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FLOOD08209
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Last modified
1/29/2010 10:15:24 AM
Creation date
10/5/2006 3:28:22 AM
Metadata
Fields
Template:
Floodplain Documents
County
Adams
Arapahoe
Douglas, Jefferson
Community
Denver Metroploitan Area
Stream Name
South Platte River, Chatfield Dam to Baseline Road
Basin
South Platte
Title
Major Drainageway Planning
Date
8/1/1984
Prepared For
Denver Metropolitan Area
Prepared By
Wright Water Engineers, Inc.
Contract/PO #
&&
Floodplain - Doc Type
Floodplain Report/Masterplan
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<br />\IT 0 <br />,...-u <br /> <br />, it \f ",i" <br />1 l.....J HI" <br /> <br />not be <br /> <br />cinni~ir~ntl\, ~~~Qrtorl <br />-' ';:I" 11 ''-'''''..... 'J "'" '-'-'-'-'"" <br /> <br />h\l tho nrnnn,.:::ar1 ~t~hili 7.:ltinn ~nrl <br />~J ...,,~ f.... ~t'~~~- ~-~~,... -~- .~.. ~..- <br /> <br />(2) A series of lakes would be advantageous relative to a single lake <br />because the most upstreiYfl lake will part.ially rf>mnve pollutants, there- <br />by providing cleaner inflows to the more downstream ldkes. Conversely, <br />while utilizing a series of lakes will enable the attainment of some <br />lakes of improved water quality, the most upstream lakes will effec- <br />tively be pollutant settling basins, and have the potential for odors, <br />algal blooms, and general unsightliness. Many of these kinds of prob- <br />1 ems c an be overcome with appropri ate mai ntenance. <br /> <br />important to the health of a river, but in a long term sense, this capabi- <br /> <br />channelization method. One immediate implication of construction activities <br />in the river, however, is that many of the heavy metals and other contami- <br />nants which have been accumul ating in sediments of the South Pl atte River <br />will be resuspended and will collect in other portions of the river down- <br />stream. <br /> <br />The stabilization and channelization modifications proposed will enhance the <br />"riffle-pool" environment which currently exists on the river. Such an <br />environment provides habitat for various forms of fish and lower order <br />organisms. Additionally, riffles provide a mechanism for aerating river <br />flows and thereby increase dissolved oxygen level s. Cobble bottoms wi 11 <br />provide habitat for periphyton. <br /> <br />(3) The South Platte River alluvium in Adams County, which serves as a <br />water supply source, has as one of its recharge sources flow in the <br />South Platte River. Concentrating pollutants into one or two lakes <br />coulo permit the migration of polluted water from the river into the <br />adj acent a 11 uv i um. <br /> <br />These kinds of considerations indicate that on the whole, the proposed sta- <br />bilization and channelization techniques in particular reaches of the South <br />Pl atte River wi 11 pose environmental benefits. <br /> <br />Implications of Lake Development <br />Developing a number of river-connected lakes in AdiiTlS County is a potential <br />alternate. The feasibility of such lakes hinges, to some extent, on water <br />quality considerations. <br /> <br />Water Quality Problems <br />The principal potential water quality problems which would be associated <br />with a lake or the uppermost lakes in a series of lakes center on the rela- <br />tively high biochemical oxygen demand (BOD), nitrogeneous oxygen demand <br />(NOD) and nutrient concentrations in inflows. A high ambient BOD and NOD <br />will limit dissolved oxygen concentrations within the lake. Particular con- <br />cern should focus on the oxygen demana associated with nitrification of <br />ammonia, because of the high ammonia concentrations in discharges (14 to 18 <br />mg/l) from sewage treatment plants. Excessive nutrient availability will <br />cause algal blooms; such blooms ul timately represent a large bOD burden. <br />Combining these problems with the fact that reaeration in a lake will be <br />minimal leaos to the conclusion that maintaining adequate dissolved oxygen <br />levels within the lake may be difficult. This problem could be exacerbated <br />in the winter if the lakes stratify or if an ice cover forms, because in <br />either case, anaerobic conditions would develop in all or a portion of the <br /> <br />Three fundamental facts must be recognized when considering the viability of <br />the lake concept from a water quality standpoint. <br /> <br />(1) Inflow quality to the lake (or into the first lake, if a series of <br />lakes are planned) will contain sufficient concentrations of nutrients <br />and organic matter to pose water quality problems. Additionally, flow <br /> <br />-...~";l~h";''';~" ....;'1 h_ .~_.-I..__~ ~.,,_..:__ ";.~.^";__.i.";_,_ _____~ h.. ....l..;.._.__..;_~ <br />ovallaUlllLY Will UC ICUUl,..CU uur lIlY Ifr lyaL.IUII ~t:'a~UII uy Ullltf~'Ull, <br /> <br />1 ake. <br /> <br />An dqUdtic envirunmenl which CUflldifl~ 1 iLlle liissolved oxygen <br /> <br />.- _.~-- <br />liar 1I1~ <br /> <br />thus reducing flushing. <br />the quality and quantity <br /> <br />The feasibility of any lake is dependent on <br />of inflow<;, <br /> <br />desirable life forms, leads to the developnent of undesirable odors, and can <br /> <br />cause heavy metals in sediments to go into solution, <br /> <br />ni <:,<:,()lvprl nxvnpn nroh- <br />-.---.--- --'JJ- ,- <br /> <br />lems could be mitigated by aerating the uppermost one or two lakes; such <br />
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