Drainage and Storm Water Standards for 4-Lot Residential Subdivisions

In Reno, the division of land into four or fewer lots is processed as a Parcel Map. The approval of these subdivisions is contingent upon a review of how the development affects existing drainage patterns and the necessity for new drainage facilities to serve the site [Section 18.08.704(d)(2)(c)].

Parcel Map Drainage Review

When reviewing an application for a four-lot single-family residential (SFR) subdivision, the Administrator evaluates the proposed parcel map specifically for:

• Its effect on existing drainage patterns.
• The need for new drainage facilities to serve the subdivided parcels [Section 18.08.704(d)(2)(c)].
• The dedication of public easements for major drainage facilities, streams, or creeks in a location consistent with the subdivision's character [Section 18.06.202(c)].

Major Drainageway Protection

If the property contains a "major drainageway"—defined as a drainageway draining a land area of 100 acres or more—specific protection standards apply [Section 18.04.104(b)].

Buffer and Width Requirements

• Width: Drainageways must generally be the width of the 100-year floodplain plus a minimum 15-foot wide area on each side [Section 18.04.104(c)(1)].
• Hydrologic Analysis: If the drainageway is not within a mapped floodplain, the width is determined by a hydrologic analysis approved by the Administrator [Section 18.04.104(c)(1)].
• Density Exclusions: For hillside developments, the 100-year floodplain plus the 15-foot buffer (up to a maximum of 80 feet in total width) must be excluded from density calculations [Section 18.04.405(a)(2)].

Structural Restrictions and Maintenance

• Piping and Filling: Drainageways cannot be piped or filled unless no other alternatives (such as re-routing or bridging) exist [Section 18.04.104(c)(5)].
• Natural State: Natural drainage courses must be preserved as open space and remain undisturbed, except for vegetation enhancement or necessary roadway/utility crossings [Section 18.04.104(d)(1)-(3)].
• Maintenance: The property owner is responsible for removing trash, clearing sediment, and controlling weeds within the drainageway [Section 18.04.104(c)(2)].
• Prohibited Materials: Soils, grading spoils, rubbish, or abandoned vehicles that impair the water transport capacity of the drainageway are prohibited [Section 18.04.104(c)(3)].

Storm Water Quality Management

Developments that require a parcel map and involve improvement plans on one or more acres of land must submit a post-construction storm water quality management plan [Section 18.04.304(c)(1)(a)(3)].

Plan Standards and LID

Management plans must emphasize Low Impact Development (LID) principles, which include:

• Minimizing soil compaction and impervious surfaces.
• Preserving natural vegetation and buffer zones.
• Utilizing on-site storm water treatment techniques [Section 18.04.304(b)(2)].

Financial and Legal Obligations

• Performance Security: The developer must provide a bond or security equal to the estimated construction cost of the storm water practices plus 20% [Section 18.04.304(g)(1)].
• Maintenance Agreement: A storm water treatment device access and maintenance agreement must be executed and recorded with Washoe County before permits are issued. This agreement is binding on all subsequent property owners [Section 18.04.304(h)(1)].

Grading and Setbacks

Grading for subdivision improvements must adhere to strict setbacks to protect adjacent properties:

• Fill Restrictions: No fill may be placed within 5 feet of a shared property line [Section 18.04.1404(a)(1)].
• Depth Limits: Within 20 feet of a residentially zoned property line, fill depths cannot exceed the natural grade by more than 4 feet. Within 50 feet, fill cannot exceed the natural grade by more than 8 feet [Section 18.04.1404(a)(2)-(3)].
• Hillside Limits: In hillside areas, fill depths are limited to a maximum of 10 feet at project edges and interfaces with major drainageways [Section 18.04.410(b)].