Description: This point feature layer represents environmental outfalls maintained and managed by the Ada County Highway District (ACHD) in Ada County, Idaho. Each feature corresponds to an individual outfall structure and may include attributes such as structure diameter, structure type, ownership, land use, inspection, maintenance area and NPDES_Permit Area. Stormwater outfalls are critical endpoints of the ACHD drainage network, designed to convey collected stormwater runoff from roadways and infrastructure to receiving water bodies, channels, or infiltration areas in a controlled manner. The dataset is intended to support stormwater management, illicit discharge detection and elimination (IDDE), environmental compliance, water quality monitoring, asset management, maintenance prioritization, and MS4 permit reporting across the ACHD jurisdiction in compliance with National Pollutant Discharge Elimination System (NPDES) permit requirements. Data was compiled and is maintained by the Ada County Highway District.
Copyright Text: Created by Ada County Highway District, 2026. Outfalls data sourced from the highway district.
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Description: This point feature layer represents storm drain structures located within the official right of way and maintained by the Ada County Highway District (ACHD) in Ada County, Idaho. Each feature corresponds to an individual storm drain structure and may include attributes such as structure identifier, structure type (catch basin, inlet, manhole, junction box, drop inlet, grate inlet), location, street name, pipe diameter, pipe material, invert elevation, rim elevation, drainage basin, condition rating, inspection date, installation year, and maintenance jurisdiction. Storm drain structures are essential components of the ACHD roadway drainage network, designed to collect and convey surface water runoff from roadways and right of way areas to downstream conveyance systems, detention facilities, or receiving water bodies. The dataset is intended to support stormwater management, drainage system inventory, infrastructure condition assessment, capital improvement planning, MS4 permit compliance, illicit discharge detection and elimination (IDDE), maintenance prioritization, and asset management across the ACHD jurisdiction in compliance with National Pollutant Discharge Elimination System (NPDES) permit requirements. Data was compiled and is maintained by the Ada County Highway District.
Copyright Text: Created by Ada County Highway District, 2026. Storm Drain Structures data sourced from the highway district.
Description: This line feature layer represents storm drain pipes maintained and managed by the Ada County Highway District (ACHD) in Ada County, Idaho. Each feature corresponds to an individual pipe segment and may include attributes such as pipe identifier, pipe type, pipe material (concrete, HDPE, CMP, PVC, RCP), pipe diameter, pipe shape, pipe slope, pipe length, flow direction, associated structures (upstream and downstream manhole or inlet), drainage basin, installation year, condition rating, inspection date, and maintenance jurisdiction. Storm drain pipes form the primary underground conveyance network of the ACHD stormwater system, transporting collected surface water runoff from catch basins, inlets, and other collection structures to detention facilities, outfalls, or receiving water bodies. The dataset is intended to support stormwater system inventory, drainage network analysis, condition assessment, capital improvement planning, illicit discharge detection and elimination (IDDE), maintenance prioritization, and asset management across the ACHD jurisdiction in compliance with National Pollutant Discharge Elimination System (NPDES) permit requirements. Data was compiled and is maintained by the Ada County Highway District.
Copyright Text: Created by Ada County Highway District, 2026. Storm Drain Pipes data sourced from the highway district.
Description: This polygon feature layer represents environmental swales maintained and managed by the Ada County Highway District (ACHD) in Ada County, Idaho. Each feature corresponds to an individual swale area and include attributes such as swale identifier, swale name, swale type (vegetated swale, dry swale, wet swale, bioswale), location, associated roadway or drainage system, length, width, inspection date, condition rating, and maintenance jurisdiction. Environmental swales are a key component of ACHD's stormwater management infrastructure, designed to slow, filter, and infiltrate roadway runoff, reduce pollutant loads, and protect downstream waterways and ecosystems in compliance with National Pollutant Discharge Elimination System (NPDES) permit requirements. The dataset is intended to support stormwater management, environmental compliance, water quality monitoring, asset management, maintenance prioritization, and green infrastructure planning across the ACHD jurisdiction. Data was compiled and is maintained by the Ada County Highway District.
Copyright Text: Created by Ada County Highway District, 2026. Swales data sourced from the highway district.
Description: This polygon feature layer represents environmental tree cells maintained and managed by the Ada County Highway District (ACHD) in Ada County, Idaho. Each feature corresponds to an individual tree cell installation and include attributes such as tree cell identifier, location, street name, installation year, condition rating, inspection date, and maintenance jurisdiction. Tree cells are engineered green infrastructure systems that combine urban tree planting with stormwater management, utilizing structured soil cells beneath paved surfaces to support tree root growth while capturing, filtering, and infiltrating roadway runoff. They are designed to improve water quality, reduce stormwater volume, enhance urban tree canopy, and contribute to livable streetscapes in compliance with National Pollutant Discharge Elimination System (NPDES) permit requirements. The dataset is intended to support stormwater management, environmental compliance, urban forestry, green infrastructure planning, asset management, and maintenance prioritization across the ACHD jurisdiction. Data was compiled and is maintained by the Ada County Highway District.
Copyright Text: Created by Ada County Highway District, 2026. Tree Cells data sourced from the highway district.
Description: This polygon feature layer represents environmental basins maintained and managed by the Ada County Highway District (ACHD) in Ada County, Idaho. Each feature corresponds to an individual basin and may include attributes such as subdivision, location, year built, jurisdiction, maintainer, HOA, storage type, stormdesign_yr, receiving waterway, instrument, basin type, project, project number, vegetated, intersection parcel no, city, gatetype, fencetype, NPDES_permitArea and maintainer. Environmental basins are a critical component of ACHD's stormwater management infrastructure, designed to manage runoff, reduce flooding, improve water quality, and protect downstream waterways in compliance with National Pollutant Discharge Elimination System (NPDES) permit requirements. The dataset is intended to support stormwater management, environmental compliance, asset management, maintenance prioritization, and infrastructure planning across the ACHD jurisdiction. Data was compiled and is maintained by the Ada County Highway District.
Copyright Text: Created by Ada County Highway District, 2026. Basins data sourced from the highway district.
Description: Sections 305(b) and 314 of the Clean Water Act (CWA) require states, territories, and authorized tribes to provide biennial reports to EPA on the condition of waters within their boundaries. EPA regulations at 40 CFR 130.7 require states to provide biennial submissions of impaired waters lists. EPA provides guidance on these reports in a way that supports the Agency's strategy for achieving a broad-scale, national inventory of water quality conditions. The guidance is from EPA to states, territories, authorized tribes, and interstate commissions ("jurisdictions") to help states prepare and submit Section 305(b) reports to EPA. Use of the integrated report (IR) format provides jurisdictions a recommended reporting format and suggested content to be used in developing a single document that integrates the reporting requirements of Sections 303(d), 305(b), and 314. This format allows jurisdictions to report on the water quality standards attained for all waters, document the availability of data and information for each segment, identify certain trends in water quality conditions, and set priorities for protecting and restoring the health of the nation's aquatic resources. Section 305(b) of the Clean Water Act requires each state to conduct water quality surveys to determine a water body's overall health, including whether or not basic uses are being met. States, tribes, and other jurisdictions define appropriate uses for a waterbody and incorporate these uses into water quality standards that are approved by EPA. Water body uses include aquatic life protection, fish and shellfish production, drinking water supply, swimming, boating, fishing, and agricultural irrigation, among others.
Copyright Text: Idaho DEQ, Research Triangle Institute (RTI), EPA/USGS-NHDPlus V 2 (100K)
Description: This feature class was created in part from Idaho Dept of Waters Resources NHD for Ada County, ACHD's mapped irrigation laterals, as well as of Ada County's Assessor's GIS water layer. ACHD GIS Hydro Layer Hydro-type Definitions Irrigation –Waterbodies that have been labeled as “Irrigation” are those that are likely man-made water features used primarily to convey irrigation water or drain irrigated land. Waterbodies identified as “Irrigation” Hydro-type have identifiers in their names that include Lateral, Sublateral, Drain or Ditch e.g. the Southern Lateral or Davis Drain. Waterway – Waterbodies that have been labeled as “Waterway” are those that are natural water features or natural water features that have been modified. Waterbodies that have Hydro-type “Waterway” have identifiers in their names that include Creek, Gulch, River e.g. Fivemile Creek. Waterway-Seasonal (previously denoted as “Waterway-Intermittent”) – Waterbodies that have been labeled as “Waterway- Seasonal” are those that are natural water features that flow or contain water on an intermittent basis, usually after the winter snow melt. These waterbodies may also flow after a heavy rain or rain on snow event. Waterbodies that have Hydro-type “Waterway-Seasonal” have identifiers in their names that include Creek, Gulch, River e.g. Fivemile Creek. Canal – Waterbodies that have been labeled as “Canal” are those that are man-made water features that convey water from a natural waterbody such as the Boise River to other waterbodies for the purpose of providing irrigation water for distribution to water users. Waterbodies that have Hydro-type “Canal” have identifiers in their names that include Canal, Aqueduct, e.g. Ridenbaugh Canal.
Copyright Text: Questions regarding ACHD GIS Hydro Layer definitions can be addressed to Erica Anderson Maguire at emaguire@achdidaho.org or 208-387-6254. Questions regarding the creation of this layer or the data therein please contact Sharon Anderson at sanderson@achdidaho.org or 208-387-6242.