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Public Works Storm Water |
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The application for the new Mixed Use building have been received by the Stormwater Section with the Department of Public Works. The current routing has not been approved; please address the following comments prior to resubmittal.
1. Permit conditions from the Discretionary Application 141133 have not been clearly addressed. Please review and address each of the following:
I. It is unclear how inflow and outflow connections are being made with the proposed water quality unit. The supplied Grading & Drainage plan does not appear to include any detail references for the shown features. Please callout each of the proposed features and include all necessary details for accurate construction (including: invert elevations, slopes, materials, surface details, flow control structure details, outlet details, clean out facilities at pipe connections/changes in grade or direction, compaction requirements, etc.). Plans should be detailed enough for construction.
II. Please provide more elaborate details to clearly show how runoff from the semi-pervious areas will be mitigated. Please update the provided watershed map to clearly show the existing and proposed watershed boundaries to support the supplied analysis.
III. Safe overflow should be clearly demonstrated on the supplied drainage plan. Portions of the site appear to drain directly onto Brommer St. & 17th Ave. while bypassing the designed drainage systems.
IV. Please include cross-section construction details for all mitigation features as well as all proposed surfacing materials. Include installation and construction specifications as well.
V. It is unclear how the pre-development release rate was determined based off of the supplied supplemental packet information. Please demonstrate how this project is replicating pre-development release rates.
VI. The utilized infiltration rate does not accurately reflect the proposed depth for the retention/detention system. According to USDA Web Soil Survey inventory, the actual infiltration rate at the proposed depth (46” – 88”) is much less than what is shown in the supplemental civil calculations. Please revise the supplied calculations to accurately reflect the proposed excavation depths and existing soil profiles.
VII. Please update the proposed silt & grease trap. It should be clearly demonstrated that all runoff will be captured by this structure and that no runoff will bypass this mitigation feature.
VIII. Please provide details for the area drains that are to be placed in the landscaped areas to include provisions for limiting materials from entering the storm drains.
IX. Please provide more detailed grading information to clearly show how runoff from the eastern landscaped area will be effectively collected and mitigated as part of the combined retention/detention system. All areas that are bypassing the mitigation facilities should not be included as part of the orifice sizing nor the storage volume calculations.
X. The currently submitted retention worksheet is an outdated/corrupted version. Please try utilizing an updated worksheet from the Department of Public Works website. Additional revisions in sizing requirements may be necessary following the re-calculated measurements.
XI. No additional information appears to have been submitted to support the chosen orifice coefficient. Please provide the requested additional specifications.
XII. Please provide more detailed elevation for the detention basin to clearly show that all of the required detention volume is being provided above the outlet invert.
XIII. Please demonstrate that the gravel storage for the retention/detention system will completely drain within the required 48 hours.
XIV. Please provide a detail for the new stormdrain manhole to be installed on 17th Avenue. Include all necessary information (invert elevations, materials, etc.)
XV. Please correct all inconsistencies between the supplied plan sets (lengths of mitigation facilities, grading volumes, invert elevations, etc.).
XVI. Proper signage will need to be placed at all storm drain inlets clearly stating ‘No Dumping – Drains to the Bay’ or an equivalent. Please provide this detail on the supplied civil plan set.
2. If the site does receive upstream offsite runoff please provide recorded document acknowledging does and will continue to receive upstream runoff and that the property owner is responsible for maintenance of the drainage pathway through the parcel. The drainage plan will need to show how this runoff is accommodated with the on site design and how runoff will bypass the proposed mitigation facilities.
3. Public Works staff will inspect for the installation of the drainage related items. Once all other reviewing agencies have approved of the building permit plans, please submit a copy of wet-signed reproducible civil plans with the DPW signature block on the first sheet. Deliver a final set of these plans to DPW for signature & approval (expect a 1 – 2 week routing time).
I. Please include an engineer’s estimate for the construction of the drainage items (the County Inspection fee will be 2% of the cost).
II. The County Inspector (Geoffery Padget) will need to be contacted at least 48 hours in advance to attend the pre-construction meeting. Please contact him at (831) 477-3954. If he is unavailable please call (831) 477-3955.
4. Please provide a recorded maintenance agreement for the entire sites mitigation facilities. Reference SWM-25B (http://dpw.co.santa-cruz.ca.us/ApplicationsandForms.aspx). This agreement will be submitted after all other reviewing agencies have approved the building permit plans, and should be submitted to the County before final inspections as a notarized and recorded document.
I. Detailed operation and maintenance instructions should be included on both the final civil plan set and with the agreement. This project is a ‘Large’ project and will be assessed an annual fee while also being required to report to the County on an annual basis. Please refer to the County Design Criteria (CDC) for further guidance. All applicable parts of the CDC maintenance requirements will be required before the formal agreement shall be accepted.
II. A copy of the CDC can be found by following the link: http://dpw.co.santa-cruz.ca.us/Portals/19/pdfs/DESIGNCRITERIA.pdf
5. Upon approval of the project, a drainage “Hold” will 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 has to be exercised:
I. The civil engineer 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’s letter shall be specific as to what got inspected whether invert elevations, pipe sizing, the size of the mitigation features and all the relevant design features. Notes of “general conformance to plans” are not sufficient.
II. 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 were shown.
III. The civil engineer 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 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 the stamp (or label affixed to the plan) stating the contractor’s name, address, license and phone number. The civil engineer will review the as-built plans for conformance with the design drawings. Upon satisfaction of the civil engineer that the as-built plans meet the design intent and are adequate in detail, the civil engineer shall submit the as-built plans and a review letter, stamped by the civil engineer to the County Public Works Department for review to process the clearance of the drainage Hold, if the submittal is satisfactory.
6. After receiving the requested information above, further comments may be made following the resubmittal. The applicant is encouraged to discuss the above comments with the reviewer, Forrest Revere, to avoid unnecessary additional routings. An additional review fee of $375.00 shall be applied to all re-submittals starting with the third routing.
Contact Forrest Revere if you have questions about the above comments: Email: dpw172@santacruzcounty.us
Counter: Monday-Friday 8:00-12:00 PM
Phone: 831-454-2160
The application for constructing a new mixed use building has been received by the Stormwater Section of the County of Santa Cruz. The submittal has not been approved; further clarification is needed. 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 viewed online at http://www.dpw.co.santa-cruz.ca.us/Portals/19/pdfs/DESIGNCRITERIA.pdf?ver=2017-04-27-134016-453
1. Please provide the following clarifications regarding the drainage calculations.
a. Referencing the supplemental drainage calculation report, Figure SWM-24 still shows a triangulated object on the form indicating that this document is corrupt and not providing accurate excavation & storage volume requirements. Please re-download the County Fig. SWM-24 and re-calculate the required retention volume requirements.
b. The site soil infiltration rate should be updated based upon the depths of the proposed retention system relative to the existing grade when using the Web Soil Survey data. Please provide technical justification for how the infiltration rate was derived and supply a geotechnical letter of approval supporting the utilized infiltration rate based on the proposed drainage systems actual retention depth. [Supplied supplemental documents measured saturated hydraulic conductivity based on a weighted average for a depth from actual grade to 12 feet below grade. The proposed retention depths will not be 144 inches below grade. ( https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx) ]
c. The chosen P60 isopleth is inaccurate, please correct this factor. P60 isopleth for this location should be closer to 1.4.
2. Conflicting information has been submitted between the plan sheets. Please revise accordingly.
a. Sheet C4, proposes a 6-inch diameter PVC pipe that collects stormwater runoff from downspouts and area drains while Sheet C5, Grading and Drainage Plan, shows the same pipe to be 4-inch diameter.
b. The manhole on Sheet C5 should reference the detail on Sheet 10 (instead of Sheet C9).
c. The graphic scale on Sheet C5 appears to be labeled incorrectly.
3. Please provide clear construction cross-section details for all permanent stormwater mitigation features, including the semi-pervious surfaces. The details must include all necessary information for the accurate construction of the proposed mitigation features. Specify pipe/material size, type, and elevations/dimensions on all details. Also, please provide elevations on the detention basin detail to demonstrate how all of the required detention storage is above the outlet invert.
a. Please specify the type of mirafi fabric that will be used for all drainage features.
4. The proposed orifice calculations do not replicate the 10 year release rate as specified in SWM-17 of the supplemental packet. Orifice calculations use a Q of 0.27 cubic feet a second (cfs) while SWM-17 requires a Q of 0.327 cfs. Please revise the orifice calculation (& all related details) to accurately reflect the required pre-development release rate.
a. Please ensure that the retention/detention mitigation feature is correctly sized to mitigate the required volumes for both the 2 year and 10 year events. Based on the supplemental packet
documents (SWM-17 & SWM-24) the system is still undersized. The supplied supplemental information shall match proposed dimensions shown on the plan set.
5. The percent air voids for the detention system sizing calculations don’t appear to be accurate, please revise based on the supplied cross-section construction details. A weighted average shall be applied based on the average storage volume between the proposed stormtech chambers & rock encasement.
6. Please clarify how roof runoff will discharge onto the interior walkway/parking lot area. No details have been provided on the civil plans to demonstrate how this runoff will be conveyed to the proposed v-ditch within the new parking lot.
a. Sheet C7, Section E-E, proposes for all runoff to be directed out onto Brommer St. Please revise this area to ensure all runoff from impervious areas are kept onsite and directed towards to proposed area drains.
7. Runoff from the stamped concrete driveway entrance appears to be left untreated & is directing runoff directly onto 17th Ave. Please revise this new impervious area to ensure all impervious area runoff is directed to the proposed water quality unit that is connected to the retention/detention system.
8. Grading details shall include specific preparation notes on minimizing the compaction and natural infiltration rates around the area that will be used for the retention/detention system. The typical subgrade material preparation notes are not sufficient for the proposed mitigation areas. Please revise.
9. All grading & drainage information shall be included on the civil plan set. Please ensure all cross-section construction details and notes pertaining to the stormwater improvements are included within the civil set.
10. The proposed new stormdrain manhole shall include a cross section detail that is in conformance with County Design Criteria standards. Please reference the CDC Part 3 Section C Figure SWM-9 for the required detail pertaining to the proposed tie-in to the existing storm drain line located on 17th Ave.
11. Please clarify who shall be held accountable for the ongoing maintenance and inspection of all drainage features.
12. Prior to final approval from DPW Stormwater, please address the following:
a. Please provide two (2) final, wet-signed and stamped, civil plan sets to the Department of Public Works. Include the Department signature block on the cover sheet which can be found in the County Design Criteria.
b. Please provide an engineer’s cost estimate for the proposed drainage system. County Inspector shall be contact prior to any construction for a pre-con meeting. Please contact Geoffery Padget at 831-477-3954.
After receiving the requested information above, further comments may be made following the resubmittal. The applicant is encouraged to discuss the above comments with the reviewer, Forrest Revere, to avoid unnecessary additional routings. An additional review fee of $390.00 shall be applied to all re-submittals starting with the third routing. This rate is subject to change.
Contact Forrest Revere, if you have questions about the above comments. Email: dpw172@santacruzcounty.us
Counter: Monday-Friday 8:00 AM - 12:00 PM
After 1:00 PM by appointment only
Phone: 831-454-2160
The application for constructing of a new mixed use building has been received by the Stormwater Section of the County of Santa Cruz. The submittal has not been approved; further clarification is needed. 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 viewed online at http://www.dpw.co.santa-cruz.ca.us/Portals/19/pdfs/DESIGNCRITERIA.pdf?ver=2017-04-27-134016-453
1. Please draft an Operation and Maintenance (O&M) agreement as part of the final SWM-25B requirement. Submit a draft upon resubmittal for review and comment. O&M will include all pertinent information relating to the proposed drainage system and will supplement the final maintenance agreement.
2. Please provide consistency in the supplied drainage report. Quantification calculations from the SWM-17 & SWM-24 don’t appear to match orifice sizing calculations. Ensure the post-development release rate replicates the required 10-year pre-development rate. Please also ensure that the calculation sheets are accurate with the submitted plans, if circular reference re-occurs please try re-downloading the County worksheet(s).
3. Please revise SWM-24 to more accurately represent the sites infiltration rates. Retention system appears to be oversized, please verify.
4. Please verify that the proposed mirafi fabric is non-woven, consistent with manufacturer specs. For stormwater review, please identify the specific type of mirafi to be used for the retention/detention system.
a. Please provide inspection risers/ports for the proposed stormtech chambers, as necessary, to ensure maintenance & observation/inspection’s can be accurately completed.
5. The proposed locations for the new area drains conflict with the landscaping plan (referencing sheets C-5 & L1). Please update the referenced sheets. Consideration of root intrusion shall be addressed.
6. Please update the drainage plan to more accurately reflect the footprint of the proposed retention/detention area. Cross-section details propose an 8 foot wide retention/detention trench, please ensure all associated sheets are revised accordingly.
7. Please provide a clear requirement for signage to be placed at all storm drain inlets and catch basins with prohibitive language and/or graphical icons to discourage illegal dumping. [CDC, Part 3 Sectionc.3.d]
8. Please verify that the sanitation line from the trash enclosure will not conflict with designed retention/detention system.
9. Please supply the engineer’s cost estimate for the entire stormwater design.
10. Prior to final approval from DPW Stormwater, please address the following:
a. Please provide two (2) final, wet-signed and stamped, civil plan sets to the Department of Public Works. Include the Department signature block on the cover sheet which can be found in the County Design Criteria.
b. Please provide an engineer’s cost estimate for the proposed drainage system. County Inspector shall be contact prior to any construction for a pre-con meeting. Please contact Geoffery Padget at 831-477-3954.
After receiving the requested information above, further comments may be made following the resubmittal. The applicant is encouraged to discuss the above comments with the reviewer, Forrest Revere, to avoid unnecessary additional routings. An additional review fee of $390.00 shall be applied to all re-submittals starting with the third routing. This rate is subject to change.
Contact Forrest Revere, if you have questions about the above comments. Email: dpw172@santacruzcounty.us
Counter: Monday-Friday 8:00 AM - 12:00 PM
After 1:00 PM by appointment only
Phone: 831-454-2160 Stormwater Management Review, DPW Forrest Revere 11/1/18 4th Routing Plan Check Comments
The drafted O&M is missing a few key components that are outlined in Part 3 Section C.3 iv – ix of the County Design Criteria. (Missing final drainage exhibit w/sub-watershed areas, notification of annual service charge and report to DPW, etc.) Please revise the drafted document, and submit directly to dpw172@santacruzcounty.us for approval. Previously recorded maintenance agreement was not complete and shall not be accepted. This item shall be completed while final civil plans are being reviewed/approved by senior DPW staff.
Stormwater Management will require a final hard copy of the entire civil plans. The cover sheet (C1) will need to also include a Flood Control Zone 5 signature block. This signature block is available within the CDC. The hard copy set needs to be a clean set, with all bubbling/notes of review iterations removed please. Pending no other comments from contributing review agencies that may require alterations to the civil plans, you can submit the hard copy at your convenience directly to DPW (701 Ocean St. Santa Cruz). Please anticipate a 2-3 week turnaround for the final approval/signatures by DPW staff.
Projects Engineering team has been contacted by email with same comments as shown above so these items can be addressed. 11/16/18: Please specify the final elevations for the retention & detention systems within the civil plan sheets (C7) to avoid construction conflicts. Clear notation of invert elevations are requested on the same sheets. Please update the maintenance table to include the pipe connecting to the new storm drain manhole proposed in 17th Avenue. For consistency please place invert elevations on the proposed area drains within the landscaped areas, consistent with supplied Landscaping plans. Prior comment on addressing potential floatables clogging the system need to be addressed within the civil plan set as well. Please evaluate the maintenance frequency proposed for the primary junction box (silt & grease inlet) at the driveway. Is this system adequately sized to capture all potential contaminants onsite? Bi-annual maintenance on this feature may no be adequate. Any questions can be directed to the Department of Public Works, (831) 454-2160. Please request Forrest Revere. |
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