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Home My WebLink AboutAttachment 02g. - Stormwater Quality Management Plan - Apr 202404-24-2023 646-010-08, 644-070-20 & 644-070-21 TM22-0005 11-14-2023 Otay Ranch Village 8 East Otay Ranch Village 8 East Otay Ranch Village 8 East Otay Ranch Village 8 East Otay Ranch Village 8 East TM22-0005 47945 12/31/23 Alisa S. Vialpando Hunsaker & Associates San Diego 04/24/2311/14/2023 Otay Ranch Village 8 East 09/30/22 04/24/23 Second Submittal05/12/23 11/14/2023 Final SubmittalX 09/14/23 Third Submittal Otay Ranch Village 8 East 23,824,296 11-14-2023 Otay Ranch Village 8 East Otay Ranch Village 8 East Otay Ranch Village 8 East is south of the extension of Main Street,north of the Otay River Valley,east of Village 8 West and west of SR-125.This urban village was originally approved by the Chula Vista City Council in 2014 and subsequently amended in 2020.Current entitlements accommodate a total of 3,276 residen- tial units,including 943 detached homes, 1,893 attached homes and 440 multi-family units in a mixed-use setting, 20,000 square feet of retail/commercial uses,an elementary school site,a neighborhood park and the 51.5-acre (gross) Otay Ranch Community Park South.Access to the village is provided via the extension of Main Street and La Media Parkway with emergency and pedestrian access to the community park provided along a utility corridor in the southeast portion of Vil- lage 8 East.Primary access to the community park is via existing Avenida Caprise within Village West. HomeFed Otay Land II, LLC, (Applicant),proposes to amend the Village 8 East land use plan to reflect current market conditions and housing needs and to ensure the community relates more closely to the adjacent Village 8 West community and future Village 9 planned east of SR-125.The replanning effort also addresses the redesign of the SR-125 interchanges at Main Street and La Media Parkway.Village 8 East Proposed Land Use:The Proposed Village 8 East Land Use Plan would include a Village Core area that would accommodate a mix of uses including multi-family residential and retail/commercial uses along with an elementary school site and a centrally located neighbor- hood park. A future multi-modal bridge,planned to accommodate Neighborhood Electric Vehicles (NEV),bicycles and pedestrians is also planned in the Village Core linking Village 8 East and future Village 9. It's important to note that a project can be classified as HMP exempt without directly discharging into an ESA. Conversely, a project might directly discharge to an ESA but not qualify as HMP exempt. Let me elaborate further: The criteria for direct discharge in the context of HMP exemption involve the outlet pipe invert being situated below the 100-year Water Surface Elevation (WSE). This is a specific technical requirement for HMP exemption. On the other hand, the definition of direct discharge in relation to an ESA refers to the pipe's discharge representing an isolated flow originating solely from our project to the ESA, without intermingling with flows from adjacent lands. This is aimed at ensuring the integrity of the discharge's contribution to the ESA's ecosystem. It's important to highlight that our project's discharge point experiences the mixing of basin outflows with bypass flows prior to reaching the ESA. As a result, while the project still satisfies the criteria for HMP exemption, its discharge is not considered "direct" into the ESA due to the flow commingling with others before entering the ESA. Otay Ranch Village 8 East Project Name: _____________________________________________________ Otay Ranch, Village 8 East Units have not yet been calculated. Project Name: _____________________________________________________ Otay Ranch, Village 8 East Otay Ranch Village 8 East Project Name.: _______________________________________________________ Otay Ranch, Village 8 East Project Name/Address/N ______________________________________________ Per Form I-7, Harvest and Use deemed to be infeasible. Otay Ranch Village 8 East Otay Ranch - Village 8 East The overall site is characterized by 3 DMAs and 3 areas that are considered Self Mitigating Areas according to Section 5.2.1. The following steps were obtained as presented in Section 5.1 on the BMP Design Manual. Step 1 1a. DMAs were delineated, and broken down per surface cover. Self mitigating areas were identified. Weighted runoff factor was calculated for each DMA based on area break down. 1b. DCV for all other DMAs were calculated using worksheet B.2-1 which determines water quality vol- ume that needs to be biofiltrated (1.5 DCV) for all DMAs Step 2 2a. Harvest and use is not used and unfeasible according to Form I-7. Step 3 3a. Using Form I-8 to conduct a preliminary feasibility screening determined that no infiltration to be feasible. 3b. Volume based Proprietary Biofiltration BMPs chosen for DMA1, and flow based Proprietary Biofiltration BMPs chosen for DMA3, Nutrient sensitive media biofiltration basin has been chosen for DMA2 . 3c. Worksheets B.5-1 was used to size the biofiltration Bf-2-2. 3d. Worksheeet B.6-1 was used to calculate the required treatment flow rates and size the flow based proprietary biofiltration BMP BF-3-3. Required Minimum retention was calculated and will be provided via site design BMPs for DMA 1 and DMA 3 Step 4-4a. Proposed BMPs fit minimum footprint required. Project meets pollutant control standards. Detention basin for DCV Storage upstream of volume based MWS units Otay Ranch - Village 8 East Basin 1 Alisa S. Vialpando Hunsaker & Associates-San Diego, Inc. 9707 Waples Street San Diego, CA 92121 HOA for Otay Ranch - Village 8 East HOA for Otay Ranch - Village 8 East Homeowners fees to the HOA for Otay Ranch -Village 8 East Otay Ranch - Village 8 East Basin 1 The proposed basin is a standard graded DCV Storage, flow control, and detention basin that is 6 feet deep with a bottom area of 90,000 sf. The basin will have installed a 4'x3' open top concrete outlet structure (riser) with a rim height of 4.96' for overflow. The water quality design capture volume will be discharged gradually through WQ flow control orifices (7-6" diameter) at invert elevation of 0 which are to control the flows downstream towards the MWS units. The storage volume was sized using worksheet B-2.1 to store the total 1.5 DCV which was calculated to be 476,562 ft^3. Calculations are shown in this report. This volume was used to size the proposed MWS units as shown previously. BF-2 Nutrient sensitive media Otay Ranch - Village 8 East BF-2-2 Alisa S. Vialpando Hunsaker & Associates-San Diego, Inc. 9707 Waples Street San Diego, CA 92121 HOA for Otay Ranch - Village 8 East HOA for Otay Ranch - Village 8 East Homeowners fees to the HOA for Otay Ranch -Village 8 East Otay Ranch - Village 8 East BF-2-2 BF-2-2 is to be designed as a biofiltration basin, working as a pollution control BMP. BF-3 Proprietary Biofiltration Otay Ranch - Village 8 East BF-3-1 Alisa S. Vialpando Hunsaker & Associates-San Diego, Inc. 9707 Waples Street San Diego, CA 92121 HOA for Otay Ranch - Village 8 East HOA for Otay Ranch - Village 8 East Homeowners fees to the HOA for Otay Ranch -Village 8 East Otay Ranch - Village 8 East BF-3-1 The required total DCV from worksheet B.2-1 is 317,708 ft^3. The design cubic feet corresponds to a 1.5 DCV of 476,562 ft^3. The proposed BF-3-1 which consists of Twenty (20) - MWS L-8-24. This is based off of volume based sizing to treat 1.5 DCV and draw-down within the 36-Hour Period. The total 1.5 DCV was provided to Contech and per their consultation the size and number of Modular Wetland Units were calculated. These details are shown in the SWQMP Report. Otay Ranch, Village 8 East Alisa S. Vialpando Hunsaker & Associates-San Diego 9707 Waples Street San Diego, CA 92121 (858)558-4500 HOA for Otay Ranch - Village 8 East HOA for Otay Ranch - Village 8 East Homeowners fees to the HOA for Otay Ranch -Village 8 East BF-3 Proprietary Biofiltration Otay Ranch, Village 8 East For DMA-3 shown on the DMA map, the section Northeast of the project will need to be treated with a 20 ft long by 8 ft wide Filterra unit with .648 cfs treatment capacity 0.593 cfs required flow was calculated using B-6-1 worksheet For DMA-3 shown on the DMA map, the Northeast section of the project will need to be treated with 2-Filterra Units (14 ft long by 8 ft wide). Each unit has a treatment ca- pacity (per Table shown in SWQMP) of 0.4537 cfs. 2 Units x 0.4537 cfs = 0.9074 cfs Final Design flow rate to be treated equates to 0.857 cfs per the Worksheet attached in SWQMP. BF-3 Proprietary Biofiltration Otay Ranch - Village 8 East BF-3-4 Alisa S. Vialpando Hunsaker & Associates-San Diego, Inc. 9707 Waples Street San Diego, CA 92121 HOA for Otay Ranch - Village 8 East HOA for Otay Ranch - Village 8 East Homeowners fees to the HOA for Otay Ranch -Village 8 East Otay Ranch - Village 8 East BF-3-4 The required total DCV from worksheet B.2-1 is 828 ft^3. The design cubic feet cor- responds to a 1.5 DCV of 1242 ft^3. The proposed BF-3-4 consists of one flow based MWS L-8-8. This is based off of flow based sizing to treat 1.5 DCV. The total 1.5 DCV was provided to Contech and per their consultation the size of the Modular Wetland Unit was provided, in lieu of this information this report also provides another way of calculating the flow based MWS unit with the use of a table provided through Contech. Otay Ranch Village 8 East Otay Ranch Village 8 East Otay Ranch Village 8 East DMA Exhibit Attachment 1A STANDARD DETAIL STORMWATER BIOFILTRATION SYSTEM MWS-L-8-24-6'-0"-V-HC FOR PATENT INFORMATION, GO TO www.ContechES.com/IP SITE SPECIFIC DATA PLAN VIEW ELEVATION VIEW RIGHT END VIEW LEFT END VIEW GENERAL NOTES INSTALLATION NOTES VILLAGE 8 EAST DMA CALCULATIONS Imp. RF Pervious RF % Imp AREA Fraction of Total Imp Area Pervious Area Summation RF x A (ac.)(ac.)(ac.) BASIN 0.90 0.10 0 2.09 0.1%0.000 2.091 0.21 PARK 0.90 0.10 20 30.43 4.7%6.086 24.344 7.91 SCHOOL 0.90 0.10 80 9.96 4.4%7.972 1.993 7.37 ROAD 0.90 0.10 90 37.75 18.4%33.974 3.775 30.95 MIXED USE 0.90 0.10 85 47.77 22.1%40.601 7.165 37.26 SLOPES/LANDSCAPE 0.90 0.30 0 23.43 4.2%0.000 23.431 7.03 MULTIFAMILY 0.90 0.10 75 109.48 45.5%82.113 27.371 76.64 COMMUNITY PURPOSE 0.90 0.10 85 1.20 0.6%1.024 0.181 0.94 0.90 0.3 85 0.0%0.000 0.000 0.00 262.12 100.0%171.769 90.350 168.31 Weighted C =0.64 Otay Ranch Village 8 East Area DMA 1 9/14/2023 R:\0920\Hyd\TM\SWQMP\Calcs\Appendix B.5 Biofiltration BMP Sizing Worksheets VILLAGE 8 EAST DMA CALCULATIONS Imp. RF Pervious RF % Imp AREA Fraction of Total Imp Area Pervious Area Summation RF x A (ac.)(ac.)(ac.) SINGLE-FAMILY (SF)0.90 0.10 75 0.78 82.6%0.582 0.194 0.54 ROAD 0.90 0.10 90 0.14 17.4%0.126 0.014 0.11 0.92 100.0%0.708 0.208 0.66 Weighted C =0.72 Otay Ranch Village 8 East Area DMA 4A 9/13/2023 R:\0920\Hyd\TM\SWQMP\Calcs\Appendix B.5 Biofiltration BMP Sizing Worksheets Project Name: _____________________________________________________ Otay Ranch - Village 8 East DMA 1, DMA 2, DMA 3, DMA 4A & 4B Planning Project Name: _____________________________________________________ Otay Ranch - Village 8 East Per the Geotechnical Report attached in this document. "Detrimental soil movement could occur if water is allowed to infiltrate the soil for prolonged periods of time." "Infiltration areas are considered infeasible due to poor percolation and lateral migration characteristics." Please refer to the geotechnical report Dated September 30, 2022 by Geocon Incorporated for additional information. Project Name: _____________________________________________________ Otay Ranch - Village 8 East Project Name: _____________________________________________________ Otay Ranch - Village 8 East Per the Geotechnical Report attached in this document. "Detrimental soil movement could occur if water is allowed to infiltrate the soil for prolonged periods of time." "Infiltration areas are considered infeasible due to poor percolation and lateral migration characteristics." Please refer to the geotechnical report Dated September 30, 2022 by Geocon Incorporated for additional information. Project Name: _____________________________________________________ Otay Ranch - Village 8 East DMA 1, DMA 2, DMA 3, DMA 4A & 4B Planning Per the Geotechnical Report attached in this document. "Detrimental soil movement could occur if water is allowed to infiltrate the soil for prolonged periods of time." "Infiltration areas are considered infeasible due to poor percolation and lateral migration characteristics." Please refer to the geotechnical report Dated September 30, 2022 by Geocon Incorporated for additional information. Project Name: _____________________________________________________ Otay Ranch - Village 8 East Project Name: _____________________________________________________ Project Name: _____________________________________________________ Per the Geotechnical Report attached in this document. "Detrimental soil movement could occur if water is allowed to infiltrate the soil for prolonged periods of time." "Infiltration areas are considered infeasible due to poor percolation and lateral migration characteristics." Please refer to the geotechnical report Dated September 30, 2022 by Geocon Incorporated for additional information. Otay Ranch - Village 8 East INFILTRATION FEASIBILITY CONDITION LETTER OTAY RANCH VILLAGE 8 EAST CHULA VISTA, CALIFORNIA PREPARED FOR MAY 5, 2023 PROJECT NO. G1006-52-05 Project No. G1006-52-05 May 5, 2023 Homefed Otay Land II, LLC 1903 Wright Place, Suite 220 Carlsbad, California 92008 Attention: Mr. Jeff O’Connor Subject: INFILTRATION FEASIBILITY CONDITION LETTER OTAY RANCH VILLAGE 8 EAST CHULA VISTA, CALIFORNIA References: 1. Update Geotechnical Report, Otay Ranch Village 8 East, Chula Vista, California, prepared by Geocon Incorporated, revised March 27, 2023 (Project No. G1006-52-05). 2. Final Report of Testing and Observation Services During Site Grading, Otay Ranch Village 8 East, Borrow and Disposal Sites, prepared by Geocon Inc., dated September 9, 2022 (Project No. G1006-52-04). 3. Proposed DMA Map – Village 8 East, City of Chula Vista, California, prepared by Hunsaker and Associates San Diego, Inc., undated, received April 17, 2023. Dear Mr. O’Connor: In accordance with the request of Mr. Brian Lessa with Hunsaker and Associates, San Diego Inc., we prepared this letter to describe the existing geotechnical conditions for the purposes of storm water management for the subject property. We reviewed the referenced update geotechnical report to evaluate the current geologic conditions on the property in accordance with the City of Chula Vista Best Management Practices (BMP) Design Manual, August 2021. SITE AND PROJECT DESCRIPTION Otay Ranch Village 8 East is located south of future Main Street (currently Rock Mountain Road) and Olympian High School, west of State Route 125, north of the Otay River drainage and Wiley Road access easement, and east of undeveloped land in the southeastern portion of Chula Vista, California. The property is approximately 575 gross acres with about 265 gross acres planned for open space resulting in the development of about 310 acres. The site consists of a series of south trending ridges and canyons draining to the south into Otay River. Site elevations range from approximately 180 feet above mean sea level (MSL) at the southwest corner of the Community Park site adjacent to the Otay River drainage to approximately 610 feet MSL at the northeast corner of the site. Cut and fill slopes exist on the northern portion of the site created during the previous grading of Main Street, Rock Geocon Project No. G1006-52-05 - 2 - May 5, 2023 Mountain Road, and Santa Luna Street. Previous grading for Main Street and Olympian High School included the construction of canyon subdrains and a buttress fill along the northern boundary of the site. Most recent grading of the consisted of placement of compacted fill from export material from Village 8 East within the disposal site. Additionally, a borrow site was utilized for fill placement in Village 8 West. A Chula Vista sewer line easement and an SDG&E overhead transmission line are located on the southern portion of the project within the un-improved Wiley Road. Wiley Road provides access to the Vulcan material plant to the west and further east within the Otay River Valley The City of San Diego’s, Otay 2nd 40-inch and Otay 3rd 54-inch-inch waterlines (constructed in the late 1920s by cut and cover techniques) cross the site from east to west in the middle portion of the project. We understand the invert elevations of the pipeline are 10 to 15 below the existing grades based on observation of portion of mass grading on Village 8 West. We understand the existing waterlines will be removed or abandoned from the eastern and western points of connection, respectively. Portions of the existing 54-inch pipeline are partially exposed above ground as it crosses several tributary drainages. Site vegetation consists of sparse native coastal sage scrub and grassland habitats disturbed by farming. Some riparian vegetation occurs on the north side of the Otay River drainage area. The Existing Site Map shows the current site conditions on the subject property. The Project Location Map shows the areas surrounding the Village 8 West development area. Project Location Map We understand the development will generally occur from the north to south property lines leaving local areas designated as open space and preserve for environmental purposes (MSCP). The site will Geocon Project No. G1006-52-05 - 3 - May 5, 2023 accommodate multi-family residential (108.8), village core (47.7 acres), park sites (73.2 acres), school site (11.3 acres), community purpose facilities (2.0 acres), parks (73.2 acres, respectively), future development lots (9.3 acres), circulation roadways (31.8 acres), active recreation (22.6 acres), and open space (253.6 acres of preserve land, and basins (31.6 acres). A large community park is proposed on the southern portion of the property adjacent to the Otay River drainage channel. In addition, water quality basins will be constructed on the southeast and southwest portion of the site to the south of the developed area and along the north side of the Otay River drainage. Mass grading of the site will consist of maximum cuts and fills of approximately 75 feet with cut and fill slopes having a maximum height of 45 and 50 feet, respectively, and a maximum slope inclination of 2:1 (horizontal to vertical). Several reinforced earth retaining walls are proposed on the site with maximum heights on the order of 25 feet. The proposed grading will require approximately 4.86 million cubic yards of excavation and fill. Based on review of the referenced Drainage Management Area (DMA), the proposed site consists of three, DMA areas 1 through 3. DMA area 1 is located along the northern property line along future Main Street, the existing roadways preclude areas of infiltration. Planned DMA areas 2 and 3 are located within the southwestern and southeastern margins of the site, respectively. Due to the planned fill thickness and planned slopes greater than 5 feet precludes areas of infiltration within DMA areas 2 and 3, respectively, preclude areas of infiltration. The proposed Drainage Management Area (DMA) plan presents the proposed project are presented on Figure 1. The locations and descriptions of the site and proposed development are based on the referenced site plan and our understanding of project development. If project details vary significantly from those described herein, Geocon Incorporated should be contacted to evaluate the necessity for review and revision of this report. PREVIOUS SITE DEVELOPMENT In general, a portion of Otay Ranch Village 8 East has been partially grading during mass grading operations for Village 8 West. The disposal and borrow areas within Village 8 West consisted of remedial grading of surficial soil and placing compacted fill resulting in a total maximum thickness ranging up to approximately 40 feet. The surficial soil (topsoil) and upper weathered formational materials were excavated to expose competent Otay Formation. The topsoil and portions of the weathered Otay Formation were stockpiled for environmental purposes highlighted blue and labeled environmental stockpile. Prior to fill placement, toe drains were installed and canyon subdrains were placed within the former canyon drainages. The grading contractor generated additional fill material from within the Otay Formation and placed within the lower temporary slope zone margins subsequent to the installation of the toe drains. Excavation depths ranged from 5 feet within the former mesa areas and up to 10 feet within the flanks of the central canyon drainage. Geocon Project No. G1006-52-05 - 4 - May 5, 2023 The middle member of the Otay Formation (informally named the “gritstone” unit) is expected to be predominately exposed at the surface on the central and southern portion of the site. Subsequent to mass grading, dense to very dense, compacted fill and formational materials will be exposed at grade across the site. The formational materials are typically cemented and very difficult excavation should be expected. Localized cemented or very hard zones will be encountered within the Otay Formation that will require very heavy effort to excavate with oversize chunks generated. Based on observations during mass grading, we expect that at a minimum a D9 or D10 bulldozer would be required to perform excavations within the cemented portions of the “gritstone member” of the Otay Formation. Additionally, planned 5-foot undercuts within bentonitic claystone are planned within the resulting fill thickness of greater than feet. STORM WATER INFILTRATION FEASIBILITY The following information provided responses to discussions requested from Section C.1.1 of the 2021 City of City of Chula Vista Best Management Practices (BMP) Design Manual, August 2021. The Phase of the Project In which the geotechnical engineer first analyzed the site for infiltration feasibility: The current submittal is in the design phase. Results of previous geotechnical analyses conducted in the project area, if any. During our field investigation, disposal and borrow site grading operations, we encountered four surficial deposits (consisting of previously placed fill, undocumented fill, topsoil, and alluvium) and two formational units (consisting of Pleistocene age Terrace Deposits and Tertiary-age Otay Formation). We subdivided the Otay Formation into the upper sandstone/siltstone/claystone member (To) and an underlying middle gritstone member (Tog). The gritstone member is typically well cemented, very difficult excavation should be expected. Localized cemented or very hard zones will be encountered within the Otay Formation that will require very heavy effort to excavate with oversize chunks generated. Based on observations during mass grading within the gritstone member, we expect that at a minimum a D9 or D10 bulldozer would be required to perform excavations within the cemented portions of the “gritstone member” of the Otay Formation. We did not encounter the lower basal conglomerate member of the Otay Formation on site. Tertiary-age Otay Formation is exposed across the site or located below the surficial soil and Terrace Deposits. The upper member of this unit (To) consists of interbeds of dense to very dense, slightly cemented, silty to clayey sandstone and hard, siltstone and claystone layers. In addition, several layers of bentonitic claystone (Tob) with a maximum thickness of approximately 1 foot thick are present within this unit on the northern and middle portions of the site that can create slope instability. Some of the layers are locally discontinuous and range in elevations as high as 573 feet MSL to as low as 416 feet MSL. Additionally, some minor discontinuous layers of bentonitic claystone are also present with a thickness of 1 to 3 inches. The Tertiary-age (upper Oligocene) Otay Formation underlies the site on canyon slopes or underlying the younger geologic formations and surficial soil at depth. The Otay Formation consists of dense, silty, fine- to coarse-grained sandstone, clayey and sandy siltstone, and silty claystone with continuous and discontinuous interbeds of highly expansive bentonitic claystone. The coarse-grained portions of the Otay Formation typically possess a “very low” to “low” expansion potential (expansion index of 50 or less) and adequate shear strength. The fine- Geocon Project No. G1006-52-05 - 5 - May 5, 2023 grained siltstone and claystone portions of the formation can exhibit a “medium” to “very high” expansion potential (expansion index greater than 50). With the exception of the bentonitic claystone, the Otay Formation is suitable for the support of compacted fill and structural loads. The formational materials ae fine-grained in nature and are hard/cemented. Pleistocene-age Terrace Deposits are deposited as shallow marine and non-marine near shore soil located on the southern portion of the site and the northern flank of the Otay River canyon drainage. We expect this unit may be in excess of 50 feet thick. The Terrace Deposits are generally dense to very dense, reddish brown, silty to clayey sandstone with portions of the unit containing intermittent layers of cobbles and boulders up to about 2 feet in diameter. The Terrace Deposits are suitable for the support of proposed fill and structural loads; however, select grading operations will be required to properly place the cobble and boulders where encountered. Alluvium exists within the canyon drainages located in the central portion of the project. The alluvium within the canyon drainages is loose to medium dense, can become saturated and difficult to excavate during the rainy season. We estimate the thickness of the alluvium to range up to approximately 7 feet within the tributary canyons and 11 feet within the Otay River Drainage on the south side of the site. Due to the relatively unconsolidated nature of these deposits, remedial grading will be necessary in areas to receive proposed fill or structures and alluvium will not be present in the final graded condition. The coarse-grained units of the formational units possess a “low” to “medium” expansion potential (expansion index of 21 to 90). The fine-grained bentonitic claystone of the Otay Formation possesses a “high” to “very high” expansive potential (expansion index greater than 90). Expansion would occur on the existing soil if infiltration we to be allowed on the property. Planned development and mass grading of Otay Ranch Village 8 East area has not been completed and buttresses will need to be constructed due to the presence of bentonitic claystone layers (Tob). Buttress designs have assumed a 1:1 (horizontal to vertical) frontcut and backcut extending down to intercept the bentonite. Infiltration should not occur because we will be installing buttresses to help increase the factor of safety of the adjacent slope for the planned development. Buttress and fill slopes are presented on Figure 1. The development status of the site prior to the project application. The central area has been used as a fil placement site from rock materials generated from the Otay Ranch Village 8 West property. The remaining areas have not been graded and the topography is in a generally natural condition. Additional mass grading will be required to achieve the current design grade and construct planned BMPs. The history of design discussion for the project footprint, resulting the final design determination. Based on the discussion herein, infiltrating storm water devices will not be allowed on the property due to the fill thicknesses, the “expansive” characteristics of the soil and the planned buttress/graded fill slope. The storm water devices are planned to be lined to prevent infiltration and distress from occurring on the subject and adjacent properties. Geocon Project No. G1006-52-05 - 6 - May 5, 2023 Full/partial infiltration BMP standard setbacks to underground utilities, structures, retaining walls, fill slopes, and natural slopes applicable to the DMA that prevent full/partial infiltration. Existing utilities are located within the adjacent public right-of-way/roadways on the site. Full or partial infiltration should not be allowed in the areas of the utilities to help prevent potential damage/distress to improvements. Mitigation measures to prevent water from infiltrating the utilities consist of setbacks, installing cutoff walls around the utilities and installing subdrains and/or installing liners. The horizontal and vertical setbacks for infiltration devices should be a minimum of 10 feet and a 1:1 plane of 1 foot below the closest edge of the deepest adjacent utility, respectively. Due to the presence of bentonite layers in the Otay Formation, some buttresses will be required. Water should not be allowed in buttress areas to help reduce the potential for slope instability and movement. In addition, infiltration should not occur adjacent to proposed slopes to help prevent seepage from occurring and surficial instability. Physical impairments (i.e., fire road egress, public safety considerations, etc.) that prevent full/partial infiltration. There are existing improvements and structures located adjacent to the northern property margin. The storm drains and water lines within the site would require setbacks for infiltration if it were allowed. Infiltration near these structures and improvements should not be allowed. In addition, allowing infiltration would saturate the underlying fill and result decrease of the factor of safety for the adjacent slope. The slope is not designed as a saturated condition and the slope would possess an increased risk of movement if infiltration were to occur. Consideration of site design alternative to achieve partial/full infiltration within the DMA. Based on the existing fill materials, expansion index and adjacent slopes, full and partial infiltration should not be allowed on the property. Other options of infiltration would be deep dry wells. However, the depth of the dry wells would need to extended relatively deep to not affect the adjacent southern drainage areas. The existing materials are fine-grained where the infiltration rates would be very slow. Therefore, dry wells are not an efficient design potential in this area. The extent site design BMPs requirements were included in the overall design. BMPs are being incorporated into the site design for storm water management. The planned storm water management devices should be properly lined to prevent water infiltration. Conclusion or recommendation from the geotechnical engineer regarding the DMA’s infiltration condition. Infiltration should be considered infeasible and proposed storm water management devices should be lined due to the fill soil with thicknesses greater than 5 feet, shallow hard and dense/cemented Otay Formation and expansive soils, planned undercuts of expansive soils, the location of the descending slopes, and the requirements for buttresses on the descending slopes. Additional geotechnical investigation is not required due to our previous experience with the geologic conditions and the infiltration characteristics of the existing soil encountered during previous mass-grading operations and previous geotechnical investigations within the geologic units. In addition, other areas of potential infiltration do not exist on the property. We opine the existing soil cannot be mitigated to allow infiltration on the property. Based on the discussion Geocon Project No. G1006-52-05 - 7 - May 5, 2023 herein, we opine full and partial infiltration is considered infeasible at the site. We recommend storm water management BMPs be designed so that infiltration does not occur. Figures 1, presents the DMA Exhibit Map overlayed with our geologic map presenting the existing slope area, fill slope areas, shallow Otay Formation and expansive soils, and expected existing fill greater than 5 feet. An Exhibit for all applicable DMA’s that clearly labels: Proposed development areas and development type. All applicable features and setbacks that prevent partial or full infiltration, including underground utilities, structures, retaining walls, fill slopes, natural slopes, and existing fill materials greater than 5 feet. Potential locations for structural BMPs. Areas where full/partial infiltration BMPs cannot be proposed. The DMA Exhibit Map, Figure 1, presents the development plan as a base map. The figure shows the development area and improvements, and the area on the site infeasible to infiltration due to fill thickness greater than 5 feet, shallow hard and dense/cemented Otay Formation and expansive soils, and slope stabilization/planned sloping conditions. We opine the entire project site is infeasible for infiltration. If you have any questions regarding this letter, or if we may be of further service, please contact the undersigned at your convenience. Very truly yours, GEOCON INCORPORATED Michael C. Ertwine CEG 2659 Shawn Foy Weedon GE 2714 SFW:MCE:am (e-mail) Addressee ····· · · ··· · ··· Qudf Qal Qa l Qal Qal Qal/ Qudf/ Qt Qpf To SECONDARY DISPOSAL SITEEnvironmental Stockpile Qudf Qudf To To To To To To To To To Tog To To To To Qt Environmental Stockpile Qudf Environmental Stockpile Qudf Qt Qt Qt Qt Qt Qt Qt Qal/ Qal/ Qal/ Qal/ Qt Qt Qt Qt Qt Qt Qt Qt To Qal/ Qal/ Qal/ Qal/To Qal Qal Qal Qal Qal To To (Stockpile) Qudf Qal/ Qal/ Qal/ Qcf/ Qcf/ Qcf/ Qal/ Qcf/ Qcf/ Qal/ FALSE SOIL ROCK SLOPE FALSE SOIL ROCK SLOPE Qal Qal Qal Qal 524 WILEY R O A D Qal/ WILEY ROAD Qal/ Qal/ Qal/ Qal/ Qal/ Qt To To To Environmental Stockpile Qudf Environmental Stockpile Qudf TEMPORARY STUB FOR FUTURE CONNECTION OF SUBDRAINS TEMPORARY STUB FOR FUTURE CONNECTION EXTEND DRAINS OFF-SITE TO ALLOW DRAINAGE WITH HEADWALL OUTLET Tog Tog Tog Tog Tog To To To Tog Tog Qal NAP To Qpf NAP NAP NAP Qpf Qpf ······ ····· · Qt Qpf Qpf ··· PROJECT LIMITS PROJECT LIMITS PROJECT LIMITS PROJECT LIMITS Tog PROJECT LIMITS PROJECT LIMITS TogQal PROJECT LIMITS PROJECT LIMITS PROJECT LIMITS PROJECT LIMITS PROJECT LIMITS PROJECT LIMITS PROJECT LIMITS EXTEND DRAINS OFF-SITE TO ALLOW DRAINAGE WITH HEADWALL OUTLETEXTEND DRAINS OFF-SITE TO ALLOW DRAINAGE WITH HEADWALL OUTLET PROJECT NO. SCALE DATE FIGURE SHEET OF Plotted:05/05/2023 11:17AM | By:ALVIN LADRILLONO | File Location:Y:\PROJECTS\G1006-52-05 (Village 8 East)\SHEETS\G1006-52-05 DMA Exhibit.dwg DMA EXHIBIT MAP - OTAY RANCH VILLAGE 8 EAST VILLAGE 8 EAST CHULA VISTA, CALIFORNIA 200'05 - 04 - 2023 G1006 - 52 - 05 1 1 1 *LANDERS DRIVE - SAN DIEGO CALI*ORNIA - PHONE 88 8- - *AX 88 8- GEOTECHNICAL ENVIRONMENTAL MATERIALS 1" = ........COMPACTED FILL ........UNDOCUMENTED FILL ........PREVIOUSLY PLACED FILL ........ALLUVIUM ....TERRACE DEPOSITS (Dotted Where Buried) ........OTAY FORMATION (Dotted Where Buried) ........OTAY FORMATION (Gritstone) (Dotted Where Buried) ........APPROX. LOCATION OF GEOLOGIC CONTACT (Dotted Where Buried, Queried Where Uncertain) ........APPROX. LOCATION OF EXISTING 8-INCH SOIL-ROCK FILL SUBDRAIN ........APPROX. LOCATION OF EXISTING 6-INCH SOIL-ROCK FILL SUBDRAIN ........APPROX. LOCATION OF PROPOSED 8-INCH CANYON SUBDRAIN ........APPROX. LOCATION OF PROPOSED 6-INCH CANYON SUBDRAIN ........APPROX. LOCATION OF EXISTING 8-INCH SUBDRAIN (Geotechnics, 2005) ........APPROX. ELEVATION OF SUBDRAIN (In Feet, MSL) ........PROPOSED FILL GREATER THAN 5 FEET ........PROPOSED BUTTRESS/FILL SLOPES ........SHALLOW DENSE OTAY FORMATION AND EXPANSIVE SOILS GEOCON LEGEND Qal To ? Qudf Qcf 350 Tog Qpf Qt VILLAGE 8 EAST DMA CALCULATIONS Imp. RF Pervious RF % Imp AREA Fraction of Total Imp Area Pervious Area Summation RF x A (ac.)(ac.)(ac.) BASIN 0.90 0.10 0 2.09 0.1%0.000 2.091 0.21 PARK 0.90 0.10 20 30.43 4.7%6.086 24.344 7.91 SCHOOL 0.90 0.10 80 9.96 4.4%7.972 1.993 7.37 ROAD 0.90 0.10 90 37.75 18.4%33.974 3.775 30.95 MIXED USE 0.90 0.10 85 47.77 22.1%40.601 7.165 37.26 SLOPES/LANDSCAPE 0.90 0.30 0 23.43 4.2%0.000 23.431 7.03 MULTIFAMILY 0.90 0.10 75 109.48 45.5%82.113 27.371 76.64 COMMUNITY PURPOSE 0.90 0.10 85 1.20 0.6%1.024 0.181 0.94 0.90 0.3 85 0.0%0.000 0.000 0.00 262.12 100.0%171.769 90.350 168.31 Weighted C =0.64 Otay Ranch Village 8 East Area DMA 1 9/14/2023 R:\0920\Hyd\TM\SWQMP\Calcs\Appendix B.5 Biofiltration BMP Sizing Worksheets VILLAGE 8 EAST DMA CALCULATIONS Imp. RF Pervious RF % Imp AREA Fraction of Total Imp Area Pervious Area Summation RF x A (ac.)(ac.)(ac.) SINGLE-FAMILY (SF)0.90 0.10 75 0.78 82.6%0.582 0.194 0.54 ROAD 0.90 0.10 90 0.14 17.4%0.126 0.014 0.11 0.92 100.0%0.708 0.208 0.66 Weighted C =0.72 Otay Ranch Village 8 East Area DMA 4A 9/13/2023 R:\0920\Hyd\TM\SWQMP\Calcs\Appendix B.5 Biofiltration BMP Sizing Worksheets Project Location VILLAGE 8 EAST DCV CALCULATION 1 85th percentile 24-hr storm depth from Figure B.1-1 d=0.52 inches 2 Area tributary to BMP (s)A=262.12 acres 3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1)C=0.64 unitless 4 Street trees volume reduction TCV=0.00 cubic-feet 5 Rain barrels volume reduction RCV=0.00 cubic-feet 6 Calculate DCV= (3630 x C x d x A) - TCV - RCV DCV=317,708 cubic-feet 1.5DCV=476,562 cubic-feet 1 85th percentile 24-hr storm depth from Figure B.1-1 d=0.52 inches 2 Area tributary to BMP (s)A=12.83 acres 3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1)C=0.28 unitless 4 Street trees volume reduction TCV=0.00 cubic-feet 5 Rain barrels volume reduction RCV=0.00 cubic-feet 6 Calculate DCV= (3630 x C x d x A) - TCV - RCV DCV=6,737 cubic-feet 1.5DCV=10,106 cubic-feet 1 85th percentile 24-hr storm depth from Figure B.1-1 d=0.52 inches 2 Area tributary to BMP (s)A=3.78 acres 3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1)C=0.76 unitless 4 Street trees volume reduction TCV=0.00 cubic-feet 5 Rain barrels volume reduction RCV=0.00 cubic-feet 6 Calculate DCV= (3630 x C x d x A) - TCV - RCV DCV=5,390 cubic-feet 1 85th percentile 24-hr storm depth from Figure B.1-1 d=0.52 inches 2 Area tributary to BMP (s)A=0.92 acres 3 Area weighted runoff factor (estimate using Appendix B.1.1 and B.2.1)C=0.72 unitless 4 Street trees volume reduction TCV=0.00 cubic-feet 5 Rain barrels volume reduction RCV=0.00 cubic-feet 6 Calculate DCV= (3630 x C x d x A) - TCV - RCV DCV=1,242 cubic-feet DMA 1: Design Capture Volume Worksheet B-2.1 DMA 2: Design Capture Volume Worksheet B-2.1 DMA 3: Design Capture Volume Worksheet B-2.1 DMA 4: Design Capture Volume Worksheet B-2.1 9/13/2023 R:\0920\Hyd\TM\SWQMP\Calcs\Appendix B.5 Biofiltration BMP Sizing Worksheets Project Name BMP ID 1 11417900 sq. ft. 2 0.64 3 0.52 inches 4 317708 cu. ft. 5 0 in/hr. 6 2 7 0 in/hr. 10 7307 cu. ft. Factor of safety Area draining to the BMP Otay Ranch Village 8 East BF-3-1 Sizing Method for Volume Retention Criteria Worksheet B.5-2 Adjusted runoff factor for drainage area (Refer to Appendix B.1 and B.2) 85th percentile 24-hour rainfall depth Design capture volume [Line 1 x Line 2 x (Line 3/12)] Volume Retention Requirement Measured infiltration rate in the DMA Note: When mapped hydrologic soil groups are used enter 0.10 for NRCS Type D soils and for NRCS Type C soils enter 0.30 When in no infiltration condition and the actual measured infiltration rate is unknown enter 0.0 if there are geotechnical and/or groundwater hazards identified in Appendix C or enter 0.05 When Line 8 > 8% = 0.0000013 x Line 83 - 0.000057 x Line 82 + 0.0086 x Line 8 - 0.014 When Line 8 ≤ 8% = 0.023 Target volume retention [Line 9 x Line 4] Reliable infiltration rate, for biofiltration BMP sizing [Line 5 / Line 6] 8 Average annual volume reduction target (Figure B.5-2) 3.5 9 Fraction of DCV to be retained (Figure B.5-3) 0.023 %When Line 7 > 0.01 in/hr. = Minimum (40, 166.9 x Line 7 +6.62) When Line 7 ≤ 0.01 in/hr. = 3.5% Project Name BMP ID 1 sq. ft. 2 3 sq. ft. 4 sq. ft. 5 sq. ft. Identification 1 4 5 6 7 10 sq. ft. 11 sq. ft. 12 13 14 cu. ft. 15 cu. ft. Identification 1 cu. ft. 2 cu. ft. 3 cu. ft. 4 cu. ft. 5 cu. ft. cu. ft. 17 Effective impervious area draining to the BMP [Line 1 x Line 2]7331719 Required area for Evapotranspiration [Line 3 x 0.03]219952 Biofiltration BMP Footprint 1776 Is Line 16 ≥ Line 15?Implement Additional Site Design BMPs 0If (Line 8 >1.5, Line 6, Line 7/1.5] Sum of Landscape area [sum of Line 9 Id’s 1 to 5]0 Provided footprint for evapotranspiration [Line 5 + Line 10]1776 Volume Retention Performance Standard Is Line 11 ≥Line 4?No, Proceed to Line 13 Site Design Type Credit Site Design BMP Fraction of the performance standard met through the BMP footprint and/or landscaping [Line 11/Line 4]0.01 Area draining to the biofiltration BMP 11417900 Adjusted runoff factor for drainage area (Refer to Appendix B.1 and B.2)0.64 Volume Retention for No Infiltration Condition Worksheet B.5-6 Landscape Area (must be identified on DS-3247) 2 3 Landscape area that meet the requirements in SD-B and SD-F Fact Sheet (sq. ft.) Impervious area draining to the landscape area (sq. ft.) 8 Impervious to Pervious Area ratio 0.00 0.00 0.00 7234.206742 Target Volume Retention [Line 10 from Worksheet B.5.2]7307 Volume retention required from other site design BMPs [(1-Line 13) x Line 14] Otay Ranch Village 8 East BF-3-1 0.00 0.00 9 Effective Credit Area 0 0 0 [Line 7/Line 6] 0 16 Sum of volume retention benefits from other site design BMPs (e.g. trees; rain barrels etc.). [sum of Line 16 Credits for Id’s 1 to 5] Provide documentation of how the site design credit is calculated in the PDP SWQMP. 0 The volume retention credits will be provided in Village 8 East Final Engineering SWQMP via other means of retention credits and San Diego BMPs such as disper- sion areas SD-B & SD-F, these will incorporated in the FE SWQMP. BMP footprint was obtained by 20 MWS units 8'x'24'. wetland perimeter=88.80 square feet, 88.80 sf x 20 units = 1,776 square feet. 96 The BMP achieves 92% Average Annual Percent Capture of 1.5DCV @ 36hrs of Drawdown time. 4.96 depth area area (ac)elevation volume (cf) volume (acft) 0.0 90000 0.0000 229.5 0 0.00 0.1 90250 2.0718 229.6 9,012 0.21 0.2 90499 2.0776 229.7 18,050 0.41 0.3 90749 2.0833 229.8 27,112 0.62 0.4 90998 2.0890 229.9 36,200 0.83 0.5 91248 2.0948 230.0 45,312 1.04 0.6 91498 2.1005 230.1 54,449 1.25 0.7 91747 2.1062 230.2 63,612 1.46 0.8 91997 2.1120 230.3 72,799 1.67 0.9 92246 2.1177 230.4 82,011 1.88 1.0 92496 2.1234 230.5 91,248 2.09 1.1 92746 2.1291 230.6 100,510 2.31 1.2 92995 2.1349 230.7 109,797 2.52 1.3 93245 2.1406 230.8 119,109 2.73 1.4 93494 2.1463 230.9 128,446 2.95 1.5 93744 2.1521 231.0 137,808 3.16 1.6 93994 2.1578 231.1 147,195 3.38 1.7 94243 2.1635 231.2 156,607 3.60 1.8 94493 2.1693 231.3 166,044 3.81 1.9 94742 2.1750 231.4 175,505 4.03 2.0 94992 2.1807 231.5 184,992 4.25 2.1 95242 2.1864 231.6 194,504 4.47 2.2 95491 2.1922 231.7 204,040 4.68 2.3 95741 2.1979 231.8 213,602 4.90 2.4 95990 2.2036 231.9 223,188 5.12 2.5 96240 2.2094 232.0 232,800 5.34 2.6 96490 2.2151 232.1 242,436 5.57 2.7 96739 2.2208 232.2 252,098 5.79 2.8 96989 2.2266 232.3 261,784 6.01 2.9 97238 2.2323 232.4 271,496 6.23 3.0 97488 2.2380 232.5 281,232 6.46 3.1 97738 2.2437 232.6 290,993 6.68 3.2 97987 2.2495 232.7 300,780 6.90 3.3 98237 2.2552 232.8 310,591 7.13 3.4 98486 2.2609 232.9 320,427 7.36 3.5 98736 2.2667 233.0 330,288 7.58 3.6 98986 2.2724 233.1 340,174 7.81 Village 8 East Basin #1 Input DCV 317,708 Input Factor 1.5 WQ Ponding Depth ft Note: Find out the elevation value in relation to required WQ volume Basin #1 Stage Storage 3.7 99235 2.2781 233.2 350,085 8.04 3.8 99485 2.2839 233.3 360,021 8.26 3.9 99734 2.2896 233.4 369,982 8.49 4.0 99984 2.2953 233.5 379,968 8.72 4.1 100234 2.3010 233.6 389,979 8.95 4.2 100483 2.3068 233.7 400,015 9.18 4.3 100733 2.3125 233.8 410,076 9.41 4.4 100982 2.3182 233.9 420,161 9.65 4.5 101232 2.3240 234.0 430,272 9.88 4.6 101482 2.3297 234.1 440,408 10.11 4.7 101731 2.3354 234.2 450,568 10.34 4.8 101981 2.3412 234.3 460,754 10.58 4.9 102230 2.3469 234.4 470,964 10.81 4.96 102380 2.3503 234.5 477,103 10.95 5.0 102480 2.3526 234.5 481,200 11.05 5.1 102730 2.3583 234.6 491,460 11.28 5.2 102979 2.3641 234.7 501,746 11.52 5.3 103229 2.3698 234.8 512,056 11.76 5.4 103478 2.3755 234.9 522,392 11.99 5.5 103728 2.3813 235.0 532,752 12.23 5.6 103978 2.3870 235.1 543,137 12.47 5.7 104227 2.3927 235.2 553,548 12.71 5.8 104477 2.3985 235.3 563,983 12.95 5.9 104726 2.4042 235.4 574,443 13.19 6.0 104976 2.4099 235.5 584,928 13.43 1.5 DCV = 476,561 cfs Discharge vs Elevation Table Low orifice:6.00 "Top orifice:4 " Number:7 Number:0 Cg-low:0.61 Cg-low:0.61 invert elev:0.00 ft invert elev:3.95 ft Middle orifice:1 "Emergency inlet: number of orif:0 Rim height:4.96 ft Cg-middle:0.61 Riser Box D 4X3 ft invert elev:2.90 ft Weir Length 10.00 ft h H/D-low H/D-mid H/D-top Qlow-orif Qlow-weir Qtot-low Qmid-orif Qmid-weir Qtot-med Qtop-orif Qtop-weir Qtot-top Qpeak-top Qtot (ft)---(cfs)(cfs)(cfs)(cfs)(cfs)(cfs)(cfs)(cfs)(cfs)(cfs)(cfs) 0.0 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.0000 0.1 0.20 0.00 0.00 0.000 0.164 0.164 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.1643 0.2 0.40 0.00 0.00 0.000 0.624 0.624 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.6238 0.3 0.60 0.00 0.00 1.504 1.327 1.327 0.000 0.000 0.000 0.000 0.000 0.000 0.000 1.3268 0.4 0.80 0.00 0.00 2.606 2.212 2.212 0.000 0.000 0.000 0.000 0.000 0.000 0.000 2.2124 0.5 1.00 0.00 0.00 3.364 3.214 3.214 0.000 0.000 0.000 0.000 0.000 0.000 0.000 3.2141 0.6 1.20 0.00 0.00 3.980 4.264 3.980 0.000 0.000 0.000 0.000 0.000 0.000 0.000 3.9805 0.7 1.40 0.00 0.00 4.513 5.296 4.513 0.000 0.000 0.000 0.000 0.000 0.000 0.000 4.5134 0.8 1.60 0.00 0.00 4.990 6.250 4.990 0.000 0.000 0.000 0.000 0.000 0.000 0.000 4.9898 0.9 1.80 0.00 0.00 5.424 7.077 5.424 0.000 0.000 0.000 0.000 0.000 0.000 0.000 5.4245 1.0 2.00 0.00 0.00 5.827 7.739 5.827 0.000 0.000 0.000 0.000 0.000 0.000 0.000 5.8268 1.1 2.20 0.00 0.00 6.203 8.217 6.203 0.000 0.000 0.000 0.000 0.000 0.000 0.000 6.2031 1.2 2.40 0.00 0.00 6.558 8.514 6.558 0.000 0.000 0.000 0.000 0.000 0.000 0.000 6.5579 1.3 2.60 0.00 0.00 6.894 8.657 6.894 0.000 0.000 0.000 0.000 0.000 0.000 0.000 6.8944 1.4 2.80 0.00 0.00 7.215 8.701 7.215 0.000 0.000 0.000 0.000 0.000 0.000 0.000 7.2152 1.5 3.00 0.00 0.00 7.522 8.735 7.522 0.000 0.000 0.000 0.000 0.000 0.000 0.000 7.5224 1.6 3.20 0.00 0.00 7.817 8.883 7.817 0.000 0.000 0.000 0.000 0.000 0.000 0.000 7.8175 1.7 3.40 0.00 0.00 8.102 9.312 8.102 0.000 0.000 0.000 0.000 0.000 0.000 0.000 8.1019 1.8 3.60 0.00 0.00 8.377 10.229 8.377 0.000 0.000 0.000 0.000 0.000 0.000 0.000 8.3766 1.9 3.80 0.00 0.00 8.643 11.892 8.643 0.000 0.000 0.000 0.000 0.000 0.000 0.000 8.6426 2.0 4.00 0.00 0.00 8.901 14.610 8.901 0.000 0.000 0.000 0.000 0.000 0.000 0.000 8.9006 2.1 4.20 0.00 0.00 9.151 18.746 9.151 0.000 0.000 0.000 0.000 0.000 0.000 0.000 9.1514 2.2 4.40 0.00 0.00 9.395 24.723 9.395 0.000 0.000 0.000 0.000 0.000 0.000 0.000 9.3955 2.3 4.60 0.00 0.00 9.633 33.029 9.633 0.000 0.000 0.000 0.000 0.000 0.000 0.000 9.6334 2.4 4.80 0.00 0.00 9.866 44.215 9.866 0.000 0.000 0.000 0.000 0.000 0.000 0.000 9.8655 2.5 5.00 0.00 0.00 10.092 58.907 10.092 0.000 0.000 0.000 0.000 0.000 0.000 0.000 10.0923 2.6 5.20 0.00 0.00 10.314 77.801 10.314 0.000 0.000 0.000 0.000 0.000 0.000 0.000 10.3142 2.7 5.40 0.00 0.00 10.531 101.675 10.531 0.000 0.000 0.000 0.000 0.000 0.000 0.000 10.5313 2.8 5.60 0.00 0.00 10.744 131.387 10.744 0.000 0.000 0.000 0.000 0.000 0.000 0.000 10.7441 2.9 5.80 0.00 0.00 10.953 167.881 10.953 0.000 0.000 0.000 0.000 0.000 0.000 0.000 10.9528 3.0 6.00 1.20 0.00 11.158 212.192 11.158 0.000 0.000 0.000 0.000 0.000 0.000 0.000 11.1575 3.1 6.20 2.40 0.00 11.359 265.448 11.359 0.000 0.000 0.000 0.000 0.000 0.000 0.000 11.3586 3.2 6.40 3.60 0.00 11.556 328.872 11.556 0.000 0.000 0.000 0.000 0.000 0.000 0.000 11.5561 3.3 6.60 4.80 0.00 11.750 403.792 11.750 0.000 0.000 0.000 0.000 0.000 0.000 0.000 11.7503 3.4 6.80 6.00 0.00 11.941 491.637 11.941 0.000 0.000 0.000 0.000 0.000 0.000 0.000 11.9414 3.5 7.00 7.20 0.00 12.129 593.948 12.129 0.000 0.000 0.000 0.000 0.000 0.000 0.000 12.1295 3.6 7.20 8.40 0.00 12.315 712.377 12.315 0.000 0.000 0.000 0.000 0.000 0.000 0.000 12.3147 3.7 7.40 9.60 0.00 12.497 848.692 12.497 0.000 0.000 0.000 0.000 0.000 0.000 0.000 12.4971 3.8 7.60 10.80 0.00 12.677 1004.781 12.677 0.000 0.000 0.000 0.000 0.000 0.000 0.000 12.6770 3.9 7.80 12.00 0.00 12.854 1182.657 12.854 0.000 0.000 0.000 0.000 0.000 0.000 0.000 12.8543 4.0 8.00 13.20 0.15 13.029 1384.460 13.029 0.000 0.000 0.000 0.000 0.000 0.000 0.000 13.0292 4.1 8.20 14.40 0.45 13.202 1612.462 13.202 0.000 0.000 0.000 0.000 0.000 0.000 0.000 13.2017 4.2 8.40 15.60 0.75 13.372 1869.069 13.372 0.000 0.000 0.000 0.000 0.000 0.000 0.000 13.3721 4.3 8.60 16.80 1.05 13.540 2156.828 13.540 0.000 0.000 0.000 0.000 0.000 0.000 0.000 13.5403 4.4 8.80 18.00 1.35 13.706 2478.428 13.706 0.000 0.000 0.000 0.000 0.000 0.000 0.000 13.7064 4.5 9.00 19.20 1.65 13.871 2836.705 13.871 0.000 0.000 0.000 0.000 0.000 0.000 0.000 13.8706 4.6 9.20 20.40 1.95 14.033 3234.645 14.033 0.000 0.000 0.000 0.000 0.000 0.000 0.000 14.0328 4.7 9.40 21.60 2.25 14.193 3675.388 14.193 0.000 0.000 0.000 0.000 0.000 0.000 0.000 14.1932 4.8 9.60 22.80 2.55 14.352 4162.234 14.352 0.000 0.000 0.000 0.000 0.000 0.000 0.000 14.3518 4.9 9.80 24.00 2.85 14.509 4698.644 14.509 0.000 0.000 0.000 0.000 0.000 0.000 0.000 14.5087 4.96 9.92 24.72 3.03 14.602 5045.782 14.602 0.000 0.000 0.000 0.000 0.000 0.000 0.000 14.6020 5.0 10.00 25.20 3.15 14.664 5288.244 14.664 0.000 0.000 0.000 0.000 0.000 0.000 0.266 14.9302 5.1 10.20 26.40 3.45 14.817 5934.830 14.817 0.000 0.000 0.000 0.000 0.000 0.000 1.744 16.5617 5.2 10.40 27.60 3.75 14.969 6642.372 14.969 0.000 0.000 0.000 0.000 0.000 0.000 3.915 18.8846 5.3 10.60 28.80 4.05 15.120 7415.016 15.120 0.000 0.000 0.000 0.000 0.000 0.000 6.602 21.7216 5.4 10.80 30.00 4.35 15.269 8257.091 15.269 0.000 0.000 0.000 0.000 0.000 0.000 9.719 24.9878 5.5 11.00 31.20 4.65 15.416 9173.108 15.416 0.000 0.000 0.000 0.000 0.000 0.000 13.214 28.6303 5.6 11.20 32.40 4.95 15.562 10167.770 15.562 0.000 0.000 0.000 0.000 0.000 0.000 17.050 32.6120 5.7 11.40 33.60 5.25 15.707 11245.969 15.707 0.000 0.000 0.000 0.000 0.000 0.000 21.198 36.9051 5.8 11.60 34.80 5.55 15.851 12412.795 15.851 0.000 0.000 0.000 0.000 0.000 0.000 25.637 41.4874 5.9 11.80 36.00 5.85 15.993 13673.538 15.993 0.000 0.000 0.000 0.000 0.000 0.000 30.348 46.3412 6.0 12.00 37.20 6.15 16.134 15033.692 16.134 0.000 0.000 0.000 0.000 0.000 0.000 35.318 51.4516 Basin 1 Discharge Riser 36 Elevation QAVG (CFS)DV (CF)DT (HR)Total T 0.00 0.16 9012.48 15.24 36 0.10 0.62 9037.44 4.02 21 0.20 1.33 9062.40 1.90 17 0.30 2.21 9087.36 1.14 15 0.40 3.21 9112.32 0.79 14 0.50 3.98 9137.28 0.64 13 0.60 4.51 9062.40 0.56 13 0.70 4.99 9187.20 0.51 12 0.80 5.42 9212.16 0.47 11 0.90 5.83 9062.40 0.43 11 1.00 6.20 9262.08 0.41 11 1.10 6.56 9287.04 0.39 10 1.20 6.89 9137.28 0.37 10 1.30 7.22 9336.96 0.36 9 1.40 7.52 9361.92 0.35 9 1.50 7.82 9386.88 0.33 9 1.60 8.10 9411.84 0.32 8 1.70 8.38 9436.80 0.31 8 1.80 8.64 9461.76 0.30 8 1.90 8.90 9486.72 0.30 7 2.00 9.15 9062.40 0.28 7 2.10 9.40 9511.68 0.28 7 2.20 9.63 9561.60 0.28 7 2.30 9.87 9586.56 0.27 6 2.40 10.09 19198.08 0.53 6 2.50 10.31 9287.04 0.25 6 2.60 10.53 9661.44 0.25 5 2.70 10.74 9336.96 0.24 5 2.80 10.95 9711.36 0.25 5 2.90 11.16 9736.32 0.24 5 3.00 11.36 9761.28 0.24 4 3.10 11.56 9786.24 0.24 4 3.20 11.75 9811.20 0.23 4 3.30 11.94 9836.16 0.23 4 3.40 12.13 9861.12 0.23 3 3.50 12.31 9886.08 0.22 3 3.60 12.50 9911.04 0.22 3 3.70 12.68 9936.00 0.22 3 3.80 12.85 9960.96 0.22 2 3.90 13.03 9985.92 0.21 2 4.00 13.20 10010.88 0.21 2 4.10 13.37 10035.84 0.21 2 4.20 13.54 10060.80 0.21 2 4.30 13.71 10085.76 0.20 1 4.40 13.87 10110.72 0.20 1 4.50 14.03 10135.68 0.20 1 4.60 14.19 10160.64 0.20 1 4.70 14.35 10185.60 0.20 1 4.80 14.51 10210.56 0.20 0 4.90 14.60 5114.64 0.10 0 4.96 14.93 5120.88 0.10 0 WQ Drawdown @ Project Name BMP ID Sizing Method for Pollutant Removal Criteria 1 558682 sq. ft. 2 0.28 3 0.52 inches 4 6737 cu. ft. 5 6 inches 6 18 inches 7 15 inches 8 0 inches 9 0.2 in/in 10 0.4 in/in 11 5 in/hr. 12 6 hours 13 30 inches 15 45.6 inches 16 10106 cu. ft. 17 2659 sq. ft. 18 5053 cu. ft. 19 3887 sq. ft. 20 0.03 21 4664 sq. ft. 22 4664 sq. ft. 23 6000 sq. ft. 24 Is Line 23 ≥ Line 22? Adjusted runoff factor for drainage area (Refer to Appendix B.1 and B.2) 85th percentile 24-hour rainfall depth Design capture volume [Line 1 x Line 2 x (Line 3/12)] Porosity of aggregate storage Media filtration rate to be used for sizing (maximum filtration rate of 5 in/hr. with no outlet control; if the filtration rate is controlled by the outlet use the outlet controlled rate (includes infiltration into the soil and flow rate through the outlet structure) which will be less than 5 in/hr.) Depth filtered during storm [ Line 11 x Line 12] Media thickness [18 inches minimum], also add mulch layer and washed ASTM 33 fine aggregate sand thickness to this line for sizing calculations Aggregate storage (also add ASTM No 8 stone) above underdrain invert (12 inches typical) – use 0 inches if the aggregate is not over the entire bottom surface area Aggregate storage below underdrain invert (3 inches minimum) – use 0 inches if the aggregate is not over the entire bottom surface area Freely drained pore storage of the media Required biofiltered volume [1.5 x Line 4] Option 2 - Store 0.75 of remaining DCV in pores and ponding Required Storage (surface + pores) Volume [0.75 x Line 4] Depth of Detention Storage [Line 5 + (Line 6 x Line 9) + (Line 7 x Line 10) + (Line 8 x Line 10)] Total Depth Treated [Line 13 + Line 14] Minimum BMP Footprint [Line 1 x Line 2 x Line 20] Footprint of the BMP = Maximum(Minimum(Line 17, Line 19), Line 21) Footprint of the BMP BMP Footprint Sizing Factor (Default 0.03 or an alternative minimum footprint sizing factor from Line 11 in Worksheet B.5-4) Required Footprint [Line 16/ Line 15] x 12 Yes, Performance Standard is Met BF-2-2 Basin 2 (Biofiltration) Otay Ranch Village 8 East Provided BMP Footprint Worksheet B.5-1 Area draining to the BMP BMP Parameters Surface ponding [6 inch minimum, 12 inch maximum] Baseline Calculations Allowable routing time for sizing 14 15.6 inches Option 1 – Biofilter 1.5 times the DCV Required Footprint [Line 18/ Line 14] x 12 Appendix B: Storm Water Pollutant Control Hydrologic Calculations and Sizing Methods Worksheet B.5-1: Sizing Method for Pollutant Removal Criteria Sizing Method for Pollutant Removal Criteria Worksheet B.5-1 1 Area draining to the BMP 7,056,720 sq. ft. 2 Adjusted runoff factor for drainage area (Refer to Appendix B.1 and B.2) 0.60 3 85th percentile 24-hour rainfall depth 0.55 inches 4 Design capture volume [Line 1 x Line 2 x (Line 3/12)] 193,908 cu. ft. BMP Parameter 5 Surface ponding [6 inch minimum, 12 inch maximum] 12 inches 6 Media thickness [18 inches minimum], also add mulch layer and washed ASTM 33 fine aggregate sand thickness to this line for sizing calculations 18 inches 7 Aggregate storage (also add ASTM No 8 stone) above underdrain invert(12 inches typical) – use 0 inches if the aggregate is not over the entire bottom 24 inches 8 Aggregate storage below underdrain invert (3 inches minimum) – use 0 inches if the aggregate is not over the entire bottom surface area inches 9 Freely drained pore storage of the media 0.2 in/in 10 Porosity of aggregate storage 0.4 in/in 11 Media filtration rate to be used for sizing (maximum filtration rate of 5in/hr. with no outlet control; if the filtration rate is controlled by the outlet use the outlet- controlled rate (includes infiltration into the soil and flow rate through the outlet structure) which will be less than 5 in/hr.) 5 in/hr. Baseline Calculations 12 Allowable routing time for sizing 6 hours 13 Depth filtered during storm [ Line 11 x Line 12]30 inches 14 Depth of Detention Storage [Line 5 + (Line 6 x Line 9) + (Line 7 x Line 10) + (Line 8 x Line 10)] 25.2 inches 15 Total Depth Treated [Line 13 + Line 14]55.2 inches Option 1 – Biofilter 1.5 times the DCV 16 Required biofiltered volume [1.5 x Line 4] 290,862 cu. ft. 17 Required Footprint [Line 16/ Line 15] x 12 63,231 sq. ft. Option 2 - Store 0.75 of remaining DCV in pores and ponding 18 Required Storage (surface + pores) Volume [0.75 x Line 4] 145,431 cu. ft. 19 Required Footprint [Line 18/ Line 14] x 12 69,253 sq. ft. Footprint of the BMP 20 BMP Footprint Sizing Factor (Default 0.03 or an alternative minimum footprint sizing factor from Line 11 in Worksheet B.5-4).012 21 Minimum BMP Footprint [Line 1 x Line 2 x Line 20] 50,769 sq. ft. 22 Footprint of the BMP = Maximum (Minimum (Line 17, Line 19), Line 21) 63,231 sq. ft. 23 Provided BMP Footprint 63,743 sq. ft. 24 Is Line 23 = Line 22? If Yes, then footprint criterion is met. If No, increase the footprint of the BMP. YES BMP Design Manual-Appendices March 2019 Update B-38 SOUTH BASIN Project Name BMP ID Sizing Method for Pollutant Removal Criteria 1 55567 sq. ft. 2 0.60 3 0.55 inches 4 1528 cu. ft. 5 12 inches 6 18 inches 7 24 inches 8 0 inches 9 0.2 in/in 10 0.4 in/in 11 5 in/hr. 12 6 hours 13 30 inches 15 55.2 inches 16 2292 cu. ft. 17 498 sq. ft. 18 1146 cu. ft. 19 546 sq. ft. 20 0.12 21 4001 sq. ft. 22 4001 sq. ft. 23 12,974 sq. ft. 24 Is Line 23 ≥ Line 22?Yes, Performance Standard is Met Required Footprint [Line 18/ Line 14] x 12 Footprint of the BMP BMP Footprint Sizing Factor (Default 0.03 or an alternative minimum footprint sizing factor from Line 11 in Worksheet B.5-4) Minimum BMP Footprint [Line 1 x Line 2 x Line 20] Footprint of the BMP = Maximum(Minimum(Line 17, Line 19), Line 21) Provided BMP Footprint Total Depth Treated [Line 13 + Line 14] Option 1 – Biofilter 1.5 times the DCV Required biofiltered volume [1.5 x Line 4] Required Footprint [Line 16/ Line 15] x 12 Option 2 - Store 0.75 of remaining DCV in pores and ponding Required Storage (surface + pores) Volume [0.75 x Line 4] Depth filtered during storm [ Line 11 x Line 12] 14 Depth of Detention Storage 25.2 inches[Line 5 + (Line 6 x Line 9) + (Line 7 x Line 10) + (Line 8 x Line 10)] Aggregate storage below underdrain invert (3 inches minimum) – use 0 inches if the aggregate is not over the entire bottom surface area Freely drained pore storage of the media Porosity of aggregate storage Media filtration rate to be used for sizing (maximum filtration rate of 5 in/hr. with no outlet control; if the filtration rate is controlled by the outlet use the outlet controlled rate (includes infiltration into the soil and flow rate through the outlet structure) which will be less than 5 in/hr.) Baseline Calculations Allowable routing time for sizing 85th percentile 24-hour rainfall depth Design capture volume [Line 1 x Line 2 x (Line 3/12)] BMP Parameters Surface ponding [6 inch minimum, 12 inch maximum] Media thickness [18 inches minimum], also add mulch layer and washed ASTM 33 fine aggregate sand thickness to this line for sizing calculations Aggregate storage (also add ASTM No 8 stone) above underdrain invert (12 inches typical) – use 0 inches if the aggregate is not over the entire bottom surface area Otay Ranch Village 8 West South Basin on Village 8 West SWQMP Worksheet B.5-1 Area draining to the BMP Adjusted runoff factor for drainage area (Refer to Appendix B.1 and B.2) As shown on the previous sheet the excess BMP Footprint for South Basin in Village 8 West Tract No. 19-03 per SWQMP Report equates to 12,974 sf. This calculation is to reaffirm that the DCV of the proposed Park 2A in Village 8 East can be captured in the aforementioned basin. As shown on this worksheet the minimum BMP foot - print that is required is far less (12,974 sf - 4001 sf) than the provided additional square footage in the basin. Project Name BMP ID 1 164590 sq. ft. 2 0.76 3 0.52 inches 4 5390 cu. ft. 5 0 in/hr. 6 2 7 0 in/hr. 10 124 cu. ft. 9 Fraction of DCV to be retained (Figure B.5-3) 0.023 When Line 8 > 8% = 0.0000013 x Line 83 - 0.000057 x Line 82 + 0.0086 x Line 8 - 0.014 When Line 8 ≤ 8% = 0.023 Target volume retention [Line 9 x Line 4] Reliable infiltration rate, for biofiltration BMP sizing [Line 5 / Line 6] 8 Average annual volume reduction target (Figure B.5-2) 3.5 %When Line 7 > 0.01 in/hr. = Minimum (40, 166.9 x Line 7 +6.62) When Line 7 ≤ 0.01 in/hr. = 3.5% Adjusted runoff factor for drainage area (Refer to Appendix B.1 and B.2) 85th percentile 24-hour rainfall depth Design capture volume [Line 1 x Line 2 x (Line 3/12)] Volume Retention Requirement Measured infiltration rate in the DMA Note: When mapped hydrologic soil groups are used enter 0.10 for NRCS Type D soils and for NRCS Type C soils enter 0.30 When in no infiltration condition and the actual measured infiltration rate is unknown enter 0.0 if there are geotechnical and/or groundwater hazards identified in Appendix C or enter 0.05 Factor of safety Otay Ranch Village 8 East BF-3-3 Sizing Method for Volume Retention Criteria Worksheet B.5-2 Area draining to the BMP Project Name BMP ID 1 sq. ft. 2 3 sq. ft. 4 sq. ft. 5 sq. ft. Identification 1 4 5 6 7 10 sq. ft. 11 sq. ft. 12 13 14 cu. ft. 15 cu. ft. Identification 1 cu. ft. 2 cu. ft. 3 cu. ft. 4 cu. ft. 5 cu. ft. cu. ft. 17 Sum of volume retention benefits from other site design BMPs (e.g. trees; rain barrels etc.). [sum of Line 16 Credits for Id’s 1 to 5] Provide documentation of how the site design credit is calculated in the PDP SWQMP. 0 Is Line 16 ≥ Line 15?Implement Additional Site Design BMPs Volume retention required from other site design BMPs [(1-Line 13) x Line 14]116.5345212 Site Design BMP Site Design Type Credit 16 Is Line 11 ≥Line 4?No, Proceed to Line 13 Fraction of the performance standard met through the BMP footprint and/or landscaping [Line 11/Line 4]0.06 Target Volume Retention [Line 10 from Worksheet B.5.2]124 If (Line 8 >1.5, Line 6, Line 7/1.5] Sum of Landscape area [sum of Line 9 Id’s 1 to 5]0 Provided footprint for evapotranspiration [Line 5 + Line 10]224 Volume Retention Performance Standard 0.00 0.00[Line 7/Line 6] 9 Effective Credit Area 0 0 0 0 0 Impervious area draining to the landscape area (sq. ft.) 8 Impervious to Pervious Area ratio 0.00 0.00 0.00 Biofiltration BMP Footprint 224 Landscape Area (must be identified on DS-3247) 2 3 Landscape area that meet the requirements in SD-B and SD-F Fact Sheet (sq. ft.) Adjusted runoff factor for drainage area (Refer to Appendix B.1 and B.2)0.76 Effective impervious area draining to the BMP [Line 1 x Line 2]124388 Required area for Evapotranspiration [Line 3 x 0.03]3732 Otay Ranch Village 8 East BF-3-3 Volume Retention for No Infiltration Condition Worksheet B.5-6 Area draining to the biofiltration BMP 164590 Flow-Based Proprietary Biofiltration Sizing Description Units Filterra Drainage Basin ID or Name unitless DMA 3 Location N/A - Total Tributary Area ac 3.778 Total Tributary Area sq ft 164590 Final Adjusted Runoff Factor unitless 0.76 85th Percentile Design Rainfall Depth inches 0.52 Design Capture Volume cubic-feet 5,390 85th Percentile Design Rainfall Intensity in/hr 0.2 WQ Flow Rate CFS 0.571 Flow Rate Safety Factor unitless 1.5 Design Flow Rate CFS 0.857 Final Design Flow Rate CFS 0.857 2-Filterra 14'x8' (112ft^2) Units unitless UNIT ID Filterra Treatment Flow Rate (each)CFS 0.454 Number of Units #2 Filterra Treatment Flow Rate (Total)CFS 0.907 Is The BMP Adequately Sized?unitless Yes OTAY RANCH VILLAGE 8 EAST Filterra Infiltration Rate = 175 (in/hr) Filterra Flow per Square Foot = 0.00405 (ft3/sec/ft2) Filterra Flow Rate, Q = 0.00405 ft3/sec x Filterra Surface Area Rational Method, Q = C x I x A San Diego Multiplier, M = 1.5 Site Flowrate, Q = (C x DI x DA x M x 43560) / (12 x3600) OR DA = (12 x 3600 x Q) / (C x 43560 x DI x M) where Q = Flow (ft3/sec) DA = Drainage Area (acres) DI = Design Intensity (in/hr) C =Runoff coefficient (dimensionless) M = Multiplier (dimensionless) DI C C C 0.2 0.95 0.85 0.50 Filterra 100%Commercial Residential L W Filterra Surface Area Flow Rate, Q Imperv. DA max DA max DA (ft) (ft) (ft2) (ft3/sec) (acres) (acres) (acres) 4 4 16 0.0648 0.226 0.252 0.429 6 4 24 0.0972 0.338 0.378 0.643 6.5 4 26 0.1053 0.367 0.410 0.696 8 4 32 0.1296 0.451 0.504 0.857 12 4 48 0.1944 0.677 0.756 1.286 6 6 36 0.1458 0.507 0.567 0.964 8 6 48 0.1944 0.677 0.756 1.286 10 6 60 0.2431 0.846 0.945 1.607 12 6 72 0.2917 1.015 1.134 1.928 13 7 91 0.3686 1.283 1.434 2.437 12 8 96 0.3889 1.353 1.512 2.571 14 8 112 0.4537 1.579 1.765 3.000 16 8 128 0.5185 1.804 2.017 3.428 18 8 144 0.5833 2.030 2.269 3.857 20 8 160 0.6481 2.255 2.521 4.285 22 8 176 0.7130 2.481 2.773 4.714 Available Filterra Box Sizes Filterra Sizing Spreadsheet Uniform Intensity Approach Storm Intensity = 0.20 in/hr San Diego Region 9/20/2019 䕡捨 ⁆楬瑥牲愠畮楴 Project Name BMP ID 1 39901 sq. ft. 2 0.72 3 0.52 inches 4 1242 cu. ft. 5 0 in/hr. 6 2 7 0 in/hr. 10 29 cu. ft. 9 Fraction of DCV to be retained (Figure B.5-3) 0.023 When Line 8 > 8% = 0.0000013 x Line 83 - 0.000057 x Line 82 + 0.0086 x Line 8 - 0.014 When Line 8 ≤ 8% = 0.023 Target volume retention [Line 9 x Line 4] Reliable infiltration rate, for biofiltration BMP sizing [Line 5 / Line 6] 8 Average annual volume reduction target (Figure B.5-2) 3.5 %When Line 7 > 0.01 in/hr. = Minimum (40, 166.9 x Line 7 +6.62) When Line 7 ≤ 0.01 in/hr. = 3.5% Adjusted runoff factor for drainage area (Refer to Appendix B.1 and B.2) 85th percentile 24-hour rainfall depth Design capture volume [Line 1 x Line 2 x (Line 3/12)] Volume Retention Requirement Measured infiltration rate in the DMA Note: When mapped hydrologic soil groups are used enter 0.10 for NRCS Type D soils and for NRCS Type C soils enter 0.30 When in no infiltration condition and the actual measured infiltration rate is unknown enter 0.0 if there are geotechnical and/or groundwater hazards identified in Appendix C or enter 0.05 Factor of safety Otay Ranch Village 8 East BF-3-4 Sizing Method for Volume Retention Criteria Worksheet B.5-2 Area draining to the BMP Project Name BMP ID 1 sq. ft. 2 3 sq. ft. 4 sq. ft. 5 sq. ft. Identification 1 4 5 6 7 10 sq. ft. 11 sq. ft. 12 13 14 cu. ft. 15 cu. ft. Identification 1 cu. ft. 2 cu. ft. 3 cu. ft. 4 cu. ft. 5 cu. ft. cu. ft. 17 Sum of volume retention benefits from other site design BMPs (e.g. trees; rain barrels etc.). [sum of Line 16 Credits for Id’s 1 to 5] Provide documentation of how the site design credit is calculated in the PDP SWQMP. 0 Is Line 16 ≥ Line 15?Implement Additional Site Design BMPs Volume retention required from other site design BMPs [(1-Line 13) x Line 14]28.5669384 Site Design BMP Site Design Type Credit 16 Is Line 11 ≥Line 4?No, Proceed to Line 13 Fraction of the performance standard met through the BMP footprint and/or landscaping [Line 11/Line 4]0 Target Volume Retention [Line 10 from Worksheet B.5.2]29 If (Line 8 >1.5, Line 6, Line 7/1.5] Sum of Landscape area [sum of Line 9 Id’s 1 to 5]0 Provided footprint for evapotranspiration [Line 5 + Line 10]0 Volume Retention Performance Standard 0.00 0.00[Line 7/Line 6] 9 Effective Credit Area 0 0 0 0 0 Impervious area draining to the landscape area (sq. ft.) 8 Impervious to Pervious Area ratio 0.00 0.00 0.00 Biofiltration BMP Footprint Landscape Area (must be identified on DS-3247) 2 3 Landscape area that meet the requirements in SD-B and SD-F Fact Sheet (sq. ft.) Adjusted runoff factor for drainage area (Refer to Appendix B.1 and B.2)0.72 Effective impervious area draining to the BMP [Line 1 x Line 2]28662 Required area for Evapotranspiration [Line 3 x 0.03]860 Otay Ranch Village 8 East BF-3-4 Volume Retention for No Infiltration Condition Worksheet B.5-6 Area draining to the biofiltration BMP 39901 PROPRIETARY BIOFILTRATION FLOW-THRU SIZING CALCULATION 1 DCV DCV 1,242 cubic-feet 2 DCV Retained DCV Retained 0.00 cubic-feet 3 DCV Biofiltered DCV Biofiltered 0.00 cubic-feet 4 1.5 DCV requiring flow-thru (Line 1 - Line 2 - 0.67*Line 3)DCV flow-thru 1,242 cubic-feet 5 Adjustment Factor (Line 4 / Line1)AF=1.00 unitless 6 Design rainfall intensity i=0.2 in/hr 1 Design rainfall intensity i=0.2 in/hr 7 Area tributary to BMP(s)A=0.92 acres 7 Area tributary to BMP(s)A=1.12 acres 8 Area-weighted runoff factor (estimate using Appendix B.2)C= 0.72 unitless 8 Area-weighted runoff factor (estimate using Appendix B.2) C= 0.9 unitless 9 Calculate Flow Rate = AF x (C x i x A) Q= 0.132 cfs 10 Treamtent Flow Rate = 1.5 X Q Q= 0.3024 cfs 10 Treamtent Flow Rate = 1.5 X Q Q= 0.197 cfs 1) 2) 3) DMA 4B: Flow-thru Design Flows Worksheet B.6-1 DMA 4A: Flow-thru Design Flows Worksheet B.6-1 Adjustment factor shall be estimated considering only retention and biofiltration BMPs located upstream of flow-thru BMPs. That is, if the flow-thru BMP is upstream of the project's retention and biofiltration BMPs then the flow-thru BMP shall be sized using an adjustment factor of 1. Volume based (e.g., dry extended detention basin) flow-thru treatment control BMPs shall be sized to the volume in Line 4 and dlow based )e.g., vegetated swales) shall be sized to flow rate in Line 9. Sand filter and media filter can be designed by either volume in :ie 4 or Propietary BMPs, if used, shall provide certified treatment capacity equal to or greater than the calculated flow rate in Line 9; certified treatment capacity per unit shall be consistent with third party certifications. 9/13/2023 R:\0920\Hyd\TM\SWQMP\Calcs\Appendix B.5 Biofiltration BMP Sizing Worksheets Agriculture 0.10 0.10 0.45 1.00 1.00 1.00 1.00 0.59 1.00 0% Agriculture 0 0 % 0% Agriculture 0 0 Commercial 0.80 0.80 0.13 0.16 0.16 0.56 0.48 1.00 0.87 0% Commercial 0 0 % 0% Commercial 0 0 Education 0.50 0.50 0.13 0.20 0.11 0.14 0.25 0.39 0.13 0% Education 0 0 % 0% Education 0 0 Industrial 0.90 0.90 0.13 0.19 0.15 0.54 0.68 0.89 0.49 0% Industrial 0 0 % 0% Industrial 0 0 Multi Family Residential 0.60 0.60 0.10 0.13 0.13 0.14 0.15 0.29 0.27 0% Multi Family Residential 0 0 %0% Multi Family Residential0 0 Orchard 0.10 0.10 0.18 0.17 0.67 1.00 1.00 0.59 0.11 0% Orchard 0 0 % 0% Orchard 0 0 Rural Residential 0.30 0.30 1.00 0.51 0.14 0.10 0.71 0.13 0.19 0% Rural Residential 0 0 % 0% Rural Residential 0 0 Single Family Residential 0.78 0.40 0.40 0.13 0.20 0.15 0.27 0.43 0.35 0.63 71% Single Family Residential0.312 71 %0% Single Family Residential0 0 Transportation 0.14 0.90 1.12 0.90 0.11 0.26 0.12 0.53 0.31 0.62 0.12 29% Transportation 0.126 29 % 100% Transportation 1.008 100 Vacant / Open Space 0.10 0.10 0.16 0.10 0.10 0.12 0.10 0.10 0.10 0% Vacant / Open Space 0 0 %0% Vacant / Open Space 0 0 Water 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0% Water 0 0 % 0% Water 0 0 Total 0.92 -1.12 --------0.438 1.008 0.12 0.22 0.14 0.34 0.40 0.43 0.48 0.11 0.26 0.12 0.53 0.31 0.62 0.12 1.13 -1.18 0.65 --4.03 Notes: Example: An ACP Tributary with 5.25 acres of Commercial, 1.63 Acres of Education, and 2.65 acres of Transportation land uses produces a relative pollutant concentration 0.12 for Total Suspended Solids (assumes default runoff factors are applied). Equation 2-2:Equation 2-2 Applied to Example: Hydrologic Unit Otay (910.00) Land Use Factor 5 * Applicants must provide user input for yellow shaded cells. Values for all other cells will be automatically generated. 1. Revisions to default runoff factors must be supported to the satisfaction of the applicable Copermittee. 2. Applicant-Implemented ACPs must identify reference tributary characteristics that are representative of their specific PDP. Independent ACPs must reference Table 2-3 for appropriate area and runoff factor information applicable to their watershed management area. 3. Relative Pollutant Concentrations by Land Use have been identified through examination of available EMC data. Additional information on how these relative concentrations were developed is provided in Appendix B. FC ACP Ref Relative Pollutant Concentration for ACP Tributary 4 Relative Pollutant Concentration for Reference Tributary 4 Watershed Management Area San Diego Bay TSS TP TN TCu TPb TZn Automated Spreadsheet Calculation for Worksheet A.5: Land Use Factor Determination (Version 1.0)Effective area composition graphics are for illustrative purposes only. Land Use Designation ACP Tributary Characteristics Reference Tributary Characteristics 2 Relative Pollutant Concentrations by Land Use 3 Area (Acres) Runoff Factor 1 Area (Acres) Runoff Factor 1 Effective Area Composition - ACP Tributary 0% Agriculture 0% Commercial 0% Education 0% Industrial 0% Multi Family Residential 0% Orchard 0% Rural Residential 71% Single Family Residential 29% Transportation 0% Vacant / Open Space 0% Water Effective Area Composition - Reference Tributary 0% Agriculture 0% Commercial 0% Education 0% Industrial 0% Multi Family Residential 0% Orchard 0% Rural Residential 0% Single Family Residential 100% Transportation 0% Vacant / Open Space 0% Water For BF-3-4 Required flow to be treated = 0.197 cfs August 2021 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS) ENHANCED AND PHOSPHORUS TREATMENT For MWS-Linear Modular Wetland Ecology’s Decision Based on Modular Wetland Systems, Inc, application submissions, including the Technical Evaluation Report, dated April 1, 2014, Ecology hereby issues the following use level designation: 1. General Use Level Designation (GULD) for the MWS-Linear Modular Wetland Stormwater Treatment System for Basic, Phosphorus, and Enhanced treatment  Sized at a hydraulic loading rate of:  1 gallon per minute (gpm) per square foot (sq ft) of Wetland Cell Surface Area  Prefilter box (approved at either 22 inches or 33 inches tall)  3.0 gpm/sq ft of prefilter box surface area for moderate pollutant loading rates (low to medium density residential basins).  2.1 gpm/sq ft of prefilter box surface area for high pollutant loading rates (commercial and industrial basins). 2. Ecology approves the MWS – Linear Modular Wetland Stormwater Treatment System units for Basic, Phosphorus, and Enhanced treatment at the hydraulic loading rate listed above. Designers shall calculate the water quality design flow rates using the following procedures:  Western Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute water quality treatment design flow rate as calculated using the latest version of the Western Washington Hydrology Model or other Ecology- approved continuous runoff model.  Eastern Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute water quality treatment design flow rate as calculated using one of the three methods described in Chapter 2.2.5 of the Stormwater Management Manual for Eastern Washington (SWMMEW) or local manual.  Entire State: For treatment installed downstream of detention, the water quality treatment design flow rate is the full 2-year release rate of the detention facility. 3. These use level designations have no expiration date but may be amended or revoked by Ecology, and are subject to the conditions specified below. Ecology’s Conditions of Use Applicants shall comply with the following conditions: 1) Design, assemble, install, operate, and maintain the MWS – Linear Modular Wetland Stormwater Treatment System units, in accordance with Modular Wetland Systems, Inc. applicable manuals and documents and the Ecology Decision. 2) Each site plan must undergo Modular Wetland Systems, Inc. review and approval before site installation. This ensures that site grading and slope are appropriate for use of a MWS – Linear Modular Wetland Stormwater Treatment System unit. 3) MSW – Linear Modular Wetland Stormwater Treatment System media shall conform to the specifications submitted to and approved by Ecology. 4) The applicant tested the MWS – Linear Modular Wetland Stormwater Treatment System with an external bypass weir. This weir limited the depth of water flowing through the media, and therefore the active treatment area, to below the root zone of the plants. This GULD applies to MWS – Linear Modular Wetland Stormwater Treatment Systems whether plants are included in the final product or not. 5) Maintenance: The required maintenance interval for stormwater treatment devices is often dependent upon the degree of pollutant loading from a particular drainage basin. Therefore, Ecology does not endorse or recommend a “one size fits all” maintenance cycle for a particular model/size of stormwater treatment technology.  Typically, Modular Wetland Systems, Inc. designs MWS – Linear Modular Wetland systems for a target prefilter media life of 6 to 12 months.  Indications of the need for maintenance include effluent flow decreasing to below the design flow rate or decrease in treatment below required levels.  Owners/operators must inspect MWS – Linear Modular Wetland systems for a minimum of twelve months from the start of post-construction operation to determine site-specific maintenance schedules and requirements. You must conduct inspections monthly during the wet season, and every other month during the dry season (According to the SWMMWW, the wet season in western Washington is October 1 to April 30. According to the SWMMEW, the wet season in eastern Washington is October 1 to June 30). After the first year of operation, owners/operators must conduct inspections based on the findings during the first year of inspections.  Conduct inspections by qualified personnel, follow manufacturer’s guidelines, and use methods capable fo determining either a decrease in treated effluent flowrate and/or a decrease in pollutant removal ability.  When inspections are performed, the following findings typically serve as maintenance triggers:  Standing water remains in the vault between rain events, or  Bypass occurs during storms smaller than the design storm.  If excessive floatables (trash and debris) are present (but no standing water or excessive sedimentation), perform a minor maintenance consisting of gross solids removal, not prefilter media replacement.  Additional data collection will be used to create a correlation between pretreatment chamber sediment depth and pre-filter clogging (see Issues to be Addressed by the Company section below) 6) Discharges from the MWS – Linear Modular Wetland Stormwater Treatment System units shall not cause or contribute to water quality standards violations in receiving waters. Applicant: Modular Wetland Systems, Inc. Applicant’s Address: 5796 Armada Drive, Suite 250 Carlsbad, CA 92008 Application Documents: Original Application for Conditional Use Level Designation, Modular Wetland System, Linear Stormwater Filtration System Modular Wetland Systems, Inc., January 2011 Quality Assurance Project Plan: Modular Wetland System – Linear Treatment System Performance Monitoring Project, draft, January 2011 Revised Application for Conditional Use Level Designation, Modular Wetland System, Linear Stormwater Filtration System Modular Wetland Systems, Inc., May 2011 Memorandum: Modular Wetland System-Linear GULD Application Supplementary Data, April 2014 Technical Evaluation Report: Modular Wetland System Stormwater Treatment System Performance Monitoring, April 2014 Applicant’s Use Level Request:  General Use Level Designation as a Basic, Enhanced, and Phosphorus treatment device in accordance with Ecology’s Guidance for Evaluating Emerging Stormwater Treatment Technologies Technology Assessment Protocol – Ecology (TAPE) January 2011 Revision. Applicant’s Performance Claims:  The MWS – Linear Modular wetland is capable of removing a minimum of 80-percent of TSS from stormwater with influent concentrations between 100 and 200 mg/L.  The MWS – Linear Modular wetland is capable of removing a minimum of 50-percent of total phosphorus from stormwater with influent concentrations between 0.1 and 0.5 mg/L.  The MWS – Linear Modular wetland is capable of removing a minimum 30-percent of dissolved copper from stormwater with influent concentrations between 0.005 and 0.020 mg/L.  The MWS – Linear Modular wetland is capable of removing a minimum 60-percent of dissolved zinc from stormwater with influent concentrations between 0.02 and 0.30 mg/L. Ecology’s Recommendations:  Modular Wetland System, Inc. has shown Ecology, through laboratory and field- testing, that the MWS – Linear Modular Wetland Stormwater Treatment System filter system is capable of attaining Ecology’s Basic, Phosphorus, and Enhanced treatment goals. Findings of Fact: Laboratory Testing The MWS-Linear Modular wetland has the:  Capability to remove 99 percent of total suspended solids (using Sil-Co-Sil 106) in a quarter-scale model with influent concentrations of 270 mg/L.  Capability to remove 91 percent of total suspended solids (using Sil-Co-Sil 106) in laboratory conditions with influent concentrations of 84.6 mg/L at a flow rate of 3.0 gpm per square foot of media.  Capability to remove 93 percent of dissolved Copper in a quarter-scale model with influent concentrations of 0.757 mg/L.  Capability to remove 79 percent of dissolved Copper in laboratory conditions with influent concentrations of 0.567 mg/L at a flow rate of 3.0 gpm per square foot of media.  Capability to remove 80.5-percent of dissolved Zinc in a quarter-scale model with influent concentrations of 0.95 mg/L at a flow rate of 3.0 gpm per square foot of media.  Capability to remove 78-percent of dissolved Zinc in laboratory conditions with influent concentrations of 0.75 mg/L at a flow rate of 3.0 gpm per square foot of media. Field Testing  Modular Wetland Systems, Inc. conducted monitoring of an MWS-Linear (Model # MWS-L-4-13) from April 2012 through May 2013, at a transportation maintenance facility in Portland, Oregon. The manufacturer collected flow-weighted composite samples of the system’s influent and effluent during 28 separate storm events. The system treated approximately 75 percent of the runoff from 53.5 inches of rainfall during the monitoring period. The applicant sized the system at 1 gpm/sq ft. (wetland media) and 3gpm/sq ft. (prefilter).  Influent TSS concentrations for qualifying sampled storm events ranged from 20 to 339 mg/L. Average TSS removal for influent concentrations greater than 100 mg/L (n=7) averaged 85 percent. For influent concentrations in the range of 20-100 mg/L (n=18), the upper 95 percent confidence interval about the mean effluent concentration was 12.8 mg/L.  Total phosphorus removal for 17 events with influent TP concentrations in the range of 0.1 to 0.5 mg/L averaged 65 percent. A bootstrap estimate of the lower 95 percent confidence limit (LCL95) of the mean total phosphorus reduction was 58 percent.  The lower 95 percent confidence limit of the mean percent removal was 60.5 percent for dissolved zinc for influent concentrations in the range of 0.02 to 0.3 mg/L (n=11). The lower 95 percent confidence limit of the mean percent removal was 32.5 percent for dissolved copper for influent concentrations in the range of 0.005 to 0.02 mg/L (n=14) at flow rates up to 28 gpm (design flow rate 41 gpm). Laboratory test data augmented the data set, showing dissolved copper removal at the design flow rate of 41 gpm (93 percent reduction in influent dissolved copper of 0.757 mg/L). Issues to be addressed by the Company: 1. Modular Wetland Systems, Inc. should collect maintenance and inspection data for the first year on all installations in the Northwest in order to assess standard maintenance requirements for various land uses in the region. Modular Wetland Systems, Inc. should use these data to establish required maintenance cycles. 2. Modular Wetland Systems, Inc. should collect pre-treatment chamber sediment depth data for the first year of operation for all installations in the Northwest. Modular Wetland Systems, Inc. will use these data to create a correlation between sediment depth and pre-filter clogging. Technology Description: Download at http://www.modularwetlands.com/ Contact Information: Applicant: Zach Kent BioClean A Forterra Company 5796 Armada Drive, Suite 250 Carlsbad, CA 92008 zach.kent@forterrabp.com Applicant website: http://www.modularwetlands.com/ Ecology web link: http://www.ecy.wa.gov/programs/wg/stormwater/newtech/index.html Ecology: Douglas C. Howie, P.E. Department of Ecology Water Quality Program (360) 870-0983 douglas.howie@ecy.wa.gov Revision History Date Revision June 2011 Original use-level-designation document September 2012 Revised dates for TER and expiration January 2013 Modified Design Storm Description, added Revision Table, added maintenance discussion, modified format in accordance with Ecology standard December 2013 Updated name of Applicant April 2014 Approved GULD designation for Basic, Phosphorus, and Enhanced treatment December 2015 Updated GULD to document the acceptance of MWS – Linear Modular Wetland installations with or without the inclusion of plants July 2017 Revised Manufacturer Contact Information (name, address, and email) December 2019 Revised Manufacturer Contact Address July 2021 Added additional prefilter sized at 33 inches August 2021 Changed “Prefilter” to “Prefilter box” 1 September 2019 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS), ENHANCED, PHOSPHORUS & OIL TREATMENT For CONTECH Engineered Solutions Filterra® Ecology’s Decision: Based on Contech’s submissions, including the Final Technical Evaluation Reports, dated August 2019, March 2014, December 2009, and additional information provided to Ecology dated October 9, 2009, Ecology hereby issues the following use level designations: 1. A General Use Level Designation for Basic, Enhanced, Phosphorus, and Oil Treatment for the Filterra® system constructed with a minimum media thickness of 21 inches (1.75 feet), at the following water quality design hydraulic loading rates: Treatment Infiltration Rate (in/hr) for use in Sizing Basic 175 Phosphorus 100 Oil 50 Enhanced 175 2. The Filterra is not appropriate for oil spill-control purposes. 3. Ecology approves Filterra systems for treatment at the hydraulic loading rates listed above, to achieve the maximum water quality design flow rate. Calculate the water quality design flow rates using the following procedures:  Western Washington: for treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using the latest version of the Western Washington Hydrology Model or other Ecology-approved continuous runoff model.  Eastern Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using one of the three flow rate based methods described in Chapter 2.2.5 of the Stormwater Management Manual for Eastern Washington (SWMMEW) or local manual.  Entire State: For treatment installed downstream of detention, the water quality design flow rate is the full 2-year release rate of the detention facility. 2 4. This General Use Level Designation has no expiration date, but Ecology may revoke or amend the designation, and is subject to the conditions specified below. Ecology’s Conditions of Use: Filterra systems shall comply with these conditions shall comply with the following conditions: 1. Design, assemble, install, operate, and maintain the Filterra systems in accordance with applicable Contech Filterra manuals and this Ecology Decision. 2. The minimum size filter surface-area for use in Washington is determined by using the design water quality flow rate (as determined in this Ecology Decision, Item 3, above) and the Infiltration Rate from the table above (use the lowest applicable Infiltration Rate depending on the level of treatment required). Calculate the required area by dividing the water quality design flow rate (cu-ft/sec) by the Infiltration Rate (converted to ft/sec) to obtain required surface area (sq-ft) of the Filterra unit. 3. Each site plan must undergo Contech Filterra review before Ecology can approve the unit for site installation. This will ensure that design parameters including site grading and slope are appropriate for use of a Filterra unit. 4. Filterra media shall conform to the specifications submitted to and approved by Ecology and shall be sourced from Contech Engineered Solutions, LLC with no substitutions. 5. Maintenance includes removing trash, degraded mulch, and accumulated debris from the filter surface and replacing the mulch layer. Use inspections to determine the site-specific maintenance schedules and requirements. Follow maintenance procedures given in the most recent version of the Filterra Operation and Maintenance Manual. 6. Maintenance: The required maintenance interval for stormwater treatment devices is often dependent upon the degree of pollutant loading from a particular drainage basin. Therefore, Ecology does not endorse or recommend a “one size fits all” maintenance cycle for a particular model/size of manufactured treatment device.  Contech designs Filterra systems for a target maintenance interval of 6 months in the Pacific Northwest. Maintenance includes removing and replacing the mulch layer above the media along with accumulated sediment, trash, and captured organic materials therein, evaluating plant health, and pruning the plant if deemed necessary.  Conduct maintenance following manufacturer’s guidelines. 7. Filterra systems come in standard sizes. 8. Install the Filterra in such a manner that flows exceeding the maximum Filterra operating rate are conveyed around the Filterra mulch and media and will not resuspend captured sediment. 9. Discharges from the Filterra units shall not cause or contribute to water quality standards violations in receiving waters. 3 Approved Alternate Configurations Filterra Internal Bypass - Pipe (FTIB-P) 1. The Filterra® Internal Bypass – Pipe allows for piped-in flow from area drains, grated inlets, trench drains, and/or roof drains. Design capture flows and peak flows enter the structure through an internal slotted pipe. Filterra® inverted the slotted pipe to allow design flows to drop through to a series of splash plates that then disperse the design flows over the top surface of the Filterra® planter area. Higher flows continue to bypass the slotted pipe and convey out the structure. 2. To select a FTIB-P unit, the designer must determine the size of the standard unit using the sizing guidance described above. Filterra Internal Bypass – Curb (FTIB-C) 1. The Filterra® Internal Bypass –Curb model (FTIB-C) incorporates a curb inlet, biofiltration treatment chamber, and internal high flow bypass in one single structure. Filterra® designed the FTIB-C model for use in a “Sag” or “Sump” condition and will accept flows from both directions along a gutter line. An internal flume tray weir component directs treatment flows entering the unit through the curb inlet to the biofiltration treatment chamber. Flows in excess of the water quality treatment flow rise above the flume tray weir and discharge through a standpipe orifice; providing bypass of untreated peak flows. Americast manufactures the FTIB-C model in a variety of sizes and configurations and you may use the unit on a continuous grade when a single structure providing both treatment and high flow bypass is preferred. The FTIB-C model can also incorporate a separate junction box chamber to allow larger diameter discharge pipe connections to the structure. 2. To select a FTIB-C unit, the designer must determine the size of the standard unit using the sizing guidance described above. Filterra® Shallow 1. The Filterra Shallow provides additional flexibility for design engineers and designers in situations where various elevation constraints prevent application of a standard Filterra configuration. Engineers can design this system up to six inches shallower than any of the previous Filterra unit configurations noted above. 2. Ecology requires that the Filterra Shallow provide a media contact time equivalent to that of the standard unit. This means that with a smaller depth of media, the surface area must increase. 3. To select a Filterra Shallow System unit, the designer must first identify the size of the standard unit using the modeling guidance described above. 4. Once the size of the standard Filterra unit is established using the sizing technique described above, use information from the following table to select the appropriate size Filterra Shallow System unit. 4 Shallow Unit Basic, Enhanced, and Oil Treatment Sizing Standard Depth Equivalent Shallow Depth 4x4 4x6 or 6x4 4x6 or 6x4 6x6 4x8 or 8x4 6x8 or 8x6 6x6 6x10 or 10x6 6x8 or 8x6 6x12 or 12x6 6x10 or 10x6 13x7 Notes: 1. Shallow Depth Boxes are less than the standard depth of 3.5 feet but no less than 3.0 feet deep (TC to INV). Applicant: Contech Engineered Solutions, LLC. Applicant’s Address: 11815 NE Glenn Widing Drive Portland, OR 97220 Application Documents:  State of Washington Department of Ecology Application for Conditional Use Designation, Americast (September 2006)  Quality Assurance Project Plan Filterra® Bioretention Filtration System Performance Monitoring, Americast (April 2008)  Quality Assurance Project Plan Addendum Filterra® Bioretention Filtration System Performance Monitoring, Americast (June 2008)  Draft Technical Evaluation Report Filterra® Bioretention Filtration System Performance Monitoring, Americast (August 2009)  Final Technical Evaluation Report Filterra® Bioretention Filtration System Performance Monitoring, Americast (December 2009)  Technical Evaluation Report Appendices Filterra® Bioretention Filtration System Performance Monitoring, Americast, (August 2009)  Memorandum to Department of Ecology Dated October 9, 2009 from Americast, Inc. and Herrera Environmental Consultants  Quality Assurance Project Plan Filterra® Bioretention System Phosphorus treatment and Supplemental Basic and Enhanced Treatment Performance Monitoring, Americast (November 2011)  Filterra® letter August 24, 2012 regarding sizing for the Filterra® Shallow System.  University of Virginia Engineering Department Memo by Joanna Crowe Curran, Ph. D dated March 16, 2013 concerning capacity analysis of Filterra® internal weir inlet tray.  Terraphase Engineering letter to Jodi Mills, P.E. dated April 2, 2013 regarding Terraflume Hydraulic Test, Filterra® Bioretention System and attachments.  Technical Evaluation Report, Filterra® System Phosphorus Treatment and Supplemental Basic Treatment Performance Monitoring. March 27th, 2014.  State of Washington Department of Ecology Application for Conditional Use Level Designation, Contech Engineered Solutions (May 2015) 5  Quality Assurance Project Plan Filterra® Bioretention System, Contech Engineered Solutions (May 2015)  Filterra Bioretention System Armco Avenue General Use Level Designation Technical Evaluation Report, Contech Engineered Solutions (August 2019) Applicant’s Use Level Request: General Level Use Designation for Basic (175 in/hr), Enhanced (175 in/hr), Phosphorus (100 in/hr), and Oil Treatment (50 in/hr). Applicant’s Performance Claims: Field-testing and laboratory testing show that the Filterra® unit is promising as a stormwater treatment best management practice and can meet Ecology’s performance goals for basic, enhanced, phosphorus, and oil treatment. Findings of Fact: Field Testing 2015-2019 1. Contech completed field testing of a 4 ft. x 4 ft. Filterra® unit at one site in Hillsboro, Oregon from September 2015 to July 2019. Throughout the monitoring period a total of 24 individual storm events were sampled, of which 23 qualified for TAPE sampling criteria. 2. Contech encountered several unanticipated events and challenges that prevented them from collecting continuous flow and rainfall data. An analysis of the flow data from the sampled events, including both the qualifying and non-qualifying events, demonstrated the system treated over 99 % of the influent flows. Peak flows during these events ranged from 25 % to 250 % of the design flow rate of 29 gallons per minute. 3. Of the 23 TAPE qualified sample events, 13 met requirements for TSS analysis. Influent concentrations ranged from 20.8 mg/L to 83 mg/L, with a mean concentration of 46.3 mg/L. The UCL95 mean effluent concentration was 15.9 mg/L, meeting the 20 mg/L performance goal for Basic Treatment. 4. All 23 TAPE qualified sample events met requirements for dissolved zinc analysis. Influent concentrations range from 0.0384 mg/L to 0.2680 mg/L, with a mean concentration of 0.0807 mg/L. The LCL 95 mean percent removal was 62.9 %, meeting the 60 % performance goal for Enhanced Treatment. 5. Thirteen of the 23 TAPE qualified sample events met requirements for dissolved copper analysis. Influent concentrations ranged from 0.00543 mg/L to 0.01660 mg/L, with a mean concentration of 0.0103 mg/L. The LCL 95 mean percent removal was 41.2 %, meeting the 30 % performance goal for Enhanced Treatment. 6. Total zinc concentrations were analyzed for all 24 sample events. Influent EMCs for total zinc ranged from 0.048 mg/L to 5.290 mg/L with a median of 0.162 mg/L. Corresponding effluent EMCs for total zinc ranged from 0.015 mg/L to 0.067 mg/L with a median of 6 0.029 mg/L. Total event loadings for the study for total zinc were 316.85 g at the influent and 12.92 g at the effluent sampling location, resulting in a summation of loads removal efficiency of 95.9 %. 7. Total copper concentrations were analyzed for all 24 sample events. Influent EMCs for total copper ranged from 0.003 mg/L to 35.600 mg/L with a median value of 0.043 mg/L. Corresponding effluent EMCs for total copper ranged from 0.002 mg/L to 0.015 mg/L with a median of 0.004 mg/L. Total event loadings for total copper for the study were 1,810.06 g at the influent and 1.90 g at the effluent sampling location, resulting in a summation of loads removal efficiency of 99.9 %. Field Testing 2013 1. Filterra completed field-testing of a 6.5 ft x 4 ft. unit at one site in Bellingham, Washington. Continuous flow and rainfall data collected from January 1, 2013 through July 23, 2013 indicated that 59 storm events occurred. Water quality data was obtained from 22 storm events. Not all the sampled storms produced information that met TAPE criteria for storm and/or water quality data. 2. The system treated 98.9 % of the total 8-month runoff volume during the testing period. Consequently, the system achieved the goal of treating 91 % of the volume from the site. Stormwater runoff bypassed Filterra treatment during four of the 59 storm events. 3. Of the 22 sampled events, 18 qualified for TSS analysis (influent TSS concentrations ranged from 25 to 138 mg/L). The data were segregated into sample pairs with influent concentration greater than and less than 100 mg/L. The UCL95 mean effluent concentration for the data with influent less than 100 mg/L was 5.2 mg/L, below the 20- mg/L threshold. Although the TAPE guidelines do not require an evaluation of TSS removal efficiency for influent concentrations below 100 mg/L, the mean TSS removal for these samples was 90.1 %. Average removal of influent TSS concentrations greater than 100 mg/L (three events) was 85 %. In addition, the system consistently exhibited TSS removal greater than 80 % at flow rates equivalent to a 100 in/hr infiltration rate and was observed at 150 in/hr. 4. Ten of the 22 sampled events qualified for TP analysis. Americast augmented the dataset using two sample pairs from previous monitoring at the site. Influent TP concentrations ranged from 0.11 to 0.52 mg/L. The mean TP removal for these twelve events was 72.6 %. The LCL95 mean percent removal was 66.0, well above the TAPE requirement of 50 %. Treatment above 50 % was evident at 100 in/hr infiltration rate and as high as 150 in/hr. Consequently, the Filterra test system met the TAPE Phosphorus Treatment goal at 100 in/hr. Influent ortho-P concentrations ranged from 0.005 to 0.012 mg/L; effluent ortho-P concentrations ranged from 0.005 to 0.013 mg/L. The reporting limit/resolution for the ortho-P test method is 0.01 mg/L, therefore the influent and effluent ortho-P concentrations were both at and near non-detect concentrations. 7 Field Testing 2008-2009 1. Filterra completed field-testing at two sites at the Port of Tacoma. Continuous flow and rainfall data collected during the 2008-2009 monitoring period indicated that 89 storm events occurred. The monitoring obtained water quality data from 27 storm events. Not all the sampled storms produced information that met TAPE criteria for storm and/or water quality data. 2. During the testing at the Port of Tacoma, 98.96 to 99.89 % of the annual influent runoff volume passed through the POT1 and POT2 test systems respectively. Stormwater runoff bypassed the POT1 test system during nine storm events and bypassed the POT2 test system during one storm event. Bypass volumes ranged from 0.13 % to 15.3% of the influent storm volume. Both test systems achieved the 91 % water quality treatment-goal over the 1-year monitoring period. 3. Consultants observed infiltration rates as high as 133 in/hr during the various storms. Filterra did not provide any paired data that identified percent removal of TSS, metals, oil, or phosphorus at an instantaneous observed flow rate. 4. The maximum storm average hydraulic loading rate associated with water quality data is <40 in/hr, with the majority of flow rates < 25 in/hr. The average instantaneous hydraulic loading rate ranged from 8.6 to 53 in/hr. 5. The field data showed a removal rate greater than 80 % for TSS with an influent concentration greater than 20 mg/L at an average instantaneous hydraulic loading rate up to 53 in/hr (average influent concentration of 28.8 mg/L, average effluent concentration of 4.3 mg/L). 6. The field data showed a removal rate generally greater than 54 % for dissolved zinc at an average instantaneous hydraulic loading rate up to 60 in/hr and an average influent concentration of 0.266 mg/L (average effluent concentration of 0.115 mg/L). 7. The field data showed a removal rate generally greater than 40 % for dissolved copper at an average instantaneous hydraulic loading rate up to 35 in/hr and an average influent concentration of 0.0070 mg/L (average effluent concentration of 0.0036 mg/L). 8. The field data showed an average removal rate of 93 % for total petroleum hydrocarbon (TPH) at an average instantaneous hydraulic loading rate up to 53 in/hr and an average influent concentration of 52 mg/L (average effluent concentration of 2.3 mg/L). The data also shows achievement of less than 15 mg/L TPH for grab samples. Filterra provided limited visible sheen data due to access limitations at the outlet monitoring location. 9. The field data showed low percentage removals of total phosphorus at all storm flows at an average influent concentration of 0.189 mg/L (average effluent concentration of 0.171 mg/L). We may relate the relatively poor treatment performance of the Filterra system at this location to influent characteristics for total phosphorus that are unique to the Port of Tacoma site. It appears that the Filterra system will not meet the 50 % removal performance goal when the majority of phosphorus in the runoff is expected to be in the dissolved form. 8 Laboratory Testing 1. Filterra performed laboratory testing on a scaled down version of the Filterra unit. The lab data showed an average removal from 83-91 % for TSS with influents ranging from 21 to 320 mg/L, 82-84 % for total copper with influents ranging from 0.94 to 2.3 mg/L, and 50-61 % for orthophosphate with influents ranging from 2.46 to 14.37 mg/L. 2. Filterra conducted permeability tests on the soil media. 3. Lab scale testing using Sil-Co-Sil 106 showed removals ranging from 70.1 % to 95.5 % with a median removal of 90.7 %, for influent concentrations ranging from 8.3 to 260 mg/L. Filterra ran these laboratory tests at an infiltration rate of 50 in/hr. 4. Supplemental lab testing conducted in September 2009 using Sil-Co-Sil 106 showed an average removal of 90.6 %. These laboratory tests were run at infiltration rates ranging from 25 to 150 in/hr for influent concentrations ranging from 41.6 to 252.5 mg/L. Regression analysis results indicate that the Filterra system’s TSS removal performance is independent of influent concentration in the concentration rage evaluated at hydraulic loading rates of up to 150 in/hr. Contact Information: Applicant: Jeremiah Lehman Contech Engineered Solutions, LLC. 11815 Glenn Widing Dr Portland, OR 97220 (503) 258-3136 jlehman@conteches.com Applicant’s Website: http://www.conteches.com Ecology web link: http://www.ecy.wa.gov/programs/wq/stormwater/newtech/index.html Ecology: Douglas C. Howie, P.E. Department of Ecology Water Quality Program (360) 407-6444 douglas.howie@ecy.wa.gov Date Revision December 2009 GULD for Basic, Enhanced, and Oil granted, CULD for Phosphorus September 2011 Extended CULD for Phosphorus Treatment September 2012 Revised design storm discussion, added Shallow System. January 2013 Revised format to match Ecology standards, changed Filterra contact information February 2013 Added FTIB-P system March 2013 Added FTIB-C system April 2013 Modified requirements for identifying appropriate size of unit 9 June 2013 Modified description of FTIB-C alternate configuration March 2014 GULD awarded for Phosphorus Treatment. GULD updated for a higher flow-rate for Basic Treatment. June 2014 Revised sizing calculation methods March 2015 Revised Contact Information June 2015 CULD for Basic and Enhanced at 100 in/hr infiltration rate September 2019 GULD for Basic and Enhanced at 175 in/hr infiltration rate Otay Ranch Village 8 East NOT APPLICABLE Otay Ranch, Village 8 East Otay Ranch Village 8 East NOT APPLICABLE Village 3, R-6 & R-20 Maintenance agreement to be provided in Final Engineering Stage INSPECTION FREQUENCY MAINTENANCE FREQUENCY MAINTENANCE ACTION MONTHLY AS-NEEDED RE-SEED, RE-PLANT OR RE- ESTABLISH POOR VEGETATION. REMOVE DEAD OR DISEASED VEGETATION. MAKE APPROPRIATE CORRECTIVE MASURES TO SOLVE STANDING WATER IN VEGETATED PERVIOUS AREA FOR LONGER THAN 24 HRS AND PRESENCE OF MOSQUITOS. WEEKLY ANNUAL DETERMINE REAPPLICATION REQUIREMENTS OF AMENDED SOIL. ANNUAL BI-ANNUAL REPAINT AS NECESSARY BI-ANNUAL 6-12 MONTHS AS NEEDED REMOVE TRASH FROM SCREENING DEVICE. ANNUAL 12-24 MONTHS REMOVE SEDIMENT FROM SEPARATION CHAMBER. REPLACEMENT OF MEDIA IN THE PRE- FILTER CARTRIDGE. REPLACEMENT OF DRAIN DOWN FILTER MEDIA. QUARTERLY 6-12 MONTHS AS NEEDED REMOVE DEBRIS AS NEEDED, AND CHECK ORIFICES DESCRIPTION:IMPERVIOUS AREA DISPERSION SITE DESIGN, SOURCE CONTROL AND POLLUTANT CONTROL BMP OPERATION + MAINTENANCE PROCEDURE STORM WATER MANAGEMENT AND DISCHARGE CONTROL MAINTENANCE AGREEMENT APPROVAL NO.: O&M RESPONSIBLE PARTY DESIGNEE: PROPERTY OWNER: HomeFed Village II Master, LLC BMP DESCRIPTION SITE DESIGN ELEMENTS DESCRIPTION:DETENTION BASIN WITH ORIFICES FOR WATER QUALITY DISCHARGE RATE CONTROL DESCRIPTION: AMENDED SOIL POLLUTANT CONTROL BMP(S) SOURCE CONTROL ELEMENTS DESCRIPTION: STORM DRAIN STENCILING DESCRIPTION:PROPRIETARY BIOFILTRATION UNIT, MODULAR WETLAND SYSTEMS, BIO CLEAN KRAKEN MEDIA FILTERS, BIO CLEAN DVERT SYSTEM Otay Ranch Village 8 East Otay Ranch Village 8 East Otay Ranch Village 8 East DRAINAGE REPORT TO BE PROVIDED SEPARATELY Otay Ranch Village 8 East GEOTECHNICAL REPORT TO BE PROVIDED SEPARATELY