Como Park Stormwater Inventory and Watershed Analysis

Transcription

1 Como Park Stormwater Inventory and Watershed Analysis Capitol Region Watershed District Saint Paul, MN (March, 2016)

2 Como Park Stormwater Inventory and Watershed Analysis BY CAPITOL REGION WATERSHED DISTRICT Project conducted in partnership with: City of Saint Paul Report prepared by: Houston Engineering Inc. Saint Paul, Minnesota March, 2016

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4 TABLE OF CONTENTS Table of Contents Introduction and Purpose... 2 Como Regional Park Background... 2 Como Lake Watershed Description... 2 Project Purpose... 4 Stormwater Inventory and Watershed Assessment Description Stormwater Inventory Data Sources St. Paul Public Works Department St. Paul Parks and Recreation Department Capitol Region Watershed District Ramsey County Public Works... 6 Data Summary Storm Sewer Conveyance Stormwater Treatment BMPs Previous Water Quality Modeling Files Data Catalog Watershed Assessment Model Inputs Precipitation and Temperature Treatment BMPs Watershed Characteristics Water Quality Particle Parameters and Components Model Calibration and Validation Results Annual Average Results Treatment of the 1.1-inch Storm Event Appendix COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 1

5 1 INTRODUCTION AND PURPOSE COMO REGIONAL PARK BACKGROUND Como Regional Park was first secured and developed by the City of Saint Paul beginning in The park is a total of 450 acres (378 acres land and 72 acres in Como Lake), and currently has a range of facilities including a golf course, park and picnic facilities, a sports complex, and a zoo and conservatory garden complex known as the Como Campus. The approximate boundary of the park is shown on Figure 1. Como is also part of various other citywide facilities such as the Grand Round system, and Saint Paul s system of parkways. As a regional park it attracts visitors from across the metropolitan area, and is one of the highest attended parks in the Twin Cities. COMO LAKE WATERSHED DESCRIPTION The 1,773 acre Como Lake watershed, shown on Figure 1, consists of 1,123, 420, and 230 acres within the cities of St. Paul (which includes Como Lake), Roseville and Falcon Heights respectively. The land use within the watershed is a combination of primarily open space/parkland, single family residential, and commercial. Como Park itself is largely maintained open space and wooded areas along with developed features including roads, parking lots, trails, memorials, the zoo, the pool, and associated buildings. Como Lake is the predominant water resource feature. Other smaller water bodies are located within the watershed several of which are in the Como Golf Course. The watershed contributing to Como Lake mostly drains to the lake through the storm sewer system. Como Lake overflows to the Mississippi River through the Trout Brook storm sewer, which is owned by the Capitol Region Watershed District (CRWD). Runoff from most impervious surface in the Park is collected in an underground storm sewer system that ultimately drains easterly to Como Lake. What does not drain through storm sewer is located adjacent to the Como Lake. Como Lake also receives stormwater via the street sewer systems from its densely populated, mostly single family residential watershed. A significant number of permanent stormwater treatment best management practices are in place many of which have been installed through CRWD s capital projects, permit and cost-share programs. The areas within the watershed mapped in the SSURGO soils database as primarily classified as hydrologic soil group B having moderately high infiltration potential. Much of the area is mapped as urban/unknown in the SSURGO database but is known to have good infiltration potential from CRWD s past stormwater management projects. COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 2

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7 PROJECT PURPOSE The CRWD as an organization is intent on improving and protecting the water resources of the district, including Como Lake. CRWD has initiated this stormwater inventory and subwatershed assessment project to ultimately develop a stormwater management plan collaboratively with St. Paul Parks and Recreation (SPPR) for improved efficiency in design and implementation of improvements, increased coordination and more effectively achieve improved water quality within Como Park. Several other planning efforts and analysis have occurred in the watershed. CRWD s Como Lake Strategic Management Plan (CLSP), completed in 2002, provides significant analysis of the water quality conditions and issues, and provides projection of a plan to address the findings. The Como Lake TMDL study was a conversion of the CLSP completed by CRWD in 2010, and identifies lake water impairment, sources, TMDL allocations, and monitoring and implementation strategy recommendations. The Saint Paul Comprehensive Plan and Parks and Recreation Plan, adopted in 2008, includes strategies to: 1) Promote Active Lifestyles; 2) Create Vibrant Places; 3) Promote a Vital Environment; 4) Respond Creatively to Change; 5) Innovate in Every Decision; and 6) Connect the Entire City. Strategy #3 includes actions to: Utilize stormwater as a sustainable resource Help protect water quality throughout Saint Paul Approach Parks and Recreations environmental responsibilities comprehensively rather than on a project-by- project basis. Como Regional Park is a major location where all of these strategies are involved in development and operation decisions. The City and CRWD share goals of intentional management of stormwater as a resource, and protection of the water resources within Como Park. The two agencies are working together to develop a comprehensive stormwater management plan for the park. Such a plan will improve efficiency for design and implementation of stormwater improvements within the park, coordinate interdepartmental efforts such as maintenance and operation of stormwater facilities, and more effectively achieve the mutual goal of improved water quality in Como Lake. STORMWATER INVENTORY AND WATERSHED ASSESSMENT DESCRIPTION The initial phase to develop the Como Park comprehensive stormwater management plan is to inventory existing stormwater features in both the Park and in the Lake s watershed. The inventory helps to understand the source of pollutants reaching Como Lake, the location and amount of existing treatment and will help to prioritize future projects. During the inventory process, the majority of effort is in reviewing and interpreting plans of storm sewers to identify movement of stormwater runoff and the location and characteristics of existing treatment BMPs. Once the inventory process is complete, an assessment of watershed loads and treatment of existing treatment BMPs using a water quality model was performed to calculate the following: 1. Calculate annual stormwater volume and pollutant loads entering the park 2. Calculate annual stormwater volume and pollutant loads generated within the park COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 4

8 3. Analyze and quantify benefit of existing treatment facilities 4. Determine current annual stormwater discharge to Como Lake 2 STORMWATER INVENTORY The initial task of this project was to review all available data on stormwater conveyance and treatment features in the watershed. Data was provided from multiples sources including CRWD, SPPW, SPPR and Ramsey County Public Works. Additionally, a limited amount fieldwork was completed to verify several items not found within the available data. The following paragraphs summarize the data received from each source. 2.1 DATA SOURCES ST. PAUL PUBLIC WORKS DEPARTMENT Storm sewer data was obtained from the SPPW GIS database and Public Works Portal. It is understood that the city GIS data is accurate and current with some isolated data gaps or outdated segments, and the SPPW Portal contains sewer data prior to 2006 in the form of.tiff files. The GIS database includes layers of storm sewer mainlines, manholes, catch basins, fittings, and outfall points. Storm sewer infrastructure not owned or operated by SPPW is not included in the GIS data but is shown in site drawings within the SPPW Portal. HEI was given access to the SPPW Portal to review permits and as-built plans that document additional (non-sppw owned) storm sewer within the Park. The SPPW Portal is comprised of information for both sanitary and storm sewers. Within the portal, strip maps show collector sewer alignments along with references to permit numbers. The sewer permits themselves were obtained from the Sewer Utility Data Service in the SPPW Portal. The permits contain sketches of proposed storm sewers, as well as the permit document. A GIS shapefile of permit locations augmented the review and inventory process. Strip maps, permit files, and as-builts were cataloged by region and are indexed in the excel file titled Como Park Stormsewer Files. See Figure A-1 for the file structure ST. PAUL PARKS AND RECREATION DEPARTMENT The SPPR provided various files throughout the stormwater inventory process. The files primarily consisted of scanned site drawings, hand-drawn sketches of storm sewer alignments, and construction or as-built plan sets as PDF files. The files are listed in Table A CAPITOL REGION WATERSHED DISTRICT CRWD provided access to their BMP database which contained information for permanent treatment BMPs across their capital project, grant and permit programs. For most BMP records in the database, sufficient detail was available for simulating in the water quality model. The details were available in various documents such as construction plans or sketches, hydrologic models, design reports or related documents. Table A-2 lists the BMPs found in the database. COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 5

9 2.1.4 RAMSEY COUNTY PUBLIC WORKS During the review of data from the previously mentioned sources, a few specific items were requested from Ramsey County Public Works. They primarily were details regarding the ponds within the eastern portion of the golf course. DATA SUMMARY STORM SEWER CONVEYANCE Existing storm sewer in the Park manages runoff from site improvements within the Park and also conveys stormwater collected from outside the Park. The majority of the storm sewer in the watershed was built in the 1970 s and 1980 s, with remaining storm sewer built in subsequent years during Park improvements or road reconstructions. Storm sewer discharges to Como Lake or the ponds on the eastern end of the golf course (which is then pumped via lift stations into Como Lake). The known storm sewer lines are shown in Figure A-2. The prominent storm sewer feature is the 60-inch collector that runs from west to east through Como Golf Course. The sewer conveys all of the collected stormwater from the northwest portion of the watershed and discharges into Como Lake. It also collects water from Lexington Parkway and Nausbaumer Drive within the Park. Formerly, much of the runoff collected in the sewer was conveyed through a concrete open channel, which is now abandoned. The sewer was originally constructed to replace the open channel in 1929, and lined in A distinctive stormwater practice within the Park is at Como Zoo. In the outdoor animal exhibits the runoff is managed by the sanitary sewer system, not the storm sewer system. This is a partial assumption based on plans found for several animal exhibits but not all. This results in a complex sewer system segregating runoff into underground storm or sanitary systems. The stormwater within the zoo drains northwest into a city storm sewer that flows into the 60-inch collector. The conservatory drains into what is called the lily pond or frog pond (southeast of the conservatory). Lily pond outlets into a catch basin and storm sewer system on Estabrook Drive and discharges in the wooded area to the south. COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 6

10 2.2.2 STORMWATER TREATMENT BMPS There are 55 stormwater treatment BMPs in the Como Lake watershed included in the model. Of these, 27 are within the Park and 28 are located in the watershed but outside of the Park. Table 1 categorizes all BMPs within the Como Lake watershed by BMP type and location relative to the Park. Table 1: BMPs within the Como Lake Watershed Categorized by Type and Location Outside Como Within Como BMP Type Regional Park Regional Park Total Bioretention Hydrodynamic Device 2 2 Permeable Hardscape 1 1 Pond Underground Device Total Of the 55 modeled BMPs, data for 36 of them were obtained from the CRWD via the MS4Front BMP database. Three BMPs were identified and measured in the field, as no documentation was attained in data collection process. These three BMPs are: a small bioretention basin in the Como Town amusement park, a raingarden east of Como Lake for parking near Lakeview Ave W, and a bioretention basin north of Como Lake at the corner of Lexington Pkwy N and Nebraska Ave W. Data from three other BMPs were obtained through the existing P8 model: are Gottfrieds Pit (also Como 8), the Lily Pond (aka Frog Pond), and the southern golf course pond (named Como_LL). Table 2 categorizes all BMPs within the Como Lake watershed by BMP type and the source where the data was retrieved. Figures 2 and A-2 identifies the locations of each BMP. BMP Type Table 2: BMPs within the Como Lake Watershed Categorized by Type and Ownership CRWD Ramsey County SPPR SPPW SPPS* Private Total Bioretention Hydrodynamic Device 2 2 Permeable Hardscape 1 1 Pond Underground Total * St. Paul Public Schools A total of four BMPs were classified as being in the Como Lake watershed in the CRWD BMP database but were determined to drain out of the watershed. Two of these are underground infiltration BMPs from the Front-Victoria RSVP project located on Chatsworth Street North. The other two are bioretention BMPs from the Arlington Pascal Stormwater Improvement Project located at the intersection of Asbury Street and Frankson Avenue. These four BMPs are not included in the BMP totals listed. The two Arlington Pascal Stormwater Improvement Project BMPs are included in the model, however, the two Front-Victoria RSVP BMPs are not included in the model. COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 7

11 Several small scale BMPs were excluded from the model due to their relative size to the watershed. 19 are BMPs (rain gardens, rain barrels, and pervious pavers) in the CRWD BMP database and are located on residential properties in the watershed that treat a drainage area of less than 2,000 square feet. Also excluded were two buffer plantings into Gottfrieds Pit and three cisterns near the Como Park Conservatory. The SPPW Portal was searched for any BMPs within the Park and seven additional BMPs were found. A search within the SPPW Portal was not performed for additional BMPs outside of the Park. Three of the seven BMPs are the easternmost ponds in the Como Golf Course alongside Lexington Parkway which are components of the Como Lake Stormsewer Diversion project dated 1986 (SPPW as-built serial number 8628 to 8633). Stormwater from the north and northeast areas of the watershed have been routed to these ponds via multiple storm sewer lines and diversion structures. The treated water from the ponds is then pumped through a lift station into Como Lake. An additional pond in the southern portion of the golf course exists but it is unclear whether or not it receives any stormwater runoff. The lily pond adjacent to the Conservatory is unique in the fact that it receives runoff but outlets via storm sewer that terminates across Estabrook Drive at a perforated sump manhole presumably infiltrating any pond discharge. The remaining two BMPs are hydrodynamic devices. One accepts drainage from the lily pond prior to reaching the perforated sump manhole and the other from the parking lot adjacent Putter There Miniature Golf (which also discharges to a perforated sump manhole). At least four sump structures exist on the east side of Como Lake along East Como Lake Drive. These are not included in the BMP totals and are not included in the water quality model. COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 8

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13 2.2.3 PREVIOUS WATER QUALITY MODELING FILES Several previous P8 water quality models exist within the Como Lake watershed. They are summarized in the following paragraphs. During the Como Lake TMDL, a P8 model was developed and is described in a report dated October although the model was created in It is assumed that this model instituted the original delineation of the 8 subwatersheds which are referenced as Como 1 to Como 8. The P8 model was calibrated up to 1994 data using the NURP 50% particle file to study TP watershed loading into Como Lake. A more detailed P8 model was developed in 2003 for the Como 7 subwatershed and parts of Como 8 to evaluate potential BMP alternatives in conjunction with storm sewer improvements as part of City of St. Paul street reconstruction 2. In 2010, a P8 model was developed for the Como 3 subwatershed in order to identify phosphorus loading and prioritize BMP location opportunities 3. The methodology and assumptions in the Como 7 study from 2003 were utilized in this model. Simulation was run from September 30 th, 1994 through October 1 st, 1995 on Minneapolis/St. Paul Airport climate data. The most recent existing model was the Arlington Pascal BMP update of the Como 7 subwatershed in This model was received from CRWD (file name Como_2011_R8.p8c ). It focused on the Como 7 and Como 8 subwatersheds, which drain to the 60-inch trunk storm sewer through Como Golf Course. Also incorporated are the other subwatersheds of Como Lake, specifically the Como 3 model (mentioned above) with delineated drainage areas. This model was calibrated with data monitoring the Como 7 and Como 8 subwatersheds and at many of the Arlington Pascal BMPs from 2007 to The calibration procedure set consistent watershed parameters (barring the watershed area) for the raingardens and trenches. The infiltration rates were then adjusted to match the monitored depths for the individual BMPs. For water quality parameters, the CRWD particle file was applied to the watershed and calibrated to 2.0 and 1.3 for TSS and TP scale factors, respectively. Climate data for this model was from the University of Minnesota St. Paul campus site. The P8 model developed during this study utilizes assumptions and the calibration of the 2011 Arlington Pascal BMP Model Update. DATA CATALOG The files gathered from SPPW, SPPR and Ramsey County have all been placed on a DVD and provided to CRWD. 1 Como Lake TMDL, Capitol Region Watershed District and Emmons & Olivier Resources, Inc. October Como 7 Subwatershed Analysis, Capitol Region Watershed District and Emmons & Olivier Resources, Inc. November Como 3 Subwatershed Analysis (Draft). HR Green, Inc. July Technical Memorandum: Arlington Pascal P8 Model Calibration Report, Emmons & Olivier Resources, Inc. April COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 10

14 3 WATERSHED ASSESSMENT An assessment of watershed loads and treatment of existing treatment BMPs was performed to determine the following: 1. Calculate annual stormwater volume and pollutant loads entering the park 2. Calculate annual stormwater volume and pollutant loads generated within the park 3. Analyze and quantify benefit of existing treatment facilities 4. Determine current annual stormwater discharge to Como Lake A Program for Predicting Polluting Particle Passage thru Pits, Puddles, & Ponds (P8) water quality model was developed to estimate watershed loadings and removals from existing BMPs to calculate Total Phosphorous (TP) and Total Suspended Solids (TSS) delivered to Como Lake on an annual average basis. P8 Version 3.5 is a draft version from March 2015 that was used for this assessment. The Como Lake model was differentiated into two separate P8 files due to the devices exceeding the maximum nodes that P8 allows. The files are for the north and south portions of the watershed and are named Como_North_2015.p8p and Como_South_2015.p8p, respectively. The north portion contains subwatersheds Como 4, 5, 6, 7 and 8, which in small storm events all drain to the eastern Como Golf Couse ponds. The south portion contains subwatersheds Como 1, 2 and 3 that discharge into Como Lake at various locations. MODEL INPUTS The P8 model requires input relative to local precipitation and temperature, watershed characteristics, and treatment device geometry. The following sections discuss preparation of the P8 model input parameters to assess the existing BMPs PRECIPITATION AND TEMPERATURE P8 uses hourly precipitation records to generate runoff volumes and also requires daily temperature data. For this study, data was readily available from Precipitation and temperature data were provided by CRWD and is understood to be obtained from the nearby University of Minnesota St. Paul campus site (station identifier ) from 2011 through August This 15 minute precipitation data was converted to hourly data and minor data gaps (limited to a few hours on several days) were substituted with National Weather Service data from the Minneapolis/St. Paul Airport. Where data was missing from both sites (limited to a total of a few hours), no precipitation data was input. The precipitation and temperature files from the previous model in 2011 where then supplemented by this data so that the simulation period was extended through August 31, Often water quality models simulate multi-year periods to determine annual average loading values as shorter simulation periods may be impacted by abnormally dry or wet years. Periods of 30 years or longer are generally used for long-term simulations to compute annual average values. Annual average values listed as model results are based on a 34-year simulation period that begins in Precipitation and temperature data was taken from the Minneapolis/St. Paul Airport TREATMENT BMPS The P8 model simulates pollutant removal at features that provide water quality treatment. These features are referred to as devices in P8. Treatment devices can be detention ponds, infiltration basins, swales, or a user-defined general device. Non-treatment devices with hydraulic residence time inputs are pipes, flow COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 11

15 splitters, or aquifers. Required pond inputs include the bottom surface area, permanent pool area and depth, flood pool area and volume, infiltration rates, and the outlet type and size. Infiltration basins model the storage pool area and volume, and infiltration rate. Swales use length, slope, bottom width, berm side slope, overflow elevation, Manning s n, and an infiltration rate. A general device is versatile in modeling with an area and discharge vs. elevation table, and outflow by infiltration, normal, or overflow discharge rates. These inputs in all of the devices are used to model treatment of TP and TSS based on retention (i.e., hydraulic residence) time, subsequent settling of particles, and through infiltration. The P8 model calculates pollutant removals for 55 BMPs modeled as 7 ponds, 44 infiltration devices, 1 swale, and 3 general devices (2 ponds, 1 underground infiltration). There are an additional 31 devices that do not provide treatment, including 27 pipes for network routing and 4 flow diversion structures modeled as general devices. An overall routing diagram is shown on Figures A-3 and A-4. A general review of the soils in the Como Lake Watershed indicate generally high infiltrating soils. Limited SSURGO soils data shows predominantly A and B Hydrologic Soil Groups in the watershed. The single indication of poor infiltrating soils found was near the southeast corner of the lake where 2 sites used filtration practices instead of infiltrating. Table A-3 depicts a summary of infiltration rates and the source or rational used to identify the infiltration rate for newly modeled BMPs. See Table A-4 for a list of infiltration rates used in non-infiltration P8 devices. A Sizing Hydrodynamic Separators and Manholes (SHSAM) water quality model was developed for the two Stormceptors at the west picnic grounds lot and downstream of the lily pond. P8 does not have the capability to model hydrodynamic separators. Therefore, the SHSAM models were used to augment P8 by adjusting the particle load factor within each device (pond) to achieve the same TSS percent load reduction SHSAM modeled. This method assumes that TP will scale proportionately to TSS removals. It was found that P8 actually overestimated the removals for these devices. Accordingly, the particle load factor for the Lily Pond Stormceptor (COMO3_Lily_HD) was adjusted to 0.48 and the west parking lot Stormceptor (COMO3_WpicnicLot_HD) was adjusted to Routing errors were found in the previous model and corrected in this model. Devices RG2_McPascM and RG3_McPascS s outflow were both routed to ARL-HAM_SS-MH but actually discharge to stormsewer travelling north, which discharges into COMO7_GolfPond. Device RG5_FrnksMc was also routed in the previous model to ARL-HAM_SS-MH, but the routing was changed to correctly outflow to COMO7_Monitoring. The routing correction in the model was deemed to have a minor impact and not significantly influence the previous calibration effort. The three devices, all raingardens, are now correctly routed. P8 models have a limit of 75 devices per modeling file. The overall number of devices in the Como Lake watershed exceeded this limit and was therefore split into a North and South model. The physical length of an underground infiltration BMP collecting runoff from the Palm Lot in Como Park was unknown. The length was estimated by using an assumed volume of 0.8 over the direct impervious area resulting in a length of 190 ft. There are a number of BMPs that are excluded from the model: Within the CRWD BMP database, there are approximately 20 small residential scale BMPs that individually treat or capture runoff from less than 2,000 square feet of impervious area. Three cisterns near the conservatory are not in the model. Front-Victoria infiltration trenches 1 and 2 were included in the CRWD BMP Database under the Como subwatershed, but were determined outside of the Como Lake watershed. Standard sumps were not modeled. COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 12

16 Additionally, the following are drainage areas within existing Como Lake watershed that area routed out of the model (meaning they are not discharged into Como Lake) but were included in the previous P8 model: Depression area and catch basins near the corner of Wynne Ave and Beulah Ln (COMO3_4_6) Curtis Pond (COMO7_CURTIS) The southern Como Golf Course pond (ComoGolfLL) o Includes Japanese Garden Experience underground infiltration (COMO7_Japanese) Asbury RG North (RG6_AsbFrnksN) Asbury RG South (RG7_AsbFrnksS) WATERSHED CHARACTERISTICS The model simulates a total of 55 stormwater treatment BMPs, some of which are hydraulically connected and linked together in the model (i.e., loads discharged from an upstream ponds is routed to a downstream pond). Catchment area delineations are based on a combination of pervious P8 models, planning and design reports, construction plans, LiDAR topography and existing storm sewer infrastructure. The P8 model uses a Curve Number representing the pervious surfaces in a catchment to calculate the amount of stormwater runoff from those areas. The P8 model utilizes Event Mean Concentrations (EMC) for TP and TSS applied to the runoff volume from pervious areas to determine pollutant loads for the pervious portion of the watershed. The P8 model also relies upon an estimate of impervious area in each catchment and separately computes the runoff volume and pollutant loading from the impervious portion. The P8 model utilizes stormwater runoff data collected during the National Urban Runoff Program (NURP) development to generate pollutant loading estimates from these impervious areas. The amount of the overall impervious area that is directly connected to the conveyance system is also an important component in determining the watershed loading. Runoff from indirectly connected impervious area first passes over pervious area before entering the conveyance system and the model reduces runoff volume and loads as a result. P8 has street sweeping component that was not utilized in previous models, nor was utilized in this model. Subwatersheds that are not directly routed to a newly identified BMP maintained their Curve Number, runoff coefficient, and impervious fractions from the previous model. For watershed directly connected to newly identified BMPs, a pervious curve number of 61 was used in order to be consistent with the calibration parameters from the Arlington Pascal P8 model. However, for these BMPs, new impervious fractions were delineated and runoff coefficients were not maintained from the previous model. The watershed inputs are shown in Table A-5. COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 13

17 Without the benefit of the previous models delineated drainage areas, it required considerable effort to reconcile previous models drainage areas with new BMP and updated drainage delineations. The best available data source was chosen between the CRWD database, delineation by LiDAR, aerial photography, and city storm sewer data, and existing model. In most cases, the new BMP drainage area was subtracted from existing model areas. In some cases, new drainage areas were delineated. The overall drainage modeled within the P8 model is 1,774 acres including 62 acres considered to not be contributing runoff to Como Lake. A total of 8 acres is not included in the modeled area since it is routed to sanitary sewer. There are several notable features that divert water in the Como Lake Watershed. The largest is a diversion project which diverted storm sewer from Como 4, Como 5, and Como 6 through diversion structures that send low flow stormwater to the pond network at the east side of the golf course, and allow a bypass of high flows to Como Lake. Como 7 also has diversion structures. The first diverts water to the western golf course pond and the second diverts flow from the 60 golf course storm sewer to the eastern golf course ponds. There are also two major lift stations that transfer stormwater through the watershed. All of Como 8 drains to the regional stormwater pond known as Gottfried s Pit and its only outlet is a lift station that ultimately discharges to the western golf pond. The second lift station pumps water from the eastern golf course ponds (located at device COMO5_EGolfPond4, disjointed from the previous COMO48 device) to Como Lake. Several minor changes to the previous model s Como 3 subwatershed delineation or routing: The entire Como3_2_3 area is routed to the Front/Victoria underground infiltration trench (Como3_FrontVict_Trench) The area east of the Lily Pond and west of Kaufman Drive was added to Como3_5_3 The western portion of Como3_4_1 which drains to Midway Parkway was distinguished as a new drainage area, labeled Como3_5_4, and routed to Como3_5_3. Subsequently, the previous watershed labeled Como3_5_4 was renamed to Como3_5_5. It was determined that two areas have stormwater that is collected into sanitary sewer, and therefore were not included in the drainage areas of the model: All animal pens within Como Zoo Como Regional Park Pool WATER QUALITY PARTICLE PARAMETERS AND COMPONENTS The particle file used in the model is named crwdpart.p8p and was provided by CRWD. The same particle data was used in the previous model for the Como 7 watershed, and was calibrated by adjusting the particle scale factor to a value of 2 for TSS and 1.3 for TP. These adjustments were assumed to be reasonable and apply to the entire Como Lake watershed and were used in the model. MODEL CALIBRATION AND VALIDATION Model calibration, the process of evaluating the behavior of the model and adjusting input parameters to match measured data, is an important component of the model development and application process. Model validation is the process of examining the model to justify its correctness and usefulness. COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 14 14

18 CRWD collects both water quantity and quality monitoring data at several locations in the Como Lake watershed. The drainage areas monitored include the Como 7 and Como 3 subwatersheds. The monitoring stations locations, data collection, methods are included in CRWD s 2014 annual stormwater monitoring report. From the monitoring data, total discharge volume and pollutant loads are calculated by CRWD for each year s monitoring period and presented in the report. The P8 model updated in 2011 used monitoring data collected from within the Como 7 subwatershed at 11 locations. The model update was done following the installation of the Arlington- Pascal Stormwater improvement project BMPs in 2006 and 2007 and the collection of monitoring data in 2008, 2009 and The monitoring stations were a combination of crest level gages and full water quality gages. The calibration process is described in the Arlington-Pascal P8 Calibration Report dated April, During the 2011 P8 model update significant effort was spent to modify model inputs based upon monitoring data at multiple locations in In the years since, only the Como 7 and golf course pond outlet monitoring stations have been installed. Since detailed calibration was previously done, the model results were compared to new monitoring data to validate the new P8 model in the Como 7 subwatershed. Table 3 compares the monitored and P8 model output for runoff volumes and TP and TSS loads. Table 3. Como 7 Subwatershed Comparison of Monitored and Modeled Runoff Volumes and Loads Runoff Volume (ac-ft/year) TP Load (lbs/year) TSS Load (lbs/year) Monitoring P8 % P8 P8 Monitoring % Diff Monitoring Results Diff Results Results % Diff /17-11/ % % 20,479 8,317-59% /6-11/ % % 22,833 11,931-48% /9-11/ % % 31,780 49,509 56% /13-11/ % % 51,921 57,663 11% /28-11/ % % 24,719 24,337-2% /9-11/ % % 46,545 38,888-16% /21-11/ % % 67,775 36,554-46% Average % % 25,031 23,252-17% Average % % 43,346 33,260-13% Average % % 38,007 32,457-15% Comparing years , the annual average runoff volume and TSS load maintain a similar percentage difference 2011 calibration for period. Annual variation does exist between the monitored loads and P8 model output but the average annual percent difference is reasonable over the monitoring period. No watershed loading or device removal factors were modified from the previously calibrated P8 model in the Como 7 watershed. No past calibration has been completed outside of the Como 7 watershed. Initially, the gross assumption was to apply the watershed settings such as pervious CN and depressional storage determined during the 2011 Arlington Pascal BMP project to the entire Como Lake watershed. A full water quality station was installed in the Como 3 watershed in The monitoring location for Como 3 (P8 model device Como3_Monitoring) is only a portion of the Como 3 subwatershed, namely the COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS

19 watersheds Como3_4_1a through Como3_4_4 having a drainage area of 175 acres. P8 model output was compared to the monitored loads for and are shown in Table 4. Table 4. Como 3 Subwatershed Comparison of Monitored and Modeled Runoff Volumes and Loads Runoff Volume (ac-ft) TP Load (lbs) TSS Load (lbs) Period of P8 P8 P8 Record Monitoring % Diff Monitoring % Diff Monitoring % Diff Results Results Results /2-11/ % % 36,792 51,113 39% /29-11/ % % 62,966 43,840-30% /21-11/ % % 59,170 75,777 28% Average % % 52,976 56,910 12% The P8 model runoff volume and TSS loads were approximately 10% greater than monitored loads and TP loads were 60% higher. Since relatively small of treatment is provided by existing BMPs in the monitored Como 3 watershed, the watershed inputs were closely reviewed in the P8 model. Slight adjustments were made to the impervious percentage and drainage boundaries in the Como Park and ballfield area. Additionally, the catchment loading factor was modified for several catchments to reflect lower TP and TSS loads. These catchments were located in predominantly industrial and warehouse areas where a larger portion of the impervious area is building rooftops. The TP and TSS scaling factors to were lowered to 0.75 and 1.15 respectively. They were initially 1.3 and 2 based on the previous Como 7 calibration work. This scaling factor adjustment is limited to the Como3_4_3 and COMO3_4_4 subwatersheds via lowering the watersheds impervious scale factor to The modifications to the model inputs had the cumulative impact on the P8 model loads as shown in Table 5. Table 5. Como3 Subwatershed Comparison of Monitored and Modeled Runoff Volumes and Loads after Adjustments Runoff Volume (ac-ft) TP Load (lbs) TSS Load (lbs) Period of P8 P8 P8 Record Monitoring % Diff Monitoring % Diff Monitoring % Diff Results Results Results /2-11/ % % 36,792 44,384 21% /29-11/ % % 62,966 37,826-40% /21-11/ % % 59,170 69,138 17% Average % % 52,976 50,449-1% Some variation from year to year does exist between the monitored and modeling output but the average percent difference is reasonable over the monitoring period. The most extreme annual variation occurred for TP in 2014 where the P8 model over predicts TP load by 80%. An explanation for this was not found within the P8 model inputs. It was observed that the CRWD monitoring data reported a lower Flow Weighted Average of 0.23 mg/l for TP compared in 2014 to values of 0.28 and 0.31 in 2012 and The P8 model did not produce a similar reduction. COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS

20 RESULTS ANNUAL AVERAGE RESULTS Figures 3 and 4 provide responses to the following watershed loading and BMP removal statistics identified in the project scope. Annual stormwater volume and pollutant loads entering the park Annual stormwater volume and pollutant loads generated within the park Benefit of existing treatment facilities Current annual stormwater discharge to Como Lake Figure 3. Average Annual Stormwater Volume and Pollutant Loads COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 17

21 Figure 4. Average Annual Stormwater Discharge to Como Lake and Benefit of Existing Treatment Facilities Tables A-6, 6 and 7 summarize the average annual loading from the landscape for runoff TP and TSS yields loads. Figures A-5, A-6 and A-7 show the runoff volume (in inches), TP and TSS yields (in lbs/acre) generated by each subwatershed. Figures A-8, A-9 and A-10 show the average annual runoff volume, TP and TSS yields delivered to Como Lake taking into account the treatment provided by existing BMPs across the entire watershed. Figures A-11, A-12 and A-13 show the average annual runoff volume, TP and TSS yields delivered to Como Lake from areas within Como Park. As expected, untreated areas have higher TP and TSS yields to Como Lake while treated areas have lower yields. COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS

22 Table 6. Annual Average Summary of Watershed Loading and BMP Removals Runoff Volume (acre-feet) TSS Load (lbs) TP Load (lbs) Year Average Total Watershed Load Volume Generated Within Park Volume Generated Outside Park Load delivered to Como Lake Volume Removed % Removed Total Watershed Load Load generated within park Load generated outside park Delivered to Como Lake Removed % Removed Total Watershed Load 1, % 668,054 89, , , , % 1, , % Load generated within park Load generated outside park Delivered to Como Lake Removed % Removed Table 7. Annual Average BMP Loading and Removals BMP Name Runoff Volume (acre-feet) TSS Load (lbs) TP Load (lbs) Percent Percent Percent Load Discharge Removed Load Discharge Removed Load Discharge Removed Removed Removed Removed RG1_McPascN % % % RG2_McPascM % % % RG3_McPascS % % % RG4_ArlMc % % % RG5_FrnksMc % ,083 92% % Trench % % % Trench % % % Trench % 1, ,226 94% % Trench % 2, ,971 89% % Trench % % % Trench % % % Trench % % % Trench % ,481 84% % COMO7_AHUG % 18, , % % COMO8_Rainbow % 3, % % COMO8_Walgreens % % % Gottfrieds Pit % 164,065 22, ,971 87% % COMO7_Gorilla1* % % % COMO7_Gorilla2* % % % COMO7_ChelsHi % % % COMO7_ComoTown* % 1, ,055 78% % COMO7_HMRAIN* % 3, ,694 89% % COMO7_PolarBear* % 1, ,225 94% % COMO5_Nebraska* % 1, ,240 94% % COMO5_EGolfPond1* % % % COMO5_EGolfPond2* % 1, ,687 92% % COMO7_LanSchool % % % COMO7_GOLFPOND* % 71,622 23,048 48,574 68% % COMO7_Japanese* % % % COMO5_EGolfPond3* % 133,331 62,190 71,141 53% % COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 19 19

23 BMP Name Runoff Volume (acre-feet) TSS Load (lbs) TP Load (lbs) Load Discharge Removed Percent Percent Percent Load Discharge Removed Load Discharge Removed Removed Removed Removed COMO5_EGolfPond4* % 63,254 54,062 9,192 15% % COMO3_4_5* % 1, ,208 97% % COMO3_FVict_Pavers % % % COMO3_FVict_Trench % 7,392 1,693 5,699 77% % COMO3_PoolRG2* % % % COMO3_PoolRG3* % % % COMO3_PoolRG1* % % % COMO3_PoolRG4* % % % COMO3_TCGermImr % % % COMO3_Lily_HD* % 1,947 1, % % COMO3_Lily_Drain* % 1,600 1, % % COMO3_PalmLot* % 2, ,951 89% % COMO2_Victoria1* % 4,112 1,515 2,596 63% % COMO2_LakeviewRG* % % % COMO2_CPESchool % % % COMO2_CPESchool % % % COMO3_PoolRG5* % % % COMO2_Victoria2* % 1, % % COMO3_Soccer1* % 1, % % COMO3_Soccer2* % 1, ,224 69% % COMO3_Soccer3* % 1, ,147 59% % COMO3_WPicnicLot_HD* % 1,692 1, % % COMO3_WPicnicLot_Drain* % 1,358 1, % % Sum of Como Park BMPs , Sum of All BMPs , * Located in Como Park Table 7 Continued. COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 20

24 3.3.2 TREATMENT OF THE 1.1-INCH STORM EVENT CRWD enforces a 1.1-inch treatment requirement for development and redevelopment activity within its jurisdiction. The P8 model was used assess performance of existing BMPs in the Como Lake watershed compared to this standard. A synthetic rainfall event can be input into P8 in lieu of historical rainfall data. The P8 help file states that [design storms] can be used in preliminary model runs. The original intent of this feature in P8 was to use a synthetic 1-inch storm event to predict long term simulations in order to reduce computing time. P8 provides no documentation on the modeling capability or accuracy of using specific synthetic events to determine load removals during these events. Therefore, when modeling the 1.1-inch event, guidance was used from P8 regarding the prediction of long term simulation: to use 5 passes thru storm file with a 72 hour interval between storm midpoints (according to P8 Urban Catchment Model Program Documentation Version 1.1, dated October 1990). A sensitivity analysis on number of passes through the storm file indicated no significant change in BMP removal percentages from increasing the passes through storm file greater than 5. Table A-7 lists the modeled removal percentages of Volume, TSS and TP for the 1.1-inch 24 hour synthetic storm event. Figures A-14, A-15 and A-16 show the 1.1-inch storm event runoff volume, TP and TSS removal fractions taking into account the treatment provided by existing BMPs across the entire watershed. As modeled, 33 out of 55 BMPs infiltrate 100% of the flow from a synthetic 1.1-inch storm event and thereby treats 100% of TSS and TP. COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 21

25 4 APPENDIX TABLES Table A-1: SPPR Como Regional Park Storm Sewer File Directory Location File Name Type Arlington Ave - Chelsea St X_ _0012 Scanned stormsewer sketch Arlington-Pascal RG, Arlington-Pascal As-Builts Central Como Park Como - Palm Lot storm sewer Survey West Picnic Ground Drywell - Plan Construction Plans West Picnic Ground Drywell Construction Plans X_ _0006, X_ _0022, X_ _0023, X_ _0024, Scanned stormsewer sketch X_ _0029 Como - Palm Lot storm sewer Survey Storm water Recharge - Plan Survey Storm Water Recharge Construction Plans Como Pool Como Pool - Parking lots Survey Como Pool - pool drainage Construction Plans Como Zoo X_ _0010, X_ _0017 Scanned stormsewer sketch Conservatory X_ _0018 Scanned stormsewer sketch Cisterns, Como_Park_Visitor, Construction Plans Re-Bid Civil Plans Construction Plans Golf Course X_ _0019 Scanned stormsewer sketch Hole 2 (hole6), Hole 4 (hole 8) Grading and Utility Como Course Green plans Grading and Utility Como Clubhouse Site Improv 1986 Construction Plans Lake Como X_ _0005, X_ _0021, X_ _0026, X_ _0027, X_ _0028, X_ _0033, Scanned stormsewer sketch X_ _0034, X_ _0035, X_ _0036 Lexington Parkway X_ _0014, X_ _0015, X_ _0020, X_ _0025 Scanned stormsewer sketch Lexington Ave Plan/Profile Others McMurray - Artificial turf drainage Construction Plans Overall Park X_ _0001, X_ _0004 Scanned stormsewer sketch Existing Sewers Scanned stormsewer sketch Como Park sewers-old Scanned stormsewer sketch COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS

26 Table A-2: BMPs within the CRWD BMP Database Project Name BMP Name Program: Capital Project (CP), Permit, or Grant Arlington Pascal Stormwater Improvement Project Frankson McKinley RG CP Arlington Pascal Stormwater Improvement Project Arlington McKinley RG CP Arlington Pascal Stormwater Improvement Project Pascal RG South CP Arlington Pascal Stormwater Improvement Project Pascal RG CP Arlington Pascal Stormwater Improvement Project Pascal RG North CP Arlington Pascal Stormwater Improvement Project Hamline Midway RG CP Arlington Pascal Stormwater Improvement Project Como Park Regional Pond CP Arlington Pascal Stormwater Improvement Project Infiltration Trench 1 CP Arlington Pascal Stormwater Improvement Project Infiltration Trench 2 CP Arlington Pascal Stormwater Improvement Project Infiltration Trench 3 CP Arlington Pascal Stormwater Improvement Project Infiltration Trench 4 CP Arlington Pascal Stormwater Improvement Project Infiltration Trench 5 CP Arlington Pascal Stormwater Improvement Project Infiltration Trench 6 CP Arlington Pascal Stormwater Improvement Project Infiltration Trench 7 CP Arlington Pascal Stormwater Improvement Project Infiltration Trench 8 CP Arlington Pascal Stormwater Improvement Project Arlington-Hamline Facility CP Polar Bear Exhibit Infiltration Basin Permit Roseville Rainbow Foods 1st Infiltration Trench Permit Victoria Street Infiltration Basin 1 Permit Victoria Street Infiltration Basin 2 Permit Front-Victoria RSVP Infiltration Trench 3 Permit Front-Victoria RSVP Pervious Pavers Permit Como Pool 1st Rain Garden Permit Como Pool 2nd Rain Garden Permit Como Pool 3rd Rain Garden Permit Como Pool 4th Rain Garden Permit Como Pool 5th Rain Garden Permit Gorilla Forest Subsurface Infiltration Pipes Permit Gorilla Forest 2nd Subsurface Infiltration Pipes Permit Larpenteur Walgreens Infiltration System Permit Como Golf Course Pond Como Golf Course Pond CP Twin Cities German Immersion School Grant Chelsea Heights Elementary School Chelsea Heights Rain Garden Grant Como Park and Language School Rain Garden Grant COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS

27 Table A-3: Infiltration BMP Inputs Type P8 Device Name Infiltration Rate (in/hr) Source Rain Garden COMO7_ChelsHi, COMO7_PolarBear, COMO5_Nebraska, COMO7_LanSchool, COMO7_Japanese, COMO3_PoolRG1 to RG4, COMO3_TCGermImr, COMO2_LakeviewRG 4 Majority of Arlington-Pascal Calibrated BMPs Underground Infiltration Underground Filtration Bioretention w/underdrain COMO8_Rainbow, COMO8_Walgreens, COMO7_Gorilla1 & 2, COMO3_FVict_Trench, COMO3_Lily_Drain, COMO3_PalmLot, COMO2_CPESchool1 & 2, COMO3_Soccer1 to 3, COMO3_WPicnicLot_Drain 0.75 Majority of Arlington-Pascal Calibrated BMPs COMO2_CPESchool1 & CRWD Database COMO2_Victoria1 & CRWD Database Pavers COMO3_FVict_Pavers 0.75 Match COMO3_FVict_Trench (directly underneath pavers) Other COMO7_ComoTown 0.45 SM Soils, unknown design type Table A-4: Non-infiltration BMPs Input Parameters Type P8 Device Name Infiltration Rate (in/hr) Source Pond: Permanent Pool COMO5_EGolfPond1 to 4 0 Match existing model (Como48) Pond: Flood Pool COMO5_EGolfPond1 to Match existing model (Como48) Swale COMO3_PoolRG5 0.7 CRWD Database COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS

28 Table A-5. P8 Model Watershed Inputs Directly Connected Areas Total Pervious Indirect Pervious Depress Imperv Total Watershed Area Outflow Curve Imperv Load Imperv Storage Runoff Load Imperv Model Label (acres) Device Number Fraction Factor Fraction (inches) Coef Factor Fraction North COMO COMO North COMO COMO North COMO COMO North COMO Gottfrieds Pit North COMO7_GolfLL COMO7_GolfLL North COMO7_AHUG_Central ARL-HAM_SS-MH North COMO7_Curtis COMO7_CURTIS North COMO7_GolfPond COMO7_GOLFPOND North COMO7_HMRAIN 6.49 COMO7_HMRAIN North COMO7_Midway COMO7_MIDWAY North COMO7_South COMO7_SOUTH North COMO7_AHUG_West 4.33 ARL-HAM_SS-MH North SAP1_RG6 0.4 RG6_AsbFrnksN North SAP1_RG RG7_AsbFrnksS North RG1_McPascN RG1_McPascN North RG2_McPascM RG2_McPascM North RG3_McPascS RG3_McPascS North RG4_ArlMc RG4_ArlMc North RG5_FrnksMc RG5_FrnksMc North Trench Trench North Trench Trench North Trench Trench North Trench Trench North Trench Trench North Trench6 2.6 Trench North Trench Trench North Trench Trench North COMO7_GolfPond-Direct COMO7_GOLFPOND North COMO3_4_1_ComoTown 3.98 COMO7_ComoTown North COMO8_Rainbow COMO8_Rainbow North COMO7_Gorilla COMO7_Gorilla North COMO7_Gorilla COMO7_Gorilla North COMO8_Walgreens 1.11 COMO8_Walgreens North COMO8_ChelsHi COMO7_ChelsHi COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS

29 Table A-5. P8 Model Watershed Inputs Directly Connected Areas Total Pervious Indirect Pervious Depress Imperv Total Watershed Area Outflow Curve Imperv Load Imperv Storage Runoff Load Imperv Model Label (acres) Device Number Fraction Factor Fraction (inches) Coef Factor Fraction North COMO7_LanSchool COMO7_LanSchool North COMO5_EGolfPond COMO5_EGolfPond North COMO5_Nebraska COMO5_Nebraska North COMO7_PolarBear 3.39 COMO7_PolarBear North COMO7_Japanese COMO7_Japanese North COMO5_EGolfPond COMO5_EGolfPond North COMO5_EGolfPond COMO5_EGolfPond North COMO5_EGolfPond COMO5_EGolfPond South COMO COMO South COMO COMO South COMO3_2_1 7.9 COMO3_2_ South COMO3_1_ COMO3_1_ South COMO3_2_ COMO3_2_ South COMO3_2_ COMO3_2_ South COMO3_3_ COMO3_3_ South COMO3_3_ COMO3_3_ South COMO3_4_1a 23.4 COMO3_4_1a South COMO3_4_1b 26.4 COMO3_4_1b South COMO3_4_ COMO3_4_ South COMO3_4_ COMO3_4_ South COMO3_4_4 65 COMO3_4_ South COMO3_4_ COMO3_4_ South COMO3_4_ COMO3_4_ South COMO3_5_1 8.6 COMO3_5_ South COMO3_5_2 5.1 COMO3_5_ South COMO3_5_ COMO3_5_ South COMO3_5_ COMO3_5_ South COMO3_6_ COMO3_6_ South COMO3_6_ COMO3_6_ South COMO2_Victoria 9.5 COMO2_Victoria South COMO2_LakeviewRG COMO2_LakeviewRG South COMO2_CPESchool COMO2_CPESchool South COMO2_CPESchool COMO2_CPESchool South COMO3_WPicnicLot COMO3_WPicnicLot_HD South COMO3_PoolRG COMO3_PoolRG South COMO3_PoolRG COMO3_PoolRG COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 17

30 Table A-5. P8 Model Watershed Inputs Directly Connected Areas Total Pervious Indirect Pervious Depress Imperv Total Watershed Area Outflow Curve Imperv Load Imperv Storage Runoff Load Imperv Model Label (acres) Device Number Fraction Factor Fraction (inches) Coef Factor Fraction South COMO3_PoolRG COMO3_PoolRG South COMO3_PoolRG COMO3_PoolRG South COMO3_PoolRG COMO3_PoolRG South COMO3_Soccer COMO3_Soccer South COMO3_Soccer COMO3_Soccer South COMO3_Soccer COMO3_Soccer South COMO3_TCGermImr 0.7 COMO3_TCGermImr South COMO3_FVict_Trench COMO3_FVict_Trench South COMO3_FVict_Pavers 1.59 COMO3_FVict_Pavers South COMO3_PalmLot 3.97 COMO3_PalmLot South COMO3_LilyHD COMO3_Lily_HD South COMO3_5_ COMO3_5_ COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 18

31 Table A-6. Average Annual P8 Model Watershed Loading for the Period from 1981 to 2014 Subwatershed Name Area (acres) Runoff Volume (acre-feet) TSS Load (lbs) TP Load (lbs) COMO , COMO , COMO7_CURTIS* , COMO7_MIDWAY , COMO7_SOUTH , RG1_McPascN RG2_McPascM RG3_McPascS RG4_ArlMc RG5_FrnksMc , RG6_AsbFrnksN* RG7_AsbFrnksS* Trench Trench Trench , Trench , Trench Trench , Trench Trench , COMO7_AHUG , COMO8_Rainbow , COMO8_Walgreens Gottfrieds Pit , COMO7_Gorilla COMO7_Gorilla COMO7_ChelsHi COMO7_ComoTown , COMO7_HMRAIN , COMO7_PolarBear , COMO5_Nebraska , COMO , COMO5_EGolfPond COMO5_EGolfPond , COMO7_LanSchool COMO7_GOLFPOND , COMO7_Japanese* COMO7_GolfLL* , COMO5_EGolfPond , COMO5_EGolfPond , COMO3_6_ , COMO3_4_6* , COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 19

32 Table A-6. Average Annual P8 Model Watershed Loading for the Period from 1981 to 2014 Area (acres) Runoff Volume (acre-feet) TSS Load (lbs) TP Load (lbs) Subwatershed Name COMO3_4_ , COMO3_4_ , COMO3_4_ , COMO3_3_ , COMO3_3_ , COMO3_2_ , COMO3_1_ , COMO3_FVict_Pavers COMO3_FVict_Trench COMO3_2_ , COMO3_2_ , COMO3_PoolRG COMO3_PoolRG COMO3_PoolRG COMO3_PoolRG COMO3_TCGermImr COMO3_Lily_HD , COMO3_PalmLot , COMO2_Victoria , COMO2_LakeviewRG COMO2_CPESchool COMO2_CPESchool COMO3_PoolRG COMO , COMO , COMO3_Soccer , COMO3_Soccer , COMO3_Soccer , COMO3_4_ , COMO3_4_1a , COMO3_4_1b , COMO3_WPicnicLot_HD , COMO3_5_ , COMO3_5_ , COMO3_5_ , COMO3_5_ , COMO3_5_ , COMO3_6_ Sum of Subwatersheds Contributing to Como Lake 1, , ,054 1,198.4 Sum of All Subatersheds 1, , ,917 1,237.3 * Subwatersheds included in the P8 model, but do not contribute to Como Lake COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 20

33 Table A-7. Watershed removal percentages from the 1.1 inch 24-hr storm event Percent Removal Subwatershed Vol TSS TP RG1_McPascN 100.0% 100.0% 100.0% RG2_McPascM 100.0% 100.0% 100.0% RG3_McPascS 100.0% 100.0% 100.0% RG4_ArlMc 100.0% 100.0% 100.0% RG5_FrnksMc 100.0% 100.0% 100.0% RG6_AsbFrnksN 100.0% 100.0% 100.0% RG7_AsbFrnksS 100.0% 100.0% 100.0% Trench % 100.0% 100.0% Trench % 100.0% 100.0% Trench % 100.0% 100.0% Trench % 100.0% 100.0% Trench % 100.0% 100.0% Trench % 100.0% 100.0% Trench % 100.0% 100.0% Trench % 100.0% 100.0% COMO7_AHUG 100.0% 100.0% 100.0% COMO8_Rainbow 100.0% 100.0% 100.0% COMO8_Walgreens 100.0% 100.0% 100.0% Gottfrieds Pit 36.4% 85.3% 54.8% COMO7_Gorilla % 100.0% 100.0% COMO7_Gorilla % 100.0% 100.0% COMO7_ChelsHi 100.0% 100.0% 100.0% COMO7_ComoTown 99.4% 100.0% 99.6% COMO7_HMRAIN 100.0% 100.0% 100.0% COMO7_PolarBear 100.0% 100.0% 100.0% COMO5_Nebraska 100.0% 100.0% 100.0% COMO5_EGolfPond1 0.0% 100.0% 72.9% COMO5_EGolfPond2 0.0% 94.1% 63.9% COMO7_LanSchool 90.9% 100.0% 90.0% COMO7_GOLFPOND 1.9% 74.5% 20.6% COMO7_Japanese 96.1% 100.0% 95.9% COMO5_EGolfPond3 0.0% 63.8% 13.6% COMO5_EGolfPond4 2.2% 21.3% 5.2% COMO3_4_ % 100.0% 100.0% COMO3_FVict_Pavers 0.0% 98.0% 64.6% COMO3_FVict_Trench 98.3% 99.4% 98.5% COMO3_PoolRG % 100.0% 100.0% COMO3_PoolRG % 100.0% 100.0% COMO3_PoolRG1 78.3% 77.8% 73.2% COMO3_PoolRG4 81.4% 81.7% 77.8% COMO3_TCGermImr 100.0% 100.0% 100.0% COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 21

34 Table A-7. Watershed removal percentages from the 1.1 inch 24-hr storm event Percent Removal Subwatershed Vol TSS TP COMO3_Lily_HD 0.0% 11.6% 0.5% COMO3_Lily_Drain 1.3% 5.9% 0.8% COMO3_PalmLot 100.0% 100.0% 100.0% COMO2_Victoria1 0.0% 74.3% 41.2% COMO2_LakeviewRG 100.0% 100.0% 100.0% COMO2_CPESchool1 0.0% 97.6% 65.0% COMO2_CPESchool2 0.0% 97.6% 64.2% COMO3_PoolRG5 53.5% 79.5% 57.1% COMO2_Victoria2 0.0% 95.1% 60.5% COMO3_Soccer % 100.0% 100.0% COMO3_Soccer % 100.0% 100.0% COMO3_Soccer % 100.0% 100.0% COMO3_WPicnicLot_HD 0.0% 14.3% 1.3% COMO3_WPicnicLot_Drain 15.6% 25.5% 13.9% COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 22

35 FIGURES Figure A-1: SPPW Como Regional Park Storm Sewer File Directory COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 23

36 Trench6 Trench3 Trench4 Roseville Gottfrieds Pit Rainbow Falcon Heights Walgreens COMO4 COMO7_GOLFPOND COMO5 COMO6 Trench1 Trench2 ChelsHi LanSchool GolfPond-Direct Nebraska AHUG_Central RG1_McPascN RG2_McPascM EGolfPond3 AHUG_WEST RG3_McPascS Trench8 EGolfPond1 EGolfPond4 Trench7 Trench5 RG4_ArlMc COMO7_MIDWAY RG5_FrnksMc AHUG_Central COMO7_SOUTH Gorilla1 HMRAIN ComoTown PolarBear Gorilla2 COMO3_4_5 Lily_HD GolfLL EGolfPond2 Japanese COMO3_4_5 COMO3_5_2 LakeviewRG COMO3_6_2 COMO3_6_1 COMO1 COMO2 PalmLot WPicnicLot_HD COMO3_5_5 COMO3_5_4 COMO3_4_1b COMO3_5_3 COMO3_5_1 St. Paul COMO3_4_1a Como Lake Victoria1 CPESchool1 CPESchool2 PoolRG5 COMO3_4_6 PoolRG3 PoolRG2 PoolRG1 PoolRG4 Soccer1 COMO3_4_2 Soccer2 Soccer3 TCGermImr COMO3_3_1 COMO3_2_1 COMO3_1_1 FVict_Trench COMO3_2_2 COMO3_4_3 COMO3_3_2 FVict_Pavers COMO3_4_4 COMO3_2_3 Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp., NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), MapmyIndia, OpenStreetMap contributors, and the GIS User Community Municipal Boundaries Subwatersheds COMO PARK Routed to Sanitary Sewer BMPs Bioretention ,500 3,000 Feet Hydrodynamic Device Permeable Hardscape Pond Underground DIAMETER 0-12 in in in in in Figure A-2 - Subwatersheds Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /28/ of 1

37 EGolfPond2 EGolfPond1 Como4 Walgreens Como5 Nebraska Gottfried's Pit Rainbow Como6 LanSchool TR4 TR2 Como Lake EGolfPond4 EGolfPond3 Como7 GolfPond TR3 TR1 ChelsHi RG2 RG1 Como7 South RG3 Como7 Midway Gorilla2 Gorilla1 Como7 Monitoring PolarBear RG5 HM Rain ComoTown Como7 AHUG Div to AHUG ACL HAM SS_MH TR8 TR7 TR6 TR5 RG4 Figure A-3: P8 Model Schematic North Area (Red outline indicates a stormwater treatment BMP) RG3 COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 0

38 Victoria2 Victoria1 LakeviewRG Como1 Como2 CPESchool1 3_1_1 CPESchool2 FVict_Pavers 3_2_1 3_2_2 FVict_Trench 3_2_3 3_3_1 3_3_2 PoolRG3 PoolRG2 PoolRG1 Como Lake Como3 Monitor 3_4_1a 3_4_2 PoolRG4 PoolRG5 Soccer3 Soccer2 Soccer1 TCGerman 3_4_3 3_4_4 Lily_Drain Lily_HD 3_4_5 (Lily Pond) 3_5_2 3_5_3 3_4_1b PalmLot 3_5_1 3_5_5 WPicnic_Drain WPicnic_HD 3_6_1 3_6_2 3_5_4 Figure A-4: P8 Model Schematic South Area (Red outline indicates a stormwater treatment BMP) COMO PARK STORMWATER INVENTORY AND WATERSHED ANALYSIS 1

39 Roseville Falcon Heights St. Paul Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp., NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), MapmyIndia, OpenStreetMap contributors, and the GIS User Community COMO PARK Municipal Boundaries Routed to Sanitary Sewer ,500 3,000 Feet Annual Runoff Depth (inch) Figure A-5 - Annual Runoff Depth in Inches Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /28/ of 1

40 Roseville Falcon Heights St. Paul COMO PARK Municipal Boundaries Routed to Sanitary Sewer ,500 3,000 Feet Annual TP Yield (lbs per acre) < > 1.26 Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp., NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), MapmyIndia, OpenStreetMap contributors, and the GIS User Community Figure A-6 - Annual TP Yield (lbs per acre) Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /28/ of 1

41 Roseville Falcon Heights St. Paul Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp., NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), MapmyIndia, OpenStreetMap contributors, and the GIS User Community COMO PARK Municipal Boundaries Routed to Sanitary Sewer ,500 3,000 Feet Annual TSS Yield (lbs/acre) < > Figure A-7 - Annual TSS Yield (lbs per acre) Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /28/ of 1

42 Roseville Falcon Heights St. Paul Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp., NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), MapmyIndia, OpenStreetMap contributors, and the GIS User Community COMO PARK Municipal Boundaries Routed to Sanitary Sewer ,500 3,000 Feet Runoff Depth (Inches) Figure A-8 - Annual Runoff Depth Delivered to Como Lake Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /28/ of 1

43 Roseville Falcon Heights St. Paul Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp., NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), MapmyIndia, OpenStreetMap contributors, and the GIS User Community COMO PARK Municipal Boundaries Routed to Sanitary Sewer ,500 3,000 Feet TP Yield (lbs/acre) Figure A-9 - Annual TP Yield (lbs/acre) Delivered to Como Lake Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /28/ of 1

44 Roseville Falcon Heights St. Paul COMO PARK Municipal Boundaries Routed to Sanitary Sewer ,500 3,000 Feet TSS Yield (lbs/acre) Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp., NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), MapmyIndia, OpenStreetMap contributors, and the GIS User Community Figure A-10 - Annual TSS Yield (lbs/acre) Delivered to Como Lake Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /28/ of 1

45 Roseville Falcon Heights St. Paul COMO PARK Municipal Boundaries Routed to Sanitary Sewer ,200 Feet Runoff Depth (Inches) Figure A-11 - Annual Runoff Depth Delivered to Como Lake Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /28/ of 1

46 Roseville Falcon Heights St. Paul COMO PARK Municipal Boundaries Routed to Sanitary Sewer ,500 Feet TP Yield (lbs/acre) Figure A-12 - Annual TP Yield (lbs/acre) Delivered to Como Lake Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /28/ of 1

47 Roseville Falcon Heights St. Paul COMO PARK Municipal Boundaries Routed to Sanitary Sewer ,500 Feet TSS Yield (lbs/acre) Figure A-13 - Annual TSS Yield (lbs/acre) Delivered to Como Lake Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /28/ of 1

48 Roseville Falcon Heights Lake Como St. Paul COMO PARK Municipal Boundaries Routed to Sanitary Sewer Runoff Vol. Frac. Removed Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp., NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), MapmyIndia, OpenStreetMap contributors, and the GIS User Community Figure A-14 - Runoff Vol. Frac. Removed, 1.1-Inch 24-hr Rainfall Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /16/ of ,500 3,000 Feet

49 Roseville Falcon Heights Lake Como St. Paul Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp., NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), MapmyIndia, OpenStreetMap contributors, and the GIS User Community COMO PARK Municipal Boundaries Routed to Sanitary Sewer ,500 3,000 Feet TP Fraction Removed Figure A-15 - TP Fraction Removed from 1.1-Inch 24-hr Rainfall Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /16/ of 1

50 Roseville Falcon Heights Lake Como St. Paul Sources: Esri, HERE, DeLorme, USGS, Intermap, increment P Corp., NRCAN, Esri Japan, METI, Esri China (Hong Kong), Esri (Thailand), MapmyIndia, OpenStreetMap contributors, and the GIS User Community como_lake COMO PARK Municipal Boundaries Routed to Sanitary Sewer ,500 3,000 Feet TSS Fraction Removed Figure A-16 - TSS Fraction Removed from 1.1-Inch 24-hr Rainfall Scale: Drawn by: Checked by: Project No.: Date: Sheet: AS SHOWN SMW JL /16/ of 1