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FLOOD09347
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Last modified
1/26/2010 10:08:56 AM
Creation date
10/5/2006 4:13:40 AM
Metadata
Fields
Template:
Floodplain Documents
County
Denver
Community
All
Stream Name
All
Basin
South Platte
Title
Nature's Building Codes: Geology and Construction in Colorado
Date
1/1/1979
Prepared For
State of Colorado
Prepared By
CGS
Floodplain - Doc Type
Educational/Technical/Reference Information
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<br />Ground Water &Construction <br /> <br />Characteristics <br /> <br />Ground water can be one of the most cost I y--even <br />rulnous--factors in construction and land development jf It <br />j 5 not understood and taken into cons j derat i on in the <br />planning phases of a project. Water is the primary cause of <br />the ground moving--up, down or laterally--because of its <br />capability of changing the chemical and physical nature of <br />rocks and salls. .~ater activates swelling and <br />hydrocompacting (collapsing) soi Is and Is a major factor in <br />slope instabll ity. <br /> <br />The value of any development is affected, directly and <br />indirectly, by the long term Impacts of ;tround water. The <br />I ack of j t or the over abundance of it is one of the most <br />prevalent and fundamental reasons for financial distress In <br />the bu i I d J ng and I and dave J opment bus I nesses. Its <br />significance Is evidenced by outright losses, delays, <br />lawsuits, improper or inadequate use of a site and post <br />construction corrective measures. <br /> <br />Aggravating Circumstances & Consequences <br /> <br />Elementary practices such as roof and pave~8nt storm runoff, <br />sewage treatment, landscaping and land grading can upset the <br />existing natural ground water regimen and create new <br />situations that did not exist prior to development. <br />3asements may flood, foundations sink or be pushed upward to <br />affect an entire structure and underground utll ities as well. <br />Pavelnents may bu I ';:Je or cave in as ground water j s af fected by <br />I and-use changes on the surface of the ground. PI ann i n9 <br />projects with knowled~e of the pre-development ground water <br />conditions and analysis of anticipatad post-development <br />conditions may indicate th3 desJrabl1 ity of mitigation <br />measures before full development. The cost of prevention is <br />ordi'narily far cheaper than trying to correct and repair <br />damage from ~round water related causes. <br /> <br />24 <br /> <br />rli;:Jh ground water tables limit land use and may require <br />special construction methods. Lowering the water table by <br />draining lOW-lying areas and then filling them with 5011 is a <br />common practice which frequently alters local ground water <br />conditions. <br /> <br />Mitigation <br /> <br />Ground water is an area-wide matter which can be managed to <br />the short and long term benefit of surface lands. It Is to <br />the advantage of contractors and devs I opers to know J n <br />advance what their project wi I J do to ground water and what <br />ground water may do to it. <br /> <br />Case History <br /> <br />A southern Aurora subd i v I sian was deve loped in the ear I y <br />1970 I 5 when the groundwater tab I e was 20 feet be I ow the <br />surface. Piecemeal development, changing of drainage <br />patterns dur i ng deve I opment, and excess i ve I awn water I ng over <br />the sandy so II s ra I sed the water tab I e and caused chron I c <br />basement flooding. Many homeowners put In sump pumps and <br />shallow lawn-watering wells. Damage Is estimated at $1,000 <br />to $4,000 each to several hundred homes. Integrated surface <br />drainage, non-basement homes, and an area-wide dewatering <br />system could have prevented such high water table damage. <br />The cl ty esti mated res I dents were spr j nk Ii n9 45 J nches of <br />water on their lawns annually, thus contributing to the <br />problem. <br />
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