Laserfiche WebLink
<br />VI-9 <br /> <br />aeration would facilitate breakdown of organic matter and enhance nitrifica- <br />tion. The economic feasibility of aeration has not been assessed. <br /> <br />ally, oxygen depletion and subsequent metals mobilization in the lakes could <br />create toxic conditions to fish. <br /> <br />Maintaining adequate flushing and mixing in the lakes may be difficult. <br />Incorporating outlet works into the proposed embankments to enable withdraw- <br />ing water from the bottom portion of the lake (hypolimnion) for quality <br />reasons would be difficult because of the excavated nature of the lakes. <br /> <br />A number of heavy metals are in the South Platte River in significant quan- <br />tities as discussed previously. The downstream movement of such metals will <br />be impeded by the creation of a lake; consequently, metals and phosphorous <br />will accumulate in the sediments in the most upstream lake (or lakes) pro- <br />posed for development. The impact of heavy metals on any given lake and its <br />surrounding habitat is difficult to assess without studying the mechanics of <br />the lake in question. Many physical, chemical, and biological factors <br />influence heavy metal availability in a lake and the interrelationships <br />among such factors should be established through modeling studies. <br /> <br />The South Platte often carries floating debris and foam. From the stand- <br />point of aesthetic appeal of the lakes, foam and floating trash pose a prob- <br />lem. Probable concentrations of bacteria and viruses are difficult to pre- <br />dict, although in the aftermath of runoff events, bacterial concentrations <br />would be expected to increase. This topic will influence the extent to <br />which body contact would be permitted. <br /> <br />Lake Feasibility With Respect to Water Quality <br />Water quality considerations will influence the feasibility of developing <br />lakes on the South Platte River in Adams County. Many problems such as <br />odors, heavy metal accumulation, excessive nutrient availability, and high <br />biochemical oxygen demand will exist. <br /> <br />Deposition of organic matter on the lake bottom would occur. Deposition of <br />organic matter poses problems for benthic organisms, provides a poor sub- <br />strate for desirable aquatic organisms, imposes a BOD demand on the lake, <br />can alter the chemistry of bottom sediments, and, in combination with other <br />factors, will enhance lake ventrophication. <br /> <br />A lake which effectively stores pollutants may lead to the focusing of pub- <br />lic attention on the pollutants issuing from the Denver area ,ewage treat- <br />ment plants. Once polluted, the lakes do not quickly recover, and any inad- <br />vertent poor quality effluent discharges would remain in the lake, rather <br />than be carried downstream. <br /> <br />Water quality and river regime impact are the primary factors against lake <br />development. <br /> <br />Despite the kinds of potential quality problems associated with lakes in <br />Adams County as discussed herein, such lakes could also improve downstream <br />water quality, and could represent a focal point and recreational opportuni- <br />ty. <br /> <br />The lowest concentration of fish on the South Platte River between Chatfield <br />and Brighton currently occurs in Adams County in the areas proposed for lake <br />development. Fish scarcity in this particular river reach is partially <br />attributable to the fact that the channel bottom consists almost entirely of <br />sand, rather than the desirable mixture of rocks, cobbles, gravels, sand and <br />silt. Substrate associated with the lake or lakes currently envisioned will <br />probably consist predominantly of sand; therefore, the capability of such <br />lakes to support desirable fish populations is open to question. Addition- <br />