of this study are summarized in Table 9 – Hydrogeological Suitability Rating.


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Table 9 –Hydrogeological Suitability Rating (50 Maximum Possible Points)

WELL SITE NO.

WELL DEPTH (FEET)

PRODUCTION POTENTIAL

(GPM)


DEPTH TO PUMPING WATER LEVEL (FEET)

ANTICIPATED GROUNDWATER

QUALITY (TDS IN MG/L)

TOTAL

1A 5 8 4 2 4 23

1B 5 8 4 2 4 23

2 5 8 4 2 4 23

3 3 10 6 2 2 23

4 1 10 6 4 2 23

5 5 10 10 4 4 33

6A 8 10 10 2 2 32

6B 3 10 10 2 2 27

7 10 10 10 8 4 42

8 5 10 10 6 4 35

CONSTRUCTABILITY AND OPERATIONS CONSTRAINTS

Well Construction Constraints

This portion of the well site assessment was developed to identify which sites were most accommodating for initial well construction, long-term operation and maintenance activities, and providing the potential for future well replacement in 30 to 50 years after the newly constructed well begins to fail. Well constructability issues considered in the well site scores include; the suitability of the well construction area (parcel size and existing grade/slope), the sensitivity of existing surrounding land uses (for 24-hour operations during well construction), site access, and onsite obstructions (i.e. overhead power lines, buried pipelines, and landscaping).

The score for each site that reflects these criteria is provided in Table 10 – Rating of Constructability, Operation, and Well Replacement. The assigned values were based on Hopkins’ experience with comparable well construction project and are appropriately subjective


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in nature. These values are believed accurate based on our understanding of the site conditions at the time of the study.

Table 10 – Rating of Constructability, Operation, and Well Replacement (30 Maximum Possible Points)

WELL SITE NO.

EASE OF WELL CONSTRUCTION,

OPERATIONS AND MAINTENANCE

WELL CONSTRUCTION

AND MAINTENANCE SCORE

PIPELINE LENGTH (FEET)

PIPELINE CONSTRUCTION

SCORE

WELL REPLACEMENT

SCORE

TOTAL SCORE

1A CHALLENGING 8 9,670 1 8 17

1B FAVORABLE 8 8,000 1 10 19

2 FAVORABLE 5 4,600 2 5 12

3 FAVORABLE 8 150 10 10 28

4 FAVORABLE 6 5,500 1 10 17

5 FAVORABLE 9 6,100 1 7 17

6A FAVORABLE 8 2,155 6 7 21

6B CHALLENGING 6 1,385 8 5 19

7 FAVORABLE 9 600 9 10 28

8 CHALLENGING 6 5,575 1 5 12

A score of up to 10 points was provided based on the effort required to develop access, conduct grading and/or tree removal, and/or create a disruption of surrounding land uses during construction, future operations and maintenance activities. Well sites that are anticipated to require only development of access and minor grading received the highest score. A score of 10 points was given to sites that were believed essentially ready for construction and will only create a temporary mitigable nuisance to adjacent land uses during construction.

The well sites were assessed based on their proximity to existing sufficiently sized raw water pipelines that feed the Bailey Water Conditioning Facility (Bailey). The distance of pipeline that would be required during facilities construction was scored for this criterion. If a water treatment plant would be required to condition the produced groundwater at the well site, the site was assigned the lowest score. The anticipated length of pipeline was scored based on the point system provided in Table 11 – Groundwater Purveyance and Treatment Rating Criteria.


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Plate 16 – Existing and Required Transmission Pipeline Location Map shows the approximate alignment and distance of the new pipelines that will be required to convey raw water from the proposed well facilities to Bailey for treatment. As shown, there are two existing transmission mains. One lies beneath Victoria Avenue and connects the City wells located at the San Buenaventura Golf Course that pump from the Oxnard Plain Pressure Basin. The other is located in Hill Street and Webster Street and connects the three existing Mound Basin wells to Bailey (see Plate 16). Both pipelines have conveyance capacity restrictions and it is important to maintain the raw water supply historically balanced between them.

Table 11 – Groundwater Purveyance and Treatment Rating Criteria

PIPELINE LENGTH (FEET)

POINTS

TREATMENT PLANT OR MORE THAN 5,000

1

4,001 TO 5,000 2

3,501 TO 4,000 3

3,001 TO 3,500 4

2,501 TO 3,000 5

2,001 TO 2,500 6

1,501 TO 2,000 7

1,001 TO 1,500 8

501 TO 1,000 9

0 TO 500 10

Operations and Maintenance

Continued operation and maintenance of well production facilities were considered as a part of this well site rating criterion. The scores were based on routine operation of deep-set line-shaft turbine pumps with above ground motors. These operations considered the same impact to surrounding land uses that were considered for well construction but are based on routine (daily) site visits and periodic mobilization of equipment for well rehabilitation, pump repair, and chemical deliveries. Generally, most sites scored higher in this category because


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these operations are typically conducted on a daily basis. A score of 10 was assigned to sites that facilitated future operations and maintenance activities where large trucks and tanks could be accommodated on or adjacent the well site. The greater the difficulty, the lower the score.

Well Replacement

Future well construction was considered by this study as an important issue given the anticipated difficulty of finding suitable well sites in developed areas within the City after another 30 to 40 years of growth. The assigned scores consider the issues described in original well construction and include anticipated land use changes that may occur on adjacent properties in the near future. The score is further weighted by consideration of the size and shape of the available lot. The well sites that scored the highest under these criteria are generally those that are presently adjacent agricultural land uses and where lot size allocation during land purchase can consider future well construction.

A score of 10 points was assigned if the site will facilitate future well construction and allow well placement of 50 feet or greater away from the proposed well location. A score of zero (0) was given for this criterion if the site could only be used to drill the proposed well. The site scores increased proportionally with the anticipated ease of future well construction.

EASE OF SITE ACQUISITION

Property Ownership

Determination of the difficulty for the City to obtain the individual sites is beyond the scope of this study and will need to be conducted by the City on the highest ranking sites that are considered most favorable. Rating the difficulty for the City to obtain the individual sites was simply conducted by determining whether the property was owned by the City, the County, or a private entity. Table 12 – Site Acquisition Rating Criteria shows the anticipated difficulty of obtaining a site based on property ownership. If the property was owned by the City the site was scored 5 points. A parcel owned by the County or other public agency results in a site score of 3 points. Privately owned property scores 1 point. XXXXXXXXXXXXXXXXXXXXXXXX

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Table 12 – Site Acquisition Rating Criteria (20 maximum possible points)

SITE NO. LAND

OWNERSHIPSCORE

LAND USE SCORE

TOTAL SCORE 2 X

(USE+OWNERSHIP)

1A 5 3 16

1B 5 3 16

2 1 2 6

3 1 2 6

4 1 5 12

5 1 2 6

6A 3 3 12

6B 3 3 12

7 5 5 20

8 1 2 6

Land Use

Some of the proposed well sites require the purchase and conversion of agricultural land to municipal use. The conversion of agricultural land within the County of Ventura falls under the Save Our Agricultural Resources (SOAR) initiative and allows the conversion of agricultural land to housing only by a majority vote of the populace. However, the conversion of agricultural land can be incorporated for municipal use as long as it does not include residential development. Because the amount of land to be converted for City use is relatively small and the sites are located along the edge or in the corner of the properties identified, we do not believe the proposed well sites will adversely impact the present agricultural industry.

Well construction work within residentially developed areas can be more difficult depending on the existing land uses. Well sites located on fallow undeveloped parcels are typically the best for accommodating well construction activities and these sites scored 5 points. Because it is believed there is a cooperative relationship between City Parks and Ventura Water, and because of the typical ease of access and flat work areas available within parks, these sites


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scored 3 points. Other land uses provide unique challenges for well construction and as such, the well site land use rating utilized the following scoring system:

Fallow/Undeveloped = 5

Unirrigated landscape = 4

Landscape or recreation use/Parks = 3

Private orchard or existing utilities easement = 2

Public parking = 1

Subsequent weighting of the ease of site acquisition was accomplished by adding the two rating categories and doubling the score (see Table 12).

SITE RANKING SUMMARY

A summary of the three important well site rating criteria scores is provided as Table 13 – Well Site Score Sheet. The maximum potential suitability score is 100 points. The sites thatscore the highest are considered the most suitable for well construction and worthy of furtherconsideration. This evaluation is provided for City guidance when reviewing if other constraintsor potential factors could affect any of the sites. As shown, there were 2 locations that scorednotably higher than the rest and one that scored considerably lower.

Utilizing the total score of each well site presented in Table 13, the final scores were sorted to rank the sites with regard to overall suitability for establishing a new well facility. The ranking results are presented in Table 14 – Well Site Ranking. The ranking shows how the scores resulted in a rather tight grouping of the sites between 52 and 58 points. This indicates that most of the sites could not provide a high score on all the criteria.


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Table 13 – Well Site Score Sheet

WELL SITE NO.

HYDROGEOLOGICAL SUITABILITY

WELL CONSTRUCTABILIT

Y

EASE OF SITE

ACQUISITION

TOTAL SCORE

POINTS POSSIBLE

50 30 20 100

1A 23 17 16 56

1B 23 19 16 58

2 23 12 6 41

3 23 28 6 57

4 23 17 12 52

5 33 17 6 56

6A 32 21 12 65

6B 27 19 12 58

7 42 28 20 90

8 35 12 6 53


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Table 14 – Well Site Ranking

SITE RANKING SITE NO. TOTAL SCORE

1 7 90

2 6A 65

3 6B 58

4 1B 58

5 3 57

6 5 56

7 1A 56

8 8 53

9 4 52

10 2 41

CONCLUSIONS AND RECOMMENDATIONS

The findings of this study indicate the City has several sites that are advantageous for well construction. All sites have some relatively unknown conditions. Each suitable site scored high in the study ranking process for different reasons, but generally because they are believed to be hydrogeologically suitable and are accommodating for well construction, maintenance, and future replacement.

Well Site No. 7 ranked highest largely because of its inferred favorable hydrogeology, which can support the desired well yield and because the City owns the property. The site is favorable because of the perceived ease of construction and short distance to the existing raw water pipeline from the Golf Course Wellfield. This well site has the added advantage of being located in the South Mound Subbasin a considerable distance from the existing City wells in the Central Mound Subbasin. This location would serve to distribute City groundwater production more evenly across the basin. However, the water quality will likely be of fair quality and require treatment prior to use.


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Well Site No. 6A ranked second highest largely because of its inferred favorable hydrogeology, which can support the desired well yield and because the County owns the property. The site is favorable because of the perceived ease of construction and only moderate distance to the existing raw water pipeline that conveys water from the existing Mound Basin wells in the Central Mound Subbasin. It is anticipated the water quality will be significantly better than Mound Well No. 1, however, the water quality will likely be of fair quality and still require treatment prior to use.

Well Site No. 6B and 1B ranked relatively high but were downgraded for different reasons. Both overly an area of inferred favorable hydrogeology that can support the desired well yield but both will require deeper well designs. Well Site No. 1B is believed more favorable because it is located on City Parks property and is located in the North Mound Subbasin and could serve to distribute the pumping stress more evenly across the basin. It is anticipated the water quality will be comparable to other Mound wells, however, there are no water quality records from historical wells. There is the potential that the groundwater could be of a higher quality because it is located close to the outcrop area that receives recharge from rainwater. It is anticipated the groundwater will also require treatment prior to use. Site 6B has a considerably shorter pipeline length, but the well is located in the Central Mound Subbasin on County owned property.

Well Site No. 3 is conveniently located adjacent the existing Mound Wellfield pipeline. The surrounding land uses would contribute to ease of construction and a parcel large enough for a replacement well could likely be obtained. However, the site scoring was reduced because the property is privately owned, is presently in agricultural production, and the well depth would be considerably greater than other sites (i.e., 6A or 6B).

Well Site No. 5 is located at the City owned Ventura Community Park and was the subject of a previous City study conducted in 2009. The well site provides favorable hydrogeology that can support the desired well yield. The site is favorable because of the perceived ease of construction and because it moves pumping further from the coastline. Well Site No. 5 is located a fair distance from Bailey and was scored lower because of the long pipeline required. It is anticipated the water quality will be significantly better than Mound Well No. 1, however, the water quality will likely be of fair quality and still require treatment prior to use.

Well Site No. 1A scored the same as Well Site No. 5 and was found favorable based on the anticipated hydrogeology and its location on City owned property. Well Site No. 1A is located closest to the base of fresh water and may encounter a quality that is degraded from upward seepage of groundwater from the marine shale deposits below the Los Posas Sand Formation. For this reason, Well Site No. 1B is believed superior in its location and where it targets the lower portion of the Saugus Formation.


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Well Site Nos. 2, 4, and 8 are not believed worth pursuing unless the other favorable sites have unforeseen constraints. The difficulty presented by the acquisition of private property, combined with the long pipeline runs to connect to the existing system, contribute to their lower well site ratings. At Well Site No. 8 it is not clear if a parcel could be obtained that is large enough for a future replacement well. Well Site No. 8 is also located in the Central Mound Subbasin where the other Mound Wells are located, and is located approximately 1 mile closer to the coastline. Well Site No. 2 does not appear to provide any greater hydrogeological benefit than Well Site No. 1B, which would be anticipated to produce from the same aquifer zones. Well Site No. 4 would require a significantly deeper well construction that will increase the difficulty and cost of future well maintenance and cost of well replacement.

Based on the findings of this study, we recommend City consider drilling and constructing the first proposed new wells at Well Site Nos. 7 and 6A (see Plate 1) to immediately supplement its existing groundwater supply facilities. These locations would augment supply using both existing transmission pipelines that feed Bailey. Well Site No. 6A would restore lost production capacity in the Central Mound Subbasin and improve quality by reducing the reliance on Mound Well No. 1. Well Site No. 7 would distribute pumping into the South Mound Subbasin and maintain capacity in the transmission pipeline that serves the Golf Course Wellfield.

We recommend that subsequent consideration be given to locating a well facility at Well Site No. 1B or Well Site No. 5. These two locations would also serve to distribute pumping within the basin and potentially produce from aquifer zones located toward the base of the Saugus Formation. It is also anticipated that water quality could be slightly better at these locations, however, it will still require treatment.

CLOSURE

This report has been prepared for the exclusive use of the City of San Buenaventura and its agents for specific application to the selection of a well site(s) that may be suitable for the construction and operation of a new municipal water supply well(s). The findings, conclusions, and recommendations presented herein were prepared in accordance with generally accepted hydrogeological engineering practices. No other warranty, express or implied is made.


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REFERENCES

California Division of Mines and Geology (1973), Geology and Mineral Resources Study of Southern Ventura County, California, Preliminary Report 14, Prepared in Cooperation with the County of Ventura and the U.S. Geological Survey.

California State Water Resources Board (SWRB, 1953), Bulletin No. 12 Ventura County Investigation, Dated October.

Dibblee, T.W. Jr., (1988), Geologic Map of the Ventura and Pitas Point Quadrangles.

Dibblee, T.W. Jr., (1992), Geologic Map of the Saticoy Quadrangles.

Hopkins Groundwater Consultants, Inc. (2009), Preliminary Hydrogeological Study, City of San Buenaventura Mound Well No. 2 Siting Study, Ventura, California, Prepared for City of San Buenaventura, Dated April 29.

United Water Conservation District (2012), Hydrogeological Assessment of the Mound Basin, United Water Conservation District Open-File Report 2012-1, Dated May.


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VENTURA

OXNARD

OXNARD PLAINBASIN

MOUND BASIN

OXNARDFOREBAY

BASIN

APPROXIMATESTUDY AREA

NORTH

3,000 6,000

FEET

0

SANTAPAULABASIN

STUDY AREA LOCATION MAP

Mound Well No. 2 Siting Study

City of VenturaVentura, California

PLA

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1


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WELL SITE LOCATION MAP



PLATE 2

Project No. 01-009-04B

��

��

��

��

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0 1250 2500

FEET

PROPOSED NEWWELL SITES

1

FOOTHILL ROAD

126 FWY

101 FWY

VIC

TO

RIA

AV

EN

UE

TELEPHONE ROAD

TELEGRAPH ROAD

KIM

BA

LL

RO

AD

DA

YR

OA

D

JO

HN

SO

ND

RIV

E

4

1B

2

3

5

6A

7

8

1A

6B


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OXNARD

OXNARD PLAINBASIN

MOUND BASIN

OXNARDFOREBAY

BASIN

SANTAPAULABASIN

B

B’

A’

C’

C

A

NORTH

3,000 6,000

FEET

0

AGRICULTURALWELL

LEGEND

MUNICIPALWELL

OIL WELL ORTESTHOLE

A CROSS-SECTIONLOCATION

A’

HYDROGEOLOGICAL CROSS-SECTION AND

WELL LOCATION MAP



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OA

K R

IDG

E F

AU

LT

ZO

NEVE

NT

UR

AFA

ULT

ZO

NE

QTlp

QTs

VENTURAFAULT

SWN 8L1VIC NO. 1

SWN 8P4

SWN 17Q4(P 600’ W)

AND101 FREEWAY

OIL WELL5917 SWN 8F1

VIC NO. 2(P 300’ E)

0

-1000

SWN 5E1(P 500’ E)

FOOTHILLROAD TELEGRAPH

ROAD HIGHWAY126

TELEPHONEROAD

-2000

ELE

VA

TIO

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FE

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L)

0 1000 2000

FEET

HORIZONTAL SCALE

QTpm

QTs

QTlp

QTpm

QTpm

-3000

-4000

500

QTlp

QTs

QTpm

B-B’OIL WELL

20500(P 3,450’ W)

OIL WELL5769

(P 2,750’ W)

QoaQoa

QogQa

9,357’

3,045’

2,954’

1,680’

1,300’ 1,119’

12,206’ 10,476’

1,500’

SWN 17G1(P 1,200’ W)

A’

A

~~~~~~~~~~~~~~~

HYDROGEOLOGICAL CROSS-SECTION A-A’



PLATE 12

SOUTH SUBBASINCENTRAL SUBBASINNORTH SUBBASIN


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KIMBALLROAD

VICTORIAAVENUE

A-A’AND

HILLROAD

OIL WELL5798

VENTURA COM. PARKMONITORING

WELLSSWN 8P4

SWN 8N1

BEND IN SECTIONSWN 7P1

SWN 7R2

SWN 9K7

0 1000 2000

FEET

HORIZONTAL SCALE

-4000

-3000

OIL WELL5810

SWN 13K4SWN 13F2

QTlp

QTs

QTpm

QTs

QTlp

Qoa

Qa

1,490’

750’

550’580’

1,440’

8,566’

482’

13,566’

1,200’

990’

HYDROGEOLOGICAL CROSS-SECTION B-B’



PLATE 13


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QTlp

QTs

QTpm

QTlp

QTsQoa

FOOTHILLROAD

LOMA VISTAROAD

SWN 5E1(P 2,500’ W)

0 1000 2000

FEET

HORIZONTAL SCALE

VE

NT

UR

AFA

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3,045’

~ ~

- Alluvium (Qa) - silt, sand and gravel of valley floodplain areas

- Older Dissected Surficial Deposits (Qoa) - remnants of weakly consolidated older alluvial deposits gravel,sand and silt

- Saugus Formation (Qts) - weakly consolidated alluvial deposits: gray to tan boulder-cobble-pebble gravel of mostlysandstone and some siliceous shale detritus in light brown sandy matrix

- Las Posas Sand (Qtlp) - weakly indurated, soft, tan to yellowish-brown fossiliferous shale and hard sandstone

- Pico Formation (Qtpm) - Mudpit Claystone Member (Santa Barbara Formation), massive to vaguely bedded soft grayclaystone or mudstone

- Electric Log Trace

LEGEND

- Fault

Qoa

Qa

QTs

QTlp

QTpm

SWN 13K4

3,045’

- Historical Well LocationWell Identification and Depth

- Older Dissected Surficial Deposits (Qog) - cobble-boulder fan gravel and fanglomerate deposits composedlargely of sandstone detritus

Qog

HYDROGEOLOGICAL CROSS-SECTION C-C’

and GEOLOGIC LEGEND



PLATE 14

NORTH SUBBASIN


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APPENDIX C GEOLOGICAL INTERPRETATIONS


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GEOLOGIC MAP



PLATE C1

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GEOLOGIC MAPS - SATICOY AND VENTURA/PITAS POINT QUADRANGLESBY THOMAS W. DIBBLEE 1992 AND 1988 XXXXXXXXXXXXXXXXXXXXXXXX

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CDMG GEOLOGIC MAP



PLATE C2


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GEOLOGY AND MINERAL RESOURCESSTUDY OF THE SOUTHERN VENTURA COUNTY, CALIFORNIA

CALIFORNIA DIVISION OF MINES AND GEOLOGY, 1973


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REGIONAL COMPOSITE GEOLOGIC MAP



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UNITED, 2012


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UWCD COMPOSITE GEOLOGIC MAP



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UNITED, 2012


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