Chemical Monitoring
Ditch 18
| Monitoring Location | at Highway 9, City of Oak Grove STORET SiteID = Ditch18_Hwy9 |
| Monitored By | ACD Staff |
| Years Monitored | 2003, and in 1998 and 2001 0.3 miles downstream from this site at Poppy Street |
| Background: Ditch 18 monitoring in 2003 was funded by The Ponds Golf Course. The City of Oak Grove required this, and periodic future monitoring, from the golf or residential developer as a condition of developing 410 acres immediately upstream of the monitoring site. Development occurred in 2002 and 2003, and continues. | |
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| Results: In 2003 total phosphorus (TP) concentration was, on average, double the 2001 readings and nearly double the median value for all Anoka County streams. It was also several-fold greater than two of the three 1998 readings. The third 1998 reading was 500 mg/l, an extraordinarily high reading that probably reflects measurement error or unusual circumstances. Fertilizer runoff and sediment eroding into the stream, along with wind erosion associated with mass grading are common ways for the development process to cause stream phosphorus to increase. Total suspended solids (TSS) also averaged about twice as great in 2003 compared to 1998 or 2001, but only for storm flows. The average TSS over all sampling events and for baseflow monitoring was similar to 1998 and 2001. Storm events are the times that erosion is most likely to occur and enter the ditch, especially if grading has occurred near the ditch itself. Wind erosion during mass grading may have not directly contributed to the stream, but may have done so indirectly by depositing light sediment in areas where it could easily be washed into the stream. All other water quality parameters were similar in 2003 to previous years, and fall within acceptable levels. The increases in phosphorus and suspended sediment are consistent with construction site erosion, increased surface runoff, and/or increased fertilization. It is recommended that: . Residential development and construction managers, golf course staff, and City of Oak Grove staff should meet to review erosion, storm water, and runoff management practices. The purpose of the meeting and site visit should be to determine if required practices were completely implemented. If the best management practices required by the City were implemented, then the focus of discussion should be to determine what additional measures are needed to protect water quality. Anoka Conservation District staff would be willing to attend such a meeting. . The residential developer should educate new residents about fertilization rates needed for turf development and maintenance. Soil tests should be taken to determine optimal fertilization rates. Tests are available from the University of Minnesota Soil Testing Laboratory for $12.50 each. Alternatively, golf course staff may be able to make recommendations based upon soil testing they have done for golf course turf development. . Ditch 18 water quality should be monitored again immediately after the above recommendations are fulfilled, preferably in 2004. Periodic monitoring every 2-3 years thereafter may be prudent, depending upon 2004 results. |
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