colinas de capistrano - via email … · 2017. 7. 3. · colinas and to protect the interests of...

VIA EMAIL ([email protected]) June 12, 2017 City of Laguna Niguel Community Development Department 30111 Crown Valley Parkway Laguna Niguel, CA 92677 Attention: Jonathan Orduna, Senior Planner Re: Colinas de Capistrano Community Association’s Public Comments on the Draft

Environmental Impact Report for the Proposed SunPointe Residential Project (SCH #2016061037)

Dear Mr. Orduna: This letter submits the public comments of the Colinas de Capistrano Community Association (“Colinas”) regarding the Draft Environmental Impact Report (“Draft EIR”) prepared by the City of Laguna Niguel (“City”) for the proposed Sunpointe Residential Project formerly known as Colinas Sur (“Proposed Project”). We are land use and environmental legal counsel for Colinas. This letter is submitted on behalf of the members of Colinas who own 920 single family homes, townhomes, and condominiums immediately adjacent to the Proposed Project’s site (“Site”).1 Over 3,000 Laguna Niguel residents reside in Colinas. Colinas homes surround the Site continuously from the southwest to the northeast, partially including all homes along the ridgeline contiguous with the westerly border of the Site and all homes contiguous with the northerly border of the Site. The sole means of ingress and egress for the Proposed Project is from Avenida Del Caballo, a street lined with Colinas homes. Given such, Colinas is the most affected stakeholder by the Proposed Project. This letter follows exhaustive participation by Colinas and its members about the Proposed Project over the past several years since the Proposed Project was first made

1 This letter is submitted through the authorization of Colinas’ Board of Directors on behalf of Colinas and to protect the interests of its members. This letter should not be construed as the exclusive and sole expression of public comments on the Draft EIR by Colinas’ members. We anticipate that a significant number of Colinas’ members will separately submit written public comments on the Draft EIR.

mailto:[email protected]

Jonathan Orduna City of Laguna Niguel

June 12, 2017

public. This participation includes, in part, written public comments on the Proposed Project’s Initial Study2, written and oral comments about the Public Scoping Meeting on the Proposed Project3, and written and oral communications with the City’s Staff, the City’s publicly elected and appointed officials, and Euland Capital Enterprises, the Proposed Project’s applicant (“Applicant”), about the Proposed Project. The predominant, though far from exclusive, concern with the Proposed Project has and continues to be the reactivation of existing and the creation of new geologic hazards on and about the Site through the sought development. Since Colinas’ homes surround and are contiguous with the Site, it is highly probable that Colinas and such homes would be damaged or otherwise negatively affected by said geologic hazards. We are thankful that the City recognized the validity of Colinas’ and its members’ concerns and required the preparation of the Draft EIR instead of completing environmental review of the Proposed Project through the proposed Mitigated Negative Declaration. The Draft EIR explains that residential development of the Site, which is on a hillside slope with over 200 feet of grade change, has been unsuccessfully attempted for nearly 45 years due to ongoing geologic hazards thereon, including multiple landslides. (See Draft EIR at ES.1 & ES.2.) While the Site is already entitled and improved for developing 35 “conventional” detached single family homes, which follows the detached single family homes which uniformly surround the site, the Applicant instead desires to double the number of units to 71 townhomes and to closely cluster those units on five terraced pads relying upon towering retainer walls to maximize its anticipated financial return. (See Draft EIR at ES.2 & ES.3.) Demonstrating the Applicant’s extraordinary request for the Proposed Project, extensive discretionary entitlements, ranging from amending the City’s General Plan to changing the Site’s zoning, are required for the Proposed Project to be approved. (See Draft EIR at ES.4.) The troubled development history of the Proposed Project’s site, the change of grade thereon, the known geologic hazards thereon (including landslides and highly expansive soil), the significant increase in the number and density of desired units thereon, the creation of terraced housing incongruent with the surrounds, the Applicant’s reliance upon an unconventional grading plan requiring up to 26 foot retaining walls to shortcut removal of dirt to remediate the ancient landslide thereon to save money, the proximity of Colinas homes to the same, among other factors, all validate Colinas’ concerns.

2 A copy of Colinas’ public comment letter, dated July 12, 2016, concerning the Proposed Project’s Initial Study is enclosed with this letter as Attachment 1. 3 A copy of Colinas’ comment letter, dated November 29, 2016, concerning the Proposed Project’s Public Scoping Meeting is enclosed with this letter as Attachment 2.


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As the largest law firm in the State of California which focuses on representing homeowner associations, our firm has and now represents numerous other homeowner associations in the City forced to address financially crippling, unfunded damage caused by pervasive geologic hazards, such as landslides, mudflows, surficial failures, soil creep, and differential settlement, due to inappropriately designed and constructed developments graded into the highly expansive soil which pervades the City (as acknowledged in the Draft EIR at 3.5-3 – 3.5-4). The sweeping history of geologic hazards throughout the City further substantiates Colinas’ concerns about the Proposed Project. Colinas does not desire to find itself in the same situations as many other Laguna Niguel homeowner associations due to shortcomings with the Proposed Project. This letter follows the undersigned’s consultation with Fei-chiu (Jerry) Huang, Ph.D., Principal Engineer, Douglas S. Danto, Chief Engineering Geologist, and Edred (Tom) Marsh, Principal Engineer of American Geotechnical, Inc. (“American Geotechnical”). American Geotechnical has conducted peer reviews of the geology and hydrology reports prepared by Stoney-Miller Consultants, Inc. relied upon in the Draft EIR and included as appendices thereto (respectively the “AG Geology Peer Review” and the “AG Hydrology Peer Review.” As explained in the peer review letters enclosed with this letter as Attachments 3 and 4, which are incorporated by reference in this letter as if set forth in this letter, American Geotechnical has noted numerous critically incomplete analyses, unsupported conclusions, and outstanding areas of investigation, which require, at minimum, a recirculated draft environmental impact report or changes to the Proposed Project. In these and other below-stated respects, the Draft EIR fails to fulfill the requirements of California Environmental Quality Act (“CEQA”) and its Guidelines and cannot support a legally-compliant final environmental impact report. Colinas provides the following additional public comments on the Draft EIR: Page(s) Section Comment ES-2 - ES-3

ES.3 Project Overview This section fails to describe type of housing units to be created in the Proposed Project (e.g., detached single family homes, townhomes, condominiums etc.). This section fails to provide a written description or visual depiction of where the housing units and five clustered housing pads would be on the Site. This section fails to describe the range of sizes of the lots and the housing units.


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This section fails to identify that the clustered housing pads rely upon a series of significant retaining walls. These failures contribute to the Project Overview not reasonably, accurately or sufficiently describing the Proposed Project.

ES-4 ES.5 Areas of Known Controversy

This section fails to list the concerns raised in acknowledged numerous responses to the Notice of Preparation.

ES-5 - ES-7

ES.7.1 Alternatives Considered

Colinas may support Alternatives 4 and 5 following a comprehensive environmental review of those alternatives if is demonstrated that Colinas’ concerns stated herein and to date would be satisfactorily resolved. The Draft EIR and the appendixes thereto do not sufficiently consider and analyze the environmental impacts of Alternatives 4 and 5 for Colinas to endorse either alternative. Colinas encourages that the City expeditiously conduct a comprehensive environmental review of Alternatives 4 and 5 so Colinas may assess whether either is agreeable.

ES-7 ES.7.2 Alternatives Considered but Rejected from Further Analysis

The cost of construction of Alternative 5: Development Consistent with Recorded Map should not be rejected from analysis due to the cost, which is not relevant to environmental consideration under CEQA.

2-3 - 2-4 2.2.5 Existing General Plan Land Use Designation

Colinas emphasizes, as noted in this section, that the Site’s residential surroundings are zoned exclusively for Residential Detached structures (i.e. detached single family homes). The Proposed Project’s required amendment to the General Plan to rezone the Site for Residential Attached structures will be inconsistent (from aesthetic and other perspectives) with the immediate residential surroundings. Colinas emphasizes, as noted in this section in Table 2-1, all of the projects in the Community Profile Area were completed consistent with the General Plan’s


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projection for dwelling units (for residential projects) or square feet (for commercial projects) and appear to have required no General Plan amendment, unlike the Proposed Project. This demonstrates the extraordinary nature of the discretionary entitlements required for the Proposed Project to be approved. Concerning ES.7.1 above, Colinas may support Alternatives 4 and 5 which maintain the 35 dwelling units approved for the Site, which follows the General Plan.

2-4 2.26 Existing Zoning Colinas emphasizes, as depicted in Figure 2-5, that the Site’s residential surroundings are zoned exclusively as RS-3 (Single Family District 3). The Proposed Project’s required zone change for the Site to RA (Attached Residential District) will be inconsistent (from aesthetic and other perspectives) with the immediate residential surroundings.

2-5 2.3 Proposed Project Description

This section fails to describe type of housing units to be created in the Proposed Project (e.g., detached single family homes, townhomes, condominiums etc.). This section fails to provide a written description or visual depiction of where the housing units and five clustered housing pads would be on the Site. This section fails to describe the range of sizes of the lots and the housing units. This section fails to identify that the clustered housing pads rely upon a series of significant retaining walls. These failures contribute to the Proposed Project Description not reasonably, accurately or sufficiently describing the Proposed Project.

2-5 2.3.1 Project Objectives

No evidentiary substantiation is provided in the Draft EIR for the assertion in this section, and elsewhere in


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the Draft EIR, that the Site is an “attractive nuisance condition.” While the Draft EIR claims that calls for service to the City’s Police Department about the Site have been made, in addition to local resident complaints, the asserted calls for service and complaints are not quantified, qualified or discretely summarized. Absent such substantiation, this claim cannot be validated.

2-6 2.3.2 General Plan Amendment

Colinas emphasizes, as noted in this section, that the Site’s residential surroundings are zoned exclusively for Residential Detached structures (i.e. detached single family homes). The Proposed Project’s required amendment to the General Plan to rezone the Site for Residential Attached structures will be inconsistent (from aesthetic and other perspectives) with the immediate residential surroundings. Colinas emphasizes, as noted in Table 2-1, the projects in the Community Profile Area were completed consistent with the General Plan’s projection for dwelling units (for residential projects) or square feet (for commercial projects) and appear to have required no General Plan amendment, unlike the Proposed Project. This demonstrates the extraordinary nature of the discretionary entitlements required for the Proposed Project to be approved.

2-6 2.3.3 Zone Change Colinas emphasizes, as depicted in Figure 2-5, that the Site’s residential surroundings are zoned exclusively as RS-3 (Single Family District 3). The Proposed Project’s required zone change for the Site to RA (Attached Residential District) will be inconsistent (from aesthetic and other perspectives) with the immediate residential surroundings. Colinas emphasizes, as noted in this section, that the creation of “custom development standards to group housing in certain portions of the site” demonstrates the extraordinary nature of the discretionary entitlements required for the Proposed


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Project to be approved. The Draft EIR does not identify any other nearby projects approved utilizing “custom development standards,” and again demonstrating the significant departure of the Proposed Project from other approved projects.

2-6 – 2-10

2.3.5 Site Development Permit

Reference is made to the AG Geology Peer Review and the AG Hydrology Peer Review and its comments on the geology and hydrology features of the Proposed Project, which apply to the geology and hydrology discussion in this section. Colinas emphasizes, as noted in this section, that the Proposed Project relies upon unconventional layered geo-grids forming retaining walls up to 26 feet in height, which is a radical departure from the approved development on the Site and creates significant cause for concern given the existing and potential future geologic hazards on the Site. Colinas emphasizes, as noted on pages 2-9 - 2-10, that a Site Development Permit is required given the Proposed Project’s numerous deviations from the City’s standards for new residential projects, demonstrating the extraordinary nature of the discretionary entitlements required for the Proposed Project to be approved. The Draft EIR does not identify any other nearby projects approved and included similar deviations from the City’s standards, again demonstrating the significant departure of the Proposed Project from other approved projects.

2-10 2.3.6 Minor Adjustment

Reference is made to the AG Geology Peer Review and the AG Hydrology Peer Review and its comments on the geology and hydrology features of the Proposed Project, which apply to the geology and hydrology discussion in this section. Colinas emphasizes, as noted in this section, that the Proposed Project relies upon unconventional layered geo-grids forming retaining walls up to 26 feet in height, which is a radical departure from the


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approved development on the Site and creates significant cause for concern given the existing and potential future geologic hazards on the Site.

3.1-1 - 3.1-2

3.1.2 Environmental Setting - Visual Conditions

This section fails to state that the residential structures surrounding the Site and near the Site are exclusively detached single family homes. This is critical to properly analyzing the aesthetic impact of the Proposed Project.

3.1-6 Impacts and Mitigation - Impact AES-3

Colinas disagrees with the proposed conclusion reached in this section and asserts that the Proposed Project will substantially degrade the existing visual character and quality of the Site and its surroundings since, in part, the Proposed Project would create attached townhomes, whereas all surrounding residential structures are detached single family homes and thus there will be a stark aesthetic contrast between the Proposed Project and its residential surrounds, and the Proposed Project would create terraced building pads relying upon numerous unconventional retaining walls up to 26 feet in height, whereas none of the surrounding residential structures are either tiered in a similar manner or rely upon similar tall retaining walls and thus there will be a stark aesthetic contrast between the Proposed Project and its residential surrounds.

3.1-8 Impacts and Mitigation - Impact AES-4

This section does not contain sufficient information to support the proposed conclusion. The Draft EIR should have included, but does not include, a lighting analysis as an appendix thereto to simulate the impact of new sources of light and glare impacting day and nighttime views in the area. Failing to include such a lighting analysis means that the Draft EIR has no reasonable basis to conclude the Proposed Project would not create a new source of substantial light or glare which would adversely affect day or nighttime views in the area.


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Colinas notes that the “simulated views” included in Figure 3.1-3a - Figure 3.1-3d do not measure the light and glare the Proposed Project would create either during daytime or nighttime conditions and cannot support the proposed conclusion. At minimum, a standard lighting analysis should be completed to analyze this impact, which requires the recirculation of the Draft EIR.

3.5-1 - 3.5-5

3.5.2 Environmental Setting

Reference is made to the AG Geology Peer Review and the AG Hydrology Peer Review and its comments on the geology and hydrology features of the Proposed Project, which apply to the geology and hydrology discussion in this section. Given the numerous relevant deficiencies noted in the AG Geology Peer Review and the AG Hydrology Peer Review, the analysis in this section is incomplete, inaccurate, and not adequately supported. At minimum, additional investigation and analysis must address these deficiencies, which require the recirculation of the Draft EIR.

3.5-8 - 3.5-9

Impacts and Mitigation - Impact GEO-2

Reference is made to the AG Geology Peer Review and the AG Hydrology Peer Review and its comments on the geology and hydrology features of the Proposed Project, which apply to the geology and hydrology discussion in this section. Given the numerous relevant deficiencies noted in the AG Geology Peer Review and the AG Hydrology Peer Review to this impact, this section does not contain sufficient information to support the proposed conclusion, including, in part, that after mitigation, impacts would be less than significant. At minimum, additional investigation and analysis must address these deficiencies, which require the recirculation of the Draft EIR.

3.5-9 Impacts and Mitigation - Impact GEO-3

Reference is made to the AG Geology Peer Review and the AG Hydrology Peer Review and its comments on the geology and hydrology features of the Proposed Project, which apply to the geology and hydrology discussion in this section. Given the


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numerous relevant deficiencies noted in the AG Geology Peer Review and the AG Hydrology Peer Review to this impact, this section does not contain sufficient information to support the proposed conclusion. At minimum, additional investigation and analysis must address these deficiencies, which require the recirculation of the Draft EIR.

3.5-9 - 3.5-12



3.5-12 - 3.5-13


Reference is made to the AG Geology Peer Review and the AG Hydrology Peer Review and its comments on the geology and hydrology features of the Proposed Project, which apply to the geology and hydrology discussion in this section. Given the numerous relevant deficiencies noted in the AG Geology Peer Review and the AG Hydrology Peer Review to this impact, this section does not contain sufficient information to support the proposed conclusion. At minimum, additional investigation and analysis must address these deficiencies, which require the recirculation of the Draft EIR.

3.5-13 - 3.5-14


Reference is made to the AG Geology Peer Review and the AG Hydrology Peer Review and its comments on the geology and hydrology features of the Proposed Project, which apply to the geology and hydrology discussion in this section. Given the numerous relevant deficiencies noted in the AG


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Geology Peer Review and the AG Hydrology Peer Review to this impact, this section does not contain sufficient information to support the proposed conclusion, including, in part, that after mitigation, impacts would be less than significant. At minimum, additional investigation and analysis must address these deficiencies, which require the recirculation of the Draft EIR.

3.5-15 Impacts and Mitigation - Impact GEO-7


3.5-15 - 3.5-16

3.5.5 Cumulative Impacts


3.8-1 - 3.8-4

3.8.2 Environmental Setting

Reference is made to the AG Geology Peer Review and the AG Hydrology Peer Review and its comments on the geology and hydrology features of the Proposed Project, which apply to the geology and hydrology discussion in this section. Given the


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numerous relevant deficiencies noted in the AG Geology Peer Review and the AG Hydrology Peer Review, the analysis in this section is incomplete, inaccurate, and not adequately supported. At minimum, additional investigation and analysis must address these deficiencies, which require the recirculation of the Draft EIR.

3.8-9 - 3.8-11

Impacts and Mitigation - Impact HYD-1


3.8-12 Impacts and Mitigation - Impact HYD-2

Reference is made to the AG Geology Peer Review and the AG Hydrology Peer Review and its comments on the geology and hydrology features of the Proposed Project, which apply to the geology and hydrology discussion in this section. Given the numerous relevant deficiencies noted in the AG Geology Peer Review and the AG Hydrology Peer Review to this impact, this section does not contain sufficient information to support the proposed conclusion. At minimum, additional investigation and analysis must address these deficiencies, which require the recirculation of the Draft EIR.

3.8-12 - 3.8-13


Reference is made to the AG Geology Peer Review and the AG Hydrology Peer Review and its comments on the geology and hydrology features of the Proposed Project, which apply to the geology and hydrology discussion in this section. Given the numerous relevant deficiencies noted in the AG


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Geology Peer Review and the AG Hydrology Peer Review to this impact, this section does not contain sufficient information to support the proposed conclusion, including, in part, that after mitigation, impacts would be less than significant. At minimum, additional investigation and analysis must address these deficiencies, which require the recirculation of the Draft EIR.






Reference is made to the AG Geology Peer Review and the AG Hydrology Peer Review and its comments on the geology and hydrology features


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of the Proposed Project, which apply to the geology and hydrology discussion in this section. Given the numerous relevant deficiencies noted in the AG Geology Peer Review and the AG Hydrology Peer Review to this impact, this section does not contain sufficient information to support the proposed conclusion, including, in part, that after mitigation, impacts would be less than significant. At minimum, additional investigation and analysis must address these deficiencies, which require the recirculation of the Draft EIR.

3.8-16 - 3.8-17



3.8-17 3.8.5 Cumulative Impacts


3.9-1 3.9.2 Environmental Setting

This section fails to state that the residential structures surrounding the Site and near the Site are


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exclusively detached single family homes. This is critical to properly analyzing the land use and planning impacts of the Proposed Project.

3.9-1 - 3.9-2

3.9.3 Regulatory Setting

Colinas emphasizes, as noted in this section, that the Site’s residential surroundings are zoned exclusively for Residential Detached structures (i.e. detached single family homes). The Proposed Project’s required amendment to the General Plan to rezone the Site for Residential Attached structures and required zone change for the Site to RA (Attached Residential District) will be inconsistent (from a land use and planning perspective) with the immediate residential surroundings.

3.9-4 - 3.9-16

Impacts and Mitigation - Impact LUP-2

Colinas disagrees with the proposed conclusion reached in this section and asserts that the Proposed Project would conflict with applicable land use plan, policy, or regulation of an agency with jurisdiction over the project adopted for the purpose of avoiding or mitigating an environmental effect since the Site’s residential surroundings are zoned exclusively for Residential Detached structures (i.e. detached single family homes) and the Proposed Project’s required amendment to the General Plan to rezone the Site for Residential Attached structures and required zone change for the Site to RA (Attached Residential District) will be inconsistent (from a land use and planning perspective) with the immediate residential surroundings, and further, the Proposed Project would create terraced building pads relying upon numerous unconventional retaining walls up to 26 feet in height, whereas none of the surrounding residential structures are either tiered in a similar manner or rely upon similar tall retaining walls and thus the Proposed Project again will be inconsistent with its residential surrounds. These inconsistencies, and the deficiencies noted in the AG Geology Peer Review and the AG Hydrology Peer Review, are contrary to various provisions of the General Plan and Zoning Code, including, in part, General Plan


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Land Use Element Policies 3.0, 3.3, 3.4, and 4.1, General Plan Open Space/Parks/Conversation Element Policies 1.2, 6.1, 6.2, 10.1, 10.2, and General Plan Seismic and Public Safety Policies 1.1, 1.3.

3.9-17 3.9.5 Cumulative Impacts

For the reasons set forth in Colinas’ comments on Sections 3.9.2, 3.9.3 and Impact LUP-2, Colinas disagrees with the proposed conclusions reached in this section.

3.10-15 - 3.10-25

Impacts and Mitigation - Impact NOI-1

Colinas agrees with the proposed conclusion reached in this section that the Proposed Project would expose persons to or generate noise levels in excess of standards established in the local general plan or noise ordinance, or applicable standards of other agencies, but disagrees with the proposed conclusion that the City’s application of Condition of Approval NOI-1 will reduce the acknowledged significant environmental impact to a less than significant level. This is due to an unconventional grading plan for the Proposed Project calling for the cutting and then filling of nearly 350,000 cubic yards of soil through heavy construction equipment and the onsite crushing of concrete and asphalt for the Proposed Project’s roadways or backfill material behind retaining walls, both of which will cause prolonged significant construction activity-related noise to emanate offsite during unreasonable times. Condition of Approval NOI-1 permits such highly disruptive construction activities to occur outside of normal business hours, including from 7:00 am to 9:00 am and 5:30 pm to 8:00 pm on Mondays through Fridays and from 7:00 am to 8:00 pm on Saturdays. Sensitive receptors, such as children and senior citizens residing within Colinas, will be materially and prejudicially affected by the Proposed Project’s construction-related activities. Accordingly, this acknowledged significant environmental impact will not be sufficiently mitigated to a less than significant level through the adoption of Condition of Approval NOI-1. At


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minimum, Condition of Approval NOI-1 should be modified to prohibit any construction-related activities from 7:00 am to 9:00 am and 5:30 pm to 8:00 pm on Mondays through Fridays and from 7:00 am to 8:00 pm on Saturdays, which requires the recirculation of the Draft EIR. Condition of Approval NOI-1 is also vague and ambiguous on whether construction-related vehicles may enter and leave the Site prior to the permitted hours of construction-related activities. Since there is only one means of ingress and egress from the Site, Avenida Del Caballo, a street lined with Colinas homes (or a combination of Charreadas, another street lined with Colinas homes, and Avenida Del Caballo), Colinas’ residents may suffer from noise levels beyond that permitted by State and City law during hours for which construction-related activities are not permitted, thereby vitiating the purported mitigation. At minimum, Condition of Approval NOI-1 should be modified to prohibit any construction-related activities from traversing Avenida Del Caballo and Charreadas, outside of the permitted hours of construction-related activities, which requires the recirculation of the Draft EIR.

3.10-25 - 3.10-26

Impacts and Mitigation - Impact NOI-2

Colinas agrees with the proposed conclusion reached in this section that the Proposed Project would expose persons to or generate excessive groundborne vibration or groundborne noise level, but disagrees with the proposed conclusion that the City’s application of Condition of Approval NOI-1 will reduce the acknowledged significant environmental impact to a less than significant level. This is due to an unconventional grading plan for the Proposed Project calling for the cutting and then filling of nearly 350,000 cubic yards of soil through heavy construction equipment and the onsite crushing of concrete and asphalt for the Proposed Project’s roadways or backfill material behind retaining walls, both of which will cause


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prolonged significant construction activity-related groundborne vibrations and noise to emanate offsite during unreasonable times. Condition of Approval NOI-1 permits such highly disruptive construction activities to occur outside of normal business hours, including from 7:00 am to 9:00 am and 5:30 pm to 8:00 pm on Mondays through Fridays and from 7:00 am to 8:00 pm on Saturdays. Sensitive receptors, such as children and senior citizens, residing within Colinas, will be materially and prejudicially affected by the Proposed Project’s construction-related activities. Accordingly, this acknowledged significant environmental impact will not be sufficiently mitigated to a less than significant level through the adoption of Condition of Approval NOI-1. At minimum, Condition of Approval NOI-1 should be modified to prohibit any construction-related activities from 7:00 am to 9:00 am and 5:30 pm to 8:00 pm on Mondays through Fridays and from 7:00 am to 8:00 pm on Saturdays, which requires the recirculation of the Draft EIR. Condition of Approval NOI-1 is also vague and ambiguous on whether construction-related vehicles may enter and leave the Site prior to the permitted hours of construction-related activities. Since there is only one means of ingress and egress from the Site, Avenida Del Caballo, a street lined with Colinas homes (or a combination of Charreadas, another street lined with Colinas homes, and Avenida Del Caballo), Colinas’ residents may suffer from groundborne vibrations and noise levels beyond that permitted by State and City law during hours for which construction-related activities are not permitted, thereby vitiating the purported mitigation. At minimum, Condition of Approval NOI-1 should be modified to prohibit any construction-related activities from traversing Avenida Del Caballo and Charreadas, outside of the permitted hours of construction-related


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activities, which requires the recirculation of the Draft EIR.

3.10-27 Impacts and Mitigation - Impact NOI-4

Colinas agrees with the proposed conclusion reached in this section that the Proposed Project would result in a substantial temporary or periodic increase in ambient noise levels in the project vicinity above levels existing without the project, but disagrees with the proposed conclusion that the City’s application of Condition of Approval NOI-1 will reduce the acknowledged significant environmental impact to a less than significant level. This is due to an unconventional grading plan for the Proposed Project calling for the cutting and then filling of nearly 350,000 cubic yards of soil through heavy construction equipment and the onsite crushing of concrete and asphalt for the Proposed Project’s roadways or backfill material behind retaining walls, both of which will cause prolonged significant construction activity-related noise to emanate offsite during unreasonable times. Condition of Approval NOI-1 permits such highly disruptive construction activities to occur outside of normal business hours, including from 7:00 am to 9:00 am and 5:30 pm to 8:00 pm on Mondays through Fridays and from 7:00 am to 8:00 pm on Saturdays. Sensitive receptors, such as children and senior citizens residing within Colinas, will be materially and prejudicially affected by the Proposed Project’s construction-related activities. Accordingly, this acknowledged significant environmental impact will not be sufficiently mitigated to a less than significant level through the adoption of Condition of Approval NOI-1. At minimum, Condition of Approval NOI-1 should be modified to prohibit any construction-related activities from 7:00 am to 9:00 am and 5:30 pm to 8:00 pm on Mondays through Fridays and from 7:00 am to 8:00 pm on Saturdays, which requires the recirculation of the Draft EIR.


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Condition of Approval NOI-1 is also vague and ambiguous on whether construction-related vehicles may enter and leave the Site prior to the permitted hours of construction-related activities. Since there is only one means of ingress and egress from the Site, Avenida Del Caballo, a street lined with Colinas homes (or a combination of Charreadas, another street lined with Colinas homes, and Avenida Del Caballo), Colinas’ residents may suffer from noise levels beyond that permitted by State and City law during hours for which construction-related activities are not permitted, thereby vitiating the purported mitigation. At minimum, Condition of Approval NOI-1 should be modified to prohibit any construction-related activities from traversing Avenida Del Caballo and Charreadas, outside of the permitted hours of construction-related activities, which requires the recirculation of the Draft EIR.

3.10-28 - 3.10-31

3.10.5 Cumulative Impacts

For the reasons set forth in Colinas’ comments on Impacts NOI-1, NOI-2, and NOI-4, Colinas disagrees with the proposed conclusions reached in this section.

4-16 4.4.4 Alternative 4: Development Consistent with General Plan Projection and Zoning

The Aesthetics discussion fails to state and acknowledge this alternative’s creation of detached single family homes would be consistent with the detached single family homes which uniformly surround the Site from the southwest to the northeast. The Geology and Soils discussion does not provide sufficient information and analysis to reasonably evaluate whether this alternative would suffer from the same deficiencies discussed in the AG Geology Peer Review and the AG Hydrology Peer Review, and thus this alternative has not been sufficiently considered, which requires the recirculation of the Draft EIR with additional information and analysis.


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The Hydrology and Water Quality discussion does not provide sufficient information and analysis to reasonably evaluate whether this alternative would suffer from the same deficiencies discussed in the AG Geology Peer Review and the AG Hydrology Peer Review, and thus this alternative has not been sufficiently considered, which requires the recirculation of the Draft EIR with additional information and analysis.

Thank you for the opportunity to comment on the Draft EIR. Colinas trusts that the City and the Applicant will work to resolve the serious concerns with the Draft EIR addressed above and make the changes necessary to protect Colinas and the health, safety, well-being, and quiet enjoyment of property of Colinas’ members, residents, and guests. Please forward a copy of the Final Environmental Report and a copy of all public notices about the Proposed Project to the undersigned pursuant to Cal. Code Regs., tit. 14, § 15087 (CEQA Guidelines Section 15087). Please note that this letter solely addresses the Draft EIR and does not state all of the Colinas’ comments on the Proposed Project. Colinas has not waived and reserves the right to submit separate written and oral comments about the Proposed Project for purposes of public hearings thereon.

Very truly yours, BERDING & WEIL LLP

Aaron J. Ehrlich Partner [email protected] Counsel for Colinas de Capistrano Community Association

AJE:aje Enclosures cc: Members of the City of Laguna Niguel’s City Council and Planning Commission (with Enclosures via U.S. Mail)



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Attachments 1. Colinas de Capistrano Community Association’s public comment letter, dated

July 12, 2016, about the Proposed Project’s Initial Study 2. Colinas de Capistrano Community Association’s comment letter, dated

November 29, 2016, about the Proposed Project’s Public Scoping Meeting 3. American Geotechnical, Inc.’s Geotechnical/Geology Review of EIR

Documents letter, dated June 9, 2017 4. American Geotechnical, Inc.’s Civil Engineering Review of EIR Documents letter,

dated June 9, 2017

ATTACHMENT 1

ATTACHMENT 2

ATTACHMENT 3

22725 Old Canal Road, Yorba Linda, CA 92887 - (714) 685-3900 - FAX (714) 685-3909 2640 Financial Court, Suite A, San Diego, CA 92117 - (858) 450-4040 - FAX (858) 457-0814 3100 Fite Circle, Suite 103, Sacramento, CA 95827 - (916) 368-2088 - FAX (916) 368-2188

5600 Spring Mountain Road, Suite 201, Las Vegas, NV 89146 - (702) 562-5046 - FAX (702) 562-2457

June 9, 2017 File No. 30923-10 Colinas De Capistrano HOA c/o Berding Weil 2175 N. California Boulevard, Suite 500 Walnut Creek, CA 94596 Attention: Mr. Aaron J. Ehrlich Subject: GEOTECHNICAL/GEOLOGIC REVIEW OF EIR DOCUMENTS SunPointe - Tentative Tract 17423 Laguna Niguel, California

Dear Mr. Ehrlich:

This report presents the results of our geotechnical/geologic review of portions of the Environmental

Impact Report (EIR) prepared for the proposed SunPointe Development, Tentative Tract 17423 located

in the City of Laguna Niguel, California. The site is generally located east of Mira Vista, south of the

intersection of Charreadas and Avenida Del Caballo, and west of Star Drive. The purpose of this

review is to complete a preliminary geotechnical/geologic evaluation of the potential effects of the

SunPointe Development on adjacent portions of the Colinas de Capistrano Homeowner Association

property generally known as the Country View Estates. Our review focused on the following report

contained in Appendix H of the EIR document:

Stoney-Miller Consultants, Inc., 10/9/14 (rev. 2/17/15), Feasibility Investigation/Review Of 50-

Scale Map SunPointe, Tentative Tract 17433 Colinas Sur, Laguna Niguel, California, Volumes

1, 2, and 3, Project No: 13662-0, Report No: 14-13813R.

The Stoney-Miller report (SMC) is a feasibility level geotechnical evaluation completed at the tentative

tract phase of project development and based on a 50-scale civil engineering plan completed by

Hunsaker & Associates, dated 1/8/15.

File No. 30923-10 June 9, 2017 Page 2 BACKGROUND AND SITE CONDITIONS

The SunPointe Development site was previously graded in the 1960s with modifications to some lots

apparently completed in 1982. The site currently includes 35 mass-graded residential lots and five

paved streets. The site is not built out. It is proposed to re-grade the site into six large building pads

suitable for 71 building units. The building pads would be separated by graded slopes and

mechanically stabilized earth (MSE) walls.

COMMENTS Engineering Geology 1. The site has had multiple generations of geologic exploration and the referenced report includes

104 individual borings, test pits, and cone penetrometer soundings. Even with this extensive list of

subsurface exploration, much of the geologic interpretation relating to landslides is largely

unconstrained by data. On Cross Section C-C’, the closest cross section to the property boundary

between the new development and Country View Estates, 13 deep borings are shown on the cross

section, but only one boring is shown to penetrate an interpreted landslide slip surface. No boring

penetrates the basal slip surface of the landslide or the headscarp of the landslide. The headscarp

is depicted as a 70° to 75° structural surface that extends from existing ground surface to a depth of

about 180 feet where it curves to join a horizontal basal slip surface that extends for more than

1,100 feet. A horizontal basal slip surface, one with no out-of-slope inclination, is an unusual

configuration. The 180-foot deep high angle headscarp is also unusual. Neither surface is

penetrated by exploration or constrained by data.

Exploration techniques are available that could penetrate and sample layers at such depths. One

exploration method that could be used is continuous core diamond drilling. This drilling method is

similar to rotary wash, but uses a small-diameter, diamond-tipped sampling shoe to obtain a

continuous sample of rock from near ground surface to the maximum depth of exploration. The

continuous sample allows a detailed log of lithology and structural features of the rock mass and

combined with downhole geophysical tools like dipmeter, provides quantitative dip measurements.

Prior to project approval, we recommend that several continuous core borings with dipmeter be

completed to verify the geologic interpretation of the landslide(s).

File No. 30923-10 June 9, 2017 Page 3 2. Geologic cross sections were completed with an orientation generally perpendicular to the overall

slope face. Examples of this are Sections A-A’, B-B’, and C-C’. These sections are useful, but do

not define the geologic conditions along the north property line of the SunPointe Development

between SunPointe and Country View Estates. The Geologic Map, Plate 1R shows a landslide in

the SunPointe Development located at the north property line with slide movement to the northeast

toward Country View Estates. We recommend additional cross sections be completed roughly

perpendicular to the property line and through the mass of the landslide. The sections should be

long enough and deep enough to fully document the limits of the slide. Geologic conditions should

be based on subsurface exploration in the area and should show strike and dip of bedding, slip

surfaces, groundwater elevation and other information that may be pertinent. Slope stability

analyses may be required depending on conditions identified.

Geotechnical Engineering General Discussion: SMC conducted slope stability analyses using available commercial software

(GSTABLE slope stability program) developed by Garry H. Gregory with the (STEDwin editor)

program developed by Harald W. Van Aller, P.E. Shear strength parameters of the on-site material

utilized in the SMC slope stability analyses were obtained from laboratory shear strength tests

performed by prior consultants during previous investigations, as well as SMC’s local experience in

similar soils and engineering judgment.

The long-term groundwater profile reflecting current monitoring data, and the planned installation of

the chimney drain and subdrains within the western keyway was utilized in all of their slope stability

analyses presented in the report.

Slope stability analyses under static and pseudostatic conditions were performed by SMC for their

design slope profiles. Searches of potential failure surfaces were conducted to determine the

minimum calculated factors-of-safety for the critical sections using either block and/or circular

modes for various cross-sections under static and seismic conditions as well as temporary backcut

conditions.

SMC conducted analyses of landslides using Cross-Sections A-A’ through E-E’. Searches of the

potential block failure surfaces were made throughout the landslide mass as well as within the

File No. 30923-10 June 9, 2017 Page 4

bedrock material beyond the slide. It should be noted that SMC considered potential landslide

failures would occur in a block failure mode; as such, SMC’s stability analyses in evaluating

potential landslide failure surfaces are identified as block failures. SMC used anisotropic shear

strengths to model Oxidized and Unoxidized zones of the landslide mass and alluvium to evaluate

potential block landslide failure surfaces.

SMC also conducted slope stability analyses for the natural slopes to the south and west sides of

the property, analyses for a 26-foot high Verdura MSE wall, and surficial stability analysis for an

engineered slope at a 2:1 (horizontal:vertical) slope ratio.

SMC analyzed the required factors-of-safety for the static condition with the inclusion of their

recommended remedial grading, reinforced concrete piers, geogrids, lime-treated fill, as specified in

their report. Stability analysis considering the effects of earthquake loads was also conducted.

When the required factors-of-safety were not achieved for pseudo-static analyses, SMC conducted

additional slope and ground deformation analysis for seismic loading conditions using the

procedure recommended by Rathje and Antonakos, published in 2011. This model uses empirical

predictive models for the sliding displacement of rigid slopes, one considering the Peak Ground

Acceleration and Magnitude (PGA, M), and the other using the Peak Ground Acceleration and Peak

Ground Velocity (PGA, PGV). Results of their seismic slope deformations ranges from 0.13 to 1.16

inches when using the PGV-model and 0.30 to 2.69 inches with the Magnitude-method.

Based on our review of the SMC report, we have several comments regarding the slope stability

analyses performed by SMC as listed below.

1. Shear Strength Parameters Used in the Slope Stability Analyses: SMC used anisotropic shear

strength parameters to model the oxidized and unoxidized zones in landslide debris as well as

Capistrano Bedrock. For static conditions, SMC used 250 pounds per square foot (psf) of

cohesion and a 12.5 degree friction angle to model potential landslide block failure surfaces

between 0 and 15 degrees measured from horizontal line within both oxidized and unoxidized

zones in landslide debris. For pseudostatic condition, SMC increased the shear strengths by

one-third and utilized 375 psf of cohesion and a 14.5 degree friction angle. It is considered

reasonable to increase the shear strength by one-third for seismic conditions. For potential

File No. 30923-10 June 9, 2017 Page 5

landslide block failure surfaces between 15 and 90 degrees within both oxidized and unoxidized

zone of landslide debris, a 300 psf cohesion and 20 degree friction angle was used in the

analyses. For potential landslide block failure surfaces between 90 and 0 degrees, a 350 psf

cohesion and 23 degree friction angle was used within oxidized zone of landslide debris, while a

higher strength of 500 psf cohesion and 29 degree friction angle was used within unoxidized

zone of landslide debris. In our opinion, the anisotropic shear strengths modeled by SMC for

both oxidized and unoxidized zone of landslide debris may not be appropriate to well represent

the actual conditions of the oxidized and unoxidized zones of landslide debris in the field.

Further investigation and laboratory testing should be conducted to demonstrate that the

anisotropic shear strengths used by SMC are well representative of the actual site soil

conditions.

Similarly, SMC used anisotropic shear strengths to model Capistrano bedrock/landslide block.

A 750 psf cohesion and a 29 degree friction angle was used to model Capistrano

bedrock/landslide block across a bedding condition and a 300 psf cohesion and a 15 degree

friction angle was used to model Capistrano bedrock/landslide block along a bedding condition.

In our opinion, lower values of cohesions and friction angles for both across bedding and along

bedding conditions should be used in the slope stability analyses to model the actual site soil

conditions. In addition, potential block failure surfaces between 0 and 5 degrees measured from

horizontal line for Capistrano bedrock/landslide block along a bedding condition, in our opinion,

may also not well represent the actual site conditions. We believe that more appropriate values

of a friction angle, say, between 8 and 12 degrees or lower, should be considered in the

analyses, and the range of along bedding angles between 0 and 5 degrees should be

increased, say, between 0 and 20 or 25 degrees, to better model along a bedding condition of

Capistrano bedrock/landside block in the slope stability analyses.

2. Long-Term Groundwater Level: As discussed earlier, SMC utilized the long-term groundwater

profile in all of their slope stability analyses. This long-term groundwater profile assumes that

the hydroaugers installed previously and the proposed chimney drains and other dewatering

techniques to be installed during construction would be effective to keep the groundwater table

at or below the long-term groundwater profile. It is essential that the future groundwater level

does not rise above the long-term groundwater level utilized by SMC in their slope stability

File No. 30923-10 June 9, 2017 Page 6

analyses. The groundwater level would possibly rise as a result of future irrigation practices by

homeowners, seasonal rainfall or heavy rains, as well as possible leaking from utility lines such

as water, sewer, or storm drain lines. Additionally, SMC should conduct slope stability analyses

to model higher groundwater level conditions (e.g., increase groundwater level by 5 feet, 10

feet, 15 feet, etc.) to determine what would be the effects on the proposed development as a

result of increasing groundwater levels.

3. Additional Slope Stability Analyses: Our review of the stability analysis by SMC revealed that

no analyses were done using specific landslide failure surface identified by SMC in their cross-

sections. We believe such stability analyses using specific landslide surface should be

performed by SMC. Additionally, SMC did not perform any back calculation stability analyses to

determine the shear strengths of the potential failure surface under factor-of-safety equals to 1

(i.e., at failure condition). Such back calculation analyses are essential to demonstrate that

whether the shear strengths used by SMC are appropriate for the site conditions and whether

the results of SMC’s laboratory testing data are reasonable or not. Furthermore, SMC did not

perform slope stability analyses using circular searches to evaluate the potential failure

surfaces. Instead, SMC utilized only a block failure mode to model the possible landslide failure

surfaces. In our opinion, circular searches of potential failure surfaces should be conducted to

determine whether such circular failure surfaces could have lower factors-of-safety.

Our further review of the geologic map prepared by SMC revealed that there is a mapped landslide

on the north side of the development. This landslide is mapped in a south-to-north orientation

toward the Colinas de Capistrano HOA properties. This landslide should be carefully analyzed by

SMC to ensure that no negative impact will occur, which in turn may affect the off-site, Colinas de

Capistrano HOA properties on the north. In addition, there are four cross-sections (Cross-Sections

12-12’, 13-13’, 15-15’ and 16-16’) presented on Plate 3R of the SMC report. These four cross-

sections are located in the vicinity of the Colinas de Capistrano HOA properties. It does not appear

that SMC performed any slope stability analyses on these four cross-sections to determine whether

or not the slopes will be stable for the proposed development. In our opinion, these four cross-

sections should be extended further south to include the mapped landsides and additional slope

stability analyses should be conducted to evaluate whether or not the proposed development will

have any negative impact on the stability of the slopes in this area. In summary, we believe that

File No. 30923-10 June 9, 2017 Page 7

additional slope stability analyses should be performed to better evaluate the site

geologic/geotechnical and groundwater conditions for the proposed development. The areas of

concern with respect to the Colinas de Capistrano HOA properties have been summarized in the

text above.

CLOSURE

This work was performed in accordance with generally accepted professional engineering geology

and geotechnical engineering principles and practice in southern California at the present time. No

warranties or guarantees are being expressed or implied. Findings presented herein are based on

document review only. No subsurface exploration or geotechnical laboratory testing was performed

or authorized. The data and findings of this evaluation were prepared for the sole use and benefit

of the Colinas De Capistrano Homeowners Association. This work was not prepared for use by

other parties and may not contain sufficient information for other uses at other times.

We thank you for choosing American Geotechnical. Should you have any questions, please do not

hesitate to contact our office.

Respectfully submitted,

AMERICAN GEOTECHNICAL, INC.

Fei-chiu (Jerry) Huang, Ph.D. Douglas S. Santo Principal Engineer Chief Engineering Geologist RCE 55670; GE 2601 C.E.G. 1866 Edred T. Marsh Principal Engineer GE 2387

Distribution: 1 - Addressee (Email: [email protected]) Wpdata/OC/30923-10 – Geo Review EIR Docs - JH DS 6-9-17


ATTACHMENT 4

22725 Old Canal Road, Yorba Linda, CA 92887 - (714) 685-3900 - FAX (714) 685-3909 2640 Financial Court, Suite A, San Diego, CA 92117 - (858) 450-4040 - FAX (858) 457-0814 3100 Fite Circle, Suite 103, Sacramento, CA 95827 - (916) 368-2088 - FAX (916) 368-2188

5600 Spring Mountain Road, Suite 201, Las Vegas, NV 89146 - (702) 562-5046 - FAX (702) 562-2457

June 9, 2017 File No. 30923-10 Colinas De Capistrano HOA c/o Berding Weil 2175 N. California Boulevard, Suite 500 Walnut Creek, CA 94596 Attention: Mr. Aaron J. Ehrlich Subject: CIVIL ENGINEERING REVIEW OF EIR DOCUMENTS SunPointe - Tentative Tract 17423 Laguna Niguel, California Dear Mr. Ehrlich:

This presents the results of our review of portions of the Environmental Impact Report (EIR) prepared for

the proposed SunPointe Development, Tentative Tract 17423 located in the City of Laguna Niguel,

California. The site is generally located east of Mira Vista, south of the intersection of Charreadas and

Avenida Del Caballo, and west of Star Drive. The purpose of this review is to complete a preliminary review

of the potential effects of the SunPointe Development on adjacent portions of the Colinas de Capistrano

Homeowner Association property generally known as Country View Estates. Our review focused on the

following preliminary hydrology report contained in Appendix K of the EIR document:

Preliminary Hydrology Report for “SunPointe”, Vesting Tentative Tract Map No. 17433, city of Laguna

Niguel, County of Orange, Site Development Permit: SP12-07P,” by Hunsaker & Associates Irvine, Inc.,

dated 4/14/15

BACKGROUND AND SITE CONDITIONS

The SunPointe Development site was previously graded in the 1960s with modifications to some lots

apparently completed in 1982. The site currently includes 35 mass-graded residential lots and five paved

streets. The site is not built out. It is proposed to re-grade the site into six large building pads suitable for 71

building units. The building pads would be separated by graded slopes and mechanically stabilized earth

(MSE) walls.

File No. 30923-10 June 9, 2017 Page 2

Review of Hydrology Report by H&A Dated April 14, 2015 1. The hydrology report was prepared by Hunsaker & Associates Irvine, Inc. (H&A) for the

proposed development of a TTM 17433, “SunPointe”. H&A performed hydrology study and

analyses for both existing and proposed development conditions to determine 100-year peak

storm runoff discharges for use as basis in design of storm drainage requirements for the

proposed development as well as determine 2-year flow discharges for hydromodification

purposes.

2. The hydrology study conducted by H&A was in general conformance with procedure and criteria

outlined in the Orange County Hydrology Manual dated 1986 and Advance Engineering

Software's (AES's) Version 20.0 was utilized by H&A to conduct hydrology analyses.

3. Hydrologic soil ratings are based on a scale of A through D, where Soil Type A is the most

pervious and Soil Type D is the least pervious. Based on the soils map contained in the Orange

County Hydrology Manual, H&A considered that the project site is comprised of Soil Type D

which is the least pervious.

4. H&A indicated that for the existing condition, runoff is conveyed northeasterly in an existing 36-

inch storm drain prior to discharging to the Oso Creek Channel (L03). Runoff from the southern

slopes is conveyed as sheet flow and concentrated flow downstream (southerly/southeasterly)

to an existing concrete channel. In addition, runoff is conveyed southerly and also discharges to

Oso Creek Channel (L03).

5. In preparation of their hydrology study, H&A divided the site into 7 drainage areas, A, B1, C1,

D1, E1, F1, and G1. Some of these areas are made up of off-site areas that drain to and away

from the Project site. Area A is the largest drainage area with approximately 20.7 acres of off-

site and on-site terrain. Runoff from Area A is approximately 76.2 cfs, which goes into an

existing developed area to the north (i.e., Mira Vista).

6. Areas B1, C1, D1, E1, F1, and G1 are several smaller drainage areas on the south border of the

property. Most of these areas end up at the same discharge point which goes into a grass

swale then into a main channel, while areas to the north of area "A" including area G1 that sheet

flows to the existing trail, hence not impacted.

7. For the proposed conditions, H&A designed runoff from residential units to be conveyed as

sheet flow, gutter flow and area drain flow to the project's proposed main storm drain line in

Avenida Del Caballo. Runoff is then conveyed along Avenida Del Caballo downstream and

discharged as in pre-project conditions (i.e., to 36-inch storm drain line and Oso Creek). Runoff

File No. 30923-10 June 9, 2017 Page 3

from the project streets and parking areas was designed to be conveyed as gutter flow to

project catch basins prior to discharging to the project's main storm drain system located in

drainage area "A".

8. Additionally, H&A proposes bioretention and/or biofiltration facilities at different locations around

the site as well as a subsurface storm water detention vault with proprietary biofiltration for the

remaining portions of the site in order to satisfy the project's requirement for Low Impact

Development (LID) BMP's and to address hydromodification impacts and storm water pollutants

of concern.

9. For the proposed conditions, flows from watershed area "A" of approximately 22.7 acres are

picked up via storm drain system. H&A calculated that the proposed 100-year (Q100) discharge

rate for the on-site and off-site (area "A") is 83.9 cfs, i.e. approximately 7.7 cfs more than the

flow under existing conditions of 76.2 cfs.

10. H&A stated that the proposed detention/retention vault has been sized to detain runoff required

to mitigate both hydromodification and Q (100) incremental flows, and to retain water quality

flows. The proposed detention vault has been sized to retain 32,652 cubic feet (0.75 ac-ft) of

water quality flows that will drain via 4-inch outlet pipe to the biofiltration unit at a rate of 0.19

cfs, for full drawdown in 48 hours. The bottom 4.87 high portion of the vault will retain flows for

water quality treatment.

11. H&A indicated that flows, from areas B 1, C 1, D 1, E 1, F 1 and G 1 are reduced due to

diversion of some area to the main drainage area "A".

12. H&A stated that existing infrastructure located downstream of the northern property line can

support 71 single-family residential dwellings, as proposed for SunPointe.

13. H&A concluded that mitigation for this project is resolved by the underground structure. This

structure mitigates for detention (0.68 ac-ft), hydromodification (0.52 ac-ft) and water quality

(0.75 ac-ft). The proposed structure size is anticipated to provide approximately 1.69 ac-ft of

volume space. With the structure in place, there will be no hydrological impact because pre and

post discharge rates during major and minor storm events (2, 5, 10 and 100-year return

frequency storms) will be maintained. There are off-site flows that are reduced have minimal

impact and calculations show that the discharges were reduced due to the diversion of drainage

area "A".

File No. 30923-10 June 9, 2017 Page 4

Comments 1. The drainage area that may have direct impact to the Colinas de Capistrano HOA property is

drainage area “A”. For the existing drainage condition, runoff from Area A, with approximately

20.7 acres of off-site and on-site terrain, is approximately 76.2 cfs, which goes into an existing

developed area to the north (i.e., Mira Vista). For the proposed drainage condition, flows from

watershed area "A" of approximately 22.7 acres are picked up via storm drain system and the

proposed 100-year (Q100) discharge rate for the on-site and off-site (area "A") is 83.9 cfs, which

is approximately 7.7 cfs more than the flow under existing conditions (i.e., 76.2 cfs). This extra

amount of flow, in our opinion, is feasible from civil engineering point of view to be mitigated

using the proposed underground structure and other surface drainage devices proposed by

H&A. However, due to site geologic/geotechnical conditions, cracking and separation in the

surface and/or subsurface drainage structures may be developed after the project is developed.

As such, long-term monitoring, cleaning, and maintenance of these surface and subsurface

drainage devices or structures are of importance for the developer and the future homeowner

association to keep these drainage structures intact. Any damages to these drainage structures

could cause soil saturation, increase of groundwater level above the designed level, and further

cause slope instabilities and possible slope failures.

2. H&A stated that mitigation for this project is resolved by the underground structure. Use of

underground structure to mitigate storm water is common for civil engineer design storm drain

system to treat on-site storm water. However, the proposed underground structure requires

long-term, periodic monitoring and maintenance to ensure that the storm water can be retained

as designed. If too much storm water is retained by the underground structure, the overflow

design of the underground structure should function to direct storm water through overflow

devices to surface drainage facilities. As such, it is essential to ensure that the overflow devices

are working properly and functioning well at all time. No blocking, clogging, or damages are

allowed for these overflow devices. In addition, it is important that no leakage of the

underground structure is allowed to prevent storm water from leaking into the surrounding

ground and further cause soil saturation or increase subsurface groundwater level above the

designed, long-term groundwater level that Stoney-Miller utilized in their slope stability analyses.

If such conditions occur, possible slope instabilities or slope failures could occur as a result of

high groundwater level and saturations of site soils conditions.

File No. 30923-10 June 9, 2017 Page 5

CLOSURE

This work was performed in accordance with generally accepted professional civil engineering

principles and practice in southern California at the present time. We make no other warranty either

express or implied. Findings presented herein are based on document review only. No other works

were performed or authorized. The data and findings of this evaluation were prepared for the sole

use and benefit of Colinas De Capistrano Homeowners Association. This work was not prepared for

use by other parties and may not contain sufficient information for other uses at other times.

We thank you for choosing American Geotechnical. Should you have any questions, please do not

hesitate to contact our office.

Respectfully submitted,

AMERICAN GEOTECHNICAL, INC.

Fei-chiu (Jerry) Huang, Ph.D. Douglas S. Santo Principal Engineer Chief Engineering Geologist RCE 55670; GE 2601 C.E.G. 1866 Edred T. Marsh Principal Engineer GE 2387

Distribution: Addressee (Email: [email protected])

Wpdata/OC/30923-10 Civil Eng Review EIR Docs - JH DS 6-9-17
