HomeMy WebLinkAboutD-20570DSTA 8 +35.87
LIMITS OF ACCESS
ROAD RECONSTRUCTION
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EXCEPT AS NOTED
Ef O811� N CONTROL PLAN
THE CONTRACTOR IS RESPONSIBLE FOR PROVIDING, INSTALLING, MAINTAINING AND REMOVING ALL EROSION CONTROL
MEASURES NECESSARY THROUGHOUT THE PROJECT SITE TO CONTROL EROSION IN WORK AREAS AND KEEP SEDIMENT,
DEBRIS, AND ANY OTHER CONTAMINATES FROM ENTERING MAPLEWOOD CREEK. EROSION CONTROL DEVICES THAT
SHOULD BE USED INCLUDE HAY BALES, SILT FENCING, SANDBAGS, OR ANY OTHER METHOD APPROVED BY THE CITY.
ANY EXPOSED SLOPES, CLEARED AREAS, DEMOLITION AREAS, TEMPORARY ACCESS ROADS, STOCKPILE AREAS,
CONTRACTOR STAGING AREAS, OR ANY OTHER AREAS WHERE SURFACE RUNOFF COULD CAUSE EROSION SHALL BE
PROTECTED BY THE HAY BALES, SILT FENCING, OR OTHER PROTECTIVE MEASURES.
SPECIAL ATTENTION TO EROSION CONTROL SHALL BE GIVEN TO INSTREAM WORK ITEMS INCLUDED IN THIS CONTRACT
THAT WILL BE PERFORMED ADJACENT TO OR IN MAPLEWOOD CREEK ITSELF. AS SHOWN ON THIS DRAWING, THERE
ARE FOUR GENERAL AREAS (DENOTED A THROUGH D) THAT HAVE BEEN IDENTIFIED AS INSTREAM WORK ITEMS.
THESE WORK ITEMS ARE EXPECTED TO BE PERFORMED IN THIS ORDER (A TO D). EROSION CONTROL MEASURES
REQUIRED FOR EACH AREA ARE DESCRIBED AS FOLLOWS:
AFEAA ACCESS ROAD IMPROVEMENTS AND INSTALLATION OF A 24 —INCH DIAMETER CMP CULVERT TO PROVIDE
ACCESS ALONG THE ROAD TO THE UPSTREAM CONCRETE WEIR WILL BE PERFORMED IN THIS AREA. PRIOR TO ANY
EXCAVATION, GRADING. OR GRAVEL SURFACING OF THE ROAD, SILT FENCING SHALL BE INSTALLED BETWEEN THE
ROAD AND MAPLEWOOD CREEK. PRIOR TO EXCAVATION ACROSS THE ROAD AND ON THE STREAM BANK FOR CULVERT
INSTALLATION, HAY BALES AND /OR SANDBAGS SHALL BE INSTALLED BETWEEN THE WORK AREA AND MAPLEWOOD
CREEK. FOLLOWING INSTALLATION OF THE CULVERT, ANY ACCUMULATED SEDIMENT SHALL BE REMOVED ALONG WITH
THE HAY BALES SO THAT THE SEDIMENT DOES NOT ENTER THE CREEK. SILT FENCING SHALL REMAIN IN PLACE
UNTIL WORK HAS BEEN COMPLETED IN AREA B.
AREAS EXCAVATION OF ACCUMULATED SEDIMENTS BEHIND THE EXISTING UPPER CONCRETE DAM, DEMOU11ON
AND DISPOSAL OF THE DAM AND STREAM BANK STABILIZATION MEASURES WILL BE PERFORMED IN THIS AREA.
PRIOR TO ANY WORK BEING PERFORMED IN THE STREAM, THE CONTRACTOR SHALL INSTALL A SMALL SANDBAG
COFFERDAM ACROSS MAPLEWOT CREEK UPSTREAM OF THE AREA THAT WILL BE EXCAVATED. FROM THIS
COFFERDAM, A TEMPORARY DIVERSION PIPE SHALL BE INSTALLED PASSING THROUGH THE WORK AREA AND
DISCHARGING BACK INTO THE CREEK DOWNSTREAM OF THE SLOPE STABILIZATION AREA. THE CONTRACTOR IS
RESPONSIBL- FOR DETERMINING THE SIZE OF THE TEMPORARY PIPE BASED ON EXISTING FLOWS DURING
CONSTRUCTION AND THE EXPECTED DURATION OF THE WORK, IN ADDITION TO THE DIVERSION PIPE, HAY BALES
SHALL BE INSTALLED ACROSS THE CREEK TO CONTROL ANY SEDIMENT EROSION THAT MIGHT OCCUR IF PIPE
CAPACITY IS EXCEEDED. WHILE THE DIVERSION PIPE IS IN PLACE, ALL INSTREAM WORK IN THIS AREA SHALL BE
PERFORMED USING THE HAY BALES DOWNSTREAM OF SMALLER WORK AREAS. THE DIVERSION PIPE WILL LIKELY
HAVE TO BE MOVED AS WORK PROGRESSES TO AVOID INTERFERENCE. WHEN WORK IS COMPLETED IN THIS AREA,
THE DIVERSION PIPE AND COFFERDAM SHALL BE REMOVED WITH ANY SEDIMENT THAT MIGHT ENTER THE CREEK
BEING CONTROLLED BY THE EXISTING SEDIMENTATION BASIN DOWNSTREAM.
AWAO INSTALLATION OF THE BYPASS PIPING AND INTAKE WILL BE PERFORMED IN THIS AREA FOLLOWING
COMPLETION OF WORK IN AREA B. SINCE EXCAVATION FOR THE BYPASS PIPING WILL CUTOFF CONTRACTOR ACCESS
TO AREAS A AND B. DURING EXCAVATION ADJACENT TO MAPLEWOOD CREEK, HAY BALES AND /OR SANDBAGS
SHALL BE INSTALLED BETWEEN THE WORK AREA AND THE CREEK. EXCAVATION AND CONSTRUCTION OF THE BYPASS
INTAKE AND INSTALLING THE BYPASS PIPING CAN THEN BE PERFORMED. FOLLOWING CONSTRUCTION OF THE INTAKE,
ANY ACCUMULATED SEDIMENT MUST BE REMOVED ALONG WITH THE HAY BALES AND /OR SANDBAGS CAN BE
REMOVED SUCH THAT NO MATERIAL ENTERS THE CREEK. AFTER INSTALLATION OF THE BYPASS PIPING, TEMPORARY
DIVERSION PIPING WILL BE REQUIRED TO EXTEND THE BYPASS PIPE BACK TO MAPLEWOOD CREEK. THE COMBINATION
OF THE BYPASS /TEMPORARY PIPING WILL BE USED FOR DIVERSION DURING WORK IN AREA D.
AF;F,A D WORK ITEMS TO BE PERFORMED IN THIS AREA INCLUDE EXCAVATION OF THE ACCUMULATED SEDIMENT
IN THE EXISTING SEDIMENTATION BASIN, REMOVAL OF THE ECOLOGY BLOCK WEIR ACROSS THE CREEK CHANNEL,
CONSTRUCTION OF THE NEW SPILLWAY AND FISHWAY STRUCTURES, REMOVAL OF EXISTING BURIED PIPES EAST
OF THE SEDIMENTATION BASIN, PLACEMENT OF THE NEW EMBANKMENT, AND INSTALLATION OF THE NEW BASIN
LINER WITH GROUND COVER. PRIOR TO WORK IN ANY OF THESE AREAS, THE BYPASS PIPING AND TEMPORARY
PIPING MUST BE IN PLACE CAPABLE OF DIVERTING THE MAPLEWOOD CREEK FLOWS AROUND THE WORK AP.EA.
ALSO, AN UPSTREAM SANDBAG COFFERDAM MUST BE INSTALLED ACROSS THE CREEK IMMEDIATELY DOWNSTREAM
OF THE BYPASS INTAKE STRUCTURE. A DOWNSTREAM COFFERDAM DOWNSTREAM OF THE NEW SEDIMENTATION
BASIN EMBANKMENT MAY BE REQUIRED, DEPENDING ON THE CREEK FLOWS, TO KEEP THE WORK AREA ISOLATED
FROM STREAM FLOWS. WHEN THE WORK IN THIS AREA IS COMPLETED, THE COFFERDAMS AND THE TEMPORARY
DIVERSION PIPING SHALL BE REMOVED. ANY SEDIMENT OR DEBRIS THAT MAY HAVE BEEN ACCUMULATED BEHIND
EACH COFFERDAM SHALL BE REMOVED ALONG WITH THE COFFERDAM SUCH THAT THE SEDIMENT AND DEBRIS ARE
NOT RELEASED INTO MAPLEWOOD CREEK.
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BELLEWE. WASHINGTON 98005
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