1. Storm Water Controls for New Development. When development occurs, the following requirements shall apply, as a means of controlling the negative effects of excessive storm water runoff:
A. The developer shall provide sufficient documentation to ensure that, when completed, new development will not increase the amount of storm water runoff onto adjacent and downstream properties. If necessary for this purpose, the developer shall also submit plans for site improvements, such as the creation of retention or detention ponds, at strategically placed locations.
B. In areas with especially steep slope or poorly drained soils, these topographical and geological limitations shall be incorporated into the development plan.
C. No existing water channel (creek, river, or stream) shall have its natural course further altered for the purpose of private development. These features shall be retained in their natural state, to ensure that patterns of topography and drainage are not disturbed.
D. Private development shall not alter the placement of trees and other riparian vegetation lining the banks of a stream channel, as these contribute to natural drainage patterns.
E. If any existing stationary water feature (lake, pond, or wetland) must be altered for the purpose of development, a water feature of equal retention capacity shall be created in the nearby vicinity, to ensure that natural patterns of topography and drainage are not disturbed.
2. Maximum Impervious Surface. For all residential properties, a certain percentage of the land shall be devoted to green space, unobstructed by impervious surfaces, defined as any form of ground cover which prevents the ready absorption and retention of water. This requirement is intended to reduce the effects of storm water runoff, and enhance the capacity of the City sewer system, in managing rainfall events in each neighborhood or subdivision.
A. This requirement shall apply to buildings, driveways, walkways, patios, tennis courts, or any other similar structure or surface which meets the definition of an impervious surface.
B. A deck is not considered impervious if it is slatted, with gaps for water to easily pass through to the soil below. If it is composed of a solid material without any gaps, a deck is considered impervious. If there is a solid barrier covering the ground underneath, any kind of deck – slatted or solid – is considered impervious.
C. This requirement shall not apply to swimming pools, as this is not considered an impervious surface, due to its retention capacity in normal rainfall events.
D. This provision shall apply exclusively to new development and redevelopment. Buildings and structures existing prior to the establishment of this provision 13 shall be exempt from its requirements.
E. The requirements shall apply, however, to any structural additions that increase the physical footprint of an existing dwelling. They shall also apply to the installation of new features such as patios, tennis courts, or walkways, where none existed previously.
(1) If the existing dwelling has already reached or exceeded the maximum impervious surface allowable, then no such additions shall be permitted.
(2) If the existing dwelling has not yet reached the maximum impervious surface allowable, then additions shall only be permitted if they do not result in the dwelling exceeding the maximum.
F. If the owner plans to rebuild or replace an existing impervious structure or surface, and this property already exceeds the amount of impervious surface allowed, then its replacement shall not increase the amount of impervious surface present. The amount must either decrease or remain the same as before the replacement. This shall also apply to the rebuilding of structures that were damaged by fire, flood, earthquake, or natural disaster.
Note: Under these conditions, any other nonconforming aspects of a property shall be required to conform, based on the stipulations of Section 165.18(3).
G. The following table lists the maximum amount of impervious surface that is allowable for each type of residential use:
Single and Two-Family Residential | |
Lot Size | Maximum Impervious Surface |
6000 SF or less | 60% of total lot area |
6,001 – 7,500 SF | 55% of total lot area |
7,501 – 10,000 SF | 50% of total lot area |
10,001 – 15,000 SF | 45% of total lot area |
15,001 – 20,000 SF | 40% of total lot area |
20,001 – 25,000 SF | 35% of total lot area |
25,001 – 30,000 SF | 30% of total lot area |
30,001 or more | 25% of total lot area |
Multi-Family Residential | |
Density | Maximum Impervious Surface |
2-4 Units per Dwelling | 55% of total area of the complex |
5 or More Units per Dwelling | 60% of the total area of the complex |
H. Substitutions. In the event that a desired building addition or paved surface conflicts with the requirement for maximum impervious surface on a lot, the following methods may be used to accommodate the proposed addition:
(1) Permeable Pavers. When adding a driveway, walkway, or patio, permeable pavers may be used as a substitute for impervious materials. In addition, existing paved surfaces may be replaced with permeable pavers, in the event that a new building addition would result in the Maximum Impervious Surface being exceeded for the lot.
(2) Rain Barrels. Above-ground devices for the collection and storage of excess rainwater may be installed, to offset the effects of storm water runoff.
(3) Cisterns. Similar to a rain barrel, an underground cistern may be used as a substitution. To ensure the safety of the device, it is required that the Building Inspector shall inspect and evaluate any cistern intended to be used for this purpose.
(4) Rain Gardens. Rain gardens planted with native plants and grass may be used, if positioned in a location especially suited to capture storm water runoff, such as adjacent to a downspout, sump pump drain line, or any elevated impervious surface.
In each case, if such components are to be installed for this purpose, the owner or developer shall produce advanced documentation, showing the precise form of materials to be used, to prove that they have sufficient capacity to handle excess runoff, and are in conformance with all applicable industry standards.
If the components are already present prior to the application for a permit, the owner shall allow the Building Inspector to inspect and evaluate them, to prove that they have sufficient capacity to handle excess runoff, and are in conformance with all applicable industry standards.
Note: All of the preceding strategies are encouraged by the City, regardless of whether or not the Maximum Impervious Surface has been reached. While they are especially helpful in such a circumstance, they are a desirable addition in any other context, alone or in combination with one another.
Notes
| 13 | 13 The Maximum Impervious Surface provision was established by an Ordinance Amendment dated July 6, 2016. |