APN: 026-531-13
Reviewer: Jennifer Buckley
1st Routing Comments
The application to construct a new residence with an attached JADU has been received by the Stormwater Section of the County of Santa Cruz. The submittal has not been approved, please review and address each of the comments below (all applicants are required to follow the design requirements as outlined in the County of Santa Cruz Design Criteria referred to as the CDC hereon). The CDC can be found on the internet by navigating to County of Santa Cruz Public Works Department, Stormwater, Design Criteria (http://www.dpw.co.santa-cruz.ca.us/).
1. Please complete Appendix A of the CDC, Project Information and Threshold Determination Form, which can be found on the internet by navigating to County of Santa Cruz Public Works Department, Flood Control & Stormwater, Permit Requirements, Project Information and Threshold Determination Form. Please include all new and/or replaced impervious and semi-impervious surfaces as part of this project in Appendix A. Semi-impervious surfacing without liners (such as gravel, base rock, paver blocks, porous pavement, etc.) may be counted at 50% for project threshold determination purposes.
2. Based upon the new and/or replaced impervious areas, please address Part 3, Section C of the CDC and implement the most feasible best management practices to minimize pollutant and hydraulic impacts due to development and re-development. Safe stormwater overflow shall be incorporated into the project design. Please note, if the project is proposing 5,000 square feet or more of new and/or replaced impervious area, then calculations are required to demonstrate that mitigations have been designed in accordance with "Large Project" requirements in the CDC.
a. Please provide topographic contours and/or spot elevations to clearly show the existing and proposed drainage patterns.
b. Sheet A1, Site Plan, states roof runoff will be directed to sidewalk, patios to landscape area. If sidewalks are planned, please show the locations of walkways on the site plan and include the area(s) in Appendix A.
c. Please update the proposed impervious area table on Sheet A1 to be consistent with what is shown on the site plan (pervious paver driveway and landing rather than concrete, etc.).
d. Please clarify how stormwater runoff from the new and/or replaced impervious areas will be conveyed, controlled, and mitigated. If downspouts to splash blocks are planned, please label their locations on the plans.
e. Sheet A1 shows a 2 percent swale will be constructed along the eastern side of the structure. On the Site Plan, please provide spot elevations along the flowline and show the entire extent of the swale. Please provide a construction cross-section detail for the swale that includes dimensions, depth of flowline, and the material the swale will be constructed with.
f. Please provide construction cross-section details for all permanent stormwater mitigation features and/or flatwork (including pervious pavers and swale). The details must include all necessary information for the accurate construction of the proposed features.
g. Please provide a maintenance schedule on the plans that includes inspection frequency, signs of failure, and maintenance requirements for each of the stormwater mitigation features proposed.
3. Please perform a site assessment and add a note to the plans that states whether there are any existing drainage issues on or near the site and if any drainage issues or adverse impacts to drainage pathways, roadways, and/or neighboring properties are anticipated resulting from the proposed improvements.
4. Zone 5 fees will be assessed on the net increase in permitted impervious area following the Unified Fee Schedule in place at building permit issuance. Reduced fees (50%) are assessed for semi-pervious surfacing without liners (such as gravel, base rock, paver blocks, porous pavement, etc.) to offset costs and encourage more extensive use of these materials. For credit for the demolished residence, provide documentation that demonstrates the impervious area was installed with a previously approved permit or was in place prior to establishment of Zone 5 in 1969.
Comments 5 and 6 below are notifications to the applicant of holds that may be placed on the permit once it is ready to be issued by the Planning Department. These items are not required to be addressed/completed prior to resubmittal.
5. Please notarize and record a maintenance agreement (SWM-25A form) that includes the approved drainage plan and maintenance schedule as a packet. It will be the responsibility of the property owner to inspect and maintain all drainage features. Please contact the County of Santa Cruz Recorder’s office for appropriate recording procedures. The maintenance agreement form can be picked up from the Public Works office or can be found online by navigating to County of Santa Cruz Public Works Department, Stormwater, Permit Requirements, SWM-25A.
6. Upon approval of the project, a drainage "Hold" may be placed on the permit and will be cleared once the construction is complete and the stormwater management improvements are constructed per the approved plans: In order to clear the Hold, one of these options shall be exercised:
a. The Civil Engineer / Designer must inspect the drainage improvements on the parcel and provide public works with a letter confirming that the work was completed per the plans. The Civil Engineer / Designer’s letter shall be specific as to what was inspected (such as invert elevations, pipe sizing, the size of the mitigation features and all relevant design features). Notes of "general conformance to plans" are not sufficient.
b. As-built plans stamped by the Civil Engineer may be submitted in lieu of the letter. The as-built stamp shall be placed on each sheet of the plans where stormwater management improvements are shown.
c. The Civil Engineer / Designer may review as-built plans completed by the contractor and provide the County with an approval letter of those plans, in lieu of the above two options. The contractor installing the drainage improvements will provide the Civil Engineer / Designer as-built drawings of the drainage system, including construction materials, invert elevations, pipe sizing and any modifications to the horizontal or vertical alignment of the system. The as-built drawings, for each sheet showing drainage improvements and/or their construction details, must be identified with a stamp (or label affixed to the plan) stating the contractor’s name, address, license and phone number. The Civil Engineer / Designer will review the as-built plans for conformance with the design drawings. Upon satisfaction of the Civil Engineer / Designer that the as-built plans meet the design intent and are adequate in detail, the Civil Engineer / Designer shall submit the as-built plans and a review letter, stamped by the Civil Engineer / Designer to the County Public Works Department for review to process the clearance of the drainage Hold, if the submittal is satisfactory.
APN: 026-531-13
Reviewer: Jennifer Buckley
2nd Routing Comments
The application to construct a new residence and associated improvements has been received by the Stormwater Section of the County of Santa Cruz. The submittal has not been approved, please review and address each of the comments below.
1. Please revise Appendix A of the CDC, Project Information and Threshold Determination Form, to include all new and/or replaced impervious, semi-impervious, and/or self-mitigating surfaces (including the driveway and parking areas). The recently submitted Appendix A shows a project threshold of 4,622 square feet; however, Sheet C2 shows 4,622 square feet of impervious area and 4,347 square feet of semi-imperious area. Semi-impervious surfacing without liners (such as gravel, base rock, paver blocks, porous pavement, etc.) may be counted at 50% for threshold determination purposes and impervious area fee calculations. If it can be shown that the paver driveway and parking areas are self-mitigating, then this area may be excluded from project threshold determination and impervious area fees.
2. If the paver driveway and parking areas are designed as self-mitigating, please specify a surface infiltration test method and minimum infiltration rate for the pavers that shall be met prior to construction final, on the permeable paver detail. A hold will be placed on the permit for a letter signed by a qualified professional who performed the tests. The letter shall document the testing method, test results, and test locations. Additionally, the civil engineer’s final drainage letter shall document the observed storage volume / thickness of rock beneath the pavers.
3. If this project is proposing over 5,000 square feet of new and/or replaced impervious and/or semi-impervious surfaces, then the project shall be designed in accordance with the "Large Project" Section C and Appendix D of the CDC. For large projects, the following is required: a stormwater management report with calculations, a description of the mitigations, a watershed area map (showing boundaries of areas draining toward each mitigation and labeling the square footage of each area), a downstream impact analysis for safe stormwater overflow.
4. Please perform a site assessment and add a note to the plans or in the report that states whether there are any existing drainage issues on or near the site and if any drainage issues or adverse impacts to drainage pathways, roadways, and/or neighboring properties are anticipated resulting from the proposed improvements.
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