VB.NET Service Memory Leak???

I have created a VB.Net service that uses WMI to check my network card statistics every 5 minutes using a Timer and posting that info to a ASP page. What I find is that the service as listed in Task Manager keeps going up in memory. I am not the best coder out there, can someone see a problem in my code or let me know if this is by design?

Private Sub Timer1_Elapsed_1(ByVal sender As System.Object, ByVal e As System.Timers.ElapsedEventArgs) Handles TimerSendNICInfo.Elapsed

        'Record log about starting service timed event
        Me.LogInfo("Send NIC Info at " & Now.ToLongDateString & " - " & Now.ToShortTimeString)

        ' Set initial variables and WMI object
        Dim oWMI
        Dim oTmp
        Dim oCtrl
        Dim web As New System.Net.WebClient
        Dim sServerNetworkDetails
        Dim strPostNetworkData As String
        Dim bytPostNetworkData() As Byte
        Dim sComputerName
        Dim sNetworkCardName
        Dim sBytesReceivedPerSec
        Dim sBytesSentPerSec
        Dim sBytesTotalPerSec

        oWMI = GetObject("winmgmts:")
        oTmp = oWMI.InstancesOf("win32_computersystem")

        For Each oCtrl In oTmp
            sComputerName = oCtrl.Caption
        Next

        oTmp = Nothing
        oWMI = Nothing
        oCtrl = Nothing

        Try
            Dim connection As New ConnectionOptions

            Dim scope As New ManagementScope( _
                "\\.\root\CIMV2", connection)
            scope.Connect()

            Dim query As New ObjectQuery( _
                "SELECT * FROM Win32_PerfFormattedData_Tcpip_NetworkInterface")

            Dim searcher As New ManagementObjectSearcher(scope, query)

            For Each queryObj As ManagementObject In searcher.Get()

                sNetworkCardName = queryObj("Name")
                sBytesReceivedPerSec = Convert.ToString(queryObj("BytesReceivedPerSec"))
                sBytesSentPerSec = Convert.ToString(queryObj("BytesSentPerSec"))
                sBytesTotalPerSec = Convert.ToString(queryObj("BytesTotalPerSec"))

                sServerNetworkDetails = "NetworkCardName=" & sNetworkCardName & "&BytesReceivedPerSec=" & sBytesReceivedPerSec & "&BytesSentPerSec=" & sBytesSentPerSec & "&BytesTotalPerSec=" & sBytesTotalPerSec

                'Make the Post Data String

                strPostNetworkData = "ComputerNameD=" & sComputerName & "&"  & sServerNetworkDetails

                web.Headers.Add("Content-Type", "application/x-www-form-urlencoded")

                bytPostNetworkData = System.Text.Encoding.ASCII.GetBytes(strPostNetworkData)
                web.UploadData("http://www.mywebsite.com/Network.asp", "POST", bytPostNetworkData)

            Next

            connection = Nothing
            scope = Nothing
            query = Nothing
            searcher = Nothing
            searcher.Dispose()

        Catch err As ManagementException
            Me.LogInfo("An error occurred while querying for WMI data: " & err.Message)
        Catch unauthorizedErr As System.UnauthorizedAccessException
            Me.LogInfo("Connection error (user name or password might be incorrect): " & unauthorizedErr.Message)


        End Try

        ' CleanUp
        oTmp = Nothing
        oWMI = Nothing
        oCtrl = Nothing
        web = Nothing
        sServerNetworkDetails = Nothing
        strPostNetworkData = Nothing
        bytPostNetworkData = Nothing
        sComputerName = Nothing
        sNetworkCardName = Nothing
        sBytesReceivedPerSec = Nothing
        sBytesSentPerSec = Nothing
        sBytesTotalPerSec = Nothing
        web.Dispose()

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