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10. Conditional Approval 2022-058_Moments_of_Chanhassen20220727_packet Page | 1 18681 Lake Drive East Chanhassen, MN 55317 952-607-6512 www.rpbcwd.org protect. manage. restore. Riley Purgatory Bluff Creek Watershed District Permit Application Review Permit No: 2022-058 (formerly 2020-003 which expired on April 3, 2022) Considered at Board of Managers Meeting: August 3, 2022 Project Procedural History: Permit application 2020-003 conditionally approved April 2, 2020. Based on the written request from the applicant, RPBCWD extended the conditional approval to April 2, 2022, after the applicant proposed permit modification. Because the application for the proposed modifications was not complete prior the expiration date, the prior approval expired April 3, 2022. The applicant subsequently submitted a new permit application. Received complete: July 26, 2022 Applicant: TMSC of Chanhassen, LLC., Elizabeth Wright Consultant: Civil Site Group, Michael Sheehan Project: The Moments of Chanhassen – The applicant proposes development of a 3.6-acre site in Chanhassen, MN. Proposed work includes construction of a multi-unit residential facility with associated parking, grading, utilities, landscaping and stormwater management facilities. Stormwater management facilities including a rainwater harvest and reuse system, underground chambers, proprietary treatment devices, a filtration basin, and a vegetated swale will be constructed to provide volume control, water quality, and rate control. Location: 1620-1660 Arboretum Blvd Chanhassen, MN 55317 Reviewer: Leslie DellAngelo, P.E. and Scott Sobiech P.E., Barr Engineering Recommended Board Action Manager __ ___ moved and Manager __ __ seconded adoption of the following resolutions based on the permit report that follows and the presentation of the matter at the April 1, 2020 meeting of the managers: Resolved that the application for Permit 2022-058 is approved, subject to the conditions and stipulations set forth in the Recommendations section of the permit application review, and the further condition as follows: Resolved that on determination by the RPBCWD administrator that the conditions of approval have been affirmatively resolved, the RPBCWD president or administrator is authorized and directed to sign and deliver Permit 2022-058 to the applicant on behalf of the RPBCWD. Upon roll call vote, the resolutions were adopted, ______. Page | 2 of 15 Applicable Rule Conformance Summary Rule Issue Conforms to RPBCWD Rules? Comments B Floodplain Management and Drainage Alterations See Comment See Rule Specific Permit Condition B1 related to providing at least 100 feet between Riley Creek and the proposed building and stipulation #2 related to proof of recordation that drainage and flowage easements over all land below the 100-year flood elevation, as required. C Erosion Control Plan See Comment See rule-specific permit condition C1 related to name of individual responsible for on-site erosion control. D Wetland and Creek Buffers See Comment See Rule Specific Permit Condition D1 related to recordation of buffer maintenance declaration. G Waterbody Crossings See Comment See Rule Specific Permit Condition G1 related to recordation of the outfall maintenance declaration. J Stormwater Management Rate Yes Volume Yes Water Quality Yes Low Floor Elev. Yes Maintenance See Comment See Rule Specific Permit Condition J1 related to recordation of stormwater facilities maintenance declaration. Chloride Management See Comment See stipulation #5 related to providing an executed chloride management plan prior to permit close-out. Wetland Protection Yes L Permit Fee Deposit Yes $3,000 received January 22, 2020. The applicant must replenish the permit fee deposit to the original amount due before the permit will be issued. As of July 27, 2022 the amount due is $13,491. M Financial Assurances See Comment The financial assurance is calculated at $366,493 Background The proposed land-disturbing activities were previously conditionally approved under RPBCWD permit 2020-003 on April 2, 2020. While working to fulfill the conditions of the board’s conditional approval, in- situ infiltration testing results showed the infiltration capacity of the soils are 0.0 inches per hour (in/hr) Page | 3 of 15 which is significantly lower than used in the design. Because the in-situ infiltration rate is less than used in the conditionally approved design, the applicant submitted a permit modification request. Based on a written request from the applicant, the review timeline was extended administratively for one year, from to April 2, 2021 until April 2, 2022. Because the application for the modification was not complete and activities under the permit had not substantially commenced, the April 2020 approval expired. Under Rule A, subsection 5, the applicant must reapply for a permit from the District. The proposed project includes development of a multi-unit residential facility with associated parking, grading, utilities, landscaping, an outfall to Riley Creek, and stormwater management facilities. The 3.6- acre site is currently undeveloped, and the open space is a combination of open grassland and wooded areas. The applicant proposes construction of a rainwater harvest and reuse system, underground chambers, two hydrodynamic separators, one proprietary cartridge filtration chamber, a filtration basin, and a vegetated swale to provide stormwater quantity, volume and rate quality control. One delineated wetland is located onsite north of the proposed building. Riley Creek is located along the northern site boundary. The 100-year floodplain of Riley Creek was found to inundate a portion of the property along the northern property boundary at varying elevations between approximately 945 to 952 feet (NGVD29). Because Riley Creek and a wetland are downgradient from the proposed land disturbing activities, wetland and creek buffer requirements apply to the proposed project. The project site information is summarized below: Project Site Information Area (acres) Total Site Area 3.6 Existing Impervious 0.01 Disturbed Impervious Area 0.01 Proposed Impervious Area 1.26 Change in Impervious Area 1.25 Regulated Impervious Area 1.26 Total Disturbed Area 2.88 The following materials were reviewed in support of the permit request: 1. Permit modification request received January 25, 2022 (Notified applicant on February 11, 2022 that submittal was incomplete, application for the proposed modifications was not complete prior the expiration date, the prior approval expired April 3, 2022. The applicant subsequently submitted a new permit application completing the new application received July 26, 2022) 2. Construction Plan Sheets (22 sheets) dated January 24, 2022 (revised May 20, 2022, July 15, 2022, and July 25, 2022) 3. Geotechnical exploration report by Haugo GeoTechnical Services data January 5, 2018 Page | 4 of 15 4. Infiltration testing results received May 20, 2022 5. Stormwater Management Report by Civil Site Group dated January 24, 2022 (revised May 20, 2022, July 15, 2022, and July 26, 2022) 6. Wetland Conservation Act Notice od Decision for the Type and Boundary dated July 19, 2019 7. Wetland Delineation Report by Jacobson Environmental dated April 11, 2019. 8. MNRAM Wetland Classification received March 6, 2020 9. Electronic HydroCAD models received on January 25, 2022 (revised May 20, 2022, July 15, 2022, and July 26, 2022) 10. Electronic MIDS water quality models received on January 25, 2022 (revised May 20, 2022, July 15, 2022, July 22, 2022, and July 26, 2022) 11. SHSAM modeling results received on July 15, 2022 12. Engineers’ opinion of probable cost dated July 15, 2022 (revised July 26, 2022) 13. Response to RPBCWD review comments received May 20, 2022 14. Response to RPBCWD review comments received July 15, 2022 Rule Specific Permit Conditions Rule B: Floodplain Management and Drainage Alterations Because the proposed project involves constructing a new outfall as well as grading and rip rap installation below the 100-year flood elevation of Riley Creek (945 NGVD29), the project activities must conform to the RPBCWD’s Floodplain Management and Drainage Alterations rule (Rule B). The 100-year flood elevations of Riley Creek along the northern site boundary are displayed on the plans (Rule B, Subsection 4.2). The proposed low floor elevation of the building (958 feet) is 13 feet above the 100-year flood elevation, complying with Rule J, Subsection 3.6 (Rule B, Subsection 3.1). The plans provide a cross-section on sheet C5.1 showing the proposed outfall including existing and proposed ground surface below the 100- year floodplain. Because the project proposes to match existing elevations at the proposed outfall, the post-development conditions will result in no net change in the existing floodplain storage. Thus, the project conforms to Rule B, Subsection 3.2. The proposed outfall includes a riprap stilling basin at the flared end section outlet prior to discharge into Riley Creek, thus reducing the velocity of the stormwater outflow to not alter the creek flows or channel stability in accordance with Rule B, Subsection 3.3. The plans show the northeast corner of the proposed building 90 feet from the centerline of Riley Creek, thus closer than the 100 feet of separation required by Rule, Subsection 3.4. Page | 5 of 15 The Applicant submitted an erosion control plan in conformance with Rule C, per Rule B, Subsection 3.5. A note on the plans indicates that activities must be conducted to minimize the potential transfer of aquatic invasive species conforming to Rule B, Subsection 3.5. To conform to the RPBCWD Rule B requirements the following revision is needed: B1. The location of the proposed building must be adjusted or the building design modified to provide a minimum of 100 feet of separation between the centerline of Riley Creek and the building. B2. Documentation that drainage and flowage easements over all land below the 100-year flood elevation have been conveyed to the municipality with jurisdiction, if required, needs to be submitted prior to project close out. Rule C: Erosion Prevention and Sediment Control Because the project will alter more than 50 cubic yards of material, the project must conform to the requirements in the RPBCWD Erosion Prevention and Sediment Control rule (Rule C, Subsection 2.1). The erosion and sediment control plans prepared by Civil Site Group include installation of perimeter control (including redundant perimeter controls at the proposed wetland and creek buffer), inlet protection for storm sewer catch basins, a rock construction entrance, protection of stormwater management facilities, placement of a minimum of 6 inches of topsoil, decompaction of pervious areas compacted during construction, and retention of native topsoil onsite. To conform to RPBCWD Rule C requirements the following revisions are needed: C1. The Applicant must provide the name and contact information of the general contractor responsible for the site. RPBCWD must be notified if the responsible party changes during the permit term. This information is required prior to issuance of the permit. Rule D: Wetland and Creek Buffers Because the proposed work triggers a permit under RPBCWD Rules B, G, and J and Riley Creek and the onsite wetland are downgradient from the proposed construction activities, Rule D, Subsections 2.1a and 3.1 require buffer along the downgradient bank of the creek and edge of the wetland. Rule D, Subsections 3.1b and 3.1c require buffer on the edge of the wetland that is downgradient from the activity and on a streambank downgradient from the land-disturbing activity in accordance with Rule D, Subsection 3.2. No land disturbing activities are proposed within the onsite wetland or in the creek. Using the MNRAM functions and values assessment dated February 4, 2020 the onsite wetland was determined to be medium value. The land-disturbing activities are located upgradient from the medium value wetland requiring a 40-foot average, 20-foot minimum buffer width (Rule D, Subsection 3.2b.iii). RPBCWD Rule D, Subsection 3.2.b.v requires an average buffer width of 50 feet from the creek centerline, minimum 30 feet for a public waters watercourse. The Applicant provided a buffer plan and Page | 6 of 15 marker location map confirming that the proposed buffer area extends the required average widths. As shown in the table below, the required buffer width for the onsite wetland and Riley Creek conform to Rule B, Subsection 3.2. Regulated Feature RPBCWD Wetland Value Required Minimum Width1 (ft) Required Average Width1 (ft) Provided Minimum Width (ft) Provided Average Width (ft) Riley Creek N/A 30 50 50.0 62.7 Onsite Delineated Wetland Medium 20 40 20.0 44.0 1 Average and minimum required buffer width based on Rule D, Subsection 3.2.b. Plan sheet L1.0 indicates disturbed areas within the proposed buffer will be revegetated with native vegetation in conformance with Rule D, Subsection 3.3. The plans identify buffer marker locations and include a design detail in conformance with design and text provided by the District (Rule D, Subsection 3.4). A note is included on the plan sheet indicating the project will be constructed so as to minimize the potential transfer of aquatic invasive species (e.g., zebra mussels, Eurasian watermilfoil, etc.) to the maximum extent possible conforming to Rule D, Subsection 3.6. To conform to the RPBCWD Rule D the following revisions are needed: D1. Buffer areas and maintenance requirements must be documented in a declaration recorded after review and approval by RPBCWD in accordance with Rule D, Subsection 3.5. The maintenance declaration must also include an exhibit clearly showing the buffer area and monument locations. Rule G: Waterbody Crossings and Structures Because the project proposes a new outfall structure along the bank of Riley Creek, a public watercourse, the project requires conformance with RPBCWD’s Waterbody Crossings and Structures Rule (Rule G). The proposed work falls within the scope of Minnesota Department of Natural Resources General Permit #2015-1192. (Rule F: Stormwater and Streambank Stabilization is not triggered because the riprap being installed in bank of the creek is to prevent erosion more so than stabilize the bank, and the relevant Rule F criteria are covered here, under Rule G.) This work represents a demonstrated public benefit by reducing pollutant loading to Riley Creek (Rule G, Subsection 3.1a). Page | 7 of 15 The project plans incorporate a small stilling basin at the outfall prior to the discharge entering Riley Creek. In addition, site runoff is conveyed to sump manholes, SciClone hydrodynamic separators, and the proposed filtration basin for entrapment of floatables, sedimentation, runoff retention and reduction of peak runoff rates to less than existing condition before the discharging to the creek, thus the design is in conformance with Rule G, Subsection 3.3. Placement of the proposed outfall structure represents the minimal impact solution because the alternative of constructing an outfall that discharges flow on the existing slope above the creek would cause soil erosion potential and could destabilized the creek bank, both of which wouldpromote sediment discharge into the creek from upgradient sources. The proposed outfall design minimizes the discharge velocity by including a drop manhole structure and limits the site disturbance adjacent to the creek, both of which minimize erosion potential and thus meet criteria in Rule G, Subsection 3.5a. The project proposes to match existing elevations along the creek at the outfall to minimize encroachment and change along the creek. Thus, design is in conformance with Rule G, Subsection 3.5b. As discussed in the Rule B narrative above, the propose project will comply with the District floodplain rule, as required by subsection 3.5c. Because the design proposes riprap sized appropriately to withstand the anticipated discharge velocity (7.5 feet per second), incorporates a stilling basin to dissipate energy, and reduces pollutant load from the site to less than existing conditions, the proposed outfall structure is not reasonably likely to cause adverse effects to water quality and the physical or biological character of the waterbody, thus conforming to Rule G, Subsection 3.5d. The project SWPPP includes a note directing the contractor that no work affecting the bed or banks of a protected water shall occur between March 15 and June 15 (Rule G, Subsection 3.7a). Disturbed areas near and along the banks will be immediately stabilized after completion of permitted work and revegetated as soon as growing conditions allow (Rule G, Subsection 3.7b). A note is included on the plan sheet indicating the project will be constructed so as to minimize the potential transfer of aquatic invasive species (e.g., zebra mussels, Eurasian watermilfoil, etc.) to the maximum extent possible (Rule G, Subsection 3.7c). Plans submitted confirm that riprap is sized appropriately in relation to the erosion potential. Riprap is sized at 12 inches in diameter which is appropriately sized to withstand the designed discharge velocity of 7.5 feet per second, thus conforming to Rule F, Subsection 3.3b (i). Plans submitted confirm the proposed outfall construction along the bank of Riley Creek will follow the natural alignment of the bank and will not cover emergent vegetation (Rule F, Subsection 3.3b (ii) and 3.3b (iv)). The plans and details indicate that a transitional layer consisting of graded gravel, at least 6 inches deep with geotextile fabric will be placed between the existing shoreline and rip rap, thus conforming to Rule F, Subsection 3.3b (iii). As shown in the riprap detail in the plans, the riprap is proposed to extend to the area around the top of the pipe below the Riley Creek 100-year floodplain elevation of 945 NGVD29, consistent with Rule Page | 8 of 15 F, Subsection 3.3b (v). The riprap design reflects energy dissipation and stabilization necessary to minimize erosion at the streambank and is not placed for cosmetic purposes per Rule F, Subsection 3.3b (vi). To conform to the RPBCWD Rule G the following revisions are needed: G1. Permit applicant must provide a draft maintenance declaration for the outfall structure for review and approval prior to recordation, in accordance with Rule G, Section 5. Rule J: Stormwater Management Because the project will disturb 2.9 acres of surface area, the project must meet the criteria of RPBCWD’s Stormwater Management rule (Rule J, Subsection 2.1). The project proposes construction of a rainwater harvest and reuse system, underground chambers, two hydrodynamic separators, a proprietary cartridge filtration chamber, a filtration basin, and a vegetated swale to provide stormwater quantity, volume and rate quality control. Pretreatment for the filtration basin is provided by a Rain Guardian Turret device which separates sediment from water flowing into the basin and the underground chambers. Rate Control In order to meet the rate control criteria listed in Subsection 3.1.a, the 2-, 10-, and 100-year post development peak runoff rates must be equal to or less than the existing discharge rates at all locations where stormwater leaves the site. The Applicant used a HydroCAD hydrologic model to simulate runoff rates for pre- and post-development conditions for the 2-, 10-, and 100-year frequency storm events using a nested rainfall distribution, and a 100-year frequency, 10-day snowmelt event. The existing and proposed 2-, 10-, and 100-year frequency discharges from the site are summarized in the table below. Modeled Discharge Location 2-Year Discharge (cfs) 10-Year Discharge (cfs) 100-Year Discharge (cfs) 10-Day Snowmelt (cfs) Ex Prop Ex Prop Ex Prop Ex Prop EX1/PR1 (Wetland/Creek) 3.9 2.7 7.4 5.2 14.4 10.2 0.5 0.4 EX2/PR2 (Adjacent Property) 1.2 0.4 2.3 0.8 4.5 1.6 0.1 <0.1 EX3/PR3 (78th Street) 0.9 <0.1 1.7 <0.1 3.3 <0.1 0.1 <0.1 The proposed stormwater management plan will provide rate control in compliance with the RPBCWD requirements for the 2-, 10-, and 100-year events. Thus, the proposed project meets the rate control requirements in Rule J, Subsection 3.1a. Page | 9 of 15 Volume Abstraction Subsection 3.1.b of Rule J requires the abstraction onsite of 1.1 inches of runoff from all impervious surface of the parcel. An abstraction volume of 5,045 cubic feet is required from the 1.26 acres (55,038 square feet) of impervious area on the project for volume retention. Pretreatment for runoff entering the filtration basin is being provided by a Rain Guardian Turret device, sump manholes and the underground chambers to conform to Rule J, Subsection 3.1.b.1. Soil borings performed by Haugo Geotechnical Services, Inc. dated January 5, 2018 show that soils onsite typically consist of Sandy Lean Clay fill with trace organic materials, gravel and wood over Sandy Lean Clay (CL) glacial till. Soil borings performed by Haugo Geotechnical show groundwater identified in the soil borings at elevations ranging from 946 feet to 950 feet. Groundwater was not encountered in the soil boring taken at the location and elevation of the proposed filtration basin at the eastern side of the property. Haugo Geotechnical Services, Inc. performed four onsite infiltration tests in the subsurface soils at the stormwater facility locations and the results show the infiltration rates of the underlying soils to be 0.0 in/hr. Because the engineer concurs that the soil boring information, infiltration testing support that the abstraction standard in subsection 3.1b of Rule J cannot practicably be met, the site is considered a restricted site and stormwater runoff volume must be managed in accordance with subsection 3.3 of Rule J. For restricted sites, subsection 3.3 of Rule J requires rate control in accordance with subsection 3.1.a and that abstraction and water-quality protection be provided in accordance with the following sequence: (a) Abstraction of 0.55 inches of runoff from site impervious surface determined in accordance with paragraphs 2.3, 3.1 or 3.2, as applicable, and treatment of all runoff to the standard in paragraph 3.1c; or (b) Abstraction of runoff onsite to the maximum extent practicable and treatment of all runoff to the standard in paragraph 3.1c; or (c) Off-site abstraction and treatment in the watershed to the standards in paragraph 3.1b and 3.1c. Because the soils on site allow for no infiltration, the applicant is proposing a rainwater harvest and reuse irrigating 1.26 acres of pervious area to achieve the abstraction standard in Subsection 3.3a of Rule J. The table below summarizes the volume abstraction required and the volume abstraction achieved by the proposed stormwater management facilities on site. The proposed project is in conformance with Rule J, Subsection 3.3.a. Page | 10 of 15 Required Abstraction Depth (inches) Required Abstraction Volume (cubic feet) Provided Abstraction Depth (inches) Provided Abstraction Volume (cubic feet) 0.55 2,523 0.57 2,618 Because the proposed stormwater reuse system requires consistent use at a specified rate to meet District requirements, performance monitoring for the site will be required to ensure that the project provides the proposed volume abstraction. Water Quality Management Subsection 3.1.c of Rule J requires the Applicant to provide for at least 60 percent annual removal efficiency for total phosphorus (TP), and at least 90 percent annual removal efficiency for total suspended solids (TSS), as well as no net increase in pollutant loading from existing conditions. MIDS water quality models were developed to estimate the TP and TSS loading from the watersheds and the removal capacity of the proposed BMPs. The results of this modeling are summarized in the following tables. The results show the proposed project will remove sufficient TSS and TP to achieve an overall pollutant reduction in accordance with the required annual removals (Rule J, Subsection 3.2c). Annual TSS and TP removal summary Pollutant of Interest Regulated Site Loading (lbs/yr) Required Load Removal (lbs/yr)1 Provided Load Reduction (lbs/yr) Total Suspended Solids (TSS) 569.7 512.8 (90%) 535.3 (93.9%) Total Phosphorus (TP) 3.14 1.88 (60%) 1.97 (62.6%) Summary of net change in TSS and TP leaving the site Pollutant of Interest Existing Site Loading (lbs/yr) Proposed Site Load after Treatment (lbs/yr) Change (lbs/yr) Total Suspended Solids (TSS) 195 34.5 -160.5 Total Phosphorus (TP) 1.64 1.16 -0.48 Low floor Elevation All new buildings must be constructed such that the lowest floor is at least two feet above the 100-year high water elevation or one foot above the emergency overflow of a stormwater-management facility according to Rule J, Subsection 3.6a. In addition, a stormwater-management facility must be constructed at an elevation that ensures that no adjacent habitable building will be brought into noncompliance with this requirement according to Rule J, Subsection 3.6b. The low floor elevation of the proposed building and the adjacent stormwater management feature or waterbody are summarized below. Page | 11 of 15 Stormwater Management Facility or Waterbody Low Floor Elevation of Proposed Building (feet) 100-year Event Flood Elevation of Adjacent Stormwater Facility or Waterbody (feet) Freeboard (feet) Filtration Basin 958.00 955.43 2.57 Underground Chamber 958.00 955.45 2.55 Riley Creek 958.00 952.1-945.00 13.00-5.9 Because there are no existing adjacent habitable structures, Rule J, Subsection 3.6b does not impose requirements on the proposed project. Maintenance Subsection 3.7 of Rule J requires the submission of a maintenance plan. All stormwater management structures and facilities must be designed for maintenance access and properly maintained in perpetuity to assure that they continue to function as designed. The stormwater management facilities include a rainwater harvest and reuse system, underground chambers, two SciClone units, one Jellyfish unit, a filtration basin, a vegetated swale, sump manhole structures and the Rain Guardian Turret device. The Applicant must provide a draft maintenance and inspection declaration in conformance with Rule J, Subsection 3.7, for approval by RPBCWD staff prior to recordation. To conform to the RPBCWD Rule J the following revisions are needed: J1. Permit applicant must provide a maintenance and inspection declaration as required by Rule J, Subsection 3.7. A maintenance declaration template is available on the permits page of the RPBCWD website (http://www.rpbcwd.org/permits/). A draft declaration must be provided for District approval prior to recordation as a condition of issuance of the permit. The maintenance plan must include operational parameters for the reuse system, as well as maintenance procedures for the proprietary systems recommended by the manufacturer or installer. Chloride Management Subsection 3.8 of Rule J requires the submission of chloride management plan that designates the individual authorized to implement the chloride management plan and the MPCA-certified salt applicator engaged in implementing the plan. To close out the permit and release the $5,000 in financial assurance held for the purpose of chloride management, the permit applicant must provide a chloride management plan that designates the individual authorized to implement the chloride management plan and the MPCA-certified salt applicator engaged in implementing the plan at the site. Wetland Protection Subsection 3.10 of Rule J requires that no activity subject to this rule may alter a site in a manner that alters the bounce in water level, duration of inundation, or change the runout elevation in the Page | 12 of 15 subwatershed in which the site is located for any wetland receiving discharge directly from the site. While the wetland is downgradient from land disturbing activities, the project proposes a swale to intercept sheet flow discharge from the patio on the north side of the proposed building and landscaping and direct the runoff away from the wetland. Because the proposed activities do not discharge to the protected wetland on the site but alter the tributary area and therefore the discharge the wetland receives from the site, the proposed activities must conform to RPBCWD wetland protection criteria (Rule J, subsection 3.10). The following table summarizes the allowable change in bounce and inundation duration from Table J1 of RPBCWD Rule J. The information summarized in the following table also summarizes the applicant’s analysis for wetland protection and the potential impacts on the wetlands. The hydrologic models demonstrate that the duration of inundation has not been increased from existing conditions. The submitted materials demonstrate, and RPBCWD engineers concurs, that project is in conformance with Rule J, Subsection 3.10a for the medium value wetland at the site. Wetland RPBCWD Wetland Value Change in Bounce for, 10-Year Event (feet) 1-year change in Inundation Period (days) 2-year change in Inundation Period (days) 10-year change in Inundation Period (days) Runout Control Elevation1 Rule J, Table J1 Criteria Medium Existing +/- 1.0 feet Existing+2 days Existing+2 days Existing +14 days 0 to 1.0 ft above existing runout On-site Wetland Medium 0.02 -0.2 -0.2 -0.2 No change Rule J, Subsection 3.10b requires that treatment of runoff to wetlands meet at the water quality treatment criteria in Rule J, subsection 3.1c. Because the site grading is such that runoff from regulated disturbed areas is directed away from the wetland, Rule J, Subsection 3.10b, does not impose requirements on this project. Rule L: Permit Fee Deposit The RPBCWD permit fee schedule requires permit applicants to submit a permit-fee deposit of $3,000 to be held in escrow and applied to reimburse RPBCWD for the permit-application processing fee and permit review and inspection-related costs. When a permit application is approved, the deposit must be replenished to the applicable deposit amount by the applicant before the permit will be issued to cover actual costs incurred to monitor compliance with permit conditions and the RPBCWD Rules. A permit fee deposit of $3,000 was received on January 22, 2020 under permit number 2020-003. Because the conditional approval under permit 2020-003 has expired and the applicant is required to apply for a new permit, the applicant must replenish the permit fee deposit to the original amount due before the permit will be issued. The replenishment must reimburse RPBCWD for the permit-application processing fee and permit reviews under permit number 2020-003 and 2022-058. Subsequently, if the costs of review, administration, inspections and closeout-related or other regulatory activities exceed the fee deposit amount, the applicant will be required to replenish the deposit to the original amount or such lesser amount as the RPBCWD administrator deems sufficient within 30 days of receiving notice that Page | 13 of 15 such deposit is due. The administrator will close out the relevant application or permit and revoke prior approvals, if any, if the permit-fee deposit is not timely replenished. L1. The applicant must replenish the permit fee deposit to the original amount due before the permit will be issued. The amount needed to replenish the permit fee deposit is $13,491 as of July 27, 2022. Rule M: Financial Assurance Unit Unit Cost # of Units Total Rules C: Silt fence: LF $2.50 4000 $10,000 Inlet protection EA $100 9 $900 Rock Entrance EA $250 1 $250 Restoration Ac $2,500 2.9 $7,250 Rules J: Chloride Management LS $5,000 1 $5,000 Rules J: Stormwater Management: 125% of engineer’s opinion of cost ($247,820– sump manhole structures and the Rain Guardian Turret device, rainwater harvest and reuse system, underground chambers, two SciClone units, one Jellyfish unit, and a filtration basin) EA 125% OPC 1 $309,775 Contingency (10%) 10% $33,318 Total Financial Assurance $366,493 Applicable General Requirements: 1. The RPBCWD Administrator and Engineer shall be notified at least three days prior to commencement of work. 2. Construction shall be consistent with the plans and specifications approved by the District as a part of the permitting process. The date of the approved plans and specifications is listed on the permit. 3. Construction must be consistent with the plans, specifications, and models that were submitted by the applicant that were the basis of permit approval. The date(s) of the approved plans, specifications, and modeling are listed on the permit. The grant of the permit does not in any way relieve the permittee, its engineer, or other professional consultants of responsibility for the permitted work. 4. The grant of the permit will not relieve the permittee of any responsibility to obtain approval of any other regulatory body with authority. 5. The issuance of this permit will not convey any rights to either real or personal property, or any exclusive privileges, nor will it authorize any injury to private property or any invasion of personal rights, nor any infringement of federal, state, or local laws or regulations. 6. In all cases where the doing by the permittee of anything authorized by this permit involves the taking, using or damaging of any property, rights or interests of any other person or persons, or Page | 14 of 15 of any publicly owned lands or improvements or interests, the permittee, before proceeding therewith, must acquire all necessary property rights and interest. 7. RPBCWD’s determination to approve the permit application was made in reliance on the information provided by the applicant. Any substantive change in the work affecting the nature and extent of applicability of RPBCWD regulatory requirements or substantive changes in the methods or means of compliance with RPBCWD regulatory requirements must be the subject of an application for a permit modification to the RPBCWD. 8. If the conditions herein are met and the permit is issued by RPBCWD, the applicant, by accepting the permit, grants access to the site of the work at all reasonable times during and after construction to authorized representatives of the RPBCWD for inspection of the work. Findings As supported and described by the analysis that follows, the engineer finds: 1. The proposed project includes the information necessary, plan sheets, modeling, and erosion control plan for review. 2. The proposed project will conform to Rules B, C, D, G and J if the Rule Specific Permit Conditions listed above are met. 3. Under Minnesota Department of Natural Resources General Permit 2015-1192 (attached to this report), approval of work under RPBCWD rule(s) G constitutes approval under applicable DNR work in waters rules. Compliance with conditions on approval and payment of applicable fees, if any, are necessary to benefit from general permit approval and the responsibility of the applicants. Recommendation: Approval, contingent upon: 1. Continued compliance with General Requirements 2. Financial Assurance in the amount of $366,493. 3. Receipt of updated drawings to a. adjust the location of the proposed building or the building design modified to provide a minimum of 100 feet of separation between the centerline of Riley Creek and the building. 4. Permit applicant must provide the name and contact information of the general contractor responsible for the site. RPBCWD must be notified if the responsible party changes during the permit term. 5. The applicant must replenish the permit fee deposit to $3,000 due before the permit will be issued. The amount needed to replenish the permit fee deposit is $13,491 as of July 27, 2022. Page | 15 of 15 6. Receipt by RPBCWD of documentation of recordation of a maintenance declaration for the outfall to Riley Creek, buffers, and stormwater management facilities. A draft must be reviewed and approved by the District prior to recordation and proof of recordation must be provided to RPBCWD prior to issuance of the permit. The maintenance plan must include operational parameters for the reuse system, as well as maintenance procedures for the proprietary systems recommended by the manufacturer or installer. By accepting the permit, when issued, the applicant agrees to the following stipulations: 1. Continued compliance with General Requirements. 2. The applicant provides proof of recordation that drainage and flowage easements over all land below the 100-year flood elevation have been conveyed to the municipality with jurisdiction, if required. 3. Per Rule J Subsection 4.5, upon completion of the site work, the permittee must submit as-built drawings demonstrating that at the time of final stabilization the stormwater management facilities conforms to design specifications and functions as intended and approved by the District. As-built/record drawings must be signed by a professional engineer licensed in Minnesota and include, but not limited to: a) the surveyed bottom elevations, water levels, and general topography of all facilities; b) the size, type, and surveyed invert elevations of all stormwater facility inlets and outlets; c) the surveyed elevations of all emergency overflows including stormwater facility, street, and other; d) other important features to show that the project was constructed as approved by the Managers and protects the public health, welfare, and safety. 4. Documentation that constructed filtration facilities perform as designed. This may include filtration testing, flood testing, or other with prior approval from RPBCWD. 5. To close out the permit and release the $5,000 in financial assurance held for the purpose of the chloride management, the permit applicant must provide an executed chloride management plan that designates the individual authorized to implement the chloride management plan and the MPCA-certified salt applicator engaged in implementing the plan at the site. 6. The work on the Moments of Chanhassen parcel under the terms of permit 2022-058, if issued, must have an impervious surface area and configuration materially consistent with the approved plans. Design that differs materially from the approved plans (e.g., in terms of total impervious area) will need to be the subject of a request for a permit modification or new permit, which will be subject to review for compliance with all applicable regulatory requirements. 7. Replenish the permit fee deposit to the original amount or such lesser amount as the RPBCWD administrator deems sufficient within 45 days of receiving notice that such deposit is due in order to cover continued actual costs incurred to monitor compliance with permit conditions and the RPBCWD Rules. 8. The Department of Natural Resources General Permit #2015-1192 applies to authorize the work in Riley Creek as long as the permittee complies with the conditions of the general permit, which is attached to this report. P ow e r s B l v d LakeDr E ButteCt HunterDr Longacres Dr AcornLaBrinker St Mallo ryCtUtica LaW 78th St Stone Creek DrPark Ct MaplewoodTerW 78th St P o n t i a c C i rShawneeLa U p l a n d C i r TecumesehLaRedman LaAudobon RdWind DrTimberwood DrFawn Hill RdMcglynn Dr Park RdSto n eCr ee k D r Park P l West Lake Ct W 78th St Lake Dr WPark DrWalnut Cv Majestic Way Powers BlvdMotor Plex CtAudobon RdGalpin BlvdPr a i r i e F l o w e r B l v d Coulter Blvd ¨©117 456717 456717 5 5 Chanhassen Lake Lucy Lake Ann BluffCreek RileyCreek Barr Footer: ArcGIS 10.7.1, 2020-03-25 11:45 File: I:\Client\RPBC_WD\Work_Orders\Monthly_General_Services\Permitting\Maps\2020\2020-003 Moments of Chanhassen.mxd User: mbs2 Permit Location Map MOMENTS OF CHANHASSEN Permit 2022-058Riley Purgatory Bluff Creek Watershed District !;N 0 1,000 Feet SITE