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HomeMy WebLinkAboutWPO201300079 Review Comments WPO VSMP 2014-10-08� OF AL ,. vIRGI1`IZP COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road, Room 227 Charlottesville, Virginia 22902 -4596 Phone (434) 296 -5832 Fax (434) 972 -4126 Project: 5'h Street Station, phase 2 Plan preparer: Bohler Engineering, [dhines @bohlereng.com] Owner or rep.: New Era Properties [dan @sjcollinsent.com] Plan received date: original: 17 Dec 2013 Rev. 1: 22 May 2014 Rev.2: 1 Oct 2014 Date of comments: original: 21 Jan 2014 Rev. 1: 11 June 2014 Rev.2: 8 Oct 2014 Reviewer: Glenn Brooks County Code section 17 -410 and Virginia Code §62.1- 44.15:34 requires the VSMP authority to act on any VSMP permit by issuing a project approval or denial. This project is denied. The rationale is given in the comments below. The application may be resubmitted for approval if all of the items below are satisfactorily addressed. The VSMP application content requirements can be found in County Code section 17 -401. A. Stormwater Pollution Prevention Plan ( SWPPP) The SWPPP content requirements can be found in County Code section 17 -405. A SWPPP must contain (1) a PPP, (2) an ESCP, (3) a SWMP, and (4) any TMDL measures necessary. Rev.2: A SWPPP document has not been provided. A registration statement was received. Please ensure the disturbed acreage for permitting matches all final plans for stormwater and erosion control to be attached to the permit. Please provide copies of all SWPPP documents. B. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code section 17 -404. 1. Rev.2: A PPP was not received. C. Erosion and Sediment Control (WP0201300079) Virginia Code §62.1- 44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is disapproved, and the reasons are provided in the comments below. The erosion control plan content requirements can be found in County Code section 17 -402. 1. The large black lines on all the sheets obscure the plan details and lines for control measures. I find this plan almost illegible because of this. Please correct. Rev.2: addressed. 2. It is not clear what is being constructed with this plan. All the road improvements are shown as complete. Therefore, this plan could not be permitted until after the road is constructed. Rev.2: Please show what is being constructed with this plan. Many sheets do not appear to show any measures for this phase, but appear to show measures and notes from the phase 1 plan. It is unclear Engineering Review Comments Page 2 of 5 which is which. The notes refer to fill, retaining walls, and the roadwork, which is not shown on this plan. It appears a phase 2b is needed which shows how the diversions and traps work with the retaining walls and fill, which are mentioned in notes. 3. Provide sediment trapping measures. Fencing is not sufficient. Rev.2: There appears to be only one trap designed for this phase, ST -5. Please show the drainage area to this trap. The other devices also need to be designed and variances requested where necessary. A variance is necessary for the "mud trap ". The "variable sediment collection area" devices also require variances and design. It is unclear how volumes and outfall will be maintained in these devices. 4. Provide protection for wall construction. There is not enough protection for Moores Creek and the wall construction. Rev.2: Please include the walls and fill in some stage on this drawing so that we can tell if protection measures are provided. 5. SSF and double X lines are not state approved symbols or standards, and this plan has no variances. Rev.2: addressed 6. Fencing is shown over rip -rap and concentrated discharges, which is not acceptable. Rev.2: Silt fence is now also shown over outfall pipes. This is the preferred location. 7. Clarify how this plan fits in with other erosion and sediment control plans, mitigation plans, and stormwater plans. Rev.2: no change 8. Adequate channels narrative on sheet 7 is referencing an out -of -date design manual. We must follow "9VAC25- 870 -66 Water quantity ". Rev.2: This reference is now in the booklet and narrative, which must be corrected. D. Stormwater Management Plan (WPO201300079) VSMP Regulation 9VAC25- 870 -108 requires the VSMP authority to approve or disapprove a SWMP. This plan is disapproved, and the reasons are provided in the comments below. The stormwater management plan content requirements can be found in County Code section 17 -403. Original comments, given on the abbreviated review form. Revised comments are preceded by "Rev.]:" 1. There is not enough detention storage for on -site areas. Rev. 1: This was not checked with this revision. Rev.2: The vault systems need more details to verify volumes, ensure maintenance, and inlet and outlet details. a. Provide dimensions for spaces between pipes and on the sides which are used for storage in stone. b. Provide dimensions for the two header pipes. c. Show all pipes leading into and out of the facility in the details to match plan views. For example, Vault A shows a 48" CMP in section B 1 -B2, but this does not appear in the plan view. The plan views shows two 15 ", a 36 ", a 30" and an unknown from STM A7. d. Provide drawdown computations for the under -drain outlets. Correct the direction of flow on the plans for Vault A. e. Provide a configuration which allows unclogging the orifices without being submerged. If the 12 "718 978 "/6" pipe inlets leading out of the vaults become clogged, there is no way to get to them. f. If the intent is to provide the stub -out for a future connection to Vaults B, show size and location. 2. System A +B areas should assume forested conditions prior to development. The previous clearing was an unfinished project. Engineering Review Comments Page 3 of 5 Rev. 1: The BMP computations are still unresolved. It is safe to say the removal rate is above 75% for each on -site drainage area. The 47 acres on the computation provided was not found on a drainage area map. The on -site areas and treatment appears to be for three or four separate drainage areas and discharges that do not add up to this. A removal rate could be provided for each discharge point, and each facility result compared to the targets. This might indicate that future development on Avon may need its own site treatment in future. Areas like floodplains and buffers, which are not developed, are not part of the project disturbed or developed area, and should not be included in treatment area computations. Rev.2: Not addressed. Please correct computations per the type IIC criteria. I will try to give some specifics; a. Section 2 of the report is using an area of 71.41 acres, but this is not found on any drainage area map. b. The report determines pollutant loads to be 167.71 lbs /yr, but there are no details on how this is computed, or what it is compared to. c. The BMP's -in -series sheets contain drainage areas for each BMP, but there is no plan sheet which shows these devices or their drainage areas, or any details or sizing for that matter. d. Areas like floodplains and buffers, which are not developed, are not part of the project disturbed or developed area, and should not be included in treatment area computations, pre or post. Sheets 9 and 10 are showing areas which encompass Moores Creek, land across Moores Creek, untouched hillsides above the development, etc. e. The computations claim removal rates of 35% for extended detention basins. I am doubtful that this number will be achieved. I find nothing in specification 3.07 that suggests that a facility deep underground was the intent of this BMP, which suggests to me that the removal rate attributed is from studies of above ground facilties with the pools and vegetated buffers specified. I am hopeful that the surface sand filters and filterras will sufficiently cover treatment, so this does not become an issue. f. The vault systems still appear to be set up like infiltration trenches combined with detention in the pipes. The details still specify perforated pipes and an open stone layer. This is problematic, as it may destabilize the fill under the parking areas, and the retaining wall which holds it all up. g. The filterra summary table and sand filter summary table contain only results. There are no plans, details or maps to explain any of the numbers or labels. h. The county spreadsheet is no longer valid, as it is not per the required state type IIC criteria. 3. All facilities, incl. level spreader, need maintenance access Rev. 1: not addressed. Rev.2: Not addressed completely. There were no details for the sand filters or stilling basins. Access to these is not shown. 4. These are non - standard sand filters. Use state approved standards, or provide DEQ approval for these systems at the desired removal efficiency. Demonstrate WQV is captured in filters. Demonstrate extended detention will not inundate filters. There is currently no way to replace for rust, or easily inspect or clean, or replace media. Design for these and provide structural certifications. Rev. 1: The sand filters are not a state standard. The DC Sand Filter referenced (VSMH 3) is limited to 1.25 acres. For larger areas you would need to use a different, separate vault placed in the drainage system closer to the inlets where drainage areas to each vault could be limited to 1.25 acres. That said, if you can produce a copy of approval from DEQ for this system, we would proceed with that approval, and review the details of the system setup. Rev.2: Partially addressed. Standard sand filters and filterras are now used, but they are not on plans Engineering Review Comments Page 4 of 5 but for incidental placement in the drainage area maps and vault details. Please provide details and plans for all facilities, including specific drainage areas. 5. The in- stream flow splitter is a clogging problem and the pond may be below the water table. I just don't see this as approvable at all. Per the zoning, build a in -line pond upstream of the culvert and pay the Army Corps fees necessary for disturbance, or request a variance /ZMA. Rev. 1: This has been addressed by removal of this system. 6. Provide DEQ approval for the landfill pond. Rev. 1: not addressed. Rev.2: not addressed. 7. Provide scaled sections and profiles through facilities. Manufacturer's generic drawings are not adequate. Rev. 1: Scaled drawings have been provided. If the filter can be approved by DEQ, some details in need of addressing; a. The end pipes appear to allow bypass of the filters b. Filling the bmp manhole with stone prevents maintenance access to outlets. c. There is no practical way of cleaning these giant vaults. It appears an Austin surface filter is more appropriate for this size, allowing machine access for maintenance. d. Groundwater data is required before approval. A wet sand filter may become anaerobic. Even if groundwater can be lowered, it is not clear a filter this size underground will ever dry out sufficiently to be effective. e. Credit cannot be given for water quality in extended detention if it follows the filters. Extended detention with no biological component is simply a settling chamber, and this has likely already occurred sufficiently in the prior treatment. Place any detention before the filters. Rev.2: Continue the profiles on sheets 13B, 14B and 15B through the systems, showing existing and proposed grades, and pipes in and out. 8. The plans are too big for storage in county files. Please separate all the computations into a sealed package. Clarify all storage volumes used and assumptions and sizing, and outlet structures, after revised hydrology per above. There were not enough plan details to verify computations for structure Rev. 1: partially addressed. There are still narratives and computations in the plan sheets. Rev.2: addressed. The VSMP permit application and all plans may be resubmitted for approval when all comments have been satisfactorily addressed. For re- submittals please provide 2 copies of the complete permit package with a completed application form. Engineering plan review staff are available from 2 -4 PM on Thursdays, should you require a meeting to discuss this review. Process; After approval, plans will need to be bonded. The bonding process is begun by submitting a bond estimate request form and fee to the Department of Community Development. One of the plan reviewers will prepare estimates and check parcel and easement information based on the approved plans. The County's Engineering Review Comments Page 5 of 5 Management Analyst will prepare bond agreement forms, which will need to be completed by the owner and submitted along with cash, certificates or sureties for the amounts specified. The agreements will need to be approved and signed by the County Attorney and County Engineer. This may take 2 -4 weeks to obtain all the correct signatures and forms. Stormwater Management Facilities Maintenance agreements will also need to be completed and recorded. The County's Management Analyst or other staff will prepare the forms and check for ownership and signature information. The completed forms will need to be submitted along with court recording fees. After bonding and agreements are complete, county staff will need to enter project information in a DEQ database for state application processing. DEQ will review the application information based on local VSMP authority approval. At this time, the DEQ portion of the application fees will need to be paid directly to the state. For fastest processing, this is done electronically with the emails provided on the application. DEQ should notify applicants with instructions on how to pay fees. When DEQ approves the application, they will issue a permit coverage letter. This should be copied to the county. After DEQ coverage is issued, via the coverage letter, the County can hold a pre - construction conference. Applicants will need to complete the request for a pre - construction conference form, and pay the remainder of the application fee. The form identifies the contractor and responsible land disturber, and the fee remaining to be paid. This will be checked by county staff, and upon approval, a pre - construction conference will be scheduled with the County inspector. At the pre - construction conference, should everything proceed satisfactorily, a joint VSMP and grading permit will be issued by the County so that work may begin. County forms can be found on the county website forms center under engineering; http://www.albemarle.org/deptforms.asp?department=cden.gwpo File: E3_ phase2_ esc, swm_GEB_5thStrStationPhase2.doc