7. SITE DESIGN, RETAINING

Transcription

1 7. SITE DESIGN, RETAINING WALLS AND DETENTION 99 CASTLE ROCK DESIGN

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3 7. SITE DESIGN, RETAINING WALLS AND DETENTION Overview and Goals These guidelines apply to all residential, commercial, and industrial land use areas and the Downtown. The objective is to encourage the development of attractive and multipurpose detention areas with a safe depth, maintainable, and are viewed as assets to the Town rather than liabilities. The intent is to design storm water management elements as landscape features and as multipurpose detention areas. There are several desirable goals for the design of detention areas and retaining walls: Environmental, aesthetic and public safety concerns should be addressed in the design and location of detention areas; and Retaining walls should be distributed throughout a site to take up grade wherever possible, rather than be located solely at the perimeter of a site. Multi-purpose detention area The following are considered undesirable design forms and are discouraged: Tall retaining walls with large expanses of blank, flat walls; and Detention areas that are deep and have steep walls. Detention with recreational features in an office area The design and appearance of detention areas can take many different forms, ranging from more engineered areas with steep walls, typically found in commercial areas, to more naturalistic forms that are incorporated into the landscaped setting of a development. A. Detention and Retaining Walls An example of detention in a residential area Intent Detention basins should be designed to blend the detention area and outlet structure into the surrounding landscape and make it appear as naturalistic as possible. 101 CASTLE ROCK DESIGN

4 Guidelines A.1 The design of storm water retention and detention systems should complement and fit in with the natural open space and landscape and should be located where they have the greatest overall benefit. Detention in Commercial areas A.2 Detention areas should have attractive natural looking features, fit into the landscape and add to the overall character of an area as opposed to having boxy and geometric features. The shape of the detention pond should be made to look as naturalistic as possible, with terracing of the slopes and bottom. The top and the toe of the slope should vary, and there should be an undulation in the shape and grading of the sides of the detention area. A.3 Multipurpose detention facilities are strongly encouraged with recreation activities such as active recreation areas, passive open space areas, pedestrian paths, and children s play areas. A.4 The slopes of detention ponds should vary. It is preferred that wherever possible, slopes should be 4:1 or flatter. A.5 Plant material should be used to soften the appearance of the detention area, and blend in with the adjacent landscaping and natural features and conceal any required guardrails. A.6 Slopes should be well vegetated to prevent erosion channels. The use of appropriate groundcovers and grasses at the top of the slope help to soften the appearance of the detention area and can incorporate the detention area into the landscape design. Appropriate plant material, such as wetland species or drought tolerant species, should be planted in the detention area and on the slopes. Shrubs and trees should be planted back from the top of the slope. Native and perennial species should be used as much as possible. Naturalistic landscaping for a detention area A.7 For parking lots, water quality detention areas can be located in inverted landscaped islands within the parking lot. The buffer areas surrounding parking areas can also be used for detention. Other creative techniques for improving water quality and providing detention in or adjacent to parking lots is encouraged. CASTLE ROCK DESIGN 102

5 A.8 Rundowns, which convey runoff from streets and parking lots into channels or storage facilities, should be incorporated into the overall design and be attractively designed. Rundowns should allow for water infiltration. A.9 The maximum height of any retaining wall should be four feet. Retaining walls should be designed to consider slope height and aesthetics, and terraced walls in no more than four foot heights are encouraged. Should walls need to be any taller, they should be stepped back in four-foot increments with areas between the walls for landscaping. A.10 Retaining walls should not form any more than fifty percent of the perimeter of the detention area. A.11 Where it is possible, the foundation of a building can form one side of a detention area. A.12 The distance between the top of any retaining wall in a detention area and any adjacent sidewalk, roadway curb or structured feature should be a minimum of three times the height of the wall, where possible. A.13 Trickle channels should be designed to be decorative as well as practical features and to accommodate for infiltration and erosion control. A.14 Where possible, porous paving materials should be used in parking lots to allow for infiltration. An example of trickle channel design A.15 Alternative detention pond methods are encouraged, wherever possible. 103 CASTLE ROCK DESIGN

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