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In order to better understand how the surface -water system works, the CSWIVIP divides the city into sub - watershed areas based on surface drainage features and the storm sewer system. The City's sub - watershed areas are shown in Figure 2. The City's storm sewer network and overall conveyance system is in place. Future changes to the system will primarily involve retrofitting to address flooding problems, to incorporate water quality treatment, or incorporate improvements at the time of redevelopment. This storm sewer system consists of: • 124 miles of pipe, • 4719 catch basins, • 2728 manholes, • 128 ponds, • 13 special features (infiltration, biofiltration, water reuse, raingardens, ect.) • 739 inlets and outlets, and • six storm -sewer lift stations. The citywide storm sewer map (Figure 3) shows the locations of the majority of these facilities and general direction of flow through the system. 2.3 Soils and Geology A large portion of the landscape is dominated by Urban land- Zimmerman complex (859B) and Urban land- Hayden - Kingsley complex (860C), as identified in the Ramsey County Soil Survey. The Natural Resource Conservation Service (MRCS) also classifies soils by the Hydrologic Soil Group (HSG) based on estimates of runoff potential (Figure 4). These are: • Hydrologic Soil Group A — Low runoff potential — high infiltration rate • Hydrologic Soil Group B — Moderate infiltration rate • Hydrologic Soil Group C — Slow infiltration rate • Hydrologic Soil Group D — High runoff potential — very slow infiltration rate The surficial geology consists of unconsolidated glacial sediments deposited during the Quaternary geologic period of two glacial ice lobes: the Superior lobe and the Grantsburg sublobe of the Des Moines lobe. The glacial deposits found in Ramsey County are primarily in the form of outwash, till, and stream and lake sediments ranging in thickness from 10 to 400 feet. Below the unconsolidated glacial sediment lies consolidated bedrock formed during the early Paleozoic age. Bedrock units from youngest to oldest in Roseville include: Decorah Shale, Platteville- Glenwood Formation, St. Peter Sandstone, Prairie Du Chien Group, and Jordan Sandstone. Maps of the surficial geology and bedrock geology from the Ramsey County Geological Atlas can be found on Figure 5 and Figure 6, respectively. 2.4 Land Use and Land Cover The City of Roseville encompasses an area of 13.8 square miles which today is made up of mixed -land uses including established neighborhoods, parks and open space, and significant retail, commercial and industrial development. Some key aspects of the existing landuse pattern are: • Low - density residential is the dominant land use. This form of housing occupies more than 34% of Roseville's total land area. Comprehensive Surface Water Management Plan ROSEV120222 City of Roseville Page 6