Agenda - Planning Commission - 02/02/2017

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6106.0160 Land Alteration and Storm Water Management Standards Uncontrolled land disturbance near water increases the probability of sediment and phosphorus pollution to surface waters.15 Small construction sites are a large source of sediment erosion, yielding up to 10 times the typical loads from rural and urban land uses.16 Executive Order 79-19 requires that all land alteration activities be regulated by local governments according to best management practices that were typical in the 1970s. Executive Order 79-19 does not regulate storm water runoff, storm water management structures, or erosion control structures such as retaining walls and riprap. Regulations adopted pursuant to Executive Order 79-19 for land alterations are overly broad and apply the same management practices across the MRCCA, regardless of the proximity of the alteration to sensitive natural resources. The erosion control practices of the 1970s era do not provide adequate resource protection consistent with contemporary development and, in most cases, are less protective than current local government regulations. Most local governments have adopted land alteration and storm water management regulations consistent with standards developed by the relevant watershed management authority and/or the National Pollution Discharge Elimination System (NPDES)/State Disposal System (SDS) permits for construction activities. The minimum land disturbance threshold triggering a local land alteration permit varies considerably across the MRCCA. The majority of communities in the MRCCA do not require a land alteration permit until at least 10,000 square feet of soil are disturbed. No community requires a permit for all land alteration activity, as required by Executive Order 79-19. The minimum impervious surface threshold triggering a local storm water permit also varies considerably. One acre is the most common threshold, as this is consistent with the NPDES/SDS permit for construction -related activities. Most communities do not vary their land alteration or storm water requirements based on proximity to sensitive natural resources. While most local regulations include contemporary best management practices, they do not regulate small to medium size land disturbance activities (i.e. disturbing less than 10,000 square feet), which can occur in sensitive bluff and near shore areas. Thus, there is often no permitting oversight in the most sensitive areas in the MRCCA. In response to identified erosion problems, especially in the northern reaches of the corridor, erosion control structures have been used to stabilize riverbanks and reduce erosion. The Anoka Conservation District, for example, found that most of the erosion problems along the Coon Rapids Dam Pool occur on public land containing few erosion control structures, while few erosion problems are found on private shores protected by manmade features such as rip rap and retaining walls.17 In the Coon Rapids Dam pool, riprap has been shown to be effective in controlling erosion at the toe of the slope. Riprap can also be effective in reducing sediment loading to the river. However, many of these features were 15 Walsh. 2005. 16 Owens. 2000. 17 Anoka Conservation District. 2012. 58